全文获取类型
收费全文 | 638篇 |
免费 | 44篇 |
专业分类
林业 | 98篇 |
农学 | 25篇 |
基础科学 | 4篇 |
92篇 | |
综合类 | 25篇 |
农作物 | 28篇 |
水产渔业 | 69篇 |
畜牧兽医 | 283篇 |
园艺 | 6篇 |
植物保护 | 52篇 |
出版年
2023年 | 6篇 |
2022年 | 7篇 |
2021年 | 19篇 |
2020年 | 36篇 |
2019年 | 31篇 |
2018年 | 28篇 |
2017年 | 23篇 |
2016年 | 32篇 |
2015年 | 18篇 |
2014年 | 25篇 |
2013年 | 44篇 |
2012年 | 40篇 |
2011年 | 33篇 |
2010年 | 23篇 |
2009年 | 23篇 |
2008年 | 32篇 |
2007年 | 39篇 |
2006年 | 32篇 |
2005年 | 24篇 |
2004年 | 16篇 |
2003年 | 11篇 |
2002年 | 16篇 |
2001年 | 16篇 |
2000年 | 14篇 |
1999年 | 7篇 |
1997年 | 11篇 |
1996年 | 2篇 |
1995年 | 4篇 |
1994年 | 2篇 |
1992年 | 11篇 |
1991年 | 8篇 |
1990年 | 5篇 |
1989年 | 3篇 |
1988年 | 2篇 |
1987年 | 5篇 |
1986年 | 4篇 |
1985年 | 4篇 |
1981年 | 2篇 |
1980年 | 1篇 |
1979年 | 2篇 |
1978年 | 3篇 |
1977年 | 1篇 |
1976年 | 1篇 |
1974年 | 1篇 |
1972年 | 2篇 |
1969年 | 1篇 |
1968年 | 2篇 |
1964年 | 2篇 |
1959年 | 1篇 |
1957年 | 4篇 |
排序方式: 共有682条查询结果,搜索用时 24 毫秒
101.
Emiru Birhane Nakiguli Fatumah Kidane Gidey Amanuel Zenebe Ssemwanga Mohammed 《林业研究》2018,29(3):675-686
Arbuscular mycorrhiza fungi(AMF) are vital in the regeneration of vegetation in disturbed ecosystems due to their numerous ecological advantages and therefore are good indicators of soil and ecosystem health at large. This study was aimed at determining how the seasonal, vegetation cover density, edaphic and anthropogenic factors affect AMF root colonization(RC) and spore density(SD)in Desa'a dry Afromontane forest. AMF RC and SD in the rhizosphere of five dominant woody species, Juniperus procera, Olea europaea, Maytenus arbutifolia, Carissa spinarum and Dodonaea angustifolia growing in Desa'a forest were studied during the rainy and the dry seasons in three permanent study vegetation cover density plots(dense, medium, and poor). Each plot(160 x40 m~2) has two management practices(fenced and unfenced plots) of area. A 100 g sample of rhizosphere soil from moisturefree composite soil was used to determine spore density.Spore density ranged from 50 to 4467 spores/100 g soil,and all species were colonized by AMF within a range of 4–95%. Glomus was the dominant genus in the rhizosphere of all species. Vegetation cover density strongly affected SD and RC. The SD was significantly higher(p 0.05) in the poor vegetation cover density than in the other two and lowest in the dense cover; root colonization showed the reverse trend. Management practices significantly(p 0.05) influenced AMF SD and RC, with the fenced plots being more favoured. Seasons significantly(p 0.05) affected RC and SD. More RC and SD were observed in the wet period than the dry period. Correlating AMF SD and RC with soil physical and chemical properties showed no significant difference(p 0.05) except for total nitrogen. Disturbance, vegetation cover density, season and total nitrogen are significant factors that control the dynamics and management interventions to maintain the forest health of dry Afromontane forests. 相似文献
102.
Issa Yar Mohammad Karimi Mohammed Abdul Mohsen Ali Salem Abdul Jaleel Cheruth Fayas Thayale Purayil Sreeramanan Subramaniam 《Journal of plant nutrition》2018,41(7):888-902
In the arid regions, turfgrass cover is an integral part of landscape to protect the soil from erosion, enhance the aesthetic value, and improve the microclimate. The salinity and the scarcity of fresh water of the arid region are the major challenging factors in turfgrass production. Therefore, the need for salt tolerant turfgrass with functional quality is necessary to improve the turf performance. The detrimental effects of salinity include growth suppression, and lowered osmotic potential ultimately leading to firing of the leaf blades. In this context, the study was undertaken to determine the relative salt tolerance and growth response of turfgrass genotypes in order to recommend turfgrass cultivars that can tolerate high salinity irrigation and maintain excellent visual and functional qualities under United Arab Emirates (UAE) condition. The paspalum cultivars maintained the highest succulence percentage compared to the bermudagrass cultivars under enhanced salinity levels. The shoots count, fresh weight (FW), and dry weight (DW) were found highest in paspalum types. The chlorophyll a, chlorophyll b and the total chlorophyll content was found higher in bermuda grass types under high salinity levels. The bermudagrass cultivars showed significantly higher carotenoids, anthocyanins and proline compared to the paspalum types under salt stress condition. In the case of princess 77 and Yukon, an inherently high amount of proline was recorded which confirmed an increase up to 10,000 ppm and drastically declined beyond this concentration. Sea Dwarf paspalum and Sea Isle 2000 maintained uniformity in the proline level at all levels of salinity without significant variation. These findings point to the fact that both paspalum and bermuda types exhibited varied responses to different physiological and biochemical parameters under the saline conditions. Paspalum types have an edge over the bermudagrass in terms of shoot density, which is a potential factor in determining the high-quality turfs. Bermudagrass types can be applied in lower salinity conditions based on the responses as evidenced from the present results. 相似文献
103.
Jasim Mohammed Saleh Norsida Binti Man 《Journal Of Agricultural & Food Information》2017,18(2):110-122
This study is based on the opinions of selected Iraqi extension workers, regarding the type and amount of training they need, given their experience in the field. The Borich Needs Assessment Model was used for measuring training needs. The data were collected through questionnaires given to 300 respondents (agricultural workers) from January 15, 2016 to March 20, 2016. The results show that crop-planting courses have the greatest benefit. The greatest training need is skill and knowledge of teaching methods, while a moderately needed skill is the use of computer and information and communication technologies (ICT); management skills are the least needed training. 相似文献
104.
Maninder Kaur Walia Yesuf Assen Mohammed 《Communications in Soil Science and Plant Analysis》2017,48(22):2652-2662
Genetic and environmental factors lead to a variation in yield and protein content of dry pea (Pisum sativum L.) seeds. The quality of seed, particularly seed vigor, also influences the establishment of crop and thus final grain yield. The area and production for dry peas are increasing in the Northern Great Plains but knowledge is lacking on how the pea lines/varieties differ in the seed vigor at seven leaf stage. This field and greenhouse study evaluated the eight dry pea lines/varieties for seedling vigor indices and correlated them with grain yield and protein concentrations. Significant differences were observed among the lines/varieties for nodule number plant?1 in greenhouse, and grain yield in field conditions. The highest number of nodules plant?1 was obtained with the line MT632, which were at par with lines MT457, and MT190. The highest Vigor Index I was achieved with line MT632 associated with their more shoot lengths as compared to other lines/varieties. The highest Vigor Index II was obtained by variety Majoret and line MT632. The variety DS Admiral yielded 5205 kg ha?1, which was 17.4 and 33.3% higher than lines MT460 and MT190, respectively. The highest seed protein content was obtained with variety Majoret (23.4%) having highest Vigor Index II and seed yield (4940 kg ha?1) at par with variety DS Admiral. The lowest seed protein was found with variety DS Admiral (20.3%). The line named MT190 showed lowest yield potential along with the lower protein contents also. Studies show a positive and significant correlation between biomass and Vigor Index I only. Plant nitrogen uptake was positively and significantly correlated with biomass and Vigor Index I in greenhouse only. The results also indicated that seed vigor indices did not reveal any significant correlations with dry peas yield and protein content, so more efforts are needed to evaluate varieties for higher yield and protein content during initial stages of growth in order to maximize their acreage and productivity. 相似文献
105.
Audrey G. Quentin Elizabeth A. Pinkard Christopher L. Beadle Timothy J. Wardlaw Anthony P. O’Grady Stephen Paterson Caroline L. Mohammed 《Annals of Forest Science》2010,67(2):203-203
106.
Miguella P Mark-Carew Yasin Khan Susan E Wade Stephanie Schaaf Hussni O Mohammed 《Acta veterinaria Scandinavica》2010,52(1):44
Background
The primary aims of this study were to determine the incidence of Giardia infections in dairy herds on farms in the New York City Watershed region and to evaluate risk factors associated with infections. Because co-infections of Giardia and Cryptosporidium spp. are common in this population, we also evaluated the effect of herd infection status on Giardia infections.Methods
Farms were grouped into three cohorts based on their prior infection status with Giardia and/or Cryptosporidium spp. The sampling plan included collecting fecal samples from all calves below 30 days of age and proportional sampling of calves, young stock, and adults. A total of 10,672 fecal samples were collected and analyzed for the presence of Giardia cysts using zinc sulfate flotation. Herds enrolled in the study were sampled seasonally for a study period of two years. The probability of shedding cysts past a certain age and the factors that influenced the likelihood of shedding were evaluated using survival analysis. Linear regression was used to evaluate factors that were associated with the intensity of shedding.Results
The majority of Giardia infections occurred in calves within their first 180 days of age, with the most number of calves shedding Giardia cysts between 11 and 20 days of age. The incidence of shedding of Giardia cysts ranged from 0.0004 per animal day for cattle in the low risk cohort to 0.0011 per animal day for cattle in the high risk cohort. The likelihood of shedding was influenced by the prior infection status of the herd and the season of collection. Infected animals shed on average 9,658 cysts/gram and the intensity of shedding Giardia cysts varied significantly with the age (p < 0.0001) and the season of collection (p = 0.0151 for Spring).Conclusion
Giardia infections are common in dairy herds in the New York City watershed, particularly in calves less than 6 months of age. Seasonality may be an important factor in the perpetuation of infections based on changes in management practices corresponding to weather patterns of a particular season. A dairy herd''s prior infection status with Cryptosporidium influences the likelihood of infection with Giardia. 相似文献107.
Ross G. Cooper Jaroslaw O. Horbańczuk Raul Villegas-Vizcaíno Salwa Kennou Sebei Aisha E. Faki Mohammed Khalid M. A. Mahrose 《Tropical animal health and production》2010,42(3):363-373
This work discusses some of the important considerations of wild ostrich evolution, behaviour and ecology, as items included
in ostrich production. In the process considerable research was conducted by collating information from peer-reviewed papers;
textbooks; manuals; and PubMed and Agricola searches. Selected areas reviewed included activity of ostriches; feeding and
water needs; sexual maturity; egg laying and natural incubation; selected physiological parameters; and predation. There is
an immediate and urgent need to conserve and protect the rapidly declining populations of wild ostriches with the committed
involvement of governments and funding bodies. 相似文献
108.
N. S. Grenager T. J. Divers H. O. Mohammed A. L. Johnson J. Albright S. M. Reuss 《Equine Veterinary Education》2010,22(9):467-472
A retrospective study of 43 cases of temporohyoid osteoarthropathy was performed to evaluate the epidemiological features and a possible association with crib‐biting. Data collected from records included case details, what diagnostics were utilised, whether medical or surgical treatment was administered, and outcome. Owners were contacted via telephone and asked whether the horse had displayed crib‐biting behaviour. Forty‐three horses were diagnosed with neurological disease associated with temporohyoid osteoarthropathy, 62.8% of which were Quarter Horse‐types. Median age at presentation was 10 years and median duration of neurological signs prior to presentation was 3 days. Skull radiographs and guttural pouch endoscopy were used to definitively diagnose temporohyoid osteoarthropathy in 72% of the cases. Of 43 horses, 21 received medical treatment and 15 surgical treatment, with an overall survival rate of 55.8%. Crib‐biting was observed in 31.3% of cases and there was a significant association between being afflicted with THO and likelihood of possessing the behaviour. Horses with neurological disease associated with THO were 8 times more likely to be crib‐biters compared to the general population. 相似文献
109.
Yaser Hassan Dewir Ayman Faisal Omar Yaser Mohamed Hafez Mohammed El-Sayed El-Mahrouk Rasha Yousef Mourad 《Phytoparasitica》2016,44(1):65-74
The present study reports on phytoplasma induced fasciation in Crassula argintea (Crassulaceae). DNA was extracted from symptomless and fasciated tissues and amplified by nested PCR using universal primers P1/P7 followed by R16F2n/R16R2 produced amplicons of 1.2 Kb. The nucleotide sequence analyses of the amplicons indicated that fasciated plants were infected by phytoplasma. Phylogenetic analysis placed the Crassula fasciation phytoplasmas in 16SrII-D group. Histochemical staining for reactive oxygen species indicated that phytoplasma infected (PI) tissues possess significantly higher levels of hydrogen peroxide (H2O2) rather than superoxide (O2 ·-) as compared with symptomless tissues. PI tissues were also associated with a significant increase in antioxidant enzyme activities (catalase, peroxidase, polyphenol oxidase, and glutathione reductase) and electrolyte leakage as compared with symptomless tissues. 相似文献
110.
In vivo and in vitro protein digestibility in juvenile bagrid catfish Mystus nemurus (Cuvier and Valenciennes 1840) fed soybean meal‐based diets 下载免费PDF全文
In vivo and in vitro protein digestibility of 0% to 60% soybean meal protein (SBM) substitution from fishmeal protein was conducted for bagrid catfish Mystus nemurus juveniles. Seven experimental diets containing 35% protein and 15% lipid were fed to bagrid catfish to determine the in vivo protein digestibility. In vitro methods were determined using pH stat, pH shift, spectrophotometric assay and sodium dodecyle sulphate polyacrylamide gel electrophoresis (SDS‐PAGE) with different enzyme mixtures (crude intestinal extract of bagrid catfish, Lazo 1‐enzyme, Hsu 3‐enzyme, Saterlee 4‐enzyme). In vivo and in vitro protein digestibility decreased with increased SBM protein substitution with highest tolerance level of 10% (in vivo). pH stat and pH drop methods showed the highest degree of hydrolysis (DH) and relative protein digestibility (RPD) using Saterlee 4‐enzyme system. However, pH stat method showed highest correlations (r2 = 0.9263) with the in vivo results using crude intestinal enzyme extract compared to other enzyme systems. The highest correlation of the in vitro methods using crude intestinal enzyme extracts of bagrid catfish was determined using spectrophotometric assay (r2 = 0.9284) followed by pH stat (r2 = 0.9263), SDS‐PAGE (r2 = 0.8348) and pH drop (r2 = 0.6777). All the in vitro methods tested are suitable to rapidly determine protein digestibility for bagrid catfish except for pH drop. 相似文献