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   113485篇
  免费   6489篇
  国内免费   335篇
林业   4242篇
农学   3449篇
基础科学   840篇
  13720篇
综合类   19413篇
农作物   4292篇
水产渔业   5378篇
畜牧兽医   60497篇
园艺   1264篇
植物保护   7214篇
  2018年   1642篇
  2017年   1832篇
  2016年   1669篇
  2015年   1441篇
  2014年   1799篇
  2013年   4514篇
  2012年   3130篇
  2011年   3823篇
  2010年   2498篇
  2009年   2628篇
  2008年   3708篇
  2007年   3436篇
  2006年   3326篇
  2005年   2949篇
  2004年   2850篇
  2003年   2842篇
  2002年   2660篇
  2001年   3650篇
  2000年   3680篇
  1999年   2822篇
  1998年   1130篇
  1997年   1152篇
  1996年   1081篇
  1995年   1321篇
  1994年   1149篇
  1993年   1066篇
  1992年   2431篇
  1991年   2680篇
  1990年   2437篇
  1989年   2493篇
  1988年   2314篇
  1987年   2389篇
  1986年   2466篇
  1985年   2305篇
  1984年   1852篇
  1983年   1606篇
  1982年   1089篇
  1979年   1806篇
  1978年   1459篇
  1977年   1249篇
  1976年   1253篇
  1975年   1313篇
  1974年   1658篇
  1973年   1678篇
  1972年   1599篇
  1971年   1413篇
  1970年   1383篇
  1969年   1299篇
  1968年   1135篇
  1967年   1163篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
991.
992.
993.
994.
Morbidity (greater than or equal to 1 disease condition) for pups sold from 3 pet stores from January 1987 through December 1988 ranged from 54 to 68%. In 1 store, morbidity was higher for store pups, compared with pups originating from private parties, for such disease conditions as "kennel cough," diarrhea, and several species of gastrointestinal parasites. In-store mortality ranged from 5 to 9.5% of pups arriving for sale.  相似文献   
995.
996.
997.
998.
Five Devon cattle with suspected ceroid-lipofuscinosis and aged between 19 and 39 months of age were humanely slaughtered and subjected to post-mortem examination. There was severe atrophy of the cerebrum, particularly of the occipital cortex. Microscopy also showed severe atrophy of the retina with complete loss of photoreceptor cells, even in the youngest animal examined. Histopathologically the disease was characterised by accumulation of a fluorescent lipopigment in neurones, including those of the retina and a severe astrocytosis. The disease, which is characterised by the accumulation of subunit c of mitochondrial ATP synthase, is similar to that extensively described in South Hampshire sheep except that the retinal lesions were more severe. In contrast, tremors were not noted in the cattle. The clinical history and similarity to the disease in sheep and other species indicated inheritance was as an autosomal recessive trait.  相似文献   
999.
The comparative efficacy of 13 of the sheep dips currently registered in New Zealand was investigated using sheep infested with the louse Bovicola ovis and carrying wool which was about 10 cm long at the shoulder. With the exception of one synthetic pyrethroid pour-on formulation, all products were able to effect a significant reduction in louse populations, relative to untreated controls, for 37 days after treatment. Only four products proved capable of eradicating lice and preventing their re-establishment up to 37 days after treatment. Variations in manufacturers' recommendations relating to the length of wool at dipping, and mode of application of dips are discussed in relation to the results.  相似文献   
1000.
The efficacy of an oral formulation of the newly developed parasiticide, moxidectin, was tested against benzimidazole-resistant Haemonchus contortus, Trichostrongylus colubriformis, and Nematodirus spathiger, levamisole-resistant Ostertagia circumcincta, and susceptible Cooperia curticei infections in weaned lambs. Thirty-two lambs were experimentally infected with mixed doses of the above strains of nematodes. They were allocated into four treatment groups by stratified randomisation using liveweights and faecal egg counts 28 days later. One group received moxidectin at 0.2 mg/kg liveweight, one group oxfendazole at 4.5 mg/kg liveweight, one group levamisole at 7.5 mg/kg liveweight and the last group remained untreated as the control. Worm burdens in the lambs at slaughter 10 days after oral treatment confirmed the resistance status of the nematode strains used, and showed that moxidectin had a greater than 99.9% efficacy (p<0.01) against all of them. No adverse effects due to treatment with moxidectin were observed in any of the animals.  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