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   2022篇
  免费   140篇
  国内免费   2篇
耳鼻咽喉   17篇
儿科学   32篇
妇产科学   63篇
基础医学   338篇
口腔科学   21篇
临床医学   253篇
内科学   305篇
皮肤病学   27篇
神经病学   164篇
特种医学   81篇
外科学   235篇
综合类   17篇
一般理论   1篇
预防医学   261篇
眼科学   16篇
药学   134篇
肿瘤学   199篇
  2021年   25篇
  2020年   21篇
  2019年   25篇
  2018年   41篇
  2017年   35篇
  2016年   29篇
  2015年   39篇
  2014年   29篇
  2013年   50篇
  2012年   88篇
  2011年   114篇
  2010年   58篇
  2009年   41篇
  2008年   94篇
  2007年   75篇
  2006年   99篇
  2005年   83篇
  2004年   98篇
  2003年   88篇
  2002年   101篇
  2001年   42篇
  2000年   40篇
  1999年   46篇
  1997年   19篇
  1992年   21篇
  1991年   25篇
  1990年   39篇
  1989年   29篇
  1988年   21篇
  1987年   40篇
  1986年   27篇
  1985年   25篇
  1984年   29篇
  1983年   37篇
  1982年   20篇
  1981年   19篇
  1980年   14篇
  1979年   42篇
  1978年   26篇
  1977年   27篇
  1976年   19篇
  1975年   25篇
  1974年   29篇
  1973年   20篇
  1972年   33篇
  1971年   19篇
  1970年   19篇
  1969年   14篇
  1968年   16篇
  1967年   21篇
排序方式: 共有2164条查询结果,搜索用时 375 毫秒
1.
Unemployment causes ill health: the wrong track   总被引:1,自引:0,他引:1  
It is not unemployment per se that causes ill health. It can be a very desirable state. There are no diseases specific to unemployment. Contrast this with employment. Unemployment shares with all other socio-environmental situations risk of exposure to common physical, social and psychological stressors that predispose to disease. Focus for action and research should be on reducing such stressors and not on provision of full employment. The former is likely to be possible and beneficial. The latter is likely to be impossible and carries a risk of making matters worse. As an immediate first step, that will reduce 'cratogenic' disease, people in authority should stop misleading the public into believing that unemployment is the cause of ill health.  相似文献   
2.
Background BMS-747158-02 is a novel fluorine 18-labeled pyridazinone derivative designed for cardiac imaging. The uptake and retention mechanisms of F-18 BMS-747158-02 in cardiac myocytes were studied in vitro, and the biodistribution of F-18 BMS-747158-02 was studied in vivo in mice. Methods and Results Fluorine 19 BMS-747158-01 inhibited mitochondrial complex I (MC-I) in bovine heart submitochondrial particles with an IC50 of 16.6±3 nmol/L that was comparable to the reference inhibitors of MC-1, rotenone, pyridaben, and deguelin (IC50 of 18.2±6.7 nmol/L, 19.8±2.6 nmol/L, and 23.1±1.5 nmol/L, respectively). F-18 BMS-747158-02 had high uptake in monolayers of neonatal rat cardiomyocytes (10.3%±0.7% of incubated drug at 60 minutes) that was inhibited by 200 nmol/L of rotenone (91%±2%) and deguelin (89%±3%). In contrast, an inactive pyridaben analog, P-0 (IC50 value>4 μmol/L in MC-1 assay), did not inhibit the binding of F-18 BMS-747158-02 in cardiomyocytes. Uptake and washout kinetics for F-18 BMS-747158-02 in rat cardiomyocytes indicated that the time to half-maximal (t1/2) uptake was very rapid (approximately 35 seconds), and washout t1/2 for efflux of F-18 BMS-747158-02 was greater than 120 minutes. In vivo biodistribution studies in mice showed that F-18 BMS-747158-02 had substatial myocardial uptake (9.5%±0.5% of injected dose per gram) at 60 minutes and heart-to-lung and heart-to-liver ratios of 14.1±2.5 and 8.3±0.5, respectively. Positron emission tomography imaging in the mouse allowed clear cardiac visualization and demonstrated sustained myocardial uptake through 55 minutes. Conclusions F-18 BMS-747158-02 is a novel positron emission tomography cardiac tracer targeting MC-I in cardiomyocytes with rapid uptake and slow washout. These characteristics allow fast and sustained accumulation in the heart.  相似文献   
3.
4.
Migration and proliferation of vascular smooth muscle cells are early and major events in the formation of atherosclerotic lesions. We report on an aorta transplant model in rabbits wherein myointimal proliferation is inhibited by 17-beta-estradiol. The abdominal aortas of outbred white New Zealand rabbits were harvested and allografted to the carotid artery of the recipient. The animals, which were fed either a normal or a high-cholesterol (0.5%) diet, were killed 3 weeks later. The degree of myointimal proliferation was measured with a digitized system attached to a light microscope. The myointimal hyperplasia was expressed as the cross section area of the intima/the area of the intima + the area of the media x 100. Transmission electron micrographs were obtained for all vessels. Intimal thickening was shown mainly to consist of proliferating smooth muscle cells. The cholesterol diet resulted in significantly higher serum total cholesterol levels compared to animals on a normal diet (p < 0.0001) but did not affect serum high-density lipoprotein-cholesterol or serum triglyceride levels. The cholesterol diet was also associated with a greater but not significant amount of intimal thickening. Treatment with 17-beta-estradiol significantly decreased both serum triglyceride concentration (p < 0.05) and myointimal thickening (p < 0.01) in cholesterol-fed animals. Transmission electron microscopy showed that the endothelial cells appeared structurally normal in the estradiol-treated animals. Further, estradiol prevented the appearance of vacuolized macrophages. Thus estradiol may decrease myointimal thickening by preserving the endothelium and preventing macrophage appearance in the intima.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   
5.
6.
The development and maintenance of the normal functional integrity of the mammalian central nervous system is under the influence of a number of growth and trophic factors. One such growth factor, epidermal growth factor, has been detected in the mammalian brain and found to be associated with various brain regions and cell types. This small ubiquitous polypeptide can influence the proliferation, Metabolism, and differentiation of both glia and neurons in the central nervous system. We discuss the effects of epidermal growth factor on glial and neuronal cell function in an attempt to understand its role in development and maintenance of normal brain integrity. In addition, we review its possible implications in several pathological states in the central nervous system and speculate on therapeutic applications for this growth factor. © 1992 Wiley-Liss, Inc.  相似文献   
7.
8.
OBJECTIVE: To examine in monochorionic pregnancies the possible value of intertwin discordance in nuchal translucency (NT) thickness in the prediction of early fetal death or severe twin-twin transfusion syndrome (TTTS). METHODS: In 512 monochorionic twin pregnancies NT was measured at 11 to 13 + 6 weeks' gestation and regression analysis was used to determine the significance of the association between the intertwin discordance in NT and subsequent early fetal death or development of severe TTTS requiring endoscopic laser surgery. RESULTS: In 412 (80.5%) pregnancies there was a normal outcome, in 58 (11.3%) there was severe TTTS requiring endoscopic laser surgery at 18-24 weeks, in 19 (3.7%) there was death of one or both fetuses at 13-18 weeks and in 23 (4.5%) there was fetal death at 21-38 weeks. In the four outcome groups the median discordance in NT was 11%, 22%, 35% and 7%, respectively. Significant prediction of early fetal death and severe TTTS was provided by the discordance in fetal NT, which was not significantly improved by including the discordance in crown-rump length. If the discordance in NT was 20% or more, the false positive rate was 20%, the detection rate of early fetal death was 63% and the detection rate of severe TTTS was 52%. CONCLUSIONS: Discordance in NT of 20% or more is found in about 25% of monochorionic twins and in this group the risk of early fetal death or development of severe TTTS is more than 30%. If the discordance is less than 20% the risk of complications is less than 10%.  相似文献   
9.
Institute of Cytology, Academy of Sciences of the USSR. I. M. Sechenov Institute of Evolutionary Physiology and Biochemistry, Academy of Sciences of the USSR, Leningrad. Institute of Physiology, Bulgarian Academy of Sciences, Sofia. (Presented by Academician of the Academy of Medical Sciences of the USSR Yu. A. Vladimirov.) Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny, Vol. 108, No. 8, pp. 160–171, August, 1989.  相似文献   
10.
Two hundred forty-eight human immunodeficiency virus (HIV)-positive and 496 HIV-negative subjects in Uganda were tested by HerpeSelect herpes simplex virus type 2 enzyme-linked immunosorbent assay (ELISA) and Western blotting to optimize the ELISA for use in this population. A higher index cutoff value was required for optimal sensitivity and specificity, and overall performance of the assay was not affected by HIV status.  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