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   19221篇
  免费   2204篇
  国内免费   60篇
耳鼻咽喉   305篇
儿科学   786篇
妇产科学   511篇
基础医学   2788篇
口腔科学   599篇
临床医学   2400篇
内科学   3742篇
皮肤病学   221篇
神经病学   1116篇
特种医学   763篇
外科学   2704篇
综合类   491篇
一般理论   18篇
预防医学   2028篇
眼科学   389篇
药学   1428篇
中国医学   87篇
肿瘤学   1109篇
  2021年   286篇
  2019年   219篇
  2018年   304篇
  2017年   229篇
  2016年   255篇
  2015年   264篇
  2014年   436篇
  2013年   608篇
  2012年   893篇
  2011年   939篇
  2010年   508篇
  2009年   424篇
  2008年   797篇
  2007年   873篇
  2006年   842篇
  2005年   832篇
  2004年   745篇
  2003年   716篇
  2002年   643篇
  2001年   654篇
  2000年   599篇
  1999年   599篇
  1998年   252篇
  1997年   259篇
  1996年   237篇
  1995年   218篇
  1994年   189篇
  1993年   163篇
  1992年   460篇
  1991年   441篇
  1990年   412篇
  1989年   387篇
  1988年   394篇
  1987年   370篇
  1986年   364篇
  1985年   369篇
  1984年   276篇
  1983年   252篇
  1982年   187篇
  1981年   182篇
  1979年   256篇
  1978年   216篇
  1977年   186篇
  1976年   162篇
  1975年   164篇
  1974年   193篇
  1973年   213篇
  1972年   169篇
  1971年   161篇
  1970年   161篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
42.
New inferior vena caval filters for percutaneous placement were made by attaching filter wires similar to those in the bird's nest inferior vena caval filter onto expandable metallic stents. These stents formed a base on which to anchor the filter to the wall of the inferior vena cava. The stent filter can be introduced through a 12- to 13-French catheter sheath system. The system was successfully tested in 13 dogs.  相似文献   
43.
Five cases of fetal ventriculomegaly are described in detail. Following ultrasonography, either computerized tomography or magnetic resonance imaging was used in an attempt to clarify the structural pathology of the ventriculomegaly. In two patients, a precise diagnosis was achieved while a probable diagnosis was established in a third patient. The diverse etiology of fetal ventriculomegaly in these five cases demonstrates that ancillary medical imaging may be necessary to achieve diagnostic precision prior to therapeutic intervention.  相似文献   
44.
While there is a burgeoning body of research linking smoking during pregnancy to problem behaviour in offspring, a major criticism of this work has been the crude measurement of exposure in these studies (e.g. retrospective, self-reported only) that could lead to biased estimates. To address this issue, we used a pregnancy cohort with repeated prospective measures of exposure as well as biological assays to generate estimates of exposure patterns using a range of modelling techniques. In this paper we report on the analytical approaches we have developed, including patterns of exposure over time and best-estimate approaches that combine self-report and cotinine measures, and compare their predictive value in relation to different dimensions of fetal growth as a first step towards examining the utility of greater precision of exposure measurement.
Surprisingly, in this sample the more complex assessments of exposure, including biological measures, generally did not perform better than simple indicators of exposure based on repeated self-report measures, with one exception: a combined self-report cotinine 'best estimate' of third trimester exposure was uniquely associated with lower brain : body ratio. Further study is needed using more sophisticated cotinine assays and testing prediction of a range of outcomes to ascertain whether these findings represent true differences or are specific to the sample, methods and outcomes used. Such research will inform the development of guidelines for adequate exposure characterisation in developmental studies.  相似文献   
45.
46.
The aim of this study was to evaluate the effectiveness of incremental and maximum bite advancement during treatment of Class II Division 1 malocclusion with the Twin-block appliance in the permanent dentition. It was performed at 3 district general hospitals in the United Kingdom with 4 operators. Two hundred three patients, 10-14 years old, were randomized. Control patients had the initial bite taken edge-to-edge for appliance construction with a standard Twin-block. Experimental patients had 2 mm initial bite advancement and subsequent 2 mm advancements at 6 weekly intervals with a Twin-block appliance incorporating advancement screws. Data were collected at the start and the finish of Twin-block treatment. The use of incremental advancement of the Twin-block did not confer any advantages in terms of process and outcome of the treatment. However, patient compliance was influenced by operator and patient age. The duration of treatment was influenced by operator and initial overjet. Incremental bite advancement produced no advantages over maximum advancement.  相似文献   
47.
48.
49.
50.
This study evaluated the effectiveness of early orthodontic treatment with the Twin-block appliance for the developing Class II Division 1 malocclusion. This multicenter trial was carried out in the United Kingdom. A total of 174 children, aged 8 to 10 years old, with Class II Division 1 malocclusion were randomly allocated to receive treatment with a Twin-block appliance or to an untreated, control group. Data were collected at the start of the study and 15 months later. Results showed that early treatment with Twin-block appliances resulted in reduction of overjet, correction of molar relationships, and reduction in severity of malocclusion. Most of this correction was due to dentoalveolar change, but some was due to favorable skeletal change. Early treatment with the Twin-block appliance is effective in reducing overjet and severity of malocclusion. The small change in the skeletal relationship might not be considered clinically significant.  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