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   198775篇
  免费   2860篇
  国内免费   102篇
耳鼻咽喉   1410篇
儿科学   7327篇
妇产科学   3445篇
基础医学   19139篇
口腔科学   2010篇
临床医学   14804篇
内科学   35843篇
皮肤病学   1046篇
神经病学   18695篇
特种医学   9606篇
外国民族医学   2篇
外科学   32547篇
综合类   2866篇
一般理论   26篇
预防医学   20078篇
眼科学   3365篇
药学   10973篇
中国医学   655篇
肿瘤学   17900篇
  2022年   204篇
  2021年   443篇
  2020年   268篇
  2019年   433篇
  2018年   22316篇
  2017年   17654篇
  2016年   19784篇
  2015年   1325篇
  2014年   1382篇
  2013年   1678篇
  2012年   8266篇
  2011年   22251篇
  2010年   19505篇
  2009年   12157篇
  2008年   20607篇
  2007年   22918篇
  2006年   1864篇
  2005年   3472篇
  2004年   4594篇
  2003年   5502篇
  2002年   3610篇
  2001年   644篇
  2000年   746篇
  1999年   536篇
  1998年   493篇
  1997年   447篇
  1996年   346篇
  1995年   308篇
  1994年   275篇
  1993年   230篇
  1992年   310篇
  1991年   321篇
  1990年   399篇
  1989年   286篇
  1988年   291篇
  1987年   271篇
  1986年   243篇
  1985年   248篇
  1984年   247篇
  1983年   245篇
  1982年   252篇
  1981年   211篇
  1980年   260篇
  1979年   220篇
  1978年   180篇
  1977年   146篇
  1976年   157篇
  1975年   133篇
  1974年   180篇
  1973年   137篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
Ischemic injury plays an important role in chronic renal transplant failure (CRTF). Down-regulation of ecto-adenosine triphosphatase (ATPase) in combination with up-regulation of ecto-5'-nucleotidase is a hallmark of ischemic injury. We studied the expression of renal ecto-5'-nucleotidase and ecto-ATPase in experimental renal transplantation. Fisher 344-to-Lewis allografted rats were either treated with an angiotensin-converting enzyme inhibitor (ACEi) or left untreated. Lewis-to-Lewis syngrafted rats served as controls. Untreated allografted rats developed proteinuria, glomerulosclerosis, and mild intimal hyperplasia. ACEi completely prevented focal and segmental glomerulosclerosis (FGS) and proteinuria, but significantly enhanced intimal hyperplasia. Untreated allografted rats revealed marked vascular ecto-5'-nucleotidase activity, which increased with ACEi. Vascular ecto-5'-nucleotidase activity was absent in syngrafted animals. Ecto-5'-nucleotidase activity correlated well with intimal hyperplasia. Glomerular ecto-ATPase expression was significantly reduced in untreated allografted rats compared to syngrafted rats and correlated well with the extent of FGS. ACEi prevented reduction in glomerular ecto-ATPase. We found de-novo expression of ecto-5'-nucleotidase at sites of renal intimal hyperplasia. Glomerular ecto-ATPase expression was markedly reduced in allografted rats and was prevented by ACEi. These enzyme expression patterns suggest local ischemic damage in experimental CRTF.  相似文献   
52.
Contemporary discourse contains numerous examples of use of the concept of culture by social and behavioral scientists. Simple reification, where the speaker makes culture into a thing capable of action exemplifies one usage in public discourse. Some quantitative social scientists attempt to characterize people’s cultural identities by means of a single categorical variable, which often “lumps” people into categories such as “Hispanic” or “Black” that in fact have numerous culturally bounded subcategories. Approaches that emphasize cultural process are preferable to those who attempt to categorize; more complex measures of acculturation help investigators to make convincing analyses of circumstances in which health disparities occur. Examples in which investigators make appropriate use of cultural characterizations demonstrate their utility in investigating health disparities in Haitian American women, injecting and noninjecting drug users, Hispanic youth, and adult Hispanics at risk of HIV infection. Focus on culture in the study of health disparities can identify entanglements between structural factors such as poverty and lack of education and cultural factors such as beliefs about health. Qualitative methods coupled with quantitative methods have great potential to improve investigators’ grasp of cultural nuance while capturing the distribution of qualitatively derived behaviors.  相似文献   
53.
Microvascular thrombosis is a prominent feature in cardiac delayed xenograft rejection (DXR). We investigated the impact of warfarin or low-molecular-weight heparin (LMWH) anti-coagulation on xenograft function using a heterotopic pig-to-primate model. Donor hearts were from CD46 transgenic pigs and baboon immunosuppression included tacrolimus, sirolimus, anti-CD20 and TPC, an alpha-galactosyl-polyethylene glycol conjugate. Three groups of animals were studied. Group 1 (n = 9) was treated with warfarin, Group 2 (n = 13) with LMWH and Group 3, received no anti-coagulant drugs. The median duration of xenograft function was 20 days (range 3-62 days), 18 days (range 5-109 days) and 15 days (range 4-53 days) in Groups 1 to 3 respectively. Anti-coagulation achieved the targeted international normalized prothrombin ratio (INR) and anti-factor Xa levels consistent with effective in vivo therapy yet, no significant impact on median xenograft function was observed. At rejection, a similar histology of thrombosis and ischemia was apparent in each group and the levels of fibrin deposition and platelet thrombi in rejected tissue was the same. Anti-coagulation with warfarin or LMWH did not have a significant impact on the onset of DXR and microvascular thrombosis. However, a role for specific anti-coagulant strategies to achieve long-term xenograft function cannot be excluded.  相似文献   
54.
55.
56.
The specific characteristics of genetic data lead to ethical-legal conflicts in the framework of genetic diagnosis. Several international organisations, including UNESCO and the Council of Europe, have enacted rules referring to the use of genetic information. This paper discusses possible legal and ethical criteria that could be used in genetic testing.  相似文献   
57.
58.
59.

Introduction  

This paper presents the results of a study on the psychometric properties of an authorized Spanish version of the McMaster Family Assessment Device, a self-report measure of family functioning.  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