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   62905篇
  免费   2834篇
  国内免费   42篇
林业   2518篇
农学   1680篇
基础科学   429篇
  6154篇
综合类   14763篇
农作物   2462篇
水产渔业   2393篇
畜牧兽医   31297篇
园艺   643篇
植物保护   3442篇
  2017年   553篇
  2014年   541篇
  2013年   1863篇
  2012年   1208篇
  2011年   1453篇
  2010年   931篇
  2009年   911篇
  2008年   1439篇
  2007年   1406篇
  2006年   1392篇
  2005年   1390篇
  2004年   1322篇
  2003年   1392篇
  2002年   1354篇
  2001年   1493篇
  2000年   1473篇
  1999年   1206篇
  1998年   542篇
  1997年   552篇
  1996年   545篇
  1995年   610篇
  1994年   590篇
  1993年   577篇
  1992年   1326篇
  1991年   1404篇
  1990年   1454篇
  1989年   1496篇
  1988年   1406篇
  1987年   1368篇
  1986年   1412篇
  1985年   1378篇
  1984年   1154篇
  1983年   1011篇
  1982年   724篇
  1981年   692篇
  1980年   652篇
  1979年   1128篇
  1978年   920篇
  1977年   821篇
  1976年   768篇
  1975年   862篇
  1974年   1129篇
  1973年   1064篇
  1972年   1130篇
  1971年   1080篇
  1970年   1027篇
  1969年   875篇
  1968年   711篇
  1967年   844篇
  1966年   693篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
There is only limited information on sheep interferon available. Recent publications have reported on: 1. an interferon (IFN) alpha subtype, which is secreted by the fetal trophectoderm into the lumen of the uterus between the 10th and 21st day of gestation. It was therefore named ovine trophoblast protein (oTP-1), and is responsible for signalling pregnancy to the ewe via high affinity receptors in the endometrium. It is thought that oTP-1 acts by directly influencing prostaglandin metabolism. 2. the role of lentivirus-induced interferon (LV-IFN) in the pathogenesis of Maedi/Visna. The results indicate that LV-IFN limits viral replication and therefore contributes to virus persistence and is also responsible for a chronic inflammatory process. 3. the mitogen- or antigen-dependent induction of ovine interferon gamma (IFN gamma) and its characterization.  相似文献   
52.
53.
Pleural effusions can cause dyspnea and cyanosis, and are caused by cardiomyopathy, pyothorax, FIP, FeLV-related disease and trauma. Thoracentesis is used to obtain fluid samples for cytologic examination and culture. Radiographs made after thoracentesis may reveal the cause. Lymphosarcoma causes a sterile exudate containing neoplastic cells. Congestive cardiomyopathy causes a transudate or modified transudate. The sterile exudate of FIP has a proteinaceous background on cytologic examination. The exudate of pyothorax is septic. Treatment depends on the cause but generally includes thoracentesis and supportive care. Cardiomyopathy causes dyspnea, cyanosis, murmurs, gallop rhythms and other arrhythmias. Radiography reveals a globoid heart in the congestive form and a "valentine-shaped" heart in the hypertrophic form. Treatment of congestive cardiomyopathy involves use of furosemide, but is usually unrewarding. Hypertrophic cardiomyopathy is treated with propranolol. Fever may be caused by infection, immune-mediated disease, neoplasia and unknown causes. Treatment is aimed at removal of the underlying cause.  相似文献   
54.
55.
Ten out of eleven subcutaneous abscesses in cats harboured anaerobic bacteria. Seven of the ten abscesses contained a mixture of obligate anaerobes and facultative anaerobes or microaerophilic bacteria. All of the anaerobic isolates were sensitive to the antibiotic metronidazole, but were resistant to streptomycin. Three isolates from one abscess were resistant to penicillin and ampicillin. Clinical resolution of subcutaneous abscesses was poor when procaine penicillin was used alone as treatment.  相似文献   
56.
57.
58.
59.
Studies into the effects of the environment on health and performance of agricultural animals are of clear-cut relevance to farming practice. The theoretical and practical importance of lymphocyte transformation to any assessment of immunological reactivity under defined environmental conditions, therefore, is reported in this paper. Communicated is methodical experience obtained from isolation of lymphocytes from peripheral blood of calves, lymphocyte culturing, and morphological evaluation of lymphocyte transformation. Views are given on the suitability of the lymphocyte transformation test. The following results have been obtained: Centrifugation of defibrinated blood, using "Visotrast-370", is recommended for lymphocyte isolation. Morphological evaluation will ensure a high degree of precision when 1 x 10(6) cells in one millilitre culturing fluid are to be cultured over three days, the culturing fluid consisting of 20 per cent of autologous serum and 80 per cent of Eagle medium, antibiotics, and a portion of 1-vol.% of phytohaemagglutinin (Wellcome). The lymphocyte transformation test, for its methodical accuracy, is good enough to detect and identify environmental effects on immunological reactivity of calf. It is likely to reflect the immunological response to an antigen application.  相似文献   
60.
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