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   2360932篇
  免费   172249篇
  国内免费   3365篇
耳鼻咽喉   32256篇
儿科学   76201篇
妇产科学   62847篇
基础医学   349673篇
口腔科学   63985篇
临床医学   212304篇
内科学   459394篇
皮肤病学   52004篇
神经病学   186247篇
特种医学   88645篇
外国民族医学   499篇
外科学   355600篇
综合类   47580篇
现状与发展   12篇
一般理论   850篇
预防医学   183535篇
眼科学   54527篇
药学   175876篇
  11篇
中国医学   4591篇
肿瘤学   129909篇
  2021年   19169篇
  2019年   19689篇
  2018年   27236篇
  2017年   20499篇
  2016年   22937篇
  2015年   25845篇
  2014年   36338篇
  2013年   54306篇
  2012年   75192篇
  2011年   79917篇
  2010年   47342篇
  2009年   44871篇
  2008年   75096篇
  2007年   79960篇
  2006年   80775篇
  2005年   78305篇
  2004年   74849篇
  2003年   72157篇
  2002年   69831篇
  2001年   109077篇
  2000年   111796篇
  1999年   93805篇
  1998年   27143篇
  1997年   23765篇
  1996年   24157篇
  1995年   22800篇
  1994年   20990篇
  1993年   19796篇
  1992年   72213篇
  1991年   70274篇
  1990年   68606篇
  1989年   65869篇
  1988年   60470篇
  1987年   59288篇
  1986年   55372篇
  1985年   53161篇
  1984年   39454篇
  1983年   33506篇
  1982年   19921篇
  1979年   35985篇
  1978年   25735篇
  1977年   21289篇
  1976年   20395篇
  1975年   21900篇
  1974年   26222篇
  1973年   24878篇
  1972年   23269篇
  1971年   22114篇
  1970年   20320篇
  1969年   19380篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
OBJECTIVES: The aim was to assess the natural course of oral lichen lesions (OLL) among unselected, non-consulting individuals. SUBJECTS AND METHODS: A cohort of 327 subjects with OLL, confirmed in 1973-1974 during a population-based survey in two Swedish municipalities, was followed through January 2002 via record linkages with nationwide and essentially complete registers. A sample of 80 drawn from the 194 surviving subjects who still resided in the area in 1993-1995 was invited for interview and oral re-examination. RESULTS: At the end of follow-up, one case of oral cancer was detected, while 0.4 were expected. The overall mortality among subjects with OLL was not significantly different from that in the 15,817 OLL-free subjects who participated in the initial population based survey in 1973-1974. The lesion had disappeared in 14 (39%) of 36 re-examined subjects with white OLLs in 1973-1974, and four (11%) had transformed into red types. In the corresponding group of 19 with red forms initially, five (26%) had become lesion free and four (21%) had switched to white types. Although the cohort size does not permit firm conclusions regarding oral cancer risk, the natural course over up to 30 years appears to be benign in the great majority.  相似文献   
992.
The aim of this study was to examine the angular distribution of the light emitted from radiation-excited scintillators in medical imaging detectors. This distribution diverges from Lambert's cosine law and affects the light emission efficiency of scintillators, hence it also affects the dose burden to the patient. In the present study, the angular distribution was theoretically modeled and was used to fit experimental data on various scintillator materials. Results of calculations revealed that the angular distribution is more directional than that predicted by Lambert's law. Divergence from this law is more pronounced for high values of light attenuation coefficient and thick scintillator layers (screens). This type of divergence reduces light emission efficiency and hence it increases the incident X-ray flux required for a given level of image brightness.  相似文献   
993.
994.
AIMS: To assess the relationship between neighbourhood deprivation and the rate of gestational diabetes mellitus (GDM) using routinely collected data from a clinical information system, in Plymouth, UK. METHODS: Between 1 January 1996 and 31 December 1997, 3933 women residing within the Plymouth Primary Care Trust (PCT) were screened for GDM using indices of neighbourhood deprivation and prevalence of GDM. Areas (n = 43) were classified according to the Townsend index, measuring material deprivation. Pregnant women with and without GDM were compared. RESULTS: The prevalence of GDM was 1.7%[95%, confidence interval (CI) 1.20, 2.11]. The prevalence of GDM ranged from 1.05% (95% CI 0.60, 1.70) in the most deprived to 2.10% (95%, CI 1.34, 3.13), in the least deprived neighbourhood. Crude rates decreased by 50%[relative prevalence (RP) (95% CI) 0.50 (0.27, 0.94); P = 0.06] amongst those living in the most-deprived compared with those living in the least-deprived areas. Using a stepwise binary logistic regression model, older age at delivery significantly increased the risk of developing GDM. [RP (95%, CI) 1.09, (1.04, 1.13)]. Townsend deprivation score had no significant independent association with GDM when other covariates were considered. CONCLUSION: These data suggest that the neighbourhood context in which women live has no impact on the risk of GDM. Diabet.  相似文献   
995.
996.
997.
Head movement presents a continuing problem in PET studies. Head restraint minimizes movement but is unreliable, resulting in the need to develop alternative strategies. These include frame-by-frame (FBF) realignment or use of motion tracking (MT) during the scan to realign PET acquisition data. Here we present a comparative analysis of these 2 methods of motion correction. METHODS: Eight volunteers were examined at rest using (11)C-raclopride PET with the radioligand administered as a bolus followed by constant infusion to achieve steady state. Binding potential (BP) was estimated using the ratio method during 2 periods of the scan at steady state. Head movement was compensated by using coregistration between frames (FBF) and 3 methods using MT measurements of head position acquired with a commercially available optical tracking system. RESULTS: All methods of realignment improved test-retest reliability and noise characteristics of the raw data, with important consequences for the power to detect small changes in radiotracer binding, and the potential to reduce false-positive and false-negative results. MT methods were superior to FBF realignment using coregistration on some indices. CONCLUSION: Such methods have considerable potential to improve the reliability of PET data with important implications for the numbers of volunteers required to test hypotheses.  相似文献   
998.
999.
1000.
Inorganic sling materials when used for treatment of urinary stress incontinence have a high success rate of achieving continence. They unfortunately attract the complication of vaginal tape erosion. When used for Transobturator tape procedure (TOT) we found the Obtape sling (Mentor-Porges, Le Plessis-Robinson, France) attracted a high rate of erosion, likely due to the tape properties. We describe a series of tape erosions with the Obtape sling, the presentation, conservative and surgical management with favourable rates of maintenance of continence. We suggest the use of larger pore sized tapes to decrease the occurrence of vaginal tape erosion.  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