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   148018篇
  免费   8057篇
  国内免费   86篇
林业   6207篇
农学   4548篇
基础科学   840篇
  16387篇
综合类   28808篇
农作物   5993篇
水产渔业   6993篇
畜牧兽医   75327篇
园艺   1809篇
植物保护   9249篇
  2018年   1861篇
  2017年   2047篇
  2016年   1919篇
  2015年   1707篇
  2014年   2062篇
  2013年   5468篇
  2012年   3792篇
  2011年   4552篇
  2010年   2994篇
  2009年   2912篇
  2008年   4452篇
  2007年   4397篇
  2006年   4102篇
  2005年   3913篇
  2004年   3736篇
  2003年   3785篇
  2002年   3559篇
  2001年   4539篇
  2000年   4441篇
  1999年   3667篇
  1998年   1514篇
  1997年   1457篇
  1995年   1593篇
  1994年   1376篇
  1993年   1402篇
  1992年   3022篇
  1991年   3038篇
  1990年   3076篇
  1989年   3102篇
  1988年   2805篇
  1987年   2885篇
  1986年   2961篇
  1985年   2879篇
  1984年   2344篇
  1983年   2131篇
  1982年   1468篇
  1979年   2141篇
  1978年   1745篇
  1977年   1487篇
  1976年   1406篇
  1975年   1568篇
  1974年   2003篇
  1973年   2047篇
  1972年   2048篇
  1971年   1912篇
  1970年   1807篇
  1969年   1674篇
  1968年   1362篇
  1967年   1441篇
  1966年   1352篇
排序方式: 共有10000条查询结果,搜索用时 218 毫秒
121.
122.
123.
124.
125.
126.
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   
127.
128.
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   
129.
Crystalluria results from oversaturation of urine with crystallogenic substance. However, oversaturation may occur as a result of in vitro as well as in vivo events. The microscopic appearance of crystals only represents a tentative identification of their composition because variable conditions associated with their formation, growth, and dissolution may alter their appearance. Definitive identification is dependent on physical methods such as optical crystallography, x-ray diffraction, and electron microscopic analysis.  相似文献   
130.
Disseminated Aspergillus terreus infection was diagnosed in ten previously healthy adult dogs--nine German shepherds and one dalmatian. The disease was characterized by the presence of multiple granulomas and infarcts in a wide range of organs. The kidney, spleen, and skeletal system were most commonly and severely affected. Fungal hyphae were demonstrated in large numbers within granulomas and thrombi, and A. terreus was readily isolated by culture. This disseminated mycosis appears unique; in this series of cases there was no apparent predisposing factor, portal of entry, or primary focus for dissemination of the infection.  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