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   856367篇
  免费   71435篇
  国内免费   1829篇
耳鼻咽喉   12794篇
儿科学   24596篇
妇产科学   25095篇
基础医学   123202篇
口腔科学   25454篇
临床医学   74950篇
内科学   162967篇
皮肤病学   16968篇
神经病学   69692篇
特种医学   35182篇
外国民族医学   171篇
外科学   135667篇
综合类   24602篇
现状与发展   2篇
一般理论   263篇
预防医学   66461篇
眼科学   20482篇
药学   64562篇
中国医学   1577篇
肿瘤学   44944篇
  2018年   7341篇
  2015年   7738篇
  2014年   11125篇
  2013年   16804篇
  2012年   22741篇
  2011年   23864篇
  2010年   13877篇
  2009年   13084篇
  2008年   22596篇
  2007年   24643篇
  2006年   24523篇
  2005年   24151篇
  2004年   23714篇
  2003年   22802篇
  2002年   21891篇
  2001年   35775篇
  2000年   36367篇
  1999年   30647篇
  1998年   8677篇
  1997年   7897篇
  1996年   7813篇
  1995年   7946篇
  1994年   7661篇
  1992年   26628篇
  1991年   26105篇
  1990年   25621篇
  1989年   24665篇
  1988年   23205篇
  1987年   22872篇
  1986年   21735篇
  1985年   21095篇
  1984年   16356篇
  1983年   13953篇
  1982年   8829篇
  1981年   8160篇
  1980年   7632篇
  1979年   16690篇
  1978年   12077篇
  1977年   10137篇
  1976年   9296篇
  1975年   10110篇
  1974年   12619篇
  1973年   12123篇
  1972年   11525篇
  1971年   10670篇
  1970年   10196篇
  1969年   9894篇
  1968年   8890篇
  1967年   8213篇
  1966年   7642篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
71.
72.
73.

Objectives

To determine the proportion of participants of a running program for novice runners that discontinued running and investigate the main reasons to discontinue and characteristics associated with discontinuation.

Design

Prospective cohort study.

Methods

The study included 774 participants of Start to Run, a 6-week running program for novice runners. Before the start of the program, participants filled-in a baseline questionnaire to collect information on demographics, physical activity and perceived health. The 26-weeks follow-up questionnaire was used to obtain information on the continuation of running (yes/no) and main reasons for discontinuation. To determine predictors for discontinuation of running, multivariable logistic regression was performed.

Results

Within 26 weeks after the start of the 6-week running program, 29.5% of the novice runners (n = 225) had stopped running. The main reason for discontinuation was a running-related injury (n = 108, 48%). Being female (OR 1.74; 95% CI 1.13–2.68), being unsure about the continuation of running after the program (OR 2.06; 95% CI 1.31–3.24) and (almost) no alcohol use (OR 1.62; 95%CI 1.11–2.37) were associated with a higher chance of discontinuation of running. Previous running experience less than one year previously (OR 0.46; 95% CI 0.26–0.83) and a higher score on the RAND-36 subscale physical functioning (OR 0.98; 95% CI 0.96–0.99) were associated with a lower chance of discontinuation.

Conclusions

In this group of novice runners, almost one-third stopped running within six months. A running-related injury was the main reason to stop running. Women with a low perceived physical functioning and without running experience were prone to discontinue running.  相似文献   
74.
75.
76.
77.
78.
79.
Objective: Performance validity test (PVT) research studies commonly utilize a known-groups design, but the criterion grouping approaches within the design vary greatly from one study to another. At the present time, it is unclear as to what degree different criterion grouping approaches might impact PVT classification accuracy statistics. Method: To analyze this, the authors used three different criterion grouping approaches to examine how classification accuracy statistics of a PVT (Word Choice Test; WCT) would differ. The three criterion grouping approaches included: (1) failure of 2+ PVTs versus failure of 0 PVTs, (2) failure of 2+ PVTs versus failure of 0–1 PVT, and (3) failure of a stand-alone PVT versus passing of a stand-alone PVT (Test of Memory Malingering). Results: When setting specificity at ≥.90, WCT cutoff scores ranged from 41 to 44 and associated sensitivity values ranged from .64 to .88, depending on the criterion grouping approach that was utilized. Conclusions: When using a stand-alone PVT to define criterion group status, classification accuracy rates of the WCT were higher than expected, likely due to strong correlations between the reference PVT and the WCT. This held true even when considering evidence that this grouping approach results in higher rates of criterion group misclassification. Conversely, when using criterion grouping approaches that utilized failure of 2+ PVTs, accuracy rates were more consistent with expectations. These findings demonstrate that criterion grouping approaches can impact PVT classification accuracy rates and resultant cutoff scores. Strengths, weaknesses, and practical implications of each of the criterion grouping approaches are discussed.  相似文献   
80.
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