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   2552701篇
  免费   196142篇
  国内免费   5051篇
耳鼻咽喉   33926篇
儿科学   83838篇
妇产科学   71591篇
基础医学   370574篇
口腔科学   73643篇
临床医学   233500篇
内科学   502517篇
皮肤病学   56985篇
神经病学   209783篇
特种医学   95368篇
外国民族医学   728篇
外科学   368013篇
综合类   54930篇
现状与发展   5篇
一般理论   1077篇
预防医学   212978篇
眼科学   57577篇
药学   181901篇
  7篇
中国医学   5530篇
肿瘤学   139423篇
  2021年   21710篇
  2019年   22531篇
  2018年   30968篇
  2017年   23660篇
  2016年   25935篇
  2015年   29487篇
  2014年   41361篇
  2013年   61121篇
  2012年   84309篇
  2011年   89740篇
  2010年   51733篇
  2009年   49305篇
  2008年   82206篇
  2007年   87258篇
  2006年   86662篇
  2005年   84803篇
  2004年   81001篇
  2003年   77114篇
  2002年   73200篇
  2001年   115721篇
  2000年   118078篇
  1999年   98912篇
  1998年   28792篇
  1997年   25999篇
  1996年   26273篇
  1995年   24793篇
  1994年   22842篇
  1993年   21348篇
  1992年   76214篇
  1991年   73842篇
  1990年   71130篇
  1989年   68547篇
  1988年   63192篇
  1987年   61745篇
  1986年   58218篇
  1985年   55376篇
  1984年   42228篇
  1983年   36264篇
  1982年   21801篇
  1979年   38592篇
  1978年   27815篇
  1977年   23166篇
  1976年   21652篇
  1975年   22842篇
  1974年   27698篇
  1973年   27020篇
  1972年   25432篇
  1971年   23451篇
  1970年   22186篇
  1969年   20791篇
排序方式: 共有10000条查询结果,搜索用时 312 毫秒
931.
The Dundee Memory Clinic was established in 1991. This paper reviews the diagnosis of the first 150 attenders and compares the findings with those of other memory clinics.  相似文献   
932.
There has been a remarkable change in the scenario of therapeutic apheresis in the last 14 years in India. The crude method of manual removal of blood followed by separation of plasma by gravity, keeping it in the bottle for a long time, has now been totally replaced by plasmapheresis, centrifugation, membrane filtration, and immunoadsorption techniques. The indications for use have also changed from a list of limited indications in the beginning to include all immune complex disorders. The clinical beneficiaries have also increased from blood bankers to nephrologists and immunologists in addition to oncologists. Efforts are now underway with the help of the Indian Society for Apheresis (founded in 1985) to popularize the newer methods of cryofiltration, photopheresis and heparin extracorporeal low-density lipoprotein (HELP) and DALI apheresis systems besides the specialized techniques of immunoadsorption using filters, columns, or ligands. This is suggestive of a positive trend for the treatment of immune complex disorders.  相似文献   
933.
934.
935.
936.
937.
PURPOSETo use functional MR imaging to measure the effect of frequency (pitch), intensity (loudness), and complexity of auditory stimuli on activation in the primary and secondary auditory cortexes.METHODSMultiplanar echo-planar images were acquired in healthy subjects with normal hearing to whom auditory stimuli were presented intermittently. Functional images were processed from the echo-planar images with conventional postprocessing methods. The stimuli included pure tones with a single frequency and intensity, pure tones with the frequency stepped between 1,000, 2,000, 3,000, or 4,000 Hz, and spoken text. The pixels activated by each task in the transverse temporal gyrus (TTG) and the auditory association areas were tabulated.RESULTSThe pure tone task activated the TTG. The 1,000-Hz tone activated significantly more pixels in the TTG than did the 4,000-Hz tone. The 4,000-Hz tone activated pixels primarily in the medial TTG, whereas the 1,000-Hz tone activated more pixels in the lateral TTG. Higher intensity tones activated significantly more pixels than did lower intensity tones at the same frequency. The stepped tones activated more pixels than the pure tones, but the difference was not significant. The text task produced significantly more activation than did the pure tones in the TTG and in the auditory association areas. The more complex tasks (stepped tones and listening to text) tended to activate more pixels in the left hemisphere than in the right, whereas the simpler tasks activated similar numbers of pixels in each hemisphere.CONCLUSIONAuditory stimuli activate the TTG and the association areas. Activation in the primary auditory cortex depends on frequency, intensity, and complexity of the auditory stimulus. Activation of the auditory association areas requires more complex auditory stimuli, such as the stepped tone task or text reading.  相似文献   
938.
939.
OBJECTIVES: To examine changes in musculoskeletal complaints over four years in groups of employees relative to age and work demands. METHODS: Repeated questionnaire data of male employees in heavy physical work (exposed group, n = 7324) and mental work (control group, n = 4686), stratified for age (20-9, 30-9, 40-9, 50-9), were analysed. For each employee, data on the occurrence of musculoskeletal complaints from two surveys with a mean interval of around four years were available. Changes in prevalences over the follow up interval were analysed. Proportions of new, recovered, and chronic cases as well as those free of complaints at both surveys were studied. RESULTS: For most complaints, there were significantly greater increases in prevalences in the exposed group compared with the control group over the follow up interval particularly within the group aged 40-9 for back, neck, and several sites of the upper and lower limbs. The 20-9 year age group also had significantly greater changes for several musculoskeletal complaints. Within the oldest age group (50-9) exposure to heavy physical work demands only affected changes in prevalences of neck and upper arm complaints. After four years in the cohort free of complaints at the start of the follow up the group aged 40-9 had the highest prevalence of complaints of the back, neck, and the upper and lower limbs. CONCLUSIONS: Middle aged and younger employees develop musculoskeletal complaints as a result of exposure to heavy physical work. In the oldest age group health related selection seems to mask the occupational health risks under study. To prevent the expected increase in musculoskeletal disorders and related work disability in our aging workforce, preventive measures should be taken at all stages of a working life.  相似文献   
940.
Fibroblasts incorporated within collagen gels induce a cell-mediated contraction of the gel to form a three-dimensional, tissue-like structure by a mechanism thought to mimic wound contraction in vivo . In this study a gel contraction model was used to investigate the ability of fibroblasts derived from adult gingiva, adult skin and fetal skin to organise a collagen matrix. In addition the effects of interleukin-1β (IL-1β) on the contraction process was also investigated. Over the concentration range 5-50 U/ml, IL-1β induced a statistically significant inhibition of gel contraction in all fibroblast cell types ( P <0.05), although fetal fibroblasts appeared least responsive and gingival fibroblasts most responsive to the inhibitory effects of this cytokine. Comparison of gel contraction by the different fibroblast strains indicated that fetal and gingival fibroblasts shared similar contraction kinetics. For the adult skin fibroblasts, three of five strains studied showed significantly diminished levels of gel contraction compared to fetal and gingival cells. This apparent difference in fibroblast phenotype may, at least in part, explain the fetal-like wound healing pattern seen in the oral mucosa.  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