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   19050篇
  免费   2183篇
  国内免费   54篇
耳鼻咽喉   302篇
儿科学   785篇
妇产科学   513篇
基础医学   2747篇
口腔科学   586篇
临床医学   2366篇
内科学   3724篇
皮肤病学   205篇
神经病学   1093篇
特种医学   770篇
外科学   2685篇
综合类   519篇
一般理论   18篇
预防医学   1997篇
眼科学   388篇
药学   1414篇
中国医学   87篇
肿瘤学   1088篇
  2021年   274篇
  2019年   218篇
  2018年   305篇
  2017年   224篇
  2016年   248篇
  2015年   255篇
  2014年   427篇
  2013年   598篇
  2012年   888篇
  2011年   930篇
  2010年   484篇
  2009年   401篇
  2008年   788篇
  2007年   856篇
  2006年   831篇
  2005年   827篇
  2004年   735篇
  2003年   718篇
  2002年   639篇
  2001年   644篇
  2000年   601篇
  1999年   600篇
  1998年   239篇
  1997年   261篇
  1996年   251篇
  1995年   211篇
  1994年   202篇
  1993年   169篇
  1992年   463篇
  1991年   439篇
  1990年   406篇
  1989年   391篇
  1988年   392篇
  1987年   367篇
  1986年   375篇
  1985年   364篇
  1984年   275篇
  1983年   251篇
  1982年   185篇
  1981年   182篇
  1979年   258篇
  1978年   217篇
  1977年   186篇
  1976年   166篇
  1975年   164篇
  1974年   193篇
  1973年   213篇
  1972年   168篇
  1971年   161篇
  1970年   160篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
22.
23.

Background  

There are few effective strategies reported for the primary prevention of low back pain (LBP). Core stabilization exercises targeting the deep abdominal and trunk musculature and psychosocial education programs addressing patient beliefs and coping styles represent the current best evidence for secondary prevention of low back pain. However, these programs have not been widely tested to determine if they are effective at preventing the primary onset and/or severity of LBP. The purpose of this cluster randomized clinical trial is to determine if a combined core stabilization exercise and education program is effective in preventing the onset and/or severity of LBP. The effect of the combined program will be compared to three other standard programs.  相似文献   
24.
25.
Memory performance of elderly patients in the early stages of Alzheimer's disease (DAT) was compared with that of elderly control subjects. In explicit tests of recognition memory, which involve conscious recollection, the DAT patients were grossly impaired. In implicit tests of anagram solution and wordstem completion, which do not require conscious recollection, the DAT patients were not impaired. These findings further support the idea that a separate memory system, episodic memory, underlies conscious recollection, that it is this system which is most commonly damaged in amnesia, and that memory systems not involving conscious recollection may be spared in the early stages of Alzheimer's disease.  相似文献   
26.
We report a case of multiple endocrine neoplasia type I and hypernephroma. Parathyroid hyperplasia, adrenocortical hyperplasia, a nodular goiter, multiple lipomas, a chromophobe adenoma of the pituitary and hypernephroma had all been diagnosed previously. All but the last are features consistent with the diagnosis of multiple endocrine neoplasia type I (Wermer's syndrome). The association of multiple endocrine neoplasia type I and hypernephroma may represent a new manifestation of this pleiotropic syndrome.  相似文献   
27.
New indole alkaloid glycosides from Nauclea orientalis   总被引:4,自引:0,他引:4  
Two new indole alkaloid glycosides, 10-hydroxystrictosamide and 6'-O-acetylstrictosamide, as well as the known alkaloids strictosamide and vincosamide were isolated from the leaves of Nauclea orientalis L. The structures of the isolated compounds were determined using spectroscopic methods, mainly 1D- and 2D-NMR spectroscopy.  相似文献   
28.
CAM 4515 and CAM 4750 are new nonpeptide tachykinin NK1 receptor antagonists with different lipophilicities. Two separate, simple, and sensitive HPLC methods for the quantitation of these two compounds in plasma and the evaluation of their oral bioavailability in rats were developed and validated. Extraction of CAM 4515 from plasma involved protein precipitation with acetonitrile, while that for CAM 4750 involved a one-step liquid-liquid extraction with methylene chloride. The analytes in extracts were chromatographed on a C18 column using two different separation buffers, 47% 0.02 M sodium citrate (pH 3.5)-53% acetonitrile for CAM 4515 and 59% 0.02 M potassium phosphate dibasic (pH 7.0)-41% acetonitrile for CAM 4750, and both compounds were detected by fluorescence (excitation 278 nm; emission 342 nm). Stability profiles of both drugs at −20°C or room temperature in plasma and in reconstituted buffers were good. The limit of quantitation for both drugs was 5 ng ml−1 with good linearity from 5 to 1000 ng ml−1 using 100–200 μl of plasma. Excellent precision (relative standard deviation < 8.3%) and accuracy (relative error ± 9.2%) were observed for both CAM 4515 and CAM 4750. Oral bioavailability studies were conducted for each compound in rats receiving a p.o. dose of 20 mg kg−1 and an i.v. dose of 5 mg kg−1. The absolute oral bioavailability of CAM 4750 (80%) was estimated to be 40-fold greater than that of CAM 4515 (2%). The experimental results suggest that incorporation of a pyridine group into the structural backbone may greatly improve bioavailability.  相似文献   
29.
30.
Intrafamilial variation of the phenotype in Bardet-Biedl syndrome   总被引:3,自引:0,他引:3       下载免费PDF全文
AIMS—To describe the variation of the phenotype within families with several individuals with Bardet-Biedl syndrome.
METHODS—The phenotypes of affected siblings in 11 Scandinavian families were compared with two or more members who had at least three of the features: retinal dystrophy, polydactyly, obesity, hypogenitalism, and mental retardation. Individuals without retinal dystrophy were excluded.
RESULTS—Intrafamilial variation of expressivity of the features obesity, polydactyly, abnormal radiograms of the extremities, hypogenitalism, short stature, paraplegia, and dental abnormalities was found. The retinal dystrophy varied with respect to both the onset of symptoms and the course of the disease. The morphology of the fundus, however, was consistent within the families. The disorder showed statistically significant genetic linkage to the BBS4 locus on chromosome 15 in the affected siblings in two of the families, but the clinical features in these patients did not differ from the other cases of Bardet-Biedl syndrome.
CONCLUSION—Comparison of siblings with the Bardet-Biedl syndrome showed variation of the typical features. In addition, the course of retinal dystrophy varied. No distinctive clinical features were found to separate the BBS4 phenotype from the remaining patients.

  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