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   151304篇
  免费   8648篇
  国内免费   137篇
林业   6443篇
农学   5058篇
基础科学   1010篇
  18035篇
综合类   26192篇
农作物   5917篇
水产渔业   7542篇
畜牧兽医   79007篇
园艺   1860篇
植物保护   9025篇
  2019年   1486篇
  2018年   2299篇
  2017年   2650篇
  2016年   2376篇
  2015年   2029篇
  2014年   2545篇
  2013年   5724篇
  2012年   4423篇
  2011年   5469篇
  2010年   3543篇
  2009年   3600篇
  2008年   5347篇
  2007年   4952篇
  2006年   4781篇
  2005年   4249篇
  2004年   4134篇
  2003年   4196篇
  2002年   3819篇
  2001年   5046篇
  2000年   4998篇
  1999年   3852篇
  1998年   1532篇
  1997年   1596篇
  1996年   1427篇
  1995年   1642篇
  1994年   1422篇
  1993年   1481篇
  1992年   3015篇
  1991年   3256篇
  1990年   3119篇
  1989年   3108篇
  1988年   2768篇
  1987年   2802篇
  1986年   2902篇
  1985年   2789篇
  1984年   2189篇
  1983年   1903篇
  1982年   1310篇
  1979年   2024篇
  1978年   1559篇
  1977年   1296篇
  1975年   1455篇
  1974年   1777篇
  1973年   1761篇
  1972年   1713篇
  1971年   1658篇
  1970年   1635篇
  1969年   1571篇
  1968年   1404篇
  1967年   1420篇
排序方式: 共有10000条查询结果,搜索用时 203 毫秒
81.
82.
83.
84.
85.
86.
87.
Observations on transplacental infection with bluetongue virus in sheep   总被引:1,自引:0,他引:1  
Twenty-four ewes were inoculated with 1 of 2 strains of bluetongue virus type 4 at 40, 60, or 80 days of gestation. Two ewes aborted, 2 ewes died, and 1 was killed during the experiment, but their fetuses were recovered. At term, 2 mummified fetuses, 4 dead lambs, and 17 clinically healthy lambs were produced by 12 sheep, and the remaining 7 sheep were barren. Porencephaly and cerebellar dysgenesis were found in term lambs born to sheep inoculated at 40 and 60 days of gestation. Radiographic examination of 12 fetuses showed developmental ages far less than their chronologic age; 8 fetuses had skeletal growth-retardation lines, which were also observed in the dead lambs. A systemic lymphoreticular hyperplasia was observed in the dead lambs and in all lambs at 12 weeks of age; in 4 of the latter, granulomatous reactions were present in the liver and kidney. Lungs of the full-term lambs were reduced in weight and showed poor alveolar development and mononuclear cell infiltration, which persisted in the 12-week-old lambs. It was concluded that bluetongue virus is capable of causing not only gross abnormalities of the CNS, but also generalized growth retardation and fetal lymphoreticular hyperplasia.  相似文献   
88.
89.
Isolated dog neutrophils exposed to known chemotactic factors assumed a bipolar configuration in suspension. This response was initiated within 2 minutes with a gradual return to spherical shape. The rate of return to sphere was positively correlated with the dose of stimulant. Dog neutrophils exposed to N-formylmethionyl-leucyl-phenylalanine (fMLP) did not adapt to bipolar conformation and did not bind radiolabeled fMLP. These findings are consistent with other species (pig and cow) that also did not respond to fMLP.  相似文献   
90.
Twenty stifles (10 dogs) were studied for a period of 1 year after various lesions of the cranial cruciate ligament and medial meniscus were produced surgicaoy. Through serial arthroscopic evaluations, degenerative processes In stifles with a "torn" cranial cruciate ligament were documented. Intra-articular changes were minimal after partial meniscectomy and were severe after total meniscectomy. Multiple arthroscopies caused no demonstrable changes.  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