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   459篇
  免费   15篇
林业   135篇
农学   12篇
  103篇
综合类   36篇
农作物   16篇
水产渔业   22篇
畜牧兽医   123篇
园艺   7篇
植物保护   20篇
  2020年   7篇
  2019年   6篇
  2018年   8篇
  2017年   6篇
  2016年   10篇
  2015年   8篇
  2014年   12篇
  2013年   11篇
  2012年   18篇
  2011年   30篇
  2010年   10篇
  2009年   15篇
  2008年   28篇
  2007年   20篇
  2006年   20篇
  2005年   17篇
  2004年   17篇
  2003年   22篇
  2002年   11篇
  2001年   7篇
  2000年   4篇
  1989年   4篇
  1988年   3篇
  1987年   3篇
  1986年   3篇
  1984年   5篇
  1983年   4篇
  1982年   4篇
  1977年   4篇
  1975年   3篇
  1974年   5篇
  1972年   6篇
  1969年   3篇
  1968年   3篇
  1967年   5篇
  1966年   3篇
  1965年   4篇
  1962年   3篇
  1956年   4篇
  1948年   7篇
  1941年   3篇
  1934年   3篇
  1933年   3篇
  1932年   12篇
  1927年   7篇
  1919年   6篇
  1918年   5篇
  1915年   4篇
  1904年   5篇
  1902年   3篇
排序方式: 共有474条查询结果,搜索用时 15 毫秒
1.
A trial was performed with heifers at the age of six to seven months. The animals were experimentally infected with the lymphocytes of a virus-productive donor. Infection was produced in all the nine cases, as demonstrated by means of the positive syncytial test. As indicated by the results of the trial, the antibodies to the enzootic bovine leucosis virus (BLV) were produced soon after experimental infection. A high sensitivity of the serum-neutralization test and the ELISA method was demonstrated in this connection: by these methods, the antibodies were identified already two to three weeks after experimental infection whereas by the immunodiffusion test they could be detected only after five weeks. Twenty-four animals were exposed to natural contact infection. Within 270 days of the trial, the disease after contact was recorded only in one heifer out of the four that were in close contact with the experimentally infected animals. In this case, as compared with experimental infection, the antibodies were produced much later--after 85 to 93 days. Leucosis was recorded in none of the remaining animals. The reasons why such a favourable result was obtained were the thorough disinfection of the stables after blood collections and the strict observance of the aseptic conditions. The results of experimental infection in three cows were identical with those obtained in young cattle. In the experimentally infected dairy cows, antibodies in milk were determined by the ELISA method. As found, in milk the antibodies to BLV appear two to three weeks later than they do in serum. The ELISA method of BLV antibody detection can be used for the identification of infected animals in herds where enzootic bovine leucosis occurs.  相似文献   
2.
3.
4.
    
Ohne Zusammenfassung  相似文献   
5.
6.
    
Ohne Zusammenfassung  相似文献   
7.
8.
European Journal of Forest Research - Anhand yon Wuchsmodellen wird die Bestandesentwicktung der Kiefer bei unterschied-licher Begrüindungsdichte und Bestandesbehandlung dargestellt. Neben...  相似文献   
9.
Veterinarians are often directly involved in clinical studies or requested for information to help interpret their results. Therefore, it is reasonable to examine the reservoir of study methods. This article transfers methodological considerations from clinical research into veterinary medicine. The study question determines the appropriate study method. Recently a ten-step procedure was suggested for selection of appropriate study designs in humans. Based on this approach, a pragmatic study design was adapted to the conditions prevailing in interventional studies in dogs and cats with disturbed behaviour. The different concepts for clinical studies are introduced. Whether or not the design and the evaluation of pragmatic studies in dogs and cats with disturbed behaviour has been maintained and the prerequisites have thereby been fulfilled so that the obtained results are suitable to be applied under everyday conditions can be tested in eight steps. Using the pragmatic design the superiority of complex interventions can be investigated. The results of pragmatic studies help to substantiate a value judgement, i. e., the recommendation or rejection of a specific therapeutic intervention for a defined disease entity in a specific therapeutic setting. The goal of pragmatic studies is to obtain results appropriate for use in everyday situations. In conclusion, the suggested procedure is useful for the selection of the appropriate study designs for specific questions. This procedure is also suitable to test whether the conclusions of published study results coincide with the chosen methods.  相似文献   
10.
The Friedrich-Loeffler-Institut, founded in 1910 by Friedrich Loeffler, the discoverer of the first animal virus, foot-and-mouth disease virus, is the oldest virological research facility in the world. Beyond viruses, its area of competence has significantly expanded since its foundation and now also covers bacterial, parasitic and prion diseases of livestock, poultry and aquatic animals. Presently located at four sites within Germany (Insel Riems, Jena,Tübingen,Wusterhausen) the tasks of the institute as delineated in the Animal Disease Act encompass research on infectious animal diseases including zoonoses, import/export examinations, epidemiological studies in case of outbreaks of notifiable animal diseases, acting as reference laboratory for notifiable animal diseases and nationwide quality management of diagnosis of notifiable animal diseases. It is obliged to publish and maintain up-to-date diagnostic regimes for notifiable animal diseases, and it publishes a yearly report on animal health in Germany. With the increasing importance of infectious diseases of animals, in particular those potentially harmful to man (zoonoses), the Friedrich-Loeffler-Institut will be moving into new facilities including laboratories and animal facilities up to the highest biosafety level at its main site Insel Riems on the occasion of its 100th anniversary.  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