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   199986篇
  免费   12926篇
  国内免费   175篇
林业   8367篇
农学   6758篇
基础科学   1357篇
  26189篇
综合类   30390篇
农作物   7506篇
水产渔业   11730篇
畜牧兽医   104620篇
园艺   2590篇
植物保护   13580篇
  2020年   2058篇
  2019年   2762篇
  2018年   3539篇
  2017年   3950篇
  2016年   3686篇
  2015年   3168篇
  2014年   3769篇
  2013年   8537篇
  2012年   6290篇
  2011年   7414篇
  2010年   5074篇
  2009年   4903篇
  2008年   7052篇
  2007年   6755篇
  2006年   6287篇
  2005年   5786篇
  2004年   5591篇
  2003年   5663篇
  2002年   5190篇
  2001年   6412篇
  2000年   6366篇
  1999年   5075篇
  1998年   2010篇
  1997年   2015篇
  1996年   1890篇
  1995年   2254篇
  1994年   1962篇
  1993年   1942篇
  1992年   4043篇
  1991年   4252篇
  1990年   4173篇
  1989年   4166篇
  1988年   3861篇
  1987年   3906篇
  1986年   3905篇
  1985年   3722篇
  1984年   2995篇
  1983年   2654篇
  1982年   1774篇
  1979年   2646篇
  1978年   2145篇
  1977年   1884篇
  1976年   1779篇
  1975年   1878篇
  1974年   2300篇
  1973年   2447篇
  1972年   2302篇
  1971年   2093篇
  1970年   2069篇
  1969年   1897篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
111.
Ohne Zusammenfassung Bergleiche Auguftheft diefer Bl?tter, in melchem gleichfalls auf die Wichtigfeit diefes Qegenftandes hingemiefen murde. Die Red.  相似文献   
112.
113.
114.
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   
115.
116.
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   
117.
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   
118.
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   
119.
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   
120.
A steam-dryer, designed and manufactured in Sweden, was evaluated for destroying Bursaphelenchus xylophilus in pine chips from southern USA. In a trial, pine chips were treated at different temperature and pressure regimes for 5 or 10min. The lowest time/temperature/pressure combination was to increase the vessel temperature from 85 to 104°C in 5 min at low pressure. Samples of pine chips were assayed for nematodes in laboratories in USA, Sweden, and Finland. No nematodes of any species were recovered from any of the treated pine-chip samples. Large and heterogeneous pieces of wood in the treated samples were also nematode-free. The apparatus was a prototype capable of handling about 400 kg h-1. The final version would have to be able to process 100-200 th-1.  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