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   223647篇
  免费   11984篇
  国内免费   220篇
林业   11343篇
农学   7538篇
基础科学   1400篇
  28095篇
综合类   35262篇
农作物   8595篇
水产渔业   11368篇
畜牧兽医   115011篇
园艺   3063篇
植物保护   14176篇
  2019年   2022篇
  2018年   3270篇
  2017年   3526篇
  2016年   3352篇
  2015年   2921篇
  2014年   3553篇
  2013年   8990篇
  2012年   6332篇
  2011年   7617篇
  2010年   5189篇
  2009年   5067篇
  2008年   7503篇
  2007年   7363篇
  2006年   6874篇
  2005年   6326篇
  2004年   6120篇
  2003年   6218篇
  2002年   5730篇
  2001年   7052篇
  2000年   6911篇
  1999年   5638篇
  1998年   2318篇
  1997年   2278篇
  1996年   2118篇
  1995年   2526篇
  1994年   2110篇
  1993年   2166篇
  1992年   4402篇
  1991年   4676篇
  1990年   4800篇
  1989年   4673篇
  1988年   4378篇
  1987年   4322篇
  1986年   4268篇
  1985年   4148篇
  1984年   3424篇
  1983年   2996篇
  1982年   2071篇
  1979年   3103篇
  1978年   2453篇
  1977年   2100篇
  1976年   2098篇
  1975年   2243篇
  1974年   2705篇
  1973年   2802篇
  1972年   2770篇
  1971年   2566篇
  1970年   2514篇
  1969年   2326篇
  1967年   2080篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
82.
83.
84.
85.
86.
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   
87.
88.
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   
89.
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   
90.
1. White blood cell responses of broilers, turkeys and ducks were examined at regular intervals after being subjected to various degrees of food restriction. 2. Restricted-fed broilers showed increases in heterophil and basophil numbers, together with a corresponding decrease in lymphocytes. The heterophil/lymphocyte ratio was raised. There were no differences between broiler strains. 3. After only one week of feeding restricted diets, heterophils were significantly raised in selected and unselected 2-week-old ducks. At 21 weeks of age, those ducks receiving 50% of food required to achieve their ad libitum-fed body weight had raised heterophils. 4. Ducks receiving food to achieve 25% of ad libitum-fed birds produced a marked basophilia, but no heterophilia. 5. After two weeks of food restriction, turkeys responded with significant heterophil/lymphocyte ratios following two degrees of restricted feeding. 6. It was concluded that in some poultry, a heterophilia may be the response to mild to moderate stress but a basophilia may result after severely stressing birds.  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