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   191262篇
  免费   10614篇
  国内免费   166篇
林业   8098篇
农学   6083篇
基础科学   1237篇
  23655篇
综合类   31027篇
农作物   7331篇
水产渔业   9375篇
畜牧兽医   100352篇
园艺   2473篇
植物保护   12411篇
  2019年   1907篇
  2018年   2860篇
  2017年   3175篇
  2016年   2922篇
  2015年   2515篇
  2014年   3184篇
  2013年   7637篇
  2012年   5692篇
  2011年   6850篇
  2010年   4569篇
  2009年   4622篇
  2008年   6806篇
  2007年   6507篇
  2006年   6117篇
  2005年   5609篇
  2004年   5451篇
  2003年   5557篇
  2002年   5081篇
  2001年   6189篇
  2000年   6101篇
  1999年   4862篇
  1998年   1945篇
  1997年   1929篇
  1996年   1816篇
  1995年   2140篇
  1994年   1786篇
  1993年   1876篇
  1992年   3825篇
  1991年   4067篇
  1990年   3996篇
  1989年   4044篇
  1988年   3650篇
  1987年   3682篇
  1986年   3660篇
  1985年   3492篇
  1984年   2801篇
  1983年   2514篇
  1982年   1707篇
  1979年   2530篇
  1978年   1976篇
  1977年   1714篇
  1976年   1622篇
  1975年   1758篇
  1974年   2150篇
  1973年   2224篇
  1972年   2179篇
  1971年   1992篇
  1970年   2019篇
  1969年   1882篇
  1967年   1647篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
101.
102.
Ohne Zusammenfassung Bergleiche Auguftheft diefer Bl?tter, in melchem gleichfalls auf die Wichtigfeit diefes Qegenftandes hingemiefen murde. Die Red.  相似文献   
103.
104.
105.
106.
The parasympathetic and sympathetic divisions of the autonomic nervous system are involved in homeostatic control of a wide variety of ocular functions, including accommodation, pupillomotor control, lacrimation, eyelid position, and aqueous humor production. Familiarity with the functional anatomy of the autonomic nervous system is paramount to the understanding and application of the large number of autonomic drugs used in veterinary ophthalmology. The cholinergic and adrenergic agents discussed in this article are commonly employed to facilitate routine ophthalmic examination, in the diagnosis of autonomic dysfunction, and in the treatment of a variety of ocular diseases.  相似文献   
107.
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   
108.
Antigens in the extracellular protein (ECP) complexes of Bacteroides nodosus, isolated from sheep with either benign or virulent footrot, were studied by immunoelectrophoresis (IEP). Rabbit antisera against ECP from virulent and benign strains, were used in homologous and heterologous crossed IEP. Four precipitin peaks unique to the virulent strain, and five peaks unique to the benign strain were identified. In an attempt to characterize the different antigens in ECP, rabbit antisera were raised against an outer membrane protein (OMP, mol. wt. 35 000 daltons), pili and various proteases of virulent and benign strains of B. nodosus. No precipitin band was observed when ECP from both B. nodosus strains were reacted against anti-OMP and anti-pilus antisera. However, single precipitin bands unique to one protease from the benign strain and one protease from the virulent strain were identified. The results suggest that specific antigens other than proteases or pili are important in determining whether a B. nodosus isolate is virulent or benign.  相似文献   
109.
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   
110.
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