首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   262篇
  免费   14篇
林业   9篇
农学   11篇
  104篇
综合类   27篇
农作物   8篇
水产渔业   10篇
畜牧兽医   78篇
园艺   8篇
植物保护   21篇
  2023年   4篇
  2022年   2篇
  2021年   12篇
  2020年   6篇
  2019年   7篇
  2018年   10篇
  2017年   8篇
  2016年   12篇
  2015年   7篇
  2014年   10篇
  2013年   12篇
  2012年   12篇
  2011年   17篇
  2010年   10篇
  2009年   11篇
  2008年   14篇
  2007年   16篇
  2006年   7篇
  2005年   10篇
  2004年   17篇
  2003年   10篇
  2002年   4篇
  2001年   2篇
  2000年   3篇
  1999年   2篇
  1998年   1篇
  1996年   1篇
  1995年   3篇
  1994年   1篇
  1992年   3篇
  1990年   4篇
  1989年   1篇
  1988年   5篇
  1987年   1篇
  1986年   3篇
  1985年   3篇
  1984年   8篇
  1983年   3篇
  1982年   2篇
  1981年   3篇
  1980年   1篇
  1977年   1篇
  1973年   3篇
  1972年   1篇
  1971年   1篇
  1964年   1篇
  1956年   1篇
排序方式: 共有276条查询结果,搜索用时 421 毫秒
91.
The purpose of this work was to investigate the effect of stabilized-dewatered sludge on the performances of a solid-phase biological treatment applied to a soil contaminated with phenolic compounds.To this aim, a soil sample was artificially contaminated with either phenol or 3-chlorophenol, with concentrations of 1 and 0.5 g kg-1 of soil, respectively. Each contaminated soil sample was treated with a solid phase process, performed in three different operating conditions: without any addition; with addition of nutrients; with addition of nutrients and stabilized-dewatered sludge, obtained from a domestic wastewater treatment plant. The results obtained clearly indicated that the use of stabilized-dewatered sludge greatly reduced the time for complete removal of both phenol and 3-chlorophenol. Besides, the microorganisms concentration was higher in the sludge-amended soil with respect to other samples. This behavior could be a consequence of the carbon and energy sources contained in the sludge, even if the sludge could also offer a source of phenols-degrading microorganisms. On the contrary, the simple addition of nutrient did not notably affect the solid phase treatment under the studied conditions. Based on these results, it was shown that the use of stabilized-dewatered sludge may represent an efficient and economical way for accelerating solid-phase treatments, since it is produced worldwide and in large quantities as residue of domestic wastewater plants.  相似文献   
92.
Summary Vicia faba belongs to the sectionFaba. While the other species of the sectionV. narbonensis, V. johannis andV. bithynica cross enough well each other,V. faba seems to be strongly isolated from them. In addition the chromosome morphology ofV. faba differs from the other species of the section which among themselves are enough homogenous in this respect.To contribute to a wider knowledge on the taxonomical position ofV. faba in its section, electrophoretical and karyological analysis of 500 individuals belonging to 50 populations of different origin were carried out.The analyzed species were:V. faba, V. narbonensis, V. serratifolia, V. bithynica, V. galilaea andV. johannis.
Beitrag zur Taxonomie derVicia-Arten der SektionFaba
Zusammenfassung Vicia faba gehört zur sect.Faba. Während andere Arten der Sektion (V. narbonensis, V. johannis undV. bithynica) untereinander relativ gut kreuzbar sind, istV. faba von ihnen deutlich isoliert. Darüberhinaus unterscheidet sichV. faba in der Morphologie seiner Chromosomen von den anderen Arten der Sektion, die in dieser Hinsicht eine relativ einheitliche Merkmalsausprägung zeigen. Um zu einer besseren Kenntnis der systematischen Stellung vonV. faba innerhalb der Sektion beizutragen, wurden chromatographische und karyologische Analysen von 500 Individuen aus 50 Populationen verschiedener Herkunft durchgeführt. Analysiert wurdenV. faba, V. narbonensis, V. serratifolia, V. bithynica, V. galilaea undV. johannis.

Vicia, Faba
Vicia faba Faba. (V. narbonensis, V. johannis, V. bithynica) ,V. faba ë . ,V. faba , . V. faba , 500 50 . :V. faba, V. narbonensis, V. serratifolia, V. bithynica, V. galilaea, V. johannis.
  相似文献   
93.
94.
This study evaluated the association between plasma anti-Mullerian hormone (AMH) concentration and fertility in Nelore (Bos indicus) heifers submitted to timed artificial insemination (TAI). At the onset of the synchronization protocol, heifers (n = 289) received a subcutaneous P4 ear implant (3 mg) and 2 mg of oestradiol benzoate. Eight days later, the P4 implant was removed and 0.5 mg of oestradiol cypionate, prostaglandin (0.265 mg, i.m.) and equine chorionic gonadotropin (300 UI, i.m.) was administered, and TAI was performed 48 hr after ear implant removal. Ovarian ultrasound evaluations were performed to measure number of ovarian follicles, dominant follicle size and ovulation response. Pregnancy diagnosis was performed by ultrasound 30 days after AI. Heifers with greater circulating AMH had more antral follicles, a smaller dominant follicle near timed ovulation and lower ovulation response to the timed AI protocol compared to heifers with lower circulating AMH. Although AMH and pregnancy outcome had a quadratic-shaped pattern, AMH was not significantly associated with fertility. In conclusion, heifers with lower AMH had larger follicles towards the end of the synchronization protocol and greater ovulation responses, whereas greater circulating AMH was unrelated to conception success.  相似文献   
95.
Summary The Ght oases are rich in plant genetic resources. During a mission in 1983 cultivated plants of this area have been studied and altogether 57 accessions of land-races collected. Compiling the results from the collections, from observations all over the Fezzan and from literature studies a check list of the cultivated plants of the Ght oases is presented. Close relationships can be demonstrated especially to land-races from Ethiopia but also from other parts of Africa. The plant genetic resources of the Ght oases may be useful in breeding programmes.
Eine Liste der Kulturpflanzen der Ght-Oasen
Zusammenfassung Die Ght-Oasen sind reich an pflanzlichen genetischen Ressourcen. Während einer Reise im Jahre 1983 wurden die Kulturpflanzen dieses Gebietes studiert und insgesamt 57 Muster gesammelt. Aus den Ergebnissen der Sammlungen, der Beobachtungen aus dem gesamten Fezzan-Gebiet und der Literaturstudien wird eine Liste der Kulturpflanzen der Ght-Oasen zusammengestellt. Enge Beziehungen können besonders zu den Landsorten Äthiopiens aber auch anderer Teile Afrikas postuliert werden. Die pflanzlichen genetischen Ressourcen der Ght-Oasen stellen ein wertvolles Ausgangsmaterial für die Pflanzenzüchtung dar.

()
() . ¶rt; 1983 . ¶rt; ; 57 . ¶rt; , . ¶rt;, . .
  相似文献   
96.
Randomly amplified polymorphic DNA (RAPD), inter-simple sequence repeat (ISSR) and a semi-random PCR system were used to analyze the genetic diversity of 16 Italian common bean landraces and their relationship to four commercial cultivars. Of the primers tested, 8 ISSR, 6 RAPD and 7 semi-random primers produced polymorphic and reproducible DNA fragments. A higher proportion of polymorphic bands were observed using ISSR (85%) and semi-random (90%) primers than RAPD (69%) method. The combination of any two semi-random markers allowed the identification of all 20 bean genotypes. In contrast ISSR (except for primer (CAC)3GC) and RAPD markers appeared to be less informative as more than two markers were necessary to achieve the same diagnostic level. Moreover, 7 ISSR, 2 RAPD and 8 semi-random exclusive bands were identified as putative population-specific markers. Semi-random and ISSR derived dendrograms showed similar tendencies in terms of genetic relatedness, whereas clustering of genotypes within groups was not similar when compared with the RAPD technique. Despite the different ability to resolve genetic variation among the investigated landraces, two major clusters with less than 60% (ISSR) and 40% (RAPD and semi-random) genetic similarity were formed with all three marker systems. The two groups were correlated with the phaseolin patterns and seed size of the landraces. The analysis showed that the cultivar ȁ8Lingua di Fuocoȁ9 and most of the landraces (13 out of 16) collected in Italy belong to the Andean gene pool, whereas only the three populations from Pratomagno belong to the Middle American gene pool.  相似文献   
97.
The aim of this study was to provide basal values of phospholipid (PL) composition in different animal species by 31P NMR analysis using detergents. This fast and accurate method allowed a quantitative analysis of PLs without any previous separation. Plasma and erythrocyte membrane PLs were investigated in mammals (pig, cow, horse). Moreover, for the first time, the composition of plasma PLs in avian (chicken and ostrich) was performed by 31P NMR. Significant qualitative and quantitative interspecies differences in plasma PL levels were found. Phosphatidilcholine (PC) and sphingomyelin (SPH) levels were significantly higher (P < 0.001) in chicken plasma than all the other species tested. In erythrocytes, cow PC and phosphatidylcholine diarachidoyl were significantly lower (P < 0.001) than for pigs and horses, whereas pig PC presented intermediate values among cows and horses. Inorganic phosphate and 2,3-diphosphoglycerate levels were also significantly different between the species under investigation. The [SPH/total PLs] molar ratios in erythrocytes confirmed interspecies differences in phospholipid composition while the PC/SPH molar ratios could be related to a distinct erythrocyte flexibility and aggregability. Diet and nutrition may contribute primarily to the interspecies differences in plasma PL amounts detected. Significant differences between chicken plasma PC and SPH levels and those of the other animal species could be ascribed to a fat metabolism specific to egg production.  相似文献   
98.
The effect of water on "antiplasticization" and plasticization of green and roasted coffee was studied by textural analysis, sorption isotherms, differential scanning calorimetry (DSC), and nuclear magnetic resonance (NMR). From BET monolayer value to a(w) = 0.61 and 0.75 for green and roasted coffee, respectively, the solid matrix hydration occurred and water induced hardening. Very short NMR T(2) values and the concomitant absence of any DSC endothermic peak assignable to water freezing were observed at these a(w) values. When solid matrix hydration was completed, water started to act as a plasticizing agent, the compressive modulus started to decrease, and NMR revealed the appearance of a new proton pool with increased mobility. According to DSC, only when the plasticizing effect became important did water present enough mobility to freeze. Above this moisture value (a(w) = 0.78 and 0.86 for green and roasted coffee, respectively), water determined a decrease of bean hardness and a further decrease of the elastic modulus.  相似文献   
99.
100.
OBJECTIVE: To evaluate the effect of passive transfer status (determined from measurements of serum IgG concentration at 24 hours after parturition [sIgG-24]) on preweaning growth performance in dairy goat kids. DESIGN: Prospective observational study. ANIMALS: 20 healthy nursing dairy doe kids in a natural nonintensive breeding environment. PROCEDURES: For each kid, sIgG-24 was measured. Body weight was measured at birth and at the time of weaning 30 days (ie, 29 to 31 days) after birth; average daily gain from birth to day 30 and weight at day 30 were used as measures of preweaning growth performance. Regression analysis was used to evaluate associations between sIgG-24 and measures of preweaning growth performance. RESULTS: Mean +/- SD sIgG-24 was 31.7 +/- 10.3 mg/mL. Mean body weights at birth and weaning were 4.105 +/- 0.981 kg (9.031 +/- 2.158 lb) and 9.310 +/- 2.554 kg (20.482 +/- 5.619 lb), respectively; average daily gain was 0.174 +/- 0.072 kg/d (0.383 +/- 0.158 lb/d). No significant association was detected between sIgG-24 and birth weight. However, sIgG-24 was significantly associated with average daily gain (R(2) = 0.48) and weight at day 30 (R(2) = 0.56). Each increase in sIgG-24 of 1 mg/mL was associated with an increase in average daily gain of 0.005 kg/d (0.011 lb/d) and an increase in weight at day 30 of 0.185 kg (0.407 lb). CONCLUSIONS AND CLINICAL RELEVANCE: Results indicated that passive transfer status (determined as sIgG-24) was a significant source of variation in preweaning growth performance in dairy doe kids reared in this nonintensive breeding environment.  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