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   59358篇
  免费   3322篇
  国内免费   36篇
林业   3411篇
农学   1895篇
基础科学   275篇
  8103篇
综合类   10346篇
农作物   2396篇
水产渔业   3272篇
畜牧兽医   28429篇
园艺   707篇
植物保护   3882篇
  2021年   536篇
  2020年   518篇
  2019年   614篇
  2018年   1146篇
  2017年   1224篇
  2016年   1110篇
  2015年   965篇
  2014年   1154篇
  2013年   2320篇
  2012年   2121篇
  2011年   2260篇
  2010年   1425篇
  2009年   1444篇
  2008年   2126篇
  2007年   2132篇
  2006年   1927篇
  2005年   1829篇
  2004年   1704篇
  2003年   1628篇
  2002年   1515篇
  2001年   1685篇
  2000年   1637篇
  1999年   1346篇
  1998年   489篇
  1997年   511篇
  1996年   494篇
  1995年   543篇
  1994年   483篇
  1993年   497篇
  1992年   968篇
  1991年   954篇
  1990年   947篇
  1989年   957篇
  1988年   892篇
  1987年   936篇
  1986年   927篇
  1985年   933篇
  1984年   753篇
  1983年   680篇
  1979年   676篇
  1978年   568篇
  1977年   482篇
  1975年   509篇
  1974年   714篇
  1973年   644篇
  1972年   702篇
  1971年   695篇
  1970年   602篇
  1969年   601篇
  1967年   515篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
2.
3.
4.
5.
6.
7.
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   
8.
Systemic and pulmonary antibody responses of calves to Pasteurella haemolytica were evaluated by measuring immunoglobulin production in blood for 9 days and in pulmonary lavage fluid for 7 days after intrapulmonary inoculation. Clinical signs, pulmonary lesions, pulmonary and systemic inflammatory response, and amount of antigen in lavage fluid were used to evaluate the response of calves to challenge with P haemolytica. The pulmonary response consisted of production of IgG, IgE, and IgM antibodies to P haemolytica antigens and a 17- to 68-fold increase of cells in lavage fluid 8 hours after inoculation, with a gradual decrease toward normal. Antibodies of the IgM isotype to P haemolytica were demonstrated as early as 8 hours through 7 days after inoculation in 3 of 3 calves. Of the anti-P haemolytica isotypes, IgM was found in the highest concentration. In all of the inoculated calves, IgE was found 1 to 2 days after inoculation, and IgG was found in 2 of 3 inoculated calves from day 1 through 7 after inoculation. Detection of IgG correlated with smaller pulmonary lesions. Immunoglobulin A was not detected in lavage fluid. Serum was evaluated for IgG and IgM antibody response to P haemolytica. Specific IgM was detectable 5 days after inoculation, and IgG was detectable 7 days after inoculation. Pasteurella haemolytica antigens were not detected in serum or plasma. A transient increase in neutrophil count was found 8 hours after inoculation, with return to baseline values by 24 hours after inoculation.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   
9.
29 samples of commonly used surfaces were tested for their water characteristics (litre weight, water capacity, water binding, water evaporation) and their contribution to airborne fungal spores (dust formation, dust setting). The results are discussed in comparison to the literature with regard to the environment. The results are: 1. Any surface--no matter of what material--eventually causes air pollution with fungal spores and dust. 2. Correct watering prevents air pollution by any surface. 3. Artificial products have no advantage over natural materials in the parameters tested. 4. The question of proper disposal of old surface material has to be clarified before purchase. The results show that a mixture of sand and wood shavings should be recommended as a surface for indoor arenas, especially in regard to environmental protection and proper disposal.  相似文献   
10.
Restriction endonuclease analysis and DNA hybridization revealed five ovine strains of Mycobacterium paratuberculosis from South Africa had identical DNA patterns to an ovine strain from Canada. Genetically this strain type has features in common with the two major groups of M. paratuberculosis.  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