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   741篇
  免费   52篇
  国内免费   4篇
耳鼻咽喉   4篇
儿科学   43篇
妇产科学   3篇
基础医学   59篇
口腔科学   14篇
临床医学   40篇
内科学   198篇
皮肤病学   10篇
神经病学   39篇
特种医学   73篇
外国民族医学   1篇
外科学   158篇
综合类   13篇
预防医学   62篇
眼科学   11篇
药学   20篇
中国医学   3篇
肿瘤学   46篇
  2021年   8篇
  2020年   6篇
  2019年   8篇
  2018年   17篇
  2017年   9篇
  2016年   7篇
  2015年   7篇
  2014年   20篇
  2013年   19篇
  2012年   47篇
  2011年   34篇
  2010年   18篇
  2009年   21篇
  2008年   25篇
  2007年   32篇
  2006年   47篇
  2005年   39篇
  2004年   35篇
  2003年   28篇
  2002年   29篇
  2001年   30篇
  2000年   20篇
  1999年   7篇
  1998年   9篇
  1997年   11篇
  1996年   21篇
  1995年   16篇
  1994年   18篇
  1993年   10篇
  1992年   13篇
  1991年   20篇
  1990年   18篇
  1989年   17篇
  1988年   8篇
  1987年   14篇
  1986年   14篇
  1985年   10篇
  1984年   8篇
  1983年   5篇
  1982年   6篇
  1981年   12篇
  1980年   10篇
  1979年   7篇
  1978年   3篇
  1977年   3篇
  1976年   6篇
  1975年   5篇
  1973年   5篇
  1972年   3篇
  1971年   4篇
排序方式: 共有797条查询结果,搜索用时 15 毫秒
81.
In 28 patients with chronic anal fissure the median anal canal pressure was 98 cmH2O, significantly higher than in control subjects (P less than 0.001). After lateral internal sphincterotomy the pressure dropped by 50 per cent to normal levels and the fissures healed with no change in pressure over 12 months. Ten patients also had normal anal pressures and were asymptomatic 4-6 years after internal sphincterotomy. Adequate internal sphincterotomy appears to reduce permanently anal canal pressure, suggesting that abnormal activity in the sphincter contributes to the development of a fissure.  相似文献   
82.
83.

Background  

The clinical use of minimum joint space width (mJSW) and cartilage volume and thickness has been limited to the longitudinal measurement of disease progression (i.e. change over time) rather than the diagnosis of OA in which values are compared to a standard. This is primarily due to lack of establishment of normative values of joint space width and cartilage morphometry as has been done with bone density values in diagnosing osteoporosis. Thus, the purpose of this pilot study is to estimate reference values of medial joint space width and cartilage morphometry in healthy individuals of all ages using standard radiography and peripheral magnetic resonance imaging.  相似文献   
84.
The serum of EH reacted with all red cells (RBCs) except her own, ficin- or trypsin-treated red cells, and En(a-) red cells. This reactivity defined an anti-EnaTS specificity. The red cells of the proposita typed as M-N+S-S+, Vw+Mur-Hil-Hut-Anek-Lane-, Wr(a-b+), EnaKT+. Red cells of five relatives were Vw+ and positive with her serum. Titration studies suggest that EH is genetically an MiI homozygote and that her Vw+ relatives are MiI heterozygotes. There is no history of consanguinity. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis and immunoblotting studies have agreed with the serologic observations. A variant sialoglycoprotein of faster mobility than normal glycoprotein A, but no normal glycoprotein A, was detected on her red cells. Treatment with N-glycanase did not alter the mobility, which indicated that there was no N-glycosylation of residue 26. These findings are in agreement with the reported properties of the Mi.I-specific glycoprotein A. The relatives' Vw+ red cells showed the variant sialoglycoprotein and normal glycoprotein A. EH appears to be the first reported MiI homozygote.  相似文献   
85.
BACKGROUND: The purpose of this study was to evaluate the criteria for assessing the appropriateness of red cell transfusions. The data were obtained by a computer search of all English-language literature from 1966 to October 1992. STUDY DESIGN AND METHODS: Nine studies were selected, which dated from 1986 to 1989 and employed explicit criteria evaluating the appropriateness of red cell transfusion in adults. The following data were abstracted from all studies: study design, timing, location, criteria for evaluating appropriateness, and rate of appropriate or inappropriate transfusions. RESULTS: Five studies evaluated transfusion appropriateness. Appropriateness rates ranged from 88 to 99 percent in three studies, and inappropriateness rates ranged from 0.3 to 57.3 percent in two studies. Four studies evaluated transfusion inappropriateness and reported inappropriateness rates of 18 to 55 percent. Substantial variation was found in the criteria for an appropriate or an inappropriate transfusion. Appropriateness rates did not depend upon characteristics of the study design, location, or timing of data collection. Restrictiveness in the criteria used to determine appropriateness and the use of additional implicit evaluation after an initial explicit review affected appropriateness rates. CONCLUSION: In the 1980s, high rates of inappropriate transfusion and low rates of appropriate transfusion were still reported. Appropriateness rates varied widely, in part because of marked variation in the criteria for an appropriate transfusion. Newly derived standards for an appropriate red cell transfusion, published in 1992, appear to provide a simple and objective means of evaluating the appropriateness of a transfusion. Appropriateness rates resulting from the application of these new standards have not yet been determined.  相似文献   
86.
The mechanisms of white cell (WBC) reduction in 16-hour-old CPDA-1 red cell (RBC) concentrates by filtration on a column filter and on three different flatbed filters were studied by electron microscopy, with special emphasis on cell-to-cell interaction, cell damage, and interaction of blood cells with the material. Generally, lymphocytes were removed by mechanical sieving and monocytes by adherence and mechanical sieving. Granulocyte depletion occurred by mechanical sieving, direct adhesion to the fibers, and indirect adhesion to activated and spread platelets. In the column filter, most granulocytes were captured by adhesion. In the coarse layers of two of the flatbed filters, indirect adhesion was most prominent, whereas direct adhesion was most prominent in the other flatbed filter. For the most part, granulocytes were captured by direct adhesion in the fine layers, but in one flatbed filter, capture apparently occurred by mechanical sieving. The results of this study suggest that the efficiency and the mechanism of WBC reduction depend on the physicochemical characteristics of the non-woven materials in the filters as well as the cellular composition of the RBC concentrates.  相似文献   
87.

Background

Producing “traditional” e-learning can be time consuming, and in a topic such as eHealth, it may have a short shelf-life. Students sometimes report feeling isolated and lacking in motivation. Synchronous methods can play an important part in any blended approach to learning.

Objective

The aim was to develop, deliver, and evaluate an international postgraduate module in eHealth using live interactive webcasting.

Methods

We developed a hybrid solution for live interactive webcasting using a scan converter, mixer, and digitizer, and video server to embed a presenter-controlled talking head or copy of the presenter’s computer screen (normally a PowerPoint slide) in a student chat room. We recruited 16 students from six countries and ran weekly 2.5-hour live sessions for 10 weeks. The content included the use of computers by patients, patient access to records, different forms of e-learning for patients and professionals, research methods in eHealth, geographic information systems, and telehealth. All sessions were recorded—presentations as video files and the student interaction as text files. Students were sent an email questionnaire of mostly open questions seeking their views of this form of learning. Responses were collated and anonymized by a colleague who was not part of the teaching team.

Results

Sessions were generally very interactive, with most students participating actively in breakout or full-class discussions. In a typical 2.5-hour session, students posted about 50 messages each. Two students did not complete all sessions; one withdrew from the pressure of work after session 6, and one from illness after session 7. Fourteen of the 16 responded to the feedback questionnaire. Most students (12/14) found the module useful or very useful, and all would recommend the module to others. All liked the method of delivery, in particular the interactivity, the variety of students, and the “closeness” of the group. Most (11/14) felt “connected” with the other students on the course. Many students (11/14) had previous experience with asynchronous e-learning, two as teachers; 12/14 students suggested advantages of synchronous methods, mostly associated with the interaction and feedback from teachers and peers.

Conclusions

This model of synchronous e-learning based on interactive live webcasting was a successful method of delivering an international postgraduate module. Students found it engaging over a 10-week course. Although this is a small study, given that synchronous methods such as interactive webcasting are a much easier transition for lecturers used to face-to-face teaching than are asynchronous methods, they should be considered as part of the blend of e-learning methods. Further research and development is needed on interfaces and methods that are robust and accessible, on the most appropriate blend of synchronous and asynchronous work for different student groups, and on learning outcomes and effectiveness.  相似文献   
88.
Asymmetric hypertrophy of the labia minora is a variant of normal anatomy that has not been described in the pediatric dermatology literature. Although often asymptomatic, in some cases, it can cause functional, emotional, and psychological problems. We report the clinical characteristics and outcomes of four children who presented with unilateral labium minus hypertrophy. This case series aims to establish awareness of this condition among pediatric dermatologists and provide recommendations regarding management.  相似文献   
89.
90.
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