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   173624篇
  免费   10017篇
  国内免费   99篇
林业   7601篇
农学   5939篇
基础科学   1061篇
  23115篇
综合类   25219篇
农作物   6412篇
水产渔业   9277篇
畜牧兽医   91071篇
园艺   2427篇
植物保护   11618篇
  2020年   1525篇
  2019年   1754篇
  2018年   3032篇
  2017年   3270篇
  2016年   3050篇
  2015年   2585篇
  2014年   3160篇
  2013年   7230篇
  2012年   5694篇
  2011年   6648篇
  2010年   4463篇
  2009年   4398篇
  2008年   6534篇
  2007年   6300篇
  2006年   5805篇
  2005年   5396篇
  2004年   5243篇
  2003年   5264篇
  2002年   4764篇
  2001年   5907篇
  2000年   5817篇
  1999年   4657篇
  1998年   1861篇
  1997年   1808篇
  1996年   1665篇
  1995年   2022篇
  1994年   1682篇
  1993年   1681篇
  1992年   3502篇
  1991年   3644篇
  1990年   3627篇
  1989年   3607篇
  1988年   3292篇
  1987年   3316篇
  1986年   3246篇
  1985年   3068篇
  1984年   2520篇
  1983年   2203篇
  1982年   1470篇
  1979年   2109篇
  1978年   1677篇
  1977年   1473篇
  1976年   1412篇
  1975年   1504篇
  1974年   1772篇
  1973年   1831篇
  1972年   1806篇
  1971年   1565篇
  1970年   1597篇
  1969年   1520篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
92.
93.
Ohne Zusammenfassung Bergleiche Auguftheft diefer Bl?tter, in melchem gleichfalls auf die Wichtigfeit diefes Qegenftandes hingemiefen murde. Die Red.  相似文献   
94.
95.
96.
97.
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   
98.
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   
99.
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   
100.
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