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   26891篇
  免费   1602篇
  国内免费   12篇
林业   974篇
农学   985篇
基础科学   175篇
  3934篇
综合类   3757篇
农作物   971篇
水产渔业   1573篇
畜牧兽医   14036篇
园艺   316篇
植物保护   1784篇
  2019年   283篇
  2018年   526篇
  2017年   614篇
  2016年   560篇
  2015年   408篇
  2014年   524篇
  2013年   1079篇
  2012年   884篇
  2011年   1063篇
  2010年   781篇
  2009年   750篇
  2008年   1073篇
  2007年   1021篇
  2006年   927篇
  2005年   820篇
  2004年   709篇
  2003年   767篇
  2002年   643篇
  2001年   868篇
  2000年   860篇
  1999年   666篇
  1998年   302篇
  1997年   303篇
  1996年   252篇
  1995年   279篇
  1993年   253篇
  1992年   453篇
  1991年   550篇
  1990年   472篇
  1989年   429篇
  1988年   418篇
  1987年   429篇
  1986年   377篇
  1985年   403篇
  1984年   351篇
  1983年   294篇
  1982年   252篇
  1979年   394篇
  1978年   297篇
  1977年   296篇
  1976年   312篇
  1975年   328篇
  1974年   336篇
  1973年   313篇
  1972年   298篇
  1971年   252篇
  1969年   296篇
  1968年   281篇
  1967年   331篇
  1966年   313篇
排序方式: 共有10000条查询结果,搜索用时 9 毫秒
61.
The purpose of this study was to assess the clinical effects of dexmedetomidine, both alone and combined with pethidine or butorphanol, in cats. A prospective randomized blind study was performed. Thirty cats were randomly assigned to three groups of 10 animals: D: dexmedetomidine (20 μg/kg IM); DP: dexmedetomidine (10 μg/kg IM) and pethidine (2.5 mg/kg IM); DB: dexmedetomidine (10 μg/kg IM) and butorphanol (0.4 mg/kg IM). Quality of sedation, analgesia, muscle relaxation and the possibility of performing some clinical procedures were compared using a multifactorial scale. Sedation, analgesia and muscle relaxation increased progressively over time and did not differ in the three protocols. The three protocols facilitated the completion of several clinical procedures. The clinical variables studied showed a similar behaviour in the three protocols and remained close to the baseline, except for a drop in heart rate in protocol D. In conclusion, dexmedetomidine, either alone or combined with pethidine or butorphanol, offers suitable sedation, analgesia and relaxation to perform various clinical procedures in cats.  相似文献   
62.
Faculty members from veterinary colleges that teach courses on food-borne, waterborne, and zoonotic diseases to non-veterinary students face unique challenges. The diversity of students' backgrounds, skills, and goals and the public nature of the science require some ingenuity in combining good science with the ability to communicate clearly in a variety of public forums. Drawing on pedagogical theory, the nature of the material, and the diverse abilities of the students, we have put together an effective teaching package for non-veterinary courses on these subjects, which includes a range of methods from outbreak investigations to town hall meetings and food diaries.  相似文献   
63.
64.
The aim of this study was to compare the development of Glasser's disease in sow-reared and colostrum-deprived piglets. Ninety piglets from a commercial pig farm in Spain were used. The farm was positive for Haemophilus parasuis. Fifty-two pigs were sow-reared (SR) and 38 were colostrum-deprived (CD) piglets. The animals were intratracheally inoculated with H. parasuis serovar 5 and sacrificed at 1, 2 and 3 days post-infection. To assess the development of disease, antibody titers, clinical signs, pathological lesions, microbiological isolation and PCR amplification were compared between the groups. Inoculation of SR pigs did not cause clinical signs or lesions of Glasser's disease. In SR pigs, H. parasuis isolation and specific PCR amplification from tissues showed a very low number of positive samples. In contrast, in CD pigs, inoculation resulted in the typical signs and lesions of Glasser's disease. Positive microbiological isolation and specific PCR products were obtained from the majority of the tissues tested, and no antibodies against H. parasuis were detected. The experimental infection using CD pigs describes a successful method to study this microorganism and confirms the important role that maternal antibodies play in protection against clinical signs and disease.  相似文献   
65.
66.
67.
68.
69.
70.
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