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   3735篇
  免费   164篇
  国内免费   3篇
林业   247篇
农学   95篇
基础科学   28篇
  657篇
综合类   596篇
农作物   122篇
水产渔业   342篇
畜牧兽医   1514篇
园艺   101篇
植物保护   200篇
  2024年   5篇
  2023年   19篇
  2022年   36篇
  2021年   69篇
  2020年   83篇
  2019年   98篇
  2018年   94篇
  2017年   109篇
  2016年   91篇
  2015年   65篇
  2014年   92篇
  2013年   156篇
  2012年   222篇
  2011年   283篇
  2010年   160篇
  2009年   142篇
  2008年   274篇
  2007年   272篇
  2006年   257篇
  2005年   265篇
  2004年   241篇
  2003年   213篇
  2002年   195篇
  2001年   25篇
  2000年   26篇
  1999年   30篇
  1998年   28篇
  1997年   26篇
  1996年   23篇
  1995年   29篇
  1994年   19篇
  1993年   25篇
  1992年   19篇
  1991年   16篇
  1990年   15篇
  1989年   13篇
  1988年   17篇
  1987年   27篇
  1986年   13篇
  1985年   7篇
  1984年   19篇
  1983年   10篇
  1982年   7篇
  1981年   3篇
  1978年   4篇
  1977年   7篇
  1975年   3篇
  1973年   9篇
  1967年   3篇
  1966年   6篇
排序方式: 共有3902条查询结果,搜索用时 0 毫秒
11.
IN MEMORIUM     
  相似文献   
12.
13.
14.
15.
16.
17.
18.
Silver and bighead carps were imported from China to the United States in the 1970s as a biological control mechanism for improving water quality. After escaping captivity, both species spread into the Mississippi River Basin and now threaten to enter the Great Lakes. Human consumption is one solution, but many Americans believe that carp is unsavory. A random sample of 2,000 licensed anglers in Missouri was asked to complete a mail-back questionnaire about Asian carp, yielding a 27% response rate (n = 465). Results indicated that knowledge and perception about carp were poor, and food neophobia (fear of new foods) scores were above average. Less than 15% of respondents had eaten carp, but nearly 53% were willing to try. Marketing should focus on the benefits of consumption while downplaying any possible concerns. Although education programs are worthwhile, taste might be more influential to change public attitudes toward Asian carp.  相似文献   
19.
OBJECTIVE: To evaluate femoral adaptation after unstable long-term cemented total hip arthroplasty (cTHA) in dogs. STUDY DESIGN: Clinical study. ANIMALS: Four dogs. METHODS: Paired femurs were examined from client-owned dogs that were donated to a retrieval program after death from causes unrelated to their cTHA. Mean (+/-SEM) dog age was 10.0+/-1.5 years and implant duration was 6.0+/-1.4 years. Implanted femurs had radiographic changes associated with implant loosening and gross mechanical instability at femur retrieval. Femurs were evaluated at 3 levels relative to implant length. Cortical area and medullary area were measured at each level, and cortical porosity was assessed at each level in 4 quadrants and in 3 regions. Implanted femurs were compared with the contralateral non-implanted femurs. RESULTS: Cortical area and cortical porosity were increased at all levels in femurs with unstable implants. Implanted femurs had increased porosity in all quadrants and regions at the proximal 2 levels, and increased porosity in only the cranial quadrant and mid-cortical area at the distal level, when compared with contralateral non-implanted femurs. Corresponding medullary areas were not different. CONCLUSIONS: Significant histomorphometric changes occur in femurs after unstable cTHA. The patterns of periosteal bone formation and endosteal bone resorption support mechanisms of stress shielding and wear debris-mediated osteolysis as factors that may contribute to femoral adaptation and implant loosening. CLINICAL RELEVANCE: Despite popularity and excellent return to function with cTHA, aseptic loosening remains a serious long-term complication. Substantial net bone loss and unfavorable environment with unstable cTHA may make revision surgery less successful.  相似文献   
20.
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