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   982041篇
  免费   65517篇
  国内免费   2528篇
耳鼻咽喉   13733篇
儿科学   31171篇
妇产科学   28380篇
基础医学   137725篇
口腔科学   26988篇
临床医学   79872篇
内科学   201362篇
皮肤病学   21395篇
神经病学   77851篇
特种医学   38097篇
外国民族医学   338篇
外科学   152075篇
综合类   19442篇
一般理论   272篇
预防医学   74245篇
眼科学   22003篇
药学   70252篇
中国医学   2070篇
肿瘤学   52815篇
  2019年   8033篇
  2018年   11955篇
  2017年   8873篇
  2016年   9296篇
  2015年   10590篇
  2014年   14333篇
  2013年   22394篇
  2012年   31201篇
  2011年   32917篇
  2010年   19383篇
  2009年   17812篇
  2008年   30711篇
  2007年   32597篇
  2006年   32603篇
  2005年   32169篇
  2004年   30576篇
  2003年   29399篇
  2002年   28816篇
  2001年   43631篇
  2000年   44935篇
  1999年   38168篇
  1998年   10337篇
  1997年   9355篇
  1996年   9314篇
  1995年   8624篇
  1994年   8232篇
  1993年   7707篇
  1992年   29172篇
  1991年   27851篇
  1990年   27259篇
  1989年   26115篇
  1988年   24258篇
  1987年   23876篇
  1986年   22903篇
  1985年   21789篇
  1984年   16273篇
  1983年   13851篇
  1982年   8254篇
  1979年   15088篇
  1978年   10512篇
  1977年   8867篇
  1976年   8418篇
  1975年   9243篇
  1974年   11147篇
  1973年   10621篇
  1972年   10020篇
  1971年   9242篇
  1970年   8963篇
  1969年   8382篇
  1968年   8031篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
Journal of Immigrant and Minority Health - COVID-19 has disproportionally affected underrepresented minorities (URM) and low-income immigrants in the United States. The aim of the study is to...  相似文献   
3.
4.
In this paper we present a coupled Finite Element Method – Boundary Element Method (FEM-BEM) approach for the solution of the free-boundary axi-symmetric plasma equilibrium problem. The proposed method, obtained from an improvement of the Hagenow-Lackner coupling method, allows to efficiently model the equilibrium problem in unbounded domains by discretizing only the plasma region; the external conductors can be modelled either as 2D or 3D models, according to the problem of interest. The paper explores different iterative methods for the solution of the nonlinear Grad-Shafranov equation, such as Picard, Newton-Raphson and Newton-Krylov, in order to provide a robust and reliable tool, able to handle large-scale problems (e.g. high resolution equilibria). This method has been implemented in the FRIDA code (FRee-boundary Integro-Differential Axisimmetric – https://github. om/matteobonotto/ FRIDA), together with a suitable Adaptive Integration Technique (AIT) for the computation of the source term. FRIDA has been successfully tested and validated against experimental data from RFX-mod device, and numerical equilibria of an ITER-like device.  相似文献   
5.
6.
Graefe's Archive for Clinical and Experimental Ophthalmology - The published online version contains mistake as the author's first name and last name have been interchanged as "Hild...  相似文献   
7.
BACKGROUND The adenoma detection rate(ADR) is inversely associated with the incidence of interval colorectal cancer and serves as a benchmark quality criterion during screening colonoscopy. However, adenoma miss rates reach up to 26% and studies have shown that a second inspection of the right colon in retroflected view(RFV) can increase ADR.AIM To assess whether inspection of the whole colon in RFV compared to standard forward view(SFV) can increase ADR.METHODS Patients presenting for screening or surveillance colonoscopy were invited to participate in this randomized controlled trial and randomized into two arms. In RFV arm colonoscopy was initially performed with SFV, followed by a second inspection of the whole colon in RFV. In the SFV arm first withdrawal was performed with SFV, followed by a second inspection of the whole colon again with SFV. Number, size and morphology of polyps found during first and second inspection in each colonic segment were recorded and all polyps were removed and sent for histopathology in separate containers.RESULTS Two hundred and five patients were randomly assigned to the RFV(n = 101) and SFV(n = 104) arm. In the RFV arm, both polyp detection rate(PDR) and ADR were increased under second inspection in RFV(PDR 1~(st) SFV: 39.8%, PDR 2~(nd)RFV: 46.6%; ADR 1~(st) SFV: 35.2%, ADR 2~(nd) RFV: 42%). Likewise, in the SFV arm,PDR and ADR were increased under second inspection(PDR 1~(st) SFV: 37.5%, PDR 2~(nd) SFV: 46.6%; ADR 1~(st) SFV: 34.1%, ADR 2~(nd)SFV: 44.3%) with no significant differences in ADR and PDR between the SFV and RFV arm. Mean number of adenomas per patient(APP) was increased in the RFV and SFV(APP RFV arm: 1~(st) SFV: 1.71; 2~(nd) RFV: 2.38; APP SFV arm: 1~(st) SFV: 1.83, 2~(nd)SFV:2.2). The majority of adenomas additionally found during second inspection in RFV or in SFV were located in the transverse and left-sided colon and were 5 mm in size.CONCLUSION Second inspection of the whole colon leads to increased adenoma detection with no differences between SFV and RFV. Hence, increased detection is most likely a feature of the second inspection itself but not of the inspection mode.  相似文献   
8.
9.
10.
Sinus venosus atrial septal defect (SV‐ASD) usually coexists with partial anomalous pulmonary vein connection (PAPVC). It is a difficult diagnosis in transthoracic echocardiography (TTE) due to eccentric position of defects. We present a rare case of atypical anatomical variation in PAPVC, which was never described before. Two right pulmonary veins drained into superior vena cava, which overrode SV‐ASD and interatrial septum, a third pulmonary vein into the right atrium. Complete diagnosis could not be set after TTE, nor transesophageal echocardiography, whereas angio‐CT was finally conclusive. This diagnostic approach allowed the surgical planning.  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