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   1372235篇
  免费   102131篇
  国内免费   1787篇
耳鼻咽喉   17380篇
儿科学   44112篇
妇产科学   37243篇
基础医学   206346篇
口腔科学   37909篇
临床医学   127081篇
内科学   268460篇
皮肤病学   28928篇
神经病学   112881篇
特种医学   51229篇
外国民族医学   281篇
外科学   192614篇
综合类   26213篇
现状与发展   4篇
一般理论   672篇
预防医学   116715篇
眼科学   29881篇
药学   99286篇
  7篇
中国医学   2229篇
肿瘤学   76682篇
  2019年   11689篇
  2018年   15651篇
  2017年   12177篇
  2016年   13330篇
  2015年   15340篇
  2014年   21101篇
  2013年   31518篇
  2012年   43708篇
  2011年   46243篇
  2010年   26450篇
  2009年   25684篇
  2008年   43389篇
  2007年   46138篇
  2006年   45575篇
  2005年   44365篇
  2004年   42126篇
  2003年   40347篇
  2002年   38790篇
  2001年   59495篇
  2000年   60501篇
  1999年   51281篇
  1998年   14804篇
  1997年   13389篇
  1996年   13831篇
  1995年   12884篇
  1994年   12033篇
  1993年   11255篇
  1992年   40439篇
  1991年   39694篇
  1990年   38425篇
  1989年   37129篇
  1988年   34390篇
  1987年   33501篇
  1986年   31950篇
  1985年   30184篇
  1984年   22957篇
  1983年   20055篇
  1982年   11852篇
  1979年   21700篇
  1978年   15848篇
  1977年   13189篇
  1976年   12173篇
  1975年   13181篇
  1974年   16000篇
  1973年   15777篇
  1972年   14927篇
  1971年   13935篇
  1970年   13101篇
  1969年   12361篇
  1968年   11541篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
141.
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   
142.
143.
This study examines the relationships between patient characteristics and surrogate decision maker characteristics on surrogates' preferences for life-sustaining treatments. Caucasian and African-American caregivers and noncaregivers (n=110) responded to a vignette involving a medical crisis in a hospitalized older man who suffered cardiac arrest, one of the most common causes of death among older Americans. This man was described as either a cognitively intact or moderately demented family member. Participants made decisions regarding cardiopulmonary resuscitation (CPR), CPR and ventilation, and CPR and tube feeding. Analyses followed a 2 (cognitive status) 2 (caregiving status) 2 (racial background) analysis of covariance design, with education and income used as covariates. In general, participants were less likely to initiate life-sustaining treatments in demented patients. Caucasian caregivers were less likely to initiate CPR and ventilation and CPR and tube feeding. Results indicate that characteristics of the patient and the interplay between cultural issues and experience with caregiving affect surrogate judgements regarding life-sustaining treatments.  相似文献   
144.
Choristomas, masses of normal tissues in aberrant locations, contain smooth muscle fibers and fibrous tissues. We describe the MR imaging features of two choristomas located in the internal auditory canals and arising from the facial and vestibulocochlear nerves. Both lesions enhanced with contrast material. In one case, enhancement was seen in the geniculate ganglion and greater superficial petrosal nerve. In the other, a medial component enhanced less than the lateral component did.  相似文献   
145.
summary The aetiology of denture stomatitis is not clear from the literature. Some studies show its aetiology as Candida albicans, while other reports point out the significance of microorganisms. In this study the existence of C. albicans and microorganisms was investigated in subjects with and without denture stomatitis. The results showed that a combination of C. albicans and microorganisms is more likely to be responsible for denture stomatitis.  相似文献   
146.
Purpose: To assess the accuracy of intraarterial measurement of transstenotic pressure gradients for the detection of hemodynamically suboptimal iliac angioplasty. Methods: In 14 patients, referred for diagnostic angiography, mean pressure gradients in the aorta and iliac artery were obtained twice, using a double-sensor pressure catheter. Additional iliac measurements were performed during pharmacologically induced flow augmentation. Repeatability was assessed by calculation of the mean difference plus standard deviation (MD ± SD) and repeatability coefficient (2 × SD). These results were extrapolated to 137 iliac angioplasty procedures with secondary stenting where there was a residual pressure gradient > 10 mmHg. Results: MD ± SD for repeated measurements at rest and during flow augmentation were 0 ± 2 mmHg and 1 ± 3 mmHg, respectively. Repeatability coefficients were 3 and 6 mmHg. Mean pressure gradients after hemodynamically insufficient angioplasty were 8 ± 7 mmHg at rest and 17 ± 5 mmHg following vasodilatation. Inaccurate pressure recordings may have led to inappropriate stent placement in less than 2.5%, and inappropriate denial of stent placement in less than 5% of the lesions. Conclusion: Variability of intraarterial pressure measurements has little consequence in the detection of hemodynamically significant stenosis after angioplasty. Received: 0/00/00/Accepted: 0/00/00  相似文献   
147.
In this paper, the authors describe some of the complexities of collecting and presenting data on race and ethnicity based on the experiences of the Bureau of the Census. Different methods of data collection, different content and format of questions, and different definitions make it difficult to collect consistent race and ethnic data across data systems. The Bureau of the Census experiences have shown that changing ethnic self-identity and concepts, intent of the question, consistency of reporting, and the classification of persons of mixed racial parentage affect the quality of the data. These are some of the issues that must be addressed as statistical agencies and researchers seek to provide comparable race and ethnic data.  相似文献   
148.
Piecewise constant incidence models were developed to estimate the force of infection in women from age-and time-specific antenatal or neonatal seroprevalence data. Differential inclusion of infected women in sero-surveys compared to uninfected women was taken into account, with respect to both changes in inclusion rate following infection, and changes in relative inclusion rate over calendar time. These models were applied to anonymous HIV seroprevalence data collected from neonates born to black and Hispanic women in New York City 1988-1992, with incidence and fertility parameters estimated by maximum likelihood. Estimates of inclusion rate parameters accorded well with what is known about the natural history of HIV. The data could not distinguish between additive and multiplicative combination of the effects of age and time on incidence. Incidence was strongly dependent on age with the highest incidence in women aged 20-34 years. There was strong evidence that incidence had been falling in Hispanic women since 1982-1984. The results illustrate the extent to which trends in incidence over time may be confounded by changes in the relative inclusion rate of infected and uninfected women.  相似文献   
149.
150.
Oxygen-sensitive F-19 magnetic resonance imaging of perfluorocarbon compounds requires that fluorocarbon T1 changes correlate with the local Po2 and not with the composition of the surrounding aqueous phase. The influence of various bioconstituents and paramagnetic ions within the aqueous phase on the F-19 fluorocarbon phase T1 for PFC emulsions was evaluated at 0.14 and 0.66 T. T1 was measured for FC-43, perflubron, and a fluorinated surfactant. Controlled variables introduced in the aqueous phase included annex solution constituents, blood, pH changes, and Gd-DTPA. For a constant Po2, the F-19 T1s were independent of the emulsion constituents, blood concentration, and pH. For FC-43 and perflubron, F-19 T1 was independent of the Gd-DTPA concentration, while the aqueous phase T1 decreased by more than an order of magnitude. XMO-10 (smallest emulsion particle size) showed a slight decrease in F-19 T1 with increasing Gd-DTPA concentration at 0.66 T.  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