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   1698886篇
  免费   126949篇
  国内免费   3800篇
耳鼻咽喉   21791篇
儿科学   55860篇
妇产科学   46363篇
基础医学   242029篇
口腔科学   49021篇
临床医学   151924篇
内科学   334735篇
皮肤病学   38713篇
神经病学   131781篇
特种医学   64237篇
外国民族医学   242篇
外科学   258031篇
综合类   39038篇
现状与发展   4篇
一般理论   538篇
预防医学   124958篇
眼科学   40328篇
药学   123999篇
  7篇
中国医学   4476篇
肿瘤学   101560篇
  2021年   12895篇
  2019年   13624篇
  2018年   20051篇
  2017年   15305篇
  2016年   16716篇
  2015年   19062篇
  2014年   26384篇
  2013年   38179篇
  2012年   53012篇
  2011年   55705篇
  2010年   32937篇
  2009年   30892篇
  2008年   51818篇
  2007年   55125篇
  2006年   55547篇
  2005年   52842篇
  2004年   51025篇
  2003年   48416篇
  2002年   46613篇
  2001年   91959篇
  2000年   93792篇
  1999年   77136篇
  1998年   19797篇
  1997年   17338篇
  1996年   17458篇
  1995年   16807篇
  1994年   15339篇
  1993年   14127篇
  1992年   57507篇
  1991年   55381篇
  1990年   53070篇
  1989年   50837篇
  1988年   46233篇
  1987年   45027篇
  1986年   42348篇
  1985年   40080篇
  1984年   29437篇
  1983年   24976篇
  1982年   13952篇
  1979年   25589篇
  1978年   17627篇
  1977年   14941篇
  1976年   13910篇
  1975年   14606篇
  1974年   17673篇
  1973年   16987篇
  1972年   15720篇
  1971年   14493篇
  1970年   13467篇
  1969年   12562篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
BACKGROUND: The role of atopy in the evolution to chronic obstructive disease remains controversial. AIM: We aimed to assess the association between individual sensitization to common allergens and lung function. METHOD: We analysed data from 12,687 subjects aged 20 to 44 years, from 34 centres in 15 countries participating in the European Community Respiratory Health Survey (ECRHS). Participants performed a blood test, lung function test, methacholine challenge, and answered an administered questionnaire. The relationships between specific IgE, FEV1 and FEV1/FVC ratio were assessed for each study centre stratified by sex, followed by random effects meta-analysis. RESULTS: Asthmatics sensitized to house dust mite had a lower FEV1 (-119 mL in women and -112 mL in men) and FEV1/FVC ratio (-1.95%, and -2.48%) than asthmatics without sensitization. Asthmatics sensitized to cat had a lower FEV1 (statistically significant for women only) and a lower FEV1/FVC ratio. Asthmatic women sensitized to grass had a lower FEV1 and a lower ratio, and those sensitized to Cladosporium had a lower FEV1. A weak association was found with sensitization to cat and to Cladosporium among non-asthmatic women, which disappeared after adjusting for BHR. CONCLUSION: We conclude that atopy was related to a lower lung function, which was only apparent among asthmatics. This relationship was explained by specific sensitization to cat and to house dust mite, the latter being homogeneous across areas.  相似文献   
992.
993.
The triphalangeal thumb-brachyectrodactyly syndrome is a very rare autosomal dominant disorder of unknown etiology characterized by an unusual pattern of limb malformations: triphalangeal thumbs and brachyectrodactyly in the hands, and ectrodactyly in the feet. In a previous report, we described the clinical and radiographical features of three related subjects with the disease and suggest that due to the unusual combination of limb defects and to its phenotypic similarity with the limb malformative pattern induced by disrupting the Hoxd13 gene in mouse, the triphalangeal thumb-brachyectrodactyly syndrome might be caused by mutations in a HOX gene. After sequencing the entire coding region of HOXD13 and the highly conserved homeodomain encoding region of HOXA13, we do not detect any deleterious mutation in any of the patients excluding that alterations at these sequences are responsible for the disease. Mutations in regulatory regions of these genes or in other genes involved in limb development might be responsible for the disease.  相似文献   
994.
995.
The authors report the association of erythroleukemia (FAB M6) and fetal hemoglobin (HbF) level of at least 65% after therapy for ovarian carcinoma. The patient's erythrocytes had many signs of reversion to fetal-like erythropoiesis including: elevated HbF with a fetal G gamma/A gamma (gly/ala) of 3/1, low hemoglobin A2 (HbA2), macrocytosis, and increased i antigen. These data and data from other case reports suggest that elevation of HbF to greater than 25% with reversion to fetal-like erythropoiesis is useful in differentiating erythroleukemia from other preleukemic disorders.  相似文献   
996.
Ranitidine influences the uptake of oral midazolam.   总被引:1,自引:0,他引:1       下载免费PDF全文
In a randomised crossover study in volunteers plasma midazolam levels were estimated for 24 h following 15 mg by mouth, either preceded by no medication or following 24 h therapy with ranitidine. Administration of the H2-receptor blocker significantly increased bioavailability of the benzodiazepine and resulted in higher plasma levels for the first 6 h after taking midazolam. This was accompanied by a greater soporific effect.  相似文献   
997.
The development of identically sited carcinomas of the colon in monozygotic twins is described. Presentation occurred with 2 years of each other. They are discussed in the context of the cancer-family syndrome.  相似文献   
998.
999.
The authors present an improvement to a sigma-filter extrapolation method for the reconstruction of magnetic resonance (MR) images from symmetric discrete Fourier data. By making use of the phase information in the image data, the proposed method can overcome the data inconsistency problem of the original method for handling MR image data with large phase variations, such as those obtained in gradient-echo pulse sequences. Reconstruction results show that its performance is comparable with that of the modified complex sigma-filter method proposed previously to handle the inconsistency problem. However, the new approach has the advantage of reducing computation time by a factor of two with use of a sigma filter applied to real instead of complex images. It is expected that this method will be more practical for use in clinical MR imaging systems.  相似文献   
1000.
Seventy seven antral biopsies were collected from patients attending endoscopy clinic at King Khalid University Hospital, Riyadh, Saudi Arabia during a period of six months between December 1988 to May 1989. Of these 69 (89.6%) showed chronic gastritis as well as Helicobacter-like organisms (HLOs) in the biopsy specimens while 63 (81.8%) of biopsies grew Helicobacter pylori on culture. These findings indicate a good correlation between the histological diagnosis of chronic gastritis and isolation of H. pylori on culture.  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