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   163篇
  免费   13篇
  国内免费   5篇
林业   3篇
农学   4篇
  13篇
综合类   27篇
农作物   7篇
畜牧兽医   113篇
园艺   4篇
植物保护   10篇
  2024年   1篇
  2023年   1篇
  2022年   2篇
  2021年   1篇
  2020年   2篇
  2019年   4篇
  2018年   2篇
  2017年   2篇
  2016年   8篇
  2015年   6篇
  2014年   5篇
  2013年   12篇
  2012年   7篇
  2011年   8篇
  2010年   14篇
  2009年   6篇
  2008年   15篇
  2007年   10篇
  2006年   9篇
  2005年   5篇
  2004年   4篇
  2003年   3篇
  2002年   3篇
  2001年   3篇
  1999年   1篇
  1998年   2篇
  1997年   2篇
  1996年   4篇
  1995年   2篇
  1994年   5篇
  1993年   5篇
  1992年   1篇
  1991年   4篇
  1990年   4篇
  1989年   4篇
  1988年   2篇
  1987年   5篇
  1985年   1篇
  1984年   1篇
  1983年   1篇
  1978年   1篇
  1911年   3篇
排序方式: 共有181条查询结果,搜索用时 15 毫秒
1.
Perception of farmers’ about the use of pesticides and genetic erosion of tetraploid wheat landraces of Ethiopia was assessed through focus group discussions with farmers, on-farm observations, personal interviews with farmers, by using structured questionnaires of temporal and spatial methods. A total of 1496 farmers from seven provinces in the country were interviewed. Farmers’ knowledge about pesticide increases suggests that they are not happy on using chemicals because of their negative impact on farm land. About 75 % of the farmers believe that, although the use of pesticides may increase the production of wheat, it has a negative impact on (human) health and environment. Women showed a higher concern for pesticides’ harmfulness than men. Farmers’ valuation of genetic erosion was estimated as reduced importance of landraces, as shown by a the lower proportion of landraces either grown or sold on the market. The four most important factors cited for loss of landraces were reduction in land area per capita, displacement by released/modern varieties of hexaploid wheat and teff, reduced benefit from landraces, and displacement by other crops and chat. Genetic erosion of 100 % was observed for Triticum dicoccon in the provinces of Gojam and Gonder and for T. polonicum in Tigray and Gojam. Overall, genetic erosion in the country was 32.0, 35.3, 55.9, 84.4 and 84.4 % for T. durum Desf., T. turgidum L., T. aethiopicum Jakubz., T. polonicum L. and T. dicoccon Schrank, respectively.  相似文献   
2.
A modified electrometric cholinesterase method has been described for use in ruminants exposed to organophosphate insecticides. The method was used to measure cholinesterase activities in the plasma and erythrocytes of sheep, goats and cattle treated with organophosphate insecticides under field conditions. The animals were treated topically to control ectoparasites with malathion (0.05%) or diazinon (0.06%). The treated animals did not suffer from adverse effects related to cholinesterase inhibition. However, 2 h after treatments, plasma and erythrocyte cholinesterase activities significantly decreased in sheep by 20% and 39% and in goats by 18% and 30%, respectively, when compared with respective untreated control values. Diazinon did not significantly affect plasma and erythrocyte cholinesterase activities in the cattle. The results suggest that the described electrometric method could be efficiently used for detecting cholinesterase inhibition in ruminants exposed to organophosphate insecticides.  相似文献   
3.
研究了不同条件下大豆水溶性多糖溶液的黏度变化情况,同时和其他常用的稳定剂如果胶等也做了比较。试验结果表明。本实验室生产的大豆水溶性多糖的水溶液的黏度随着温度的升高、浓度的降低、外加盐量的增加而降低;随着外加蔗糖量、pH值的增加而增加;相比较于其他稳定剂大豆水溶性多糖的黏度很低,使酸乳饮料具有清爽的口味。  相似文献   
4.
5.
Gorgostane steroids are isolated from marine organisms and consist of 30 carbon atoms with a characteristic cyclopropane moiety. From the pioneering results to the end of 2021, isolation, biosynthesis, and structural elucidation using 13C-NMR will be used. Overall, 75 compounds are categorized into five major groups: gorgost-5-ene, 5,6-epoxygorgostane, 5,6-dihydroxygorgostane, 9,11-secogorgostane, and 23-demethylgorgostane, in addition to miscellaneous gorgostane. The structural diversity, selectivity for marine organisms, and biological effects of gorgostane steroids have generated considerable interest in the field of drug discovery research.  相似文献   
6.
At the time of AI following Ovsynch protocol, a total of 51 buffaloes were randomly divided in a first group (n = 30) subjected to conventional AI into the uterine body with 20 million non-sex sorted frozen-thawed spermatozoa, while a second group (n = 21) was inseminated near the utero-tubal junction (UTJ) ipsilateral to the ovary carrying the preovulatory follicle with 2.5 million live (4 million total) sex-sorted frozen-thawed spermatozoa. The semen used for flowcytometric sorting was collected and processed on a farm in Italy, and then shipped to a laboratory in Germany. Eleven buffaloes were inseminated with X-chromosome bearing spermatozoa and 10 with Y-chromosome bearing spermatozoa. Conception rates after conventional and UTJ inseminations were 43.3% (n = 13) and 42.8% (n = 9) respectively (p = 0.97). Eight of the nine foetuses obtained after insemination with sexed spermatozoa corresponded to the sex as predicted by the cell sorting procedure (five male and four female foetuses by ultrasound vs six male and three female foetuses by cell sorting). In conclusion, for the first time buffalo semen has been successfully subjected to procedures for flowcytometric sperm sorting and freezing. Low doses of sexed spermatozoa have been deposited near the UTJ giving conception rates similar to those of conventional AI with full dose.  相似文献   
7.
8.
Extracellular products in culture filtrates of Aeromonas salmonicida subsp. achromogenes and Vibrio anguillarum isolated from infected fish have been shown to possess skin inflammatory factor. The extracellular products from Vibrio anguillarum were cytotoxic in HeLa and CHO cells. In addition to the skin lesions, the culture filtrates of V. anguillarum caused necrotic reaction on the rabbit skin. Five of 6 strains of V. anguillarum were lethal to mice after intraperitoneal administration of 3×107 CFU. Only 1 strain of 5 A. salmonicida subsp. achromogenes produced extracellular products which elicited cytotoxic effects in the CHO cells. None of the A. salmonicida subsp. achromogenes strains were lethal to mice. The cytotoxins were inactivated when heated at 65°C for 30 min. The results indicate that the thermolabile exotoxins are non-enterotoxic since they failed to stimulate fluid accumulation in the rabbit ileal loop and did not cause elongation of the CHO cells. The rounding off of CHO cells, as well as of HeLa cells indicate that the exotoxins may play an important role in fish diseases.  相似文献   
9.
The aim of this work was to evaluate the effect of relaxin on fertility parameters of buffalo frozen/thawed sperm. Sperm were incubated in the absence of capacitating agents (negative control), with a known capacitating agent such as heparin (positive control) and with 50 and 100 ng/ml relaxin for 2 and 4 h. Sperm viability, motility, capacitation and the effect of relaxin on the fertilizing ability after heterologous IVF were evaluated. Although viability was not affected, relaxin increased (p < 0.05) sperm motility compared to the negative and positive controls both after 2 h (60.0 ± 2.0, 60.0 ± 3.1, 68.3 ± 1.7 and 69.4 ± 2.7, respectively, in negative control, positive control, 50 and 100 ng/ml relaxin) and 4 h (55.0 ± 2.5, 53.3 ± 3.0, 62.2 ± 3.0 and 65.0 ± 3.2, respectively, in negative control, positive control, 50 and 100 ng/ml relaxin) incubation. When sperm were incubated with both 100 ng/ml relaxin and heparin, a decrease (p < 0.01) of pattern A, that is low capacitation level, was observed compared to the negative control both after 2 h (54.4, 34.3 and 36.4%, respectively, in negative control, positive control and 100 ng/ml relaxin) and 4 h (51.9, 35.0 and 34.3%, respectively, in negative control, positive control and 100 ng/ml relaxin). Moreover, an increase (p < 0.01) of pattern EA, that is high capacitation level, was recorded with 100 ng/ml relaxin and heparin compared to the negative control both after 2 h (44.1, 59.3 and 57.7%, respectively, in negative control, positive control and 100 ng/ml relaxin) and after 4 h (43.0, 54.4 and 56.0%, respectively, in negative control, positive control and 100 ng/ml relaxin). Finally, relaxin increased (p < 0.01) cleavage rate compared to the negative control (57.1 ± 4.4, 72.5 ± 6.0, 71.4 ± 5.5 and 73.6 ± 2.9, respectively, in negative control, positive control, 50 and 100 ng/ml relaxin). In conclusion, relaxin has a beneficial effect on motility, capacitation and fertilizing ability of frozen–thawed buffalo sperm.  相似文献   
10.
把依法行政分解为法律基础和行政体系2个方面,分析了开发建设项目水土保持监督管理体系在法律基础和行政体系2个方面存在的问题。法律基础方面存在的问题:一是相关法律中提到开发建设项目水土保持监督管理的内容较少,各项职责落实不到位;二是法律中没有明确流域机构的水土保持职能。行政体系方面存在的问题有:规范化建设还不够完善,个别地方水保部门对监督管理工作内容不了解,权大于法的情况时有出现。提出了完善开发建设项目水土保持监督管理体系的建议。  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