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   189825篇
  免费   10994篇
  国内免费   691篇
林业   7931篇
农学   6308篇
基础科学   1418篇
  23925篇
综合类   31779篇
农作物   7122篇
水产渔业   9406篇
畜牧兽医   98751篇
园艺   2668篇
植物保护   12202篇
  2020年   1702篇
  2019年   2054篇
  2018年   2994篇
  2017年   3401篇
  2016年   3074篇
  2015年   2785篇
  2014年   3329篇
  2013年   7579篇
  2012年   6114篇
  2011年   7343篇
  2010年   5036篇
  2009年   4935篇
  2008年   7012篇
  2007年   6788篇
  2006年   6275篇
  2005年   5802篇
  2004年   5442篇
  2003年   5551篇
  2002年   5127篇
  2001年   6114篇
  2000年   6045篇
  1999年   4877篇
  1998年   1959篇
  1997年   1902篇
  1996年   1779篇
  1995年   2055篇
  1994年   1778篇
  1993年   1802篇
  1992年   3713篇
  1991年   4006篇
  1990年   3927篇
  1989年   3920篇
  1988年   3603篇
  1987年   3632篇
  1986年   3630篇
  1985年   3365篇
  1984年   2800篇
  1983年   2435篇
  1982年   1640篇
  1979年   2427篇
  1978年   1921篇
  1977年   1652篇
  1976年   1658篇
  1975年   1721篇
  1974年   2120篇
  1973年   2181篇
  1972年   2118篇
  1971年   1882篇
  1970年   1915篇
  1969年   1773篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
111.
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.
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   
116.
A brief discussion of those aspects of neonatal physiology that pertain to anesthetic risk and selection of anesthetic techniques is followed by discussion of suggested techniques for anesthetic management in healthy foals. Preoperative preparation and management of foals with selected serious surgical conditions are also considered.  相似文献   
117.
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   
118.
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   
119.
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   
120.
The association of tumor-associated antigen (TAA) on the proliferation of BLV-infected lymphoblastoid B-cell lines (BL2M3 and BL312) was investigated. Flow cytometric analysis of the expression of TAA with monoclonal antibody (mAb) c143 showed high expression of TAA on the surfaces of BL2M3 and BL312 cells. A large amount of TAA was found in the culture supernatant of BL2M3 and BL312 cells as well as in the lysates of BL2M3 and BL312 cells. Culture supernatant but not lysates of BL2M3 and BL312 cells promoted the growth of either BL2M3 cells or BL312 cells. Furthermore, this growth promoting activity in culture supernatants of BL2M3 and BL312 cells was inhibited in a dose-dependent manner when cultured with mAb c143. These results suggested that TAA may be involved in the growth factor-mediated cell growth of bovine B-lymphoblastoid cell lines expressing TAA on their cell surface.  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