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   860807篇
  免费   71651篇
  国内免费   1838篇
耳鼻咽喉   12806篇
儿科学   24695篇
妇产科学   25129篇
基础医学   124135篇
口腔科学   25542篇
临床医学   75225篇
内科学   164093篇
皮肤病学   16975篇
神经病学   70168篇
特种医学   35230篇
外国民族医学   171篇
外科学   136160篇
综合类   24624篇
现状与发展   2篇
一般理论   266篇
预防医学   66865篇
眼科学   20509篇
药学   64864篇
中国医学   1596篇
肿瘤学   45241篇
  2018年   7386篇
  2015年   7784篇
  2014年   11172篇
  2013年   16845篇
  2012年   22816篇
  2011年   23923篇
  2010年   13924篇
  2009年   13099篇
  2008年   22669篇
  2007年   24700篇
  2006年   24552篇
  2005年   24234篇
  2004年   23790篇
  2003年   22918篇
  2002年   22021篇
  2001年   35888篇
  2000年   36528篇
  1999年   30947篇
  1998年   9245篇
  1997年   8564篇
  1996年   8495篇
  1995年   8025篇
  1994年   7737篇
  1992年   26652篇
  1991年   26144篇
  1990年   25632篇
  1989年   24687篇
  1988年   23224篇
  1987年   22879篇
  1986年   21739篇
  1985年   21106篇
  1984年   16369篇
  1983年   13970篇
  1982年   8837篇
  1981年   8168篇
  1980年   7637篇
  1979年   16710篇
  1978年   12092篇
  1977年   10146篇
  1976年   9304篇
  1975年   10120篇
  1974年   12626篇
  1973年   12132篇
  1972年   11537篇
  1971年   10676篇
  1970年   10204篇
  1969年   9908篇
  1968年   8895篇
  1967年   8220篇
  1966年   7646篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
Porocarcinoma is an unusual, locally aggressive and potentially fatal neoplasm. Several cutaneous malignancies have been described in association with porocarcinoma, including squamous cell carcinoma, basal cell carcinoma and tricholemmal carcinoma. Previous reports have indicated that the occurrence of malignant tumours in combination with porocarcinoma is extremely rare, in particular with regard to Bowen disease (BD). We report an uncommon case of porocarcinoma occurring synchronously in a single BD lesion in a 63‐year‐old woman with multiple BD lesions. The clinical and histological findings confirmed this diagnosis.  相似文献   
42.
DNA methylation at CpG dinucleotides is an important epigenetic regulator common to virtually all mammalian cell types, but recent evidence indicates that during early postnatal development neuronal genomes also accumulate uniquely high levels of two alternative forms of methylation, non-CpG methylation and hydroxymethylation. Here we discuss the distinct landscape of DNA methylation in neurons, how it is established, and how it might affect the binding and function of protein readers of DNA methylation. We review studies of one critical reader of DNA methylation in the brain, the Rett syndrome protein methyl CpG-binding protein 2 (MeCP2), and discuss how differential binding affinity of MeCP2 for non-CpG and hydroxymethylation may affect the function of this methyl-binding protein in the nervous system.  相似文献   
43.
We present a patient with both dynamic left ventricular outflow tract obstruction and valvular aortic stenosis. The aortic valve was calcified, and velocities and gradients measured by continuous‐wave Doppler met standard criteria for severe aortic stenosis. The increased subvalvular velocities invalidated assumptions of the simplified Bernoulli equation; correction using the longer form of the Bernoulli equation suggested a lower but still significant gradient. The complex shape of the subvalvular spectral Doppler envelope indicated supranormal systolic function and dynamic left ventricular outflow obstruction. Left heart catheterization with an end‐hole catheter was required to determine the subvalvular and valvular components of the obstruction.  相似文献   
44.
45.
46.
Investigative studies of white matter (WM) brain structures using diffusion MRI (dMRI) tractography frequently require manual WM bundle segmentation, often called “virtual dissection.” Human errors and personal decisions make these manual segmentations hard to reproduce, which have not yet been quantified by the dMRI community. It is our opinion that if the field of dMRI tractography wants to be taken seriously as a widespread clinical tool, it is imperative to harmonize WM bundle segmentations and develop protocols aimed to be used in clinical settings. The EADC‐ADNI Harmonized Hippocampal Protocol achieved such standardization through a series of steps that must be reproduced for every WM bundle. This article is an observation of the problematic. A specific bundle segmentation protocol was used in order to provide a real‐life example, but the contribution of this article is to discuss the need for reproducibility and standardized protocol, as for any measurement tool. This study required the participation of 11 experts and 13 nonexperts in neuroanatomy and “virtual dissection” across various laboratories and hospitals. Intra‐rater agreement (Dice score) was approximately 0.77, while inter‐rater was approximately 0.65. The protocol provided to participants was not necessarily optimal, but its design mimics, in essence, what will be required in future protocols. Reporting tractometry results such as average fractional anisotropy, volume or streamline count of a particular bundle without a sufficient reproducibility score could make the analysis and interpretations more difficult. Coordinated efforts by the diffusion MRI tractography community are needed to quantify and account for reproducibility of WM bundle extraction protocols in this era of open and collaborative science.  相似文献   
47.
48.
49.
Monatsschrift Kinderheilkunde - Bedürfnisse onkologisch erkrankter Kinder im Kontext der Versorgung sind noch wenig erforscht, was u.?a. in einem Mangel an entsprechenden...  相似文献   
50.
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