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   2236724篇
  免费   161242篇
  国内免费   6646篇
耳鼻咽喉   29067篇
儿科学   74409篇
妇产科学   61922篇
基础医学   326995篇
口腔科学   62856篇
临床医学   208045篇
内科学   430853篇
皮肤病学   48230篇
神经病学   183327篇
特种医学   81441篇
外国民族医学   651篇
外科学   315420篇
综合类   49347篇
现状与发展   1篇
一般理论   834篇
预防医学   190365篇
眼科学   51161篇
药学   164570篇
  8篇
中国医学   5232篇
肿瘤学   119878篇
  2021年   17955篇
  2019年   19191篇
  2018年   27777篇
  2017年   20654篇
  2016年   22634篇
  2015年   25707篇
  2014年   34685篇
  2013年   53634篇
  2012年   74125篇
  2011年   78652篇
  2010年   45612篇
  2009年   41527篇
  2008年   71676篇
  2007年   75892篇
  2006年   76189篇
  2005年   73231篇
  2004年   70151篇
  2003年   66933篇
  2002年   64768篇
  2001年   98302篇
  2000年   101101篇
  1999年   84691篇
  1998年   24021篇
  1997年   21597篇
  1996年   21406篇
  1995年   20484篇
  1994年   18949篇
  1993年   17759篇
  1992年   67169篇
  1991年   65953篇
  1990年   64175篇
  1989年   61205篇
  1988年   56454篇
  1987年   55813篇
  1986年   52770篇
  1985年   50609篇
  1984年   38241篇
  1983年   32372篇
  1982年   19484篇
  1979年   35222篇
  1978年   25285篇
  1977年   21051篇
  1976年   20352篇
  1975年   21095篇
  1974年   25771篇
  1973年   25121篇
  1972年   23207篇
  1971年   21661篇
  1970年   20052篇
  1969年   18558篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
992.
993.
994.
This research was designed to test the extent to which health education and health services administration students' perceptions of their roles as professionals matched the expectations of professional faculty. These perceptions were found to match in general. However, doubt was cast on the extent to which internships or practicums contributed to this result, since there was no change in student responses between the beginning of the junior year and end of the senior year, a period which includes fieldwork and most of the professional coursework presumed to influence professional development. Additional research is required to test this result with other student populations in other health professions and identify the point at which professional role and task definitions are amenable to change.  相似文献   
995.
The use of parenteral nutrition is becoming more widespread. The need for individualized parenteral nutrition solutions in pediatric patients makes the ordering and preparation of these solutions more complex and error-prone. A computer program is described which performs comprehensive management of parenteral nutrition by assisting in accurately ordering and preparing parenteral nutrition solutions. It also performs extensive error-checking and provides additional nutritional information. Data base management is also a feature which permits future large scale analysis of parenteral nutrition data for research purposes. This program, designed to run on a personal computer, is very comprehensive, yet flexible and user-friendly.  相似文献   
996.
We investigated the effects of imaging and display conditions on the detectability of low-contrast objects in digital subtraction angiographic (DSA) images. The test images were produced by superimposition of low-contrast objects on a uniform noisy background obtained with a DSA system. We employed 18-alternative forced-choice (18-AFC) experiments and predictions based on statistical decision theory to study the dependence of the threshold contrasts of the test objects on the object size, incident x-ray exposure, display window width, and display medium. The results indicated that the threshold contrast decreased with increasing object size, and that the detectability of an object of a given size increased with increasing incident x-ray exposure and decreasing width of the display window. We found that the signal-to-noise ratio (SNR) obtained from the perceived statistical decision theory model, which includes the observer's internal noise, can accurately predict the detectability of low-contrast objects in DSA images. The threshold SNR corresponding to 50% correct detection in the 18-AFC experiments had a constant value of 3.8, in agreement with results reported previously for screen-film systems. The theoretical model will be useful for prediction of the performance of a DSA system based on its physical characteristics, and for evaluation of the tradeoff between patient exposure and diagnostic accuracy for a given DSA unit.  相似文献   
997.
998.
Repeated testing attenuates conditioned place preference with cocaine   总被引:2,自引:2,他引:0  
Cocaine-treated rats acquired a preference for cocaine-associated contextual stimuli (CS) relative to saline-injected control rats. However, when animals were given repeated tests for conditioned place preference intermittent between conditioning trials, they displayed an attenuation in strength of conditioning. This attenuation was not due to pharmacologic tolerance (Experiment 1), but rather reflected a disruption in learning due to exposure to the CS alone (Experiment 2). Like other examples of classical conditioning, the strength of the conditioned response (CR) as assessed by the conditioned place preference model may be influenced by partial reinforcement.  相似文献   
999.
Forty patients suffering from asthmatic conditions, often accompanied by emphysema, were treated either with an extempore combination of salbutamol syrup plus 30-mg oxatomide tablets or with 30-mg oxatomide tablets alone for purposes of comparison. Greater efficacy was obtained with the combination, which produced positive results in terms of improved respiratory status, remission of clinical symptoms and reduced anti-asthma drug requirements in 90% of the cases treated, as against only 55% of satisfactory results obtained with oxatomide alone. The combination was very well tolerated with no incidence of adverse reactions, while the treatment with oxatomide alone, though on the whole well tolerated, gave rise to mild drowsiness in four cases.  相似文献   
1000.
Western transfer and immunoenzymatic staining with affinity-purified monospecific antiserum was used to detect a 38-Kd protein that bound to native and denatured DNA cellulose. This protein has previously been shown to be a delayed early herpes simplex virus type-2 specific protein.  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