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   2362590篇
  免费   172556篇
  国内免费   3438篇
耳鼻咽喉   32207篇
儿科学   76171篇
妇产科学   62986篇
基础医学   349902篇
口腔科学   64252篇
临床医学   212474篇
内科学   460035篇
皮肤病学   51973篇
神经病学   186762篇
特种医学   88377篇
外国民族医学   489篇
外科学   355388篇
综合类   47540篇
现状与发展   13篇
一般理论   853篇
预防医学   183980篇
眼科学   54471篇
药学   175979篇
  11篇
中国医学   4639篇
肿瘤学   130082篇
  2021年   19474篇
  2019年   19949篇
  2018年   27545篇
  2017年   20744篇
  2016年   23211篇
  2015年   26071篇
  2014年   36667篇
  2013年   54662篇
  2012年   75709篇
  2011年   80433篇
  2010年   47595篇
  2009年   45083篇
  2008年   75392篇
  2007年   80238篇
  2006年   81026篇
  2005年   78400篇
  2004年   74938篇
  2003年   72186篇
  2002年   69777篇
  2001年   108836篇
  2000年   111527篇
  1999年   93597篇
  1998年   27056篇
  1997年   23724篇
  1996年   24086篇
  1995年   22746篇
  1994年   20926篇
  1993年   19736篇
  1992年   72033篇
  1991年   70111篇
  1990年   68422篇
  1989年   65681篇
  1988年   60320篇
  1987年   59143篇
  1986年   55236篇
  1985年   53019篇
  1984年   39324篇
  1983年   33402篇
  1982年   19871篇
  1979年   35876篇
  1978年   25662篇
  1977年   21241篇
  1976年   20339篇
  1975年   21818篇
  1974年   26159篇
  1973年   24809篇
  1972年   23210篇
  1971年   22044篇
  1970年   20252篇
  1969年   19319篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
992.
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   
993.
994.
995.
996.
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   
997.
998.
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   
999.
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   
1000.
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   
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