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   2644530篇
  免费   188364篇
  国内免费   7718篇
耳鼻咽喉   35064篇
儿科学   86602篇
妇产科学   72690篇
基础医学   371029篇
口腔科学   70840篇
临床医学   240368篇
内科学   526600篇
皮肤病学   63641篇
神经病学   219279篇
特种医学   101958篇
外国民族医学   744篇
外科学   395454篇
综合类   50964篇
现状与发展   5篇
一般理论   1036篇
预防医学   200387篇
眼科学   58008篇
药学   191755篇
  11篇
中国医学   5382篇
肿瘤学   148795篇
  2021年   20989篇
  2019年   21605篇
  2018年   30506篇
  2017年   23523篇
  2016年   27349篇
  2015年   30694篇
  2014年   42116篇
  2013年   62749篇
  2012年   83833篇
  2011年   88499篇
  2010年   53177篇
  2009年   51136篇
  2008年   82494篇
  2007年   87552篇
  2006年   89281篇
  2005年   85366篇
  2004年   82160篇
  2003年   79334篇
  2002年   76416篇
  2001年   129096篇
  2000年   131910篇
  1999年   111192篇
  1998年   31930篇
  1997年   28454篇
  1996年   28717篇
  1995年   27849篇
  1994年   25437篇
  1993年   23757篇
  1992年   85570篇
  1991年   81939篇
  1990年   79176篇
  1989年   76398篇
  1988年   69830篇
  1987年   68356篇
  1986年   63883篇
  1985年   60851篇
  1984年   45246篇
  1983年   38259篇
  1982年   22779篇
  1981年   20274篇
  1979年   39221篇
  1978年   27680篇
  1977年   23469篇
  1976年   21662篇
  1975年   22972篇
  1974年   26967篇
  1973年   25536篇
  1972年   23927篇
  1971年   22115篇
  1970年   20306篇
排序方式: 共有10000条查询结果,搜索用时 0 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