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   2626235篇
  免费   187714篇
  国内免费   7665篇
耳鼻咽喉   34698篇
儿科学   86007篇
妇产科学   72176篇
基础医学   368508篇
口腔科学   70248篇
临床医学   238191篇
内科学   524518篇
皮肤病学   62833篇
神经病学   217267篇
特种医学   101460篇
外国民族医学   736篇
外科学   392500篇
综合类   50859篇
现状与发展   5篇
一般理论   1025篇
预防医学   198959篇
眼科学   57414篇
药学   190439篇
  8篇
中国医学   5373篇
肿瘤学   148390篇
  2021年   20968篇
  2019年   21535篇
  2018年   30460篇
  2017年   23384篇
  2016年   27075篇
  2015年   30519篇
  2014年   42008篇
  2013年   62281篇
  2012年   83378篇
  2011年   87591篇
  2010年   52778篇
  2009年   50716篇
  2008年   81785篇
  2007年   86700篇
  2006年   88289篇
  2005年   84501篇
  2004年   81148篇
  2003年   78336篇
  2002年   75373篇
  2001年   128642篇
  2000年   131487篇
  1999年   110724篇
  1998年   31624篇
  1997年   28241篇
  1996年   28473篇
  1995年   27624篇
  1994年   25246篇
  1993年   23598篇
  1992年   85277篇
  1991年   81658篇
  1990年   78866篇
  1989年   76135篇
  1988年   69527篇
  1987年   68050篇
  1986年   63602篇
  1985年   60592篇
  1984年   45025篇
  1983年   38022篇
  1982年   22555篇
  1981年   20071篇
  1979年   38990篇
  1978年   27481篇
  1977年   23294篇
  1976年   21535篇
  1975年   22845篇
  1974年   26822篇
  1973年   25399篇
  1972年   23759篇
  1971年   21968篇
  1970年   20197篇
排序方式: 共有10000条查询结果,搜索用时 13 毫秒
91.
OBJECTIVE: To evaluate the prenatal distribution, associated conditions and outcome of the different types of right aortic arch (RAA) detected in fetal life. METHODS: This was a retrospective review of all cases of RAA detected prenatally between 1998 and 2005 in two tertiary referral centers. RESULTS: In the study period 71 cases of RAA were detected; 26 (37%) had RAA with aberrant left subclavian artery, 23 (32%) had RAA with mirror-image branching, 20 (28%) had RAA of unknown type and two (3%) had double aortic arch. While 20/26 cases with RAA and aberrant left subclavian artery were isolated findings, all 23 cases with RAA and mirror-image branching were associated with cardiac defects, namely tetralogy of Fallot (43%) or pulmonary atresia with ventricular septal defect (22%). Of the 20 cases with RAA, 19 of unknown type were associated with heterotaxy syndromes and had additional cardiac malformations and ambiguities of the situs. The two cases with DAA were isolated findings. Seven cases in our series (10%) had a microdeletion 22q11 and these were significantly associated with extracardiac malformations. The outcome in our series depended solely on the associated cardiac and extracardiac malformations, with the exception of one infant with isolated DAA, in whom a surgical correction was warranted. CONCLUSIONS: RAA detected in fetal life is associated frequently with other cardiac/non-cardiac malformations, heterotaxy syndromes and microdeletions 22q11. The associated conditions vary depending on the branching type of the brachiocephalic vessels and the presence of extracardiac malformations.  相似文献   
92.
Southgate  M. Therese 《JAMA》2006,296(13):1564
  相似文献   
93.
Volume and profile of alcohol consumption among students and classmates as predictors of aggression and victimization: a multilevel analysis among Swiss adolescents

Objective:  

To test the effects of the volume of alcohol consumption and drinking patterns on alcohol-related aggression and victimization, both at the individual and class levels.  相似文献   
94.
95.
96.
There are no data available combining transbronchial needle aspiration (TBNA) of mediastinal lymph nodes and positron emission tomography (PET) in the staging of nonsmall cell lung cancer (NSCLC). The aim of the current study was to determine if these two methods can enhance the negative predictive value of the individual modality alone, for a specific lymph node station, and if this integrated approach can reduce the number of mediastinoscopies. A total of 113 patients with enlarged mediastinal lymph nodes (> or = 1 cm), who underwent both TBNA and PET scanning, were included. In 51 patients, histopathology, confirmed by surgical lymph node dissection, was compared with PET results and TBNA. Sensitivity, specificity, positive predictive value, negative predictive value and accuracy to detect malignant lymphadenopathy was 68 (13/19), 89 (119/134), 46 (13/28), 95 (119/125) and 86% (132/152) for PET, respectively; 54% (6/11), 100 (53/53), 100 (6/6), 91 (53/58) and 92% (59/64), respectively for TBNA; and 100 (11/11), 94 (50/53), 79 (11/14), 100 (50/50) and 95 (61/64) for combined TBNA and PET, respectively. Combination of transbronchial needle aspiration and positron emission tomography has the potential to allow adequate mediastinal staging of nonsmall cell lung cancer with enlarged lymph nodes in most patients without the need for mediastinoscopy.  相似文献   
97.
98.
99.
100.
Clinicopathological and electron microscopical findings of eight cases of enzootic nasal adenocarcinoma of sheep, diagnosed solely in one big flock in Slovenia between years 2001 and 2003 are described. All affected sheep were female, their mean age was 4.5 ± 1.5 years and they either belonged to the Istrian pramenka breed (five sheep) or were crossbreeds (three sheep). Tumours that arose from the ethmoid area of the nasal cavity were unilateral in six cases (75%) and bilateral in two cases (25%). All tumours were classified as adenocarcinomas by histopathological examination and they displayed either a combination of tubular and papillary growth or less often solely tubular proliferation. No metastases were detected in regional lymph nodes, brain or other organs. Electron microscopical studies performed on the reprocessed paraffin‐embedded tissues revealed the presence of the virus‐like particles with an average diameter between 70 and 90 nm.  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