首页 | 官方网站   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   12278篇
  免费   917篇
  国内免费   6篇
医药卫生   13201篇
  2021年   134篇
  2020年   104篇
  2019年   132篇
  2018年   191篇
  2017年   123篇
  2016年   152篇
  2015年   138篇
  2014年   226篇
  2013年   342篇
  2012年   476篇
  2011年   496篇
  2010年   247篇
  2009年   269篇
  2008年   417篇
  2007年   480篇
  2006年   490篇
  2005年   428篇
  2004年   428篇
  2003年   394篇
  2002年   434篇
  2001年   421篇
  2000年   417篇
  1999年   342篇
  1998年   135篇
  1997年   110篇
  1996年   103篇
  1995年   118篇
  1994年   119篇
  1992年   365篇
  1991年   374篇
  1990年   365篇
  1989年   311篇
  1988年   325篇
  1987年   338篇
  1986年   308篇
  1985年   287篇
  1984年   187篇
  1983年   185篇
  1982年   115篇
  1981年   111篇
  1980年   95篇
  1979年   197篇
  1978年   173篇
  1977年   122篇
  1976年   100篇
  1975年   116篇
  1974年   125篇
  1973年   124篇
  1972年   111篇
  1971年   99篇
排序方式: 共有10000条查询结果,搜索用时 187 毫秒
11.
12.
Background  Stress gated myocardial perfusion single photon emission computed tomography (gSPECT) is increasingly used before and after intercurrent therapeutic intervention and is the basis for ongoing evaluation in the Department of Veterans Affairs clinical outcomes utilizing revascularization and aggressive drug evaluation (COURAGE) trial. Methods and Results  The COURAGE trial is a North American multicenter randomized clinical trial that enrolled 2287 patients to aggressive medical therapy vs percutaneous coronary intervention plus aggressive medical therapy. Three COURAGE nuclear substudies have been designed. The goals of substudy 0 are to examine the diagnostic accuracy of the extent and severity of inducible ischemia at baseline in COURAGE patients compared with patient symptoms and quantitative coronary angiography and to explore the relationship between inducible ischemia and the benefit from revascularization when added to medical therapy. Substudy 1 will correlate the extent and severity of provocative ischemia with the frequency, quality, and instability of recurrent symptoms in postcatheterization patients. Substudy 2 (n _ 300) will examine the usefulness of sequential gSPECT monitoring 6 to 18 months after therapeutic intervention. Together, these nuclear substudies will evaluate the role of gSPECT to determine the effectiveness of aggressive risk-factor modifications, lifestyle interventions, and anti-ischemic medical therapies with or without revascularization in reducing patients’ ischemic burdens. Conclusions  The unfolding of evidence on the application of gSPECT in trials such as COURAGE defines a new era for nuclear cardiology. We hope the evidence that emerges from the COURAGE trial will further establish the role of nuclear imaging in the evidence-based management of patients with stable coronary disease. The COURAGE trial was supported by the Cooperative Studies Program of the Department of Veterans Affairs Office of Research and Development in collaboration with the Canadian Institutes of Health Research. Unrestricted research grants were obtained from Merck & Co; Pfizer Pharmaceuticals; Bristol-Myers Squibb Medical Imaging; Astellas Pharma; Kos Pharmaceuticals; Data Scope; Astra Zeneca Pharmaceuticals; Astra-Zeneca-Canada; Schering-Plough Coorporation, Ltd; Sanofi-Aventis, Inc; First Horizon; and GE Healthcare. All industrial funding for this trial was directed through the Department of Veterans Affairs. Additional funding for this substudy was provided by grants to the Department of Veterans Affairs and Canadian Institutes of Health Research from Astellas Pharma and Bristol-Myers-Squibb Medical Imaging.  相似文献   
13.
14.
A case of tumoral calcinosis simulating osteomyelitis and associated with bunion formation in a 20-year-old female is presented. The most striking findings in this patient were the soft tissue calcifications. There was no evidence of any of the known causes of heterotopic calcifications. This kind of simulation between tumoral calcinosis bunion formation and osteomyelitis has not been previously described.  相似文献   
15.
Two experiments examined the ingestive responses of streptozotocin-diabetic rats fed low-fat or high-fat diets to glucose, fructose, sucrose and maltose solutions in brief (30 min) intake tests. In Experiment 1, one-bottle acceptability tests were used whereas two-bottle preference tests were used in Experiment 2. Three main findings resulted from these studies. Firstly, diabetic rats fed the low-fat diet displayed a reduced acceptance of and preference for all concentrated sugar solutions. Secondly, glucose consumption patterns of diabetic rats fed the low-fat diet were distinctly different from their responses to the other sugars. Thirdly feeding high-fat diets, either high or low in carbohydrate, normalized the responses of diabetic rats to the sugar solutions. The results suggest that feeding high-fat diets to diabetic rats normalizes their responses to sugar solutions because of reductions in hunger and thirst associated with the provision of a utilizable source of calories and an improvement in body fluid balance.  相似文献   
16.
17.
Killer lymphocytes play a major role in host defense against tumors and infectious diseases. Previously, we reported that delta-9-tetrahydrocannabinol (THC) and II-hydroxy-delta-9-tetrahydrocannabinol (II-hydroxy-THC) suppressed the cytolytic activity of cultured natural killer (NK) cells. Also, we showed that the drugs appeared to be affecting a stage in the killing process subsequent to the binding of the killer cell to the target cell. In the present report, we have extended these studies to an examination of the effect of cannabinoids on the activity of cytotoxic T lymphocytes (CTLs). The cytolytic activity of CTLs generated by cocultivation with either allospecific stimulators or TNP-modified-self stimulators were suppressed by both THC and II-hydroxy-THC treatment. Allospecific CTLs generated in vivo were also inhibited by an in vitro exposure to either THC or II-hydroxy-THC, and the sensitivity of these cells to drug effects appeared to be greater than the sensitivity of the in vitro generated CTLs. Suppression of cytolytic function by THC and II-hydroxy-THC was maximal after a 4-h drug treatment, suggesting that the drug effects were inducible and therefore required a finite period of time to develop maximally. As seen in previous studies involving NK cells, drug treatment of mature CTLs appears to have little effect on the binding capacity of these cells for the target. However, the maximal killing capacity of the cells and the frequency of CTLs were significantly reduced by drug treatment. In addition to suppressing the cytolytic activity of mature effector CTLs, we also show that drug treatment inhibits both the proliferation of lymphocytes responding to an allogeneic stimulus and the maturation of these lymphocytes to mature CTLs. Similarly, CTL activity developing in vivo could be inhibited by THC injection. These results suggest that CTLs are inhibited by cannabinoids by at least two mechanisms. First, the cytolytic activity of mature killers is suppressed at some point beyond the binding to the target cell. Second, the cannabinoids appear to suppress the normal development of these mature effector cells from less mature precursor cells.  相似文献   
18.
This case report illustrates the magnetic resonance imaging (MRI) appearance of a typically asymptomatic renal oncocytoma as a homogeneous mass of medium signal with a stellate central region of decreased signal, representing the central scar. The MRI was correlated with computed tomography (CT), ultrasound (US), and gross pathologic appearance. The appearance of a central scar is not specific for oncocytoma and does not exclude renal cell carcinoma, as illustrated by a second case.  相似文献   
19.
20.
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-23

京公网安备 11010802026262号