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   182篇
  免费   4篇
林业   2篇
基础科学   1篇
  10篇
综合类   82篇
农作物   6篇
水产渔业   5篇
畜牧兽医   64篇
园艺   1篇
植物保护   15篇
  2021年   2篇
  2019年   2篇
  2018年   4篇
  2016年   2篇
  2015年   2篇
  2014年   6篇
  2013年   6篇
  2012年   3篇
  2011年   5篇
  2010年   4篇
  2008年   6篇
  2007年   5篇
  2006年   2篇
  2005年   5篇
  2004年   4篇
  2003年   2篇
  2002年   2篇
  1999年   2篇
  1998年   10篇
  1997年   6篇
  1996年   5篇
  1995年   5篇
  1994年   4篇
  1993年   6篇
  1991年   2篇
  1990年   2篇
  1989年   4篇
  1988年   2篇
  1987年   3篇
  1986年   4篇
  1984年   3篇
  1979年   2篇
  1978年   2篇
  1972年   2篇
  1968年   2篇
  1967年   2篇
  1966年   2篇
  1963年   3篇
  1918年   4篇
  1916年   2篇
  1911年   2篇
  1902年   2篇
  1898年   1篇
  1896年   1篇
  1893年   2篇
  1892年   1篇
  1886年   1篇
  1883年   1篇
  1881年   1篇
  1880年   1篇
排序方式: 共有186条查询结果,搜索用时 15 毫秒
91.
During 1973-1976, 833 isolations of salmonellae were made from the aquatic biosphere of the Wabash River, Lafayette, Ind. Of the isolants, 643 were definitively serotyped. Salmonella typhimurium represented 34.4% of the cultures. Salmonella eimsbuettel previously had not been recognized in Indiana. A total of 35 serotypes and 1 untypable group C1 was obtained from the aquatic samples, ie, river water, river bottom sediment, fish, and mussels. Most of the isolants were presumed to be of human origin, because many samplings were made in close proximity to sewage treatment plant outfalls. During the survey period, epidemic salmonellosis had not been reported for the Lafayette-West Lafayette metropolitan area.  相似文献   
92.
A competitive ELISA (enzyme-linked immunosorbent assay) technique was evaluated for quantifying titres of imidacloprid in homogenates of leaf discs sampled from avocado plants treated with systemic applications of imidacloprid 240 g litre(-1) SC (Admire). Matrix effects were evident with undiluted leaf tissue homogenates, but these were effectively eliminated by dilution of homogenates in water. In a field trial conducted in a commercial nursery, there was an excellent correlation between imidacloprid residues within leaves and avocado thrips (Scirtothrips perseae Nakahara) mortality. However, with subsequent sampling over a 2-month period, the relationship between mortality and apparent imidacloprid concentration became less robust, suggesting that the material was being degraded within the plant to non-toxic metabolites. Nevertheless, assessments of thrips mortality on leaves that had been recently treated with imidacloprid established a lower threshold of activity for imidacloprid residues of 6 ng cm(-2) leaf. Limitations on the use of ELISA to quantify the impact of systemic insecticides on pest populations are discussed.  相似文献   
93.
The main objective of the present study was to evaluate the influence of pH and bicarbonate concentration in the activation or inhibition of European eel (Anguilla anguilla) spermatozoa and to evaluate the effect of different cryoprotectants: dimethyl sulphoxide (DMSO), acetamide, ethylene glycol, propanol, glycerol and methanol (MeOH). The effect of these factors was evaluated comparing the percentage of motile cells, the percentage of alive cells (by Hoechst staining) and the spermatozoa morphometry pre- and post-cryopreservation (by computer-assisted morphology analysis). Based on the above findings, three cryoprotectants (DMSO, MeOH and glycerol) were chosen and evaluated in two media (P1 and P1 modified) with different concentrations of NaHCO(3) and in the presence or absence of foetal bovine serum (FBS). The effect of these factors was evaluated comparing the percentage of alive and motile cells post-cryopreservation. DMSO was the cryoprotectant showing better results in relation to the percentage of spermatic alive cells post-freezing and caused a smaller modification of the head spermatozoa morphology. The combination of P1-modified medium with DMSO and containing FBS increased slightly but significantly the percentage of motile spermatozoa post-cryopreservation.  相似文献   
94.
A central component of successful wildlife conservation is the understanding of public perceptions toward a species. We administered an online survey to Alabama waterfowl hunters (n = 284) to examine differences in awareness and knowledge of and attitudes toward Whooping Cranes. We investigated if these variables and/or birding specialization influenced likeliness to participate in conservation behaviors. Specialization level was positively related to awareness, knowledge, and conservation attitudes. Respondents with greater knowledge and favorable attitudes toward cranes were more likely to donate to a hypothetical crane conservation fund, and expert birdwatchers were more likely to belong to a birding organization than novice or intermediate birdwatchers. Our research supplements existing birding specialization literature by incorporating cognitive variables specific to Whooping Cranes. Findings suggested that enhancing knowledge regarding Whooping Crane conservation may be an advantageous strategy for promoting conservation and positive behaviors toward the species.  相似文献   
95.
A monoclonal antibody against Mycoplasma gallisepticum (MG) (strain S6) was prepared in mice and identified as isotype IgG1 by standard procedures. Although it did react at high titers (1:100,000) in the enzyme-linked immunosorbent assay (the original method for its identification), it failed to react in the agglutination, hemagglutination-inhibition, and growth-inhibition tests. When conjugated to fluorescein isothiocyanate, the monoclonal antibody reacted with the homologous and eight "atypical" strains of MG but not with M. meleagridis or M. synoviae in the direct fluorescent-antibody test. This reagent may be useful for detecting field infections involving atypical strains of MG.  相似文献   
96.
97.
The efficacies of four systemic neonicotinoid insecticides applied to potted avocado trees at manufacturer-recommended rates were assessed against the avocado thrips, Scirtothrips perseae Nakahara. At the time of treatment, fully expanded first-flush young leaves were tagged for identification, and a proportion of these leaves was used in bioassays with second-instar thrips. At 7 weeks post-treatment, a second flush of leaves had fully expanded on the trees, and these leaves were included in additional bioassays comparing avocado thrips mortality on both first- and second-flush leaves. In bioassays with first-flush leaves, imidacloprid (273 mg AI pot(-1)) was the most effective insecticide, providing at least 70% mortality of thrips for 14 weeks. Thiamethoxam (137 mg AI pot(-1)), clothianidin (109 mg AI pot(-1)) and dinotefuran (241 mg AI pot(-1)) provided good control in bioassays that were conducted within 4 weeks of treatment, but thereafter their efficacies were inconsistent. In bioassays with second-flush leaves, imidacloprid provided at least 70% mortality up to 9 weeks after the insecticide application. Thereafter, mortality declined to 30% or lower. Bioassays with second-flush leaves collected from trees treated with thiamethoxam, clothianidin and dinotefuran resulted in unacceptably low thrips mortality. Monitoring of imidacloprid and thiamethoxam residues by ELISA showed that the greater persistence of imidacloprid in both first and second leaf flushes was due to a steadier uptake of this material. Although thiamethoxam residues rose quickly within the first leaf flush, levels had already begun to dissipate by the time the second leaf flush had started to develop.  相似文献   
98.
99.
100.
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