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   2350125篇
  免费   171864篇
  国内免费   3347篇
耳鼻咽喉   32057篇
儿科学   75901篇
妇产科学   62686篇
基础医学   348216篇
口腔科学   63634篇
临床医学   211380篇
内科学   457531篇
皮肤病学   51736篇
神经病学   185348篇
特种医学   88011篇
外国民族医学   489篇
外科学   353970篇
综合类   47520篇
现状与发展   12篇
一般理论   848篇
预防医学   182743篇
眼科学   54330篇
药学   175107篇
  11篇
中国医学   4581篇
肿瘤学   129225篇
  2021年   18983篇
  2019年   19539篇
  2018年   27066篇
  2017年   20360篇
  2016年   22750篇
  2015年   25642篇
  2014年   36096篇
  2013年   53962篇
  2012年   74683篇
  2011年   79413篇
  2010年   47064篇
  2009年   44571篇
  2008年   74613篇
  2007年   79485篇
  2006年   80302篇
  2005年   77787篇
  2004年   74377篇
  2003年   71715篇
  2002年   69373篇
  2001年   108742篇
  2000年   111453篇
  1999年   93498篇
  1998年   26999篇
  1997年   23661篇
  1996年   24057篇
  1995年   22718篇
  1994年   20899篇
  1993年   19719篇
  1992年   72004篇
  1991年   70071篇
  1990年   68396篇
  1989年   65667篇
  1988年   60307篇
  1987年   59128篇
  1986年   55222篇
  1985年   53005篇
  1984年   39312篇
  1983年   33398篇
  1982年   19859篇
  1979年   35867篇
  1978年   25652篇
  1977年   21232篇
  1976年   20332篇
  1975年   21816篇
  1974年   26148篇
  1973年   24803篇
  1972年   23201篇
  1971年   22037篇
  1970年   20247篇
  1969年   19315篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
Medical experts have disputed whether childhood cyclic vomiting is a manifestation of epilepsy or a migraine equivalent. Quantitative EEG provides an objective measure of changes in brain activity during and between episodes. This paper reports reversible changes involving two episodes in a patient whose history included cyclic vomiting and emotional/behavioural problems. Abnormal delta activity seen during both episodes resolved at follow-up, when the patient asymptomatic. The brain wave changes counter the hypothesis that vomiting in these patients is psychosomatic, and support the interpretation of cyclic vomiting as a migraine equivalent.  相似文献   
992.
993.
994.
995.
A model of sleep phasic events such as vertex waves, K complexes, delta waves and sleep spindles is proposed. It consists of feedback loops that are driven by white noise (simulating tonic delta and sigma activity) and by isolated random impulses, simulating vertex waves or K complexes, depending on the background tonic activity. A model-based method for the detection of sleep phasic events was implemented in a personal computer. Its performance was investigated using simulated and real whole-night EEG signals. The method was able to detect K complexes and vertex waves in a reliable way in spite of their variable shapes and in the presence of a variety of background activities. The detector appears to have superior performance to those so far reported in the literature. The performance of the detector was also compared to that of an electroencephalographer using normal sleep EEG records of 8 h duration from 6 subjects. The performance was satisfactory both in terms of accuracy and reliability. The problem of detecting K complexes in stages 3 and 4 of sleep is discussed.  相似文献   
996.
997.
Sodium nucleinate, an officinal preparation (Na PHK), added to the growth medium in concentrations of 10 to 50 micrograms/ml enhanced the growth of hybridoma cells in vitro. Na PHK presence in the cultivation medium in the above concentrations enhanced the specific antibody-producing activity of hybridomas.  相似文献   
998.
The Barnes Hospital Apheresis Blood Collection and Blood Transfusion Unit is part of Barns Hospital Blood Bank. Because of its size and complexity, we report our experience which may be useful to administrators and physicians involved in the planning or management of similar services. From 1985 through 1988 we collected platelets from 1,976 different donors, the majority of which (87%) were community donors. Sixty-nine percent of 1,976 donors donated in 1988 an average of 4.9 times. Of 6,568 apheresis products collected. 1.1% were discarded because of positive screening tests and 0.7% were discarded because of outdating or presence of fibrin clot. In 1988 a total of nine cell separators were used. All donor apheresis were done with seven blood separators, and on average a separator produced an apheresis product every 4.5 worked hours. All therapeutic apheresis (338) were done on two separators. Most of them (88%) were performed during work hours. In 1988 donor and therapeutic apheresis were done by 17 1/2 full-time employees (FTEs) during work hours. Considering the Workload Unit Value per procedure given by the College of American Pathologists (CAP) and that each FTE worked 1,864 hours per year, the worked hour productivity for donor and therapeutic apheresis was 78.2%. Blood collections, therapeutic bleeds, and outpatient transfusions (1,127, 114 and 1,745 respectively) were accomplished by two FTEs, for a worked hour productivity of 35.5%. Because 95.1% of total worked units was produced by efficient donor and therapeutic apheresis activities, overall efficiency remained high at 73.8%.  相似文献   
999.
A simple gas chromatographic procedure has been developed for the determination of methyltestosterone in bulk powders and in tablets. Two new silyl ether derivatives of methyltestosterone have been prepared using dimethylethylsilylimidazole (DMESI) and dimethylisopropylsilylimidazole (DMiPSI). The method is accurate and selective for methyltestosterone within the concentration range 0.1-1.5 micrograms microliters-1.  相似文献   
1000.
The working clothes and individual protective devices recommended by the industrial Rules for the production of ampicillin trihydrate and its medicinal derivatives such as natrium salt ampicillin, do not provide adequate protection of the skin and respiratory mucous from antibiotic contamination. The use of the overalls in combination with the pressurized helmet (designed and produced at the 'Sintez' enterprise) which provided air supply for breathing and, partially, under the overalls, significantly decreased contamination of the body. At the stages of manual handling of the finished products, adequate protection was attained by using the protective paste produced at the 'Altaivitamine' enterprise.  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