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   1684102篇
  免费   115828篇
  国内免费   2017篇
耳鼻咽喉   21877篇
儿科学   54995篇
妇产科学   45120篇
基础医学   260262篇
口腔科学   45039篇
临床医学   155507篇
内科学   321827篇
皮肤病学   36852篇
神经病学   129288篇
特种医学   62801篇
外国民族医学   316篇
外科学   241649篇
综合类   32251篇
现状与发展   4篇
一般理论   661篇
预防医学   135956篇
眼科学   37798篇
药学   125245篇
  7篇
中国医学   2964篇
肿瘤学   91528篇
  2018年   17852篇
  2017年   13501篇
  2016年   14997篇
  2015年   17204篇
  2014年   23522篇
  2013年   35775篇
  2012年   49753篇
  2011年   53579篇
  2010年   30989篇
  2009年   29267篇
  2008年   50003篇
  2007年   54062篇
  2006年   53336篇
  2005年   51836篇
  2004年   50109篇
  2003年   48097篇
  2002年   46676篇
  2001年   72867篇
  2000年   74392篇
  1999年   62506篇
  1998年   17553篇
  1997年   15617篇
  1996年   16065篇
  1995年   15165篇
  1994年   13961篇
  1992年   49274篇
  1991年   49886篇
  1990年   48784篇
  1989年   47414篇
  1988年   43853篇
  1987年   43278篇
  1986年   40949篇
  1985年   38863篇
  1984年   29446篇
  1983年   25624篇
  1982年   14722篇
  1981年   13395篇
  1979年   28179篇
  1978年   20518篇
  1977年   16993篇
  1976年   16415篇
  1975年   18292篇
  1974年   21734篇
  1973年   21348篇
  1972年   19999篇
  1971年   18823篇
  1970年   17738篇
  1969年   16588篇
  1968年   15585篇
  1967年   13918篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
161.
Levels of the soluble form of the triggering receptor expressed on myeloid cells (sTREM)-1 are elevated in severe sepsis. However, it is not known whether sTREM-1 measurements can distinguish milder bacterial infections from noninfectious inflammation. The present authors studied whether serum sTREM-1 levels differ in community-acquired pneumonia, exacerbations of chronic obstructive pulmonary disease (COPD), asthma and controls, and whether sTREM-1 may be used as a surrogate marker for the need for antibiotics. Serum sTREM-1 levels in 150 patients with pneumonia, COPD and asthma exacerbations and 62 healthy controls were measured. Serum sTREM-1 levels were significantly elevated in pneumonia (median 295.2 ng x mL(-1)), COPD (280.3 ng x mL(-1)) and asthma exacerbations (184.0 ng x mL(-1)) compared with controls (83.1 ng x mL(-1)). Levels were higher in pneumonia and Anthonisen type 1 COPD exacerbations than in type 2 and 3 COPD and asthma exacerbations. The area under the receiver operating characteristics curve for sTREM-1 as a surrogate marker for the need for antibiotics was 0.77. Serum levels of the soluble form of the triggering receptor expressed on myeloid cells-1 were elevated predominantly in pneumonia and Anthonisen type 1 COPD exacerbations versus type 2 and 3 chronic obstructive pulmonary disease exacerbations, asthma and controls. Serum levels of the soluble form of the triggering receptor expressed on myeloid cells-1 has moderate but insufficient accuracy as a surrogate marker for the need for antibiotics in lower respiratory tract infections.  相似文献   
162.
163.
Choledochojejunostomy (CJS) is commonly used for biliary reconstruction in liver transplantation for primary sclerosing cholangitis (PSC). We alternatively performed choledochoduodenostomy (CDS) and side-to-side choledochodocholedochstomy in a large cohort of patients. Fifty-one patients with PSC, transplanted between 1988 and 2000, were analyzed retrospectively. Biliary reconstruction was CDS in 25 (49%), CJS in 20 (39%) and CC in 6 transplantations (12%). Biliary leaks occurred in the early follow-up (< or =41 days) only in CDS patients (20%). However, in the late follow-up (>4 months), stricturing of anastomosis was found once in CDS (4%) and CJS (5%). Later (>9 months), intrahepatic bile duct strictures were diagnosed in four CDS (16%), one CJS (5%) and one CC (17%) patient(s). In 48% of CDS (12/25), 60% of CJS (12/20) and 17% of CC (1/6) at least one incidence of cholangitis was observed. Overall, biliary complication rates were significantly higher in CDS (40%) than CJS (10%) and CC (17%); of those none in CC and 12% in CDS were anastomosis-related. Graft/patient survival showed no significant differences among groups. Based on our results we consider CJS the standard method for biliary reconstruction in PSC; however, in selected cases where CJS is difficult to accomplish because of previous surgery or for retransplantation, CDS may present an alternative technique.  相似文献   
164.
Sugar and tooth decays are bound closely. The mechanisms of destruction of the tooth from the glycolyse are known. The role played by the food in the development of the caries is unique. Foods sweetened of all ways, rich in sucrose are responsible of the intervening of the carious lesions. The transformation of the fermentable sugars in lactic with the absence of hygiene and the action conjugated of the bacteria leads to tooth decays in temporary and permanent denture that evolve very quickly in the absence of treatment. Reasons for which the authors put in evidence in this survey, the influence of the food sweetened on the teeth at the children while showing the cases of caries and its complications due to the excessive consumption of fermentable hydrates of carbon.  相似文献   
165.
166.
Aim:To investigate the clinical characteristics of patients with Peyronie's disease(PD)and diabetes mellitus(DM).Methods:During an 8-year period,a total of 307 men seen at our outpatient clinic were diagnosed with PD.Clinicalcharacteristics,penile deformities and the erectile status of patients with PD and DM together(n=102)were retro-spectively analyzed and compared to patients with PD alone with no risk factors for systemic vascular diseases(n=97).Results:The prevalence of PD among men with DM and sexual dysfunction was 10.7%.The mean ageof diabetic patients with PD was(55.9±8.9)years;in the no risk factor group it was(48.5±9.0)years(P<0.05).The median duration of DM was 5 years.The majority of diabetic patients with PD(56.0%)presented in the chronicphase(P<0.05),and they were more likely to have a severe penile deformity(>60°)than the no risk factor group(P<0.05).In the diabetic group,the most common presenting symptom was penile curvature(81.4 %),followedby a palpable nodule on the shaft of the penis(22.5%)and penile pain with erection(14.7 %).A total of 19.6 % ofpatients were not aware of their penile deformities in the diabetic group.Erectile function,provided by history and inresponse to intracavernosal injection and a stimulation test,was significantly diminished in patients with PD and DM(P<0.05).Conclusion:DM probably exaggerates the fibrotic process in PD.Diabetic patients with PD have ahigher risk of severe deformity and erectile dysfunction(ED).PD seems to be a silent consequence of DM andshould be actively sought in diabetic men.(Asian J Androl 2006 Jan;8:75-79)  相似文献   
167.
168.
The typical empirical study in health services and outcomes research is aimed at estimating the causal effect that an exogenously imposed condition (e.g. a policy mandate) will have (or has had) on a specified outcome of interest. Controlling for unobservable confounding influences is of primary importance in such analyses. The instrumental variables (IV) method has been widely used for this purpose in the linear regression context. The present paper examines the pros and cons of alternative versions of the generalized method of moments (GMM) [of which the IV estimator is a special case] for the estimation of policy effects when endogeneity is present in a nonlinear regression setting. We show that conventional GMM is difficult to implement for policy analysis because it does not typically accommodate symmetry—similar treatment of both observable and unobservable confounders in the regression specification. Although, simple additive (nonsymmetric) regression specifications afford practical GMM estimators, they are difficult to defend from both intuitive and conceptual standpoints. Moreover, as we show via simulation, if symmetry is ignored and conventional GMM is applied based on an incorrectly specified non-symmetric model, then policy analytic estimates can be seriously biased. As a result, prospects for the development and application of intuitive consistent GMM-based policy effect estimators are dim. The problem stems from the reasonable desire on the part of the researcher to derive GMM estimators in the nonlinear framework that are based solely upon the conventional minimalist linear IV assumptions. We show, in the context of our formulation of a simple but consistent alternative to GMM in the probit case, that intuitively appealing additional assumptions about the data generating process of the policy variable will often be sufficient for the development of desirable alternatives to the GMM.  相似文献   
169.
BACKGROUND: The aim of this study was to estimate the cost effectiveness of screening for abdominal aortic aneurysm (AAA). MATERIAL AND METHODS: All 12,639 men born in the years 1921-1933 (aged 64-73) living in Viborg County, Denmark, were randomly allocated either to receive an invitation to abdominal ultrasound scanning for AAA or to be controls. Costs for screening and surveillance were assessed prospectively. Diagnosis Related Group (DRG) costs from 1999 were used concerning admissions with uncomplicated and complicated operations. Admissions for AAA surgery were retrospectively classified according to complications in patient records. RESULTS: Mean follow-up time was 52 months. 76.6% of invited men attended screening, and 191 (4.0%) had an AAA. As previously reported, the cumulative 5-year AAA-specific mortality in the invited group was significantly reduced by 67% compared to the control group (P = 0.003). The costs were estimated to be Euro 11.23 per scan. The costs per life-year saved were Euro 9057 (Euro 5872-20,063) after 5 years, and were expected to decrease to Euro 2708 (Euro 1758-6031) after 10 years and to Euro 1825 (Euro 1185-4063) after 15 years. CONCLUSION: Screening of 64-73 years old males in Denmark seems cost effective.  相似文献   
170.
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