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   55061篇
  免费   3025篇
  国内免费   35篇
林业   2908篇
农学   1647篇
基础科学   253篇
  6514篇
综合类   10906篇
农作物   2128篇
水产渔业   2558篇
畜牧兽医   27102篇
园艺   664篇
植物保护   3441篇
  2019年   529篇
  2018年   829篇
  2017年   873篇
  2016年   792篇
  2015年   713篇
  2014年   881篇
  2013年   1943篇
  2012年   1689篇
  2011年   1929篇
  2010年   1240篇
  2009年   1298篇
  2008年   1875篇
  2007年   1869篇
  2006年   1780篇
  2005年   1688篇
  2004年   1546篇
  2003年   1550篇
  2002年   1451篇
  2001年   1589篇
  2000年   1558篇
  1999年   1293篇
  1998年   497篇
  1997年   508篇
  1996年   503篇
  1995年   552篇
  1994年   497篇
  1993年   511篇
  1992年   959篇
  1991年   963篇
  1990年   951篇
  1989年   958篇
  1988年   895篇
  1987年   954篇
  1986年   927篇
  1985年   943篇
  1984年   757篇
  1983年   690篇
  1982年   465篇
  1979年   670篇
  1978年   560篇
  1977年   474篇
  1976年   483篇
  1975年   516篇
  1974年   708篇
  1973年   629篇
  1972年   689篇
  1971年   686篇
  1970年   619篇
  1969年   617篇
  1967年   520篇
排序方式: 共有10000条查询结果,搜索用时 15 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