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   28081篇
  免费   2096篇
  国内免费   105篇
耳鼻咽喉   291篇
儿科学   672篇
妇产科学   599篇
基础医学   3812篇
口腔科学   830篇
临床医学   3094篇
内科学   5510篇
皮肤病学   264篇
神经病学   2954篇
特种医学   1093篇
外国民族医学   2篇
外科学   3410篇
综合类   997篇
一般理论   27篇
预防医学   2271篇
眼科学   502篇
药学   2174篇
中国医学   22篇
肿瘤学   1758篇
  2023年   96篇
  2021年   415篇
  2020年   275篇
  2019年   377篇
  2018年   429篇
  2017年   390篇
  2016年   438篇
  2015年   537篇
  2014年   775篇
  2013年   1135篇
  2012年   1709篇
  2011年   1865篇
  2010年   1099篇
  2009年   953篇
  2008年   1855篇
  2007年   1815篇
  2006年   1858篇
  2005年   1907篇
  2004年   1783篇
  2003年   1736篇
  2002年   1544篇
  2001年   404篇
  2000年   348篇
  1999年   433篇
  1998年   417篇
  1997年   328篇
  1996年   306篇
  1995年   286篇
  1994年   234篇
  1993年   200篇
  1992年   250篇
  1991年   231篇
  1990年   197篇
  1989年   207篇
  1988年   194篇
  1987年   195篇
  1986年   190篇
  1985年   196篇
  1984年   215篇
  1983年   190篇
  1982年   217篇
  1981年   185篇
  1980年   207篇
  1979年   151篇
  1978年   140篇
  1977年   140篇
  1976年   106篇
  1975年   117篇
  1974年   104篇
  1973年   111篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Nidogen 1 (NID1) is a glycoprotein found in basement membranes involved in cross-linking collagen IV and laminin. The role of NID in breast cancer has only been evaluated in a small number of studies and the findings of these studies have been inconsistent. Our previous work revealed that highly tumorigenic murine mammary tumor cells express high levels of Nid1 while weakly tumorigenic mammary tumor cells express low levels of Nid1. To investigate Nid1, two stable knockdown lines were created, and Nid1 knockdown was confirmed at both the mRNA and protein level. Nid1 knockdown significantly reduced cell proliferation and migration/invasion and these reductions in proliferation and migration/invasion could be rescued by conditioned media containing NID1 protein. The reduced migration/invasion observed in the Nid1 knockdown cells was not associated with significant alterations in the epithelial gene Cdh1 or the mesenchymal genes Snai1, Snai2, Twist1, Twist2, Zeb1 and Zeb2. Therefore, suppression of Nid1 expression reduces proliferation and migration/invasion in claudin-low murine mammary tumor cells.  相似文献   
2.
3.
4.
5.
6.
ObjectivesTo fill an empirical gap in the literature by examining changes in quality of care measures occurring when multispecialty clinic systems were acquired by hospital-owned, vertically integrated health care delivery systems in the Twin Cities area.ConclusionsMoving a clinic system into a vertically integrated delivery system resulted in limited increases in quality of care indicators. Caution is warranted when the acquisition causes disruption in referral patterns.  相似文献   
7.
8.
Objective: This study investigated the association between fruit and vegetable intake and stomach cancer, with considering the impacts of Helicobacter pylori (H. pylori) infection and tobacco smoking. Methods: A case-control study featuring 80 male incident stomach-cancer cases and 126 male controls was conducted in a general hospital in Viet Nam. A semi-quantitative food frequency and demographic lifestyle questionnaire were used; and venous blood samples were collected to determine H. pylori status by IgG ELISA. The respective associations between fruit and vegetable intake and stomach cancer were examined using unconditional logistic regression analysis with adjustments for possible cofactors. Results: Fruit intake and stomach cancer showed a weak inverse association when this became non-significant after adjusting for H. pylori infection (OR = 0.50, 95%CI: 0.22–1.12, p trend = 0.094). Stratifying by H. pylori status returned a negative trend for fruit intake and stomach cancer among H. pylori-negative participants (OR = 0.21, 95%CI: 0.06–0.69, p trend = 0.010), but no significant interaction for H. pylori-positive participants (OR = 0.76, 95%CI: 0.21–2.68, p trend = 0.670). Vegetable intake and stomach cancer showed no association, regardless of H. pylori status. Compared to ever-smokers with low intake, never-smokers with high vegetable (OR = 0.25, 95% CI: 0.06–0.95) and fruit intake (OR = 0.20, 95%CI: 0.06–0.65) showed the lowest odds of stomach cancer. Conclusions: Fruit, but not vegetable, intake showed a weak inverse association with stomach cancer. H. pylori infection and tobacco-smoking status may influence the protective effects of fruit and vegetable intake on stomach cancer.  相似文献   
9.
Abstract

The purpose of this study was to investigate the strength of the relationships between self-efficacy and (i) functional exercise capacity and (ii) physical activity in chronic obstructive pulmonary disease (COPD), and whether self-efficacy assessment type (i.e., COPD symptoms, exercise-task, exercise-barrier, general, falls) and physical activity assessment type (i.e., self-report vs. objective) are moderators. A systematic search of COPD and self-efficacy concepts was conducted using eight databases from inception to 23 January 2019. Studies were included if they provided correlation coefficients of the relationship between self-efficacy and functional exercise capacity or physical activity, were conducted in adults diagnosed with COPD, and were published in English-language journals. A total of 14 correlation coefficients were included in the self-efficacy and functional exercise capacity meta-analysis, and 16 in the self-efficacy and physical activity meta-analysis. Data were screened, reviewed, and extracted independently by two reviewers, with discrepancies resolved by a third reviewer. Stronger self-efficacy was associated with better functional exercise capacity (weighted r?=?0.38, 95%CI [0.25, 0.50]), and greater physical activity (weighted r?=?0.25, 95%CI [0.17, 0.34]). Exercise-task self-efficacy had the strongest relationship to functional exercise capacity (weighted r?=?0.64, 95% CI [0.51, 0.73]). For physical activity, the type of self-efficacy most strongly related was inconclusive. In COPD, self-efficacy has a relationship to functional exercise capacity and physical activity, the strength of which is influenced by the choice of self-efficacy measure. An understanding of these relationships will assist clinicians in selecting the self-efficacy measure most closely related to the outcome of interest.  相似文献   
10.
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