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   188991篇
  免费   10616篇
  国内免费   108篇
林业   7722篇
农学   6019篇
基础科学   1321篇
  22566篇
综合类   33298篇
农作物   7060篇
水产渔业   9553篇
畜牧兽医   96566篇
园艺   2384篇
植物保护   13226篇
  2018年   2456篇
  2017年   2658篇
  2016年   2512篇
  2015年   2194篇
  2014年   2710篇
  2013年   7018篇
  2012年   5015篇
  2011年   6202篇
  2010年   4021篇
  2009年   4102篇
  2008年   6224篇
  2007年   5856篇
  2006年   5709篇
  2005年   5293篇
  2004年   5264篇
  2003年   5249篇
  2002年   5080篇
  2001年   5982篇
  2000年   5786篇
  1999年   4741篇
  1998年   2018篇
  1997年   1982篇
  1996年   1890篇
  1995年   2237篇
  1994年   2100篇
  1993年   2019篇
  1992年   3987篇
  1991年   4166篇
  1990年   4266篇
  1989年   4152篇
  1988年   3857篇
  1987年   3864篇
  1986年   3988篇
  1985年   3828篇
  1984年   3256篇
  1983年   2900篇
  1982年   1970篇
  1981年   1850篇
  1980年   1823篇
  1979年   2947篇
  1978年   2442篇
  1977年   2105篇
  1976年   1922篇
  1975年   2028篇
  1974年   2570篇
  1973年   2625篇
  1972年   2569篇
  1971年   2345篇
  1970年   2211篇
  1969年   2097篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
101.
102.
103.
104.
105.
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   
106.
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   
107.
Periodontal disease. Etiology and pathogenesis   总被引:1,自引:0,他引:1  
Periodontal disease is the number-one cause of the early loss of teeth in dogs and cats. Some of the factors in the adult animal that play a major role in the development of periodontal diseases are discussed in this article, including overcrowding, malocclusions, diet, developmental defects, and metabolic and systemic disease.  相似文献   
108.
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   
109.
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   
110.
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