首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献，搜索用时 62 毫秒
1.
Summary. The average air-dry yield of weeds on fallow plots was about four times as large (2660 kg/ha) as the yield of weeds which developed among spring cereal crops (740 kg/ha). Application of fertilizers increased the number of weeds and their average weight on both irrigated and non-irrigated plots. Treatment with MCPA reduced the weed yield to 36% on fallow plots and to 26% on weedy cereal plots. It was more effective on fertilized plots than on unfertilized plots, but irrigation made little difference to its effectiveness. The space left by the destroyed weeds was mainly occupied by Agropyron repens . Oats were better able to compete with weeds than were wheat and barley. On unfertilized and non-irrigated plots spraying with MCPA (1-26 kg/ha) at the beginning of shooting significantly reduced the yields of weed-free barley. The yields of sprayed oats and wheat were also below the yields from the unsprayed although the reductions were not significant at the 5% level. However, on a number of fertilized and irrigated plots, both weedy and hand-weeded , on which the plants had better growing conditions, MCPA resulted in a significant increase in the grain yield of barley and oats.
Influence de l'irrigation, de la fertilisation et du MCPA sur la compétition entre céréales de printemps et mauvaises herbes  相似文献   

2.
Summary. This project was designed to study various aspects of wild oat competition in spring wheat and flax. From ten to forty wild oat plants/yd2 were sufficient to cause significant yield reductions in wheat when grown on summerfallow land or when ammonium phosphate fertilizer was added to stubble land. However, when wheat was grown on stubble land without the benefit of a fertilizer treatment, seventy to one hundred wild oat plants/yd2 were needed to suppress wheat yields significantly. This would suggest that on stubble land, soil fertility was a more important factor than moderate densities of wild oats in determining eventual crop yields. In these experiments, wild oats reduced the number of tillers per plant, but did not significantly affect the protein content of the harvested grain. Only ten wild oat plants/yd2 were sufficient to reduce flax yields significantly on both summerfallow and stubble land. The only exception was in 1966, when flax grown on summerfallow land was not significantly affected until the density of wild oats reached forty plants/yd2. This confirms the general observation that flax is a poor competitor with wild oats. The results suggest that wild oat competition had already commenced prior to emergence of wheat, particularly with the higher densities of wild oats. In general, competitive effects increased with time and with wild oat density. In flax, severe competition had already taken place prior to the 2–3-Ieaf stage of the weed in 1964, but did not become severe until after the 2–3-leaf stage of wild oat growth in 1965 and 1966. Again, competitive effects increased with time and with wild oat density. Results of a final series of experiments, suggested that the optimum seeding date for flax in Manitoba is the latter part of May or the first week of June. Yield reductions due to wild oat competition became very severe as seeding dates were delayed. La compétition de la folle avoine (A vena fatua L.) avec le blé et le lin  相似文献   

3.
Summary. A study of the emergence and development of Avena fatua in winter wheat showed that after the mild winter of 1960/61 autumn-germinated wild oats constituted a far more serious weed problem than spring-germinated plants. It was concluded that the application of barban should be timed in relation to these autumn-germinated plants. As an extension of their work on spring cereals, the authors investigated the effect of barban on the yield ratio of winter wheat and cultivated winter oats grown as a mixture. A reduction in the oats fraction as a result of barban treatment was accompanied by an increase in wheat giving a total yield which was almost the same as untreated. Experimental data are also presented on the occurrence, and significance of an interesting variation in crop tolerance during the winter. No obvious correlation was found between increased crop sensitivity and development stage or temperature. The capacity of the crop to recover was found to be high.
Quelques données sur l'utilisation du barbane dans la lutte contre la folle avoine dans le blé d'hiver  相似文献   

4.
S. Andersson 《EPPO Bulletin》1982,12(4):463-475
Control of Heterodera avenae should largely aim to keep densities below tolerance limits at sowing-time (in spring oats < 1 egg/g soil, in susceptible barley < 3 eggs/g soil; spring wheat is only slightly less sensitive than oats, autumn-sown cereals are more tolerant than spring-sown ones). To obtain this, knowledge of population dynamics is important. Essential items in population dynamics are the host properties of different plants (characterized by two factors which do not always covary: maximum rate of multiplication and equilibrium density of the nematode), population decline of the nematode under fallow and non-hosts and the external factors influencing these characteristics. For cereals the following host efficiency order is found: winter oats (best), spring oats, spring wheat, spring barley, winter wheat, rye. Winter barley may be close to spring barley, and maize is a bad host. Grasses are generally less good hosts than cereals and usually cause high and moderate densities of H. avenae to decline. However, especially in first-year leys, rather high equilibrium densities may sometimes be maintained. Host properties of plants vary between sites and years and also relations between hosts may change. Populations decline under fallow, non-hosts and resistant cereals, usually in the order of 70–85 96 annually. H. avenae populations are favoured by lighter soils and heavier soils with a proper structure and also by good plant nutrient conditions. Soil moisture in interaction with temperature influences population dynamics in a complex way, in which natural enemies of the nematodes may also be involved, not least certain fungi. In many fields these may keep nematode populations at harmless levels. Traditional control measures like proper crop rotations can only be used to a limited extent. The most promising approach for controlling H. avenae is an appropriate use of resistant cultivars, of which barley cultivars are also tolerant, while oat cultivars are usually very sensitive. Biological control has hitherto not been used actively. Chemical control is profitable in Australia but not under European conditions. Farmers should check the need for control through soil sample investigations or by other means.  相似文献   

5.
W. KOCH 《Weed Research》1967,7(1):22-28
Summary. Pot experiments on the competitive effects of charlock (Sinapis arvensis L.) on oats and wild oat (Avena fatua L.) on barley had the following results:
(1) During the period up to tillering there was an appreciable effect of the weeds on crop growth with depression in plant weight of 10–15% from that in the absence of weeds.
(2) The greatest competitive effect occurred up to the middle of shooting of the cereals, when there were depressions in plant weight of 25–32%.
(3) After this stage, the competitive effects of the weeds were much less in pots with a high nutrient level, and at low nutrient level there was almost no competitive effect.
(4) The reduction in growth at the time of weeding was somewhat less at the low nutrient level than at the high nutrient level, and it is concluded that at the high level the competitive ability of the weeds was favoured more than that of the cereal crops.
(5) The cereals were not able to overcome the initial damage caused by the weeds even when the weeds were removed at the beginning of tillering. A partial recovery did how ever occur at the high but not at the low nutrient level.
(6) Both combinations, oats with charlock and barley with wild oat, behaved similarly, but some differences could be observed.
Compétition entre plantes cultivées et mauvaises herbes II. Action des mauvaises herbes annuelles sur les céréales  相似文献   

6.
Summary. Survival of wild oat seeds (mainly Avena fatua ) under leys on clay soils was investigated in two field experiments. During the first year under ley the number of seeds decreased by 41 % and 86% respectively. Subsequent decreases were less, and after 5 years under ley there were still enough of the original seeds left to produce infestation of a cereal crop. These results suggest that a long ley is not an efficient way of eliminating wild oat seeds from soil, and that a 1-year ley may be almost as effective as one of 5 years.
When a ley was ploughed, the number of wild oats germinating decreased as the number of years under ley and the age of the seeds increased, but was scarcely affected by the weather. In contrast, charlock ( Sinapis arvensis ) germination did not decrease with increasing age of seeds up to 5 years, but was greatest in years with most rain during April and May.
Survivance de semences de Folle Avoine (Avena fatua L . et A . ludovieiana Dur.) et de Moutarde des champs (Sinapis arvensis L.) dans le sol sous prairie temporaire  相似文献   

7.
Nitrogen fertilizer in three forms, urea, sulphate of ammonia and calcium ammonium nitrate, was applied at three rates, 26, 52 and 104 kg N/ha, early (January) and late (May) during land preparation for three consecutive barley crops, to determine the effect of fertilization on wild oat populations. On the fertilized areas there was significantly greater germination of wild oats prior to sowing than on the unfertilized areas, with calcium ammonium nitrate and sulphate of ammonia tending to be more effective in stimulating germination than urea. Despite the destruction of these heavy populations of wild oat seedlings by cultivation prior to sowing, in-crop infestations of the weed were still heavy. Late-applied nitrogen by comparison with the early application tended to produce greater numbers of wild oat panicles in the crop, particularly at the lower fertilizer rates. The overall effect after three annual dressings of nitrogen was one of greatly increased wild oat seed reserves in the soil. These had increased five-fold in no-nitrogen plots, six-fold in early-fertilized plots and eight-fold in late-fertilized plots. It was concluded that annual dressings of nitrogen fertilizer on winter cereals in wild-oat-infested areas led to an increase in the population of the weed. Some suggestions are made as to why nitrogen fertilizer stimulated wild oats to germinate, and the overall results are discussed in the light of the agricultural situation of the Darling Downs.  相似文献   

8.
Summary. The object of the work described in this paper was to obtain information on the relationship between the effects of crop competition and barban treatment on oats growing in another cereal. The work was carried out on barley cross-drilled with cultivated oats. Variation in crop competition was obtained by using different barley seed-rates and nitrogen levels. Increasing the seedrate of barley without applying barban resulted in a reduction of the initial oat population. This reduction applied to weight of individual shoots, number of shoots and panicles per unit area and number of spikelets per panicle. The application of barban at selective rates gave an independent reduction of oats of the order of 80%. This value proved almost constant at each seedrate of barley. Crop competition and barban accordingly seem to art independently and their effects appear to be simply additive. The barley fresh weights per unit area increased substantially when oat competition was reduced by barban treatment. The highest increase occurred on the plots with the lowest barley seedrate in spite of the fact that these plots still appeared infested with oats at harvest time. Nitrogen application stimulated the growth of barley and oats to a similar degree and did not in consequence lead to a selective suppression of oats.
Etude de l'influence de la densité du Semis, du taux de fertilisation azotée et du traitement au barbane, sur la concurrence entre une Orge et une Avoine  相似文献   

9.
The relative resistance of 15 winter barley, three winter wheat and three winter oat cultivars on the UK recommended list 2003 and two spring wheat cultivars on the Irish 2003 recommended list were evaluated using Microdochium nivale in detached leaf assays to further understand components of partial disease resistance (PDR) and Fusarium head blight (FHB) resistance across cereal species. Barley cultivars showed incubation periods comparable to, and latent periods longer than the most FHB resistant Irish and UK wheat cultivars evaluated. In addition, lesions on barley differed from those on wheat as they were not visibly chlorotic when placed over a light box until sporulation occurred, in contrast to wheat cultivars where chlorosis of the infected area occurred when lesions first developed. The pattern of delayed chlorosis of the infected leaf tissue and longer latent periods indicate that resistances are expressed in barley after the incubation period is observed, and that these temporarily arrest the development of mycelium and sporulation. Incubation periods were longer for oats compared to barley or wheat cultivars. However, oat cultivars differed from both wheat and barley in that mycelial growth was observed before obvious tissue damage was detected under macroscopic examination, indicating tolerance of infection rather than inhibition of pathogen development, and morphology of sporodochia differed, appearing less well developed and being much less abundant. Longer latent periods have previously been related to greater FHB resistance in wheat. The present results suggest the longer latent periods of barley and oat cultivars, than wheat, are likely to play a role in overall FHB resistance if under the same genetic control as PDR components expressed in the head. However the limited range of incubation and latent periods observed within barley and oat cultivars evaluated was in contrast with wheat where incubation and latent periods were shorter and more variable among genotypes. The significance of the various combinations of PDR components detected in the detached leaf assay as components of FHB resistance in each crop requires further investigation, particularly with regard to the apparent tolerance of infection in oats and necrosis in barley, after the incubation period is observed, associated with retardation of mycelial growth and sporulation.  相似文献   

10.
Crop rotation is the oldest, and perhaps the best cultural practice for reducing the risk of take-all. The effects of crops sown before wheat in a rotation are known in detail, but we know little about the opportunities for reducing take-all risk by planting certain crops in the summer period between wheat harvest and the planting of a subsequent winter wheat crop. We investigated the effects on take-all of five summer fallow crops, two soil tillage treatments and a fungicide seed treatment, in a five site-year experiment. We tested the effects of oats, oilseed rape, mustard, ryegrass and volunteer wheat crops. Bare-soil plots were also included. Take-all epidemics varied with year and site. Summer fallow crops had a greater effect on tilled plots. The incidence and severity of take-all were significantly higher in the wheat volunteer plots, whereas maintaining bare soil provided the lowest level of disease. Oilseed rape had no significant effect on take-all incidence in our experiment. The best candidates for reducing take-all risk appeared to be oats, mustard and ryegrass. These summer fallow crops decreased disease levels only when associated with conventional tillage. Summer fallow crops did not alter take-all decline in the same way as a break crop after a wheat monoculture.  相似文献   

11.
Summary. Seeds of Avena fatua and A. ludoviciana were sown at a depth of 15 cm or mixed into the top 5 cm of soil in small field-plots at Rothamsted and subjected to 5 different regimes of depth and frequency of cultivation for 3 years, after which all plots were dug to 15 cm in spring and autumn for a further 4 years. Seedlings were counted and no plants were allowed to produce seeds. After 7 years, soil-samples showed that very few intact seeds of A. fatua and none of A. ludoviciana remained, although less than 20% of the seeds sown had produced seedlings. Laboratory tests after 4 to 8 years'dry slorage showed seeds of both species to be viable. The maximum survival of viable seeds, estimated by seedling-emergence, was 61 months for A. fatua and 33 months for A. Indoviciana . Seeds of A. fatua survived slightly longer at 15 cm than in the top 5 cm of soil. Survival of A. ludoviciana was less affected by depth and cultivation, except that birds ate some shallow-sown spikelets in the first fortnight after sowing. A. fatua germinated in spring and autumn, and A. tudoviciana in winter, irrespective of age of seed and cultivation of soil. Frozen soil delayed emergence of A. ludoviciana seedlings lor varying periods between December and March. Seedlings of A. ludoviciana were slightly more winter-hardy than A. fatua . More seedlings of A. fatua appeared in the second spring than at any other time, but 80% of the seedlings of A. ludoviciana appeared in the first autumn and winter.
Effets de la profondeur d'enfouissement des graines et de la fréquence des façons culturalles sur la longévité et la germination des semences de Folle-Avoine (Avena fatua L. et A. ludoviciana Dur .)  相似文献   

12.
Barban was combined with benzoylprop ethyl, flamprop methyl, or flamprop isopropyl, and the eflects of the combinations on wild oat control and crop yield were assessed, tn greenhouse experiments, the interaction in all three combinations was synergistic, following application at the 2- or 4-leaf stage of wild oats. Under field conditions, combinations of barban + benzoylprop ethyl applied at the 2- or 4-leaf stage of wild oats were as eflective for wild oat control and wheat yield response as barban at 028 kg/ha applied at the 2-leaf or benzoylprop ethyl at 14 kg/ha applied at the 4-leaf stage of wild oats. Mixtures of barban + flamprop methyl applied at the 2- or 4-leaf stage of wild oats provided excellent wild oat control and wheat yield increases. Mixtures of barban + flamprop isopropyl applied at the 2- or 4-leaf stage of wild oats provided comparable wild oat control and barley yield increases to barban (028 kg/ha) applied at the 2-leaf or flamprop isopropyl (14 kg/ha) applied at the 4-leaf stage of wild oats.  相似文献   

13.
A screening test was developed to study the effect of different quantities of inoculum of Rhizoctonia solani on root rot and growth of cultivars of wheat, barley, oats, rye and triticale in a controlled environment and the field in two seasons. The ranking of relative susceptibility to disease of cultivars within a cereal differed between the controlled environment and field experiments, and between seasons in the field. The ranking of relative susceptibility between cereals also differed between experiments. In the controlled-environment experiment, wheat had the highest disease rating, followed by oats, barley, triticale and rye, but in the field barley had the highest rating followed by wheat and then oats. The overall differences between the cereals were small.  相似文献   

14.
Host plant preference of the Russian wheat aphid Diuraphis noxia (Kurdj.) was studied on 11 cultivars of 9 plant species: winter barley, spring barley, winter wheat, spring wheat, rye, oat, Triticale, canary grass, red millet yellow millet and maize. Seeds of the host plants were sown in a circle near the edge of pots. The host plant choice was evaluated 24 hours after releasing 55 Diuraphis noxia female adults in the middle of each pot. The suitability of different hosts for aphid development was evaluated 2, 7 and 14 days after infestation based on the mean number of Russian wheat aphid individuals per plant. Red millet, yellow millet and maize were chosen by significantly fewer aphids than grain crops. Winter and spring barley were chosen as hosts most frequently, and the progeny production was also the highest on these plants. The growth rate of D. noxia was significantly affected by the host plants and the date of assessment and their interaction.  相似文献   

15.
Weed suppression characteristics of different winter cereal species and cultivars were studied in two field experiments in two successive years. Two cultivars each of barley, oats and wheat were studied using the weed Galium aparine L. at a range of densities. Significant differences were found in the suppressive abilities of the crop species: oats being the most suppressive, followed by barley and then wheat. Percentage yield loss was related to G. aparine density using a rectangular hyperbolic model. In 1995–96, significant differences between the two wheat cultivars were found, with cv. Avalon being able to suppress G. aparine growth much more effectively than cv. Spark. However, in 1996–97, high rainfall in May, June and July enabled G. aparine to escape suppression by the cultivars. Cultivar competitive ability was associated with high overall leaf area, resistance to loss of tillers under competitive pressure, greater height, canopy structure and development. The oat cultivars were more competitive at early growth stages than could be accounted for by their canopy structure; the possible contribution of allelopathic exudates to their suppressive ability is discussed.  相似文献   

16.
为了探讨不同茬口对土壤肥力及后茬油菜产量的影响,以休闲田为对照,研究了西北黄土区冬油菜、马铃薯、玉米、冬小麦、春小麦、蚕豆等6种主要农作物茬口土壤耕作层肥力效应及其对后茬白菜型冬油菜产量和农艺性状的影响,结果表明：（1）不同作物茬口土壤养分含量总体表现为越冬作物>休闲田>春播作物,除固氮作物蚕豆茬口碱解氮含量较高外,冬油菜茬口土壤营养各项指标、土壤微生物种群结构及土壤物理性状均显著优于其它作物茬口,其有机质、全氮、全磷、全钾、碱解氮、速效磷、速效钾含量分别比休闲田增加32.6%、12.1%,5.9%、7.2%、11.6%、99.8%、44.2%,其次为蚕豆、冬小麦茬口和休闲田,玉米和春小麦茬口肥力状况较差;与休闲田相比,冬油菜、冬小麦和蚕豆茬口耕层（0~20 cm）土壤容重分别降低10.14%、5.80%和5.80%,而冬油菜茬口土壤总孔隙度、毛管孔隙度和田间持水量分别提高7.33%、4.12%和5.65%,马铃薯、玉米、春小麦茬口均有不同程度下降,冬小麦与蚕豆茬口无明显差异;（2）前茬对白菜型冬油菜农艺性状的影响主要表现在株高、根量、全株角果数、角果粒数及千粒重等指标,其中蚕豆茬口白菜型冬油菜比休闲田增产4.50%,冬小麦茬口与休闲田相当,而马铃薯、玉米、春小麦、冬油菜茬口分别较休闲田减产11.05%、15.04%、16.27%、21.14%。白菜型冬油菜的最佳前茬是豆类作物,休闲田和冬小麦茬口次之,但白菜型冬油菜连作可能会产生自毒作用或病害加重,从而造成显著减产。  相似文献   

17.
Fusarium head blight (FHB) is a complex cereal disease associated with trichothecene production; these mycotoxins are factors of aggressiveness in wheat. Six species (bread and durum wheat, triticale, rye, barley and oats) were submitted to point inoculations with two isogenic strains of Fusarium graminearum; a wild strain (Tri5 +) produced trichothecenes and the mutated strain (Tri5 –) did not. The trichothecene-producing strain was generally more aggressive than the non-producing strain, but this varied according to crop species. The difference in aggressiveness was less pronounced in rye, a very resistant species. High resistance levels were observed in oats due to the large spacing between florets. In six-row barley, despite the existence of a moderate Type II resistance, the fungus was often observed to move externally from one floret to another within the dense spike, without penetrating the rachis. Bread wheat had low resistance to the trichothecene-producing strain and good resistance to the non-producing strain. Triticale responded to the strains in a similar way but was somewhat more resistant to both: symptoms on the spikelets and rachis of the triticales were restricted to below the point of inoculation. Durum wheat was susceptible to the trichothecene-producing strain and only moderately resistant to the non-producing strain, which was able to cause serious damage only to this species. Our study confirmed that the role of trichothecenes in FHB pathogenesis differs among species. The failure of the trichothecene non-producing F. graminearum strain to spread within the inflorescence of wheat, triticale, rye and barley, and the significant reduction of spread in the durum wheat spike strongly suggested that trichothecenes are a major determinant of fungal spread and disease development in Triticeae.  相似文献   

18.
The aim of this study was to investigate how big a proportion of the spray liquid applied in a typical application was deposited on the soil surface below the crop. From an agronomical point of view this part of the spray is an undesirable loss of foliar acting pesticides during application and it also constitutes a primary source of leaching and surface run‐off. The investigation was carried out during 1998–2001 in winter wheat and in spring barley. Applications were carried out at approximate intervals of 10 days during the whole growing season in the two cereal crops. The results showed that a high proportion of the spray liquid reaches the soil below the crop during applications at early growth stages corresponding to the growth stages where weed control on farms is carried out. At later growth stages soil deposition declined and reached values below 5% of the applied dose in winter wheat after inflorescence emergence (50–59 BBCH). The spring barley crops remained more open and minimum soil deposit values were approximately 15% of the applied dose at growth stages (50–59 BBCH). During ripening soil deposition values increased again as crop cover decreased.  相似文献   

19.
The influences of cultural control measures on invertebrate pests and their natural enemies in cereals (wheat, barley and oats) are described and discussed, with emphasis on the major pests in north-west Europe. Possibilities for additive and synergistic combinations of cultural measures are identified, together with opportunities for integrating cultural measures with chemical and biological control where appropriate. Recent studies confirm the central role of cultural control measures in integrated pest management and integrated production of cereal crops. However, cultural measures often have opposing effects on different pests as well as diseases and weeds, so that appropriate measures must be selected on the basis of an assessment of the risks from key pests, diseases and weeds. Crop rotation is not an important means of controlling cereal pests, but its use is recommended for control of cereal diseases and weeds, as well as pests of crops grown in rotation with cereals. Diversification of crops and non-crop habitats in predominantly cereal growing areas is thought to increase numbers of certain parasitoids and polyphagous predators of cereal pests. The presence of weeds or an intercrop in a field together with cereals may reduce the severity of aphid and slug damage to cereals. Trap cropping has not yet been adequately tested in wheat, barley or oats. Cover crops reduce damage by wheat bulb fly in a following wheat crop, but increase the risk of slug damage. Resistance to a wide range of cereal aphid species has been identified in wheat and barley, but in Europe, more emphasis is placed on selecting cultivars with resistance to cereal diseases rather than pest resistance. Resistance in wheat to wheat bulb fly and wheat blossom midge is recorded, and resistance to slug damage has been reported in some laboratory studies. Early sowing of winter cereals results in more damage by certain dipterous pests and increased numbers of the aphid vectors of barley yellow dwarf virus (BYDV), but early sowing results in less damage by wheat bulb fly and slugs in autumn/winter and by late infestations of aphids in summer. Avoidance of ploughing results in reduced incidence of wheat bulb fly, yellow cereal fly and aphids, but increased numbers of slugs, wheat blossom midge and bibionid larvae. Avoidance of ploughing can result in greater numbers of certain polyphagous predators, particularly in the first weeks following crop establishment. The presence of straw residues results in increased slug populations, but reduced incidence of yellow cereal fly and wheat blossom midge. Preparation of fine, firm seedbeds discourages attack by slugs and wheat bulb fly on cereals. Drilling at slightly greater depth in rough cloddy seedbeds helps to protect wheat seeds from slug damage. Nitrogen fertiliser applied in spring can help cereal plants compensate for losses by wheat bulb fly or slugs. However, nitrogen applications tend to result in increased summer infestations of aphids.  相似文献   

20.
The results of a series of replicated trials and of a series of commercial grower trials conducted in the United Kingdom during 1972 and 1973, established the effectiveness of difenzoquat (1,2-dimethyl-3,5-diphenylpyrazolium ion) as the methyl sulphate as a selective post-emergence herbicide for the control of wild oats in wheat and barley. Doses of 0.75 to 1.0 kg cation/ha applied at 200 or 400 litre/ha and at 2.1 or 3.5 kg/cm2 gave good to excellent results when applied at crop growth stages 3 to 5 (Feekes—Large scale) for spring crops and at crop growth stages 4 to 6 for winter crops. In these experiments wild oats over a range of stages from 1st leaf to tillering were well controlled.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号