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   1422篇
  免费   57篇
  国内免费   1篇
林业   290篇
农学   34篇
  183篇
综合类   144篇
农作物   33篇
水产渔业   77篇
畜牧兽医   633篇
园艺   25篇
植物保护   61篇
  2022年   14篇
  2021年   32篇
  2020年   15篇
  2019年   26篇
  2018年   34篇
  2017年   31篇
  2016年   28篇
  2015年   24篇
  2014年   26篇
  2013年   62篇
  2012年   65篇
  2011年   73篇
  2010年   26篇
  2009年   42篇
  2008年   52篇
  2007年   62篇
  2006年   63篇
  2005年   44篇
  2004年   45篇
  2003年   33篇
  2002年   37篇
  2001年   30篇
  2000年   29篇
  1999年   24篇
  1993年   12篇
  1992年   13篇
  1991年   19篇
  1990年   16篇
  1989年   21篇
  1988年   10篇
  1987年   15篇
  1986年   16篇
  1985年   14篇
  1984年   20篇
  1983年   13篇
  1980年   9篇
  1979年   24篇
  1978年   13篇
  1975年   9篇
  1973年   12篇
  1972年   19篇
  1971年   9篇
  1970年   14篇
  1969年   12篇
  1968年   11篇
  1967年   12篇
  1966年   8篇
  1965年   11篇
  1951年   10篇
  1950年   8篇
排序方式: 共有1480条查询结果,搜索用时 203 毫秒
991.
A special form of keratitis in the cat is described on the basis of 8 clinical cases. The disease has been known in the United States and the United Kingdom for some time, however, it has, to our knowledge, never been described in Switzerland. This keratitis is characterized by chronicity and infiltration of the cornea by mast cells and eosinophils. It is usually an unilateral and painless condition. We describe the clinical features and diagnostic examinations of the disease. Cytology of a corneal scraping is usually diagnostic. As in the cases described in the literature the cats were successfully treated with oral megestrol acetate. The aetiology of the disease is unknown.  相似文献   
992.
In a previous experiment a group of 15 specified pathogen free (SPF) cats were experimentally infected with a Swiss isolate of feline immunodeficiency virus (FIV). A group of 15 SPF cats served as FIV negative controls. Nine cats of each group were vaccinated with a recombinant feline leukemia virus (FeLV) vaccine, six cats in each group with a placebo vaccine. All vaccinated cats developed high antibody titers to FeLV and were protected against subsequent FeLV challenge infection. In both control groups five of six cats became persistently infected with FeLV. Unexpectedly, the primary immune response to the vaccine antigen was significantly higher in the FIV positive group than in the FIV negative. The secondary response was stronger in the FIV negative cats. The goal of the present investigation was to further study the immune response in these 30 cats. They were immunized twice with the synthetic peptide L-tyrosine-L-glutamic acid-poly(DL-alanine)-poly(L-lysine) (TGAL) 21 days apart. Blood samples were collected on four occasions during the immunization process. They were tested for antibodies to TGAL, complete blood cell counts and CD4+, CD8+ and pan-T-lymphocyte counts. The following observations were made: (1) in contrast to the FeLV vaccine experiment, the primary immune response to TGAL was not significantly stronger in the FIV positive cats when tested by enzyme-linked immunosorbent assay (2). The absolute size of the CD4+ lymphocyte population was distinctly smaller in the FIV positive than in the FIV negative cats. The lowest CD4+ values were found in the dually FIV/FeLV infected cats. (3) A population of CD8+ lymphocytes was identified that was characterized by a distinctly weaker fluorescence. The size of this population increased in FIV positive and decreased in FIV negative cats during the TGAL immunization experiment. (4) The CD4+:CD8+ ratio increased in FIV negative cats during TGAL immunization from 1.9 to 2.3. In contrast, in FIV positive animals the CD4+:CD8+ ratio decreased significantly from 1.9 to 1.3 during the same period. From these and earlier data it was concluded that in short-term FIV infection the immune response to T-cell dependent antigens may be increased over that of the controls. Immune suppression develops gradually with duration of the infection. The significant drop of the CD4+:CD8+ ratio over a 5 week immunization period suggests that antigenic stimulation may accelerate the development of immune suppression in FIV positive cats. If this is a general feature, FIV infection may provide a particularly interesting model for studying the pathogenesis of AIDS.  相似文献   
993.
    
Ohne Zusammenfassung  相似文献   
994.
995.
    
Ohne Zusammenfassung  相似文献   
996.
997.
998.
Faecal samples of 2 pigs, kept on a constant diet, were analysed for Lactobacillus acidophilus and other lactic acid bacteria at 1 week intervals over a period of 3 months. Enumeration of L. acidophilus by selective methods was verified by phenotypic identification of representative isolates. The total lactic acid bacteria (LAB) population ranged between 10(8) and 10(10) colony-forming units per gram of faeces over the 3 months period. L. acidophilus contributed on average a relatively constant figure of 10% to the total LAB population.  相似文献   
999.
Classification of lung carcinomas in the dog and cat   总被引:1,自引:0,他引:1  
A total of 218 lung carcinomas from dogs and cats were examined histologically. The tumors were classified into adenocarcinoma, squamous-cell carcinoma, bronchial gland carcinoma, and alveolar-cell carcinoma. We believe that adenocarcinoma should be subdivided into differentiated and undifferentiated types because the two are distinct histologically and vary in frequency in the cat and dog. It is also important to recognize bronchial gland carcinoma, a distinct histological type, and to subdivide alveolar-cell carcinoma into three separate types: anaplastic small-cell and large-cell types, and adenomatosis type.  相似文献   
1000.
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