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   74563篇
  免费   5253篇
  国内免费   172篇
耳鼻咽喉   949篇
儿科学   2017篇
妇产科学   1768篇
基础医学   11942篇
口腔科学   2033篇
临床医学   7469篇
内科学   14625篇
皮肤病学   1049篇
神经病学   6932篇
特种医学   3019篇
外国民族医学   45篇
外科学   9361篇
综合类   697篇
一般理论   91篇
预防医学   6245篇
眼科学   1512篇
药学   5382篇
中国医学   173篇
肿瘤学   4679篇
  2022年   534篇
  2021年   1147篇
  2020年   748篇
  2019年   1089篇
  2018年   1284篇
  2017年   918篇
  2016年   1087篇
  2015年   1296篇
  2014年   1593篇
  2013年   2767篇
  2012年   3647篇
  2011年   3845篇
  2010年   2606篇
  2009年   2245篇
  2008年   3462篇
  2007年   3675篇
  2006年   3693篇
  2005年   3512篇
  2004年   3513篇
  2003年   3215篇
  2002年   3311篇
  2001年   2313篇
  2000年   2335篇
  1999年   2115篇
  1998年   1013篇
  1997年   870篇
  1996年   736篇
  1995年   763篇
  1994年   637篇
  1993年   695篇
  1992年   1548篇
  1991年   1513篇
  1990年   1430篇
  1989年   1421篇
  1988年   1177篇
  1987年   1175篇
  1986年   1115篇
  1985年   1035篇
  1984年   764篇
  1983年   732篇
  1982年   536篇
  1981年   519篇
  1980年   444篇
  1979年   679篇
  1978年   419篇
  1977年   406篇
  1975年   404篇
  1974年   461篇
  1973年   379篇
  1972年   377篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
3.
4.
BACKGROUND: Computer-assisted image analysis has been proposed for human hair growth studies. METHODS: The performances of Trichoscan, a commercially available automated system combining epiluminiscence microscopy with digital image analysis, developed for office-based hair growth measurements, have been evaluated comparatively on the same skin sites using standardized photographic equipment and calibrated processing for contrast-enhanced phototrichogram (CE-PTG) analysis. This reference method has been validated with scalp biopsies and histological examination of serial sectioning. RESULTS: Besides edge effects, hair fibres escaped the Trichoscan analysis for various reasons including, but not limited to, thickness, pigmentation, closeness and crossing. CONCLUSION: Most of these problems have been identified in the late 1980s and remain largely unsolved by the processing software that was evaluated in 2004. Therefore claims promoting the Trichoscan method for accurate hair measurements in clinical trials on scalp and body hair are not supported by the present investigation. The speed at which the analysis is performed is outweighed by the errors in signal detection. Therefore we suggest that improvements must be clearly documented before Trichoscan is established for quantified diagnostic purposes and detailed hair cycle monitoring during hair trials.  相似文献   
5.
6.
7.
Abstract: Data from the National Education Longitudinal Study were combined with census data at the zip code level to examine the impact of neighborhood racial and ethnic diversity and consolidated inequality, in addition to individual, family, and school factors, on the likelihood of dropping out of high school. Results indicate that while the effects for diversity and consolidated inequality did not support the stated hypotheses, main effects for family risk and prior academic achievement were significant and in the stated direction. Also, when controlling for individual, family, school, and neighborhood characteristics, African Americans were less likely than White students to drop out of school. Implications for contextual effects research and educational outcomes are discussed.  相似文献   
8.
9.
French asthma patients may be supervised by general practitioners (GPs) and/or specialists. Therefore, this study examined asthma management in patients exclusively supervised by specialists (SPE), GPs, (GP) and both (GP+SPE group), and compared the findings. Asthma patients were consecutively recruited in 348 pharmacies. Each patient completed a questionnaire providing data on personal characteristics, asthma management, perception of disease and asthma supervision. Asthma control was measured using the Asthma Control Test. Questionnaires were linked to computerised records of medications which had been dispensed before inclusion in the study. From the 1,256 patients (mean age = 36.1 yrs, 54.3% females), 11.4, 36.6, and 52.0% were placed in the SPE, GP, and GP+SPE groups, respectively. During the previous 4 weeks, most patients in the SPE group were properly controlled (52.2 versus 26.4 and 21.5% in GP and GP+SPE groups, respectively). The SPE group made more use of fixed combinations of long-acting beta agonist and inhaled corticosteroid, while receiving less short-acting beta agonists, antitussives and antibiotics. Striking differences in symptoms and asthma management were observed according to the type of asthma supervision. The current results strongly support the need to improve the management of asthma in primary care, and the coordination of care between general practitioners and specialists.  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