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   6216篇
  免费   431篇
  国内免费   14篇
耳鼻咽喉   47篇
儿科学   237篇
妇产科学   94篇
基础医学   746篇
口腔科学   70篇
临床医学   474篇
内科学   1630篇
皮肤病学   178篇
神经病学   325篇
特种医学   147篇
外科学   751篇
综合类   356篇
一般理论   4篇
预防医学   382篇
眼科学   120篇
药学   575篇
中国医学   33篇
肿瘤学   492篇
  2022年   52篇
  2021年   167篇
  2020年   68篇
  2019年   103篇
  2018年   122篇
  2017年   96篇
  2016年   124篇
  2015年   154篇
  2014年   173篇
  2013年   199篇
  2012年   292篇
  2011年   386篇
  2010年   202篇
  2009年   169篇
  2008年   235篇
  2007年   257篇
  2006年   243篇
  2005年   265篇
  2004年   268篇
  2003年   183篇
  2002年   147篇
  2001年   155篇
  2000年   164篇
  1999年   129篇
  1998年   42篇
  1997年   52篇
  1996年   38篇
  1995年   33篇
  1992年   144篇
  1991年   101篇
  1990年   93篇
  1989年   87篇
  1988年   91篇
  1987年   85篇
  1986年   89篇
  1985年   91篇
  1984年   76篇
  1983年   50篇
  1982年   48篇
  1979年   88篇
  1978年   71篇
  1977年   59篇
  1976年   48篇
  1975年   47篇
  1974年   57篇
  1973年   76篇
  1972年   61篇
  1971年   62篇
  1970年   62篇
  1969年   45篇
排序方式: 共有6661条查询结果,搜索用时 15 毫秒
1.
2.
3.
4.
5.
6.
CXCL12 and its receptor, CXCR4, are emerging as promising targets for modulating growth, angiogenesis, and metastasis in several human cancers. Indeed, blocking the receptor is sufficient to prevent metastasis and angiogenesis in experimental breast cancer xenografts. Recently, the biological effect of the CXCR4 in pancreatic cancer, one of the most deadly neoplastic diseases, has been reported. However, the molecular mechanism by which CXCR4 contributes to these properties is not completely understood. In this paper, we characterize the signaling pathways activated by CXCR4 in pancreatic cancer. We show that after CXCR4 activation, EGFR becomes tyrosine phosphorylated, and the kinase activity of this receptor, together with the activation of MMPs, Src, and PI3-Kinase, is required for CXCR4-mediated ERK activation. Analysis of this cascade in pancreatic cancer cells revealed that the ERK-mediated pathway regulates genes involved in angiogenesis, such as VEGF, CD44, HIF1α, and IL-8. Furthermore, ERK blockage inhibits the migration and tube formation of endothelial cells induced by CXCL12. Considering that inhibitors for several components of this pathway, including CXCR4 itself, are at different stages of clinical trials, this study provides theoretical justification for the clinical testing of these drugs in pancreatic cancer, thus extending the list of potential targets for treating this dismal disease.  相似文献   
7.
Haemangioma of the maxillary sinus is rare. Clinical diagnosis is of utmost importance for its operative treatment and prevention of hazards. A case is reported for its rarity and some unusual features.  相似文献   
8.
9.
The return of fertility following discontinuation of norethisterone oenanthate (NET EN) 200 mg injectable contraceptive after use for a minimum period of six months or more was studied in 69 women who discontinued the method for planning pregnancy. Former users of copper intra-uterine device (CuT 200) were enrolled as a control group. Another 161 women who had discontinued NET EN due to other reasons (e.g. amenorrhoea, excessive bleeding or personal reasons) were also studied for return of fertility after ensuring that they were not using any other method of contraception and were exposed to the risk of pregnancy. The subjects from both groups were followed for a period of one year. The cumulative conception rates at one year were 72.5 and 83.6 per 100 subjects for ex-NET EN and ex-CuT 200 users who had discontinued the method for planning pregnancy and this difference was not statistically significant (P > 0.05). The median time for conception for ex-NET EN users was 7.8 months as compared to 3.7 months in ex-CuT 200 users but the cumulative conception rates at the end of one year show that future return of fertility in NET EN users does not appear to be adversely affected.

In 51 subjects who had discontinued NET EN due to amenorrhoea, the return of fertility was predictably slower and less. The return of fertility in subjects who discontinued NET EN for other reasons (e.g. excessive bleeding and other personal reasons) was similar to ex-NET EN and ex-CuT 200 users.  相似文献   

10.

Background  

The objective of this study was to examine missed opportunities for participation in a prevention of mother-to-child transmission (PMTCT) programme in three sites in South Africa. A rapid anthropological assessment was used to collect in-depth data from 58 HIV-positive women who were enrolled in a larger cohort study to assess mother-to-child HIV transmission. Semi-structured interviews were conducted with the women in order to gain an understanding of their experiences of antenatal care and to identify missed opportunities for participation in PMTCT.  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