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   86670篇
  免费   6675篇
  国内免费   273篇
耳鼻咽喉   961篇
儿科学   2211篇
妇产科学   1288篇
基础医学   11872篇
口腔科学   946篇
临床医学   9392篇
内科学   18521篇
皮肤病学   966篇
神经病学   8330篇
特种医学   3367篇
外科学   13776篇
综合类   1092篇
一般理论   93篇
预防医学   6824篇
眼科学   2010篇
药学   5888篇
中国医学   95篇
肿瘤学   5986篇
  2023年   694篇
  2022年   1071篇
  2021年   2502篇
  2020年   1430篇
  2019年   2303篇
  2018年   2644篇
  2017年   1910篇
  2016年   1976篇
  2015年   2324篇
  2014年   3368篇
  2013年   4300篇
  2012年   6866篇
  2011年   7144篇
  2010年   3881篇
  2009年   3399篇
  2008年   5721篇
  2007年   5877篇
  2006年   5473篇
  2005年   5414篇
  2004年   4950篇
  2003年   4545篇
  2002年   4117篇
  2001年   889篇
  2000年   667篇
  1999年   819篇
  1998年   875篇
  1997年   667篇
  1996年   561篇
  1995年   508篇
  1994年   472篇
  1993年   458篇
  1992年   456篇
  1991年   394篇
  1990年   386篇
  1989年   321篇
  1988年   300篇
  1987年   264篇
  1986年   273篇
  1985年   275篇
  1984年   294篇
  1983年   234篇
  1982年   297篇
  1981年   279篇
  1980年   198篇
  1979年   174篇
  1978年   173篇
  1977年   147篇
  1976年   111篇
  1975年   101篇
  1974年   116篇
排序方式: 共有10000条查询结果,搜索用时 27 毫秒
111.
112.
In this study, the effect of combining anti-CD4 monoclonal antibody (mAb) and cyclosporin (CyA) therapy at the time of transplantation was examined. A mouse cardiac allograft model was used. Anti-CD4 mAb administered perioperatively induces long-term survival. The addition of a short course of CyA given subcutaneously in a regimen of either a high-dose treatment or a standard dose treatment to the anti-CD4 mAb treatment protocol did not have a detrimental effect on graft survival. Despite having no significant effect on graft survival, the addition of CyA to the treatment protocol did result in a significant decrease in the level of IL-2 present in the hearts 7 days after transplantation. The decrease in IL-2 production was directly related to the presence of CyA in vivo. When CyA treatment was continued throughout the period during which unresponsiveness to the graft is induced by anti-CD4 mAb therapy, 50 % of the grafted hearts were rejected once the CyA was discontinued. In conclusion, the combined use of anti-CD4 mAb therapy and CyA did not have a negative effect on graft survival in this model when the two agents were used concurrently at the time of transplantation. Received: 2 October 1996 Received after revision: 31 January 1997 Accepted: 5 February 1997  相似文献   
113.
114.
115.
Extensive search of the literature reveals the extreme rarity of true diverticulum of the gallbladder. Its frequency varies from 0.0008% of all resected gallbladders at the Mayo Clinic to 0.06% of a series of congenital anomalies of the gallbladder collected from the world literature. We are presenting a case of a true diverticulum of the gallbladder with sonographic demonstration and focal malignant alterations, neither one of which has been reported previously. The difference between true and false diverticula of the gallbladder is discussed.  相似文献   
116.
The effects of N-methyl-D-aspartic acid (NMDA) and phencyclidine (PCP) on extracellular levels of dopamine (DA) and dihydroxyphenylacetic acid (DOPAC) in the striatum of the rat were studied using in vivo microdialysis. Intrastriatal infusion of NMDA produced a significant dose-dependent increase in extracellular DA and a decrease in concentrations of DOPAC. Whereas both 2-amino-5-phosphonovalerate (APV) and PCP antagonized the NMDA-induced increase in extracellular levels of DA, the effect on NMDA-induced changes in extracellular concentrations of DOPAC were different for the two compounds. The APV significantly attenuated the decrease in extracellular DOPAC produced by smaller concentrations of NMDA, whereas PCP did not prevent decrease in DOPAC produced by any concentrations of NMDA. Phencyclidine alone produced a dose-dependent increase in extracellular DA but had no effect on the extracellular concentration of DOPAC. This study demonstrated that PCP, at concentrations which did not produce an increase in extracellular DA, antagonized the effect of the NMDA on DA. The data also indicated that both APV and PCP antagonized the NMDA-evoked release of DA over a range of concentrations of NMDA, even though they did so by different mechanisms.  相似文献   
117.
Study Objective . To determine the efficacy of high-dose ascorbate supplementation in lowering lipoprotein(a) [Lp(a)] levels in patients with premature coronary heart disease (CHD). Design . Randomized, double-blind, placebo-controlled trial. Setting . Outpatient clinic. Patients . Forty-four patients with documented premature CHD. defined as confirmed myocardial infarction and/or angiographically determined stenosis of 50% or greater in at least one major coronary artery before age 60 years. Interventions . Patients were block randomized on the basis of age, gender, and screening Lp(a) concentrations to receive ascorbate 4.5 g/day or placebo for 12 weeks. Measurements and Main Results . High-dose ascorbate was well tolerated and produced a marked elevation in mean plasma ascorbate levels (+1.2 mg/dl; p<0.001). Multiple linear regression analysis revealed no significant effect of supplementation on postintervention Lp(a) levels (p=0.39) in a model that included treatment group assignment, and baseline Lp(a) levels. Conclusions . Our findings do not support a clinically important lowering effect of high-dose ascorbate on plasma Lp(a) in patients with premature CHD.  相似文献   
118.
This paper introduces a design methodology for a dynamic compensator that simultaneously minimizes the upper bound of a quadratic performance index and the H-norm of a disturbance transfer function matrix of a multiple-input/multiple-output system whose model contains parameter uncertainty in the state and input matrices. The real parameter uncertainty is modelled as additional measurement outputs and as additional weights on the existing noise inputs and measurement outputs of the system. The compensator equations are derived by taking the dual of a system with parameter variation in the state and output matrices, for which the compensator equations have previously been derived, and then taking the dual of the compensator equations. An algorithm for applying this theory is given and an example is shown.  相似文献   
119.
Due to recent public debate and newly imposed resident work hour restrictions, we decided to investigate the relationship of resident call status to their ambulatory patients' satisfaction. Resident continuity clinic patients were asked to rate their level of satisfaction on a 10-point Likert-type scale. Using multiple regression approaches, these data were then assessed as a function of resident call status. We found that in 646 patient encounters, patient satisfaction scores were significantly less when the resident was postcall, 8.99 ± 1.8, than when not postcall, 9.31 ± 1.3. We herein discuss etiologies and implications of these findings for both patient care and medical education.  相似文献   
120.
Groin complications remain the most common complication of cardiac catheterization procedures. While the use of closure devices is increasing for arterial sheaths, venous sheaths tend to be removed and hemostasis achieved with manual compression. We report our experience using Perclose suture-mediated vascular closure device to achieve hemostasis and early mobility in patients who have had venous access as part of their procedure. There were a total of 42 patients (21 males; average age, 63.5 years) studied. The majority of the patients had 7 Fr sheaths (24), with access sites of sheaths up to 14 Fr being closed with this technique. Two patients developed complications at the access site: one patient requiring rehospitalization for intravenous antibiotics because of late access site infection, and one patient with deep venous thrombosis and pulmonary emboli. We conclude that the use of the Perclose suture-mediated closure device for closure of femoral venous access sites is feasible and should be considered especially in patients with larger venous sheaths and those at increased risk of groin complications.  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