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   188726篇
  免费   10591篇
  国内免费   108篇
林业   7722篇
农学   6021篇
基础科学   1322篇
  22537篇
综合类   33246篇
农作物   7058篇
水产渔业   9532篇
畜牧兽医   96412篇
园艺   2374篇
植物保护   13201篇
  2018年   2454篇
  2017年   2653篇
  2016年   2503篇
  2015年   2191篇
  2014年   2704篇
  2013年   7005篇
  2012年   5005篇
  2011年   6198篇
  2010年   4018篇
  2009年   4091篇
  2008年   6222篇
  2007年   5850篇
  2006年   5704篇
  2005年   5282篇
  2004年   5256篇
  2003年   5242篇
  2002年   5079篇
  2001年   5970篇
  2000年   5774篇
  1999年   4734篇
  1998年   2016篇
  1997年   1980篇
  1996年   1890篇
  1995年   2237篇
  1994年   2099篇
  1993年   2016篇
  1992年   3980篇
  1991年   4158篇
  1990年   4260篇
  1989年   4144篇
  1988年   3847篇
  1987年   3861篇
  1986年   3983篇
  1985年   3823篇
  1984年   3253篇
  1983年   2896篇
  1982年   1970篇
  1981年   1847篇
  1980年   1822篇
  1979年   2950篇
  1978年   2439篇
  1977年   2104篇
  1976年   1919篇
  1975年   2024篇
  1974年   2567篇
  1973年   2625篇
  1972年   2565篇
  1971年   2341篇
  1970年   2208篇
  1969年   2096篇
排序方式: 共有10000条查询结果,搜索用时 15 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