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   87507篇
  免费   4829篇
  国内免费   142篇
林业   3795篇
农学   2473篇
基础科学   538篇
  10409篇
综合类   15977篇
农作物   3577篇
水产渔业   4106篇
畜牧兽医   45357篇
园艺   982篇
植物保护   5264篇
  2021年   751篇
  2020年   851篇
  2019年   1061篇
  2018年   1394篇
  2017年   1523篇
  2016年   1385篇
  2015年   1134篇
  2014年   1522篇
  2013年   3163篇
  2012年   2626篇
  2011年   3157篇
  2010年   1911篇
  2009年   2055篇
  2008年   3050篇
  2007年   2847篇
  2006年   2677篇
  2005年   2511篇
  2004年   2425篇
  2003年   2435篇
  2002年   2260篇
  2001年   2583篇
  2000年   2635篇
  1999年   2029篇
  1998年   770篇
  1997年   773篇
  1996年   766篇
  1995年   846篇
  1993年   775篇
  1992年   1619篇
  1991年   1793篇
  1990年   1685篇
  1989年   1694篇
  1988年   1524篇
  1987年   1574篇
  1986年   1630篇
  1985年   1592篇
  1984年   1217篇
  1983年   1095篇
  1979年   1182篇
  1978年   910篇
  1977年   772篇
  1975年   790篇
  1974年   1041篇
  1973年   1046篇
  1972年   1064篇
  1971年   1011篇
  1970年   1011篇
  1969年   916篇
  1968年   820篇
  1967年   809篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
42.
43.
44.
45.
46.
47.
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   
48.
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   
49.
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   
50.
Antiserum to a partially purified neuraminidase fromPasteurella multocida, type A:3, was adsorbed with protease-digestedP. multocida type 3 lipopolysaccharide (LPS) to remove LPS immunoreactivity. The LPS-adsorbed antineuraminidase caused a 77% reduction in the neuraminidase activity of homologousP. multocida in anin vitro enzyme neutralization test. All 14 mice passively immunized with the adsorbed antineuraminidase were protected against challenge infection with homologousP. multocida in a mouse protection test. Ten out of 14 mice in one group that received antisera containing antibodies to both neuraminidase and LPS were protected. In contrast, only 1 out of 14 mice that were immunized with pre-immune serum survived the challenge. These results suggest that antiserum toP. multocida neuraminidase was, at least partly, responsible for the protection observed in this study. Neuraminidase may be one of the immunogenic protective proteins present in aqueous extracts ofPasteurella multocida.  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