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   2590302篇
  免费   185240篇
  国内免费   7581篇
耳鼻咽喉   34288篇
儿科学   85260篇
妇产科学   71594篇
基础医学   363994篇
口腔科学   69748篇
临床医学   234693篇
内科学   516298篇
皮肤病学   62490篇
神经病学   213656篇
特种医学   99978篇
外国民族医学   736篇
外科学   386932篇
综合类   50410篇
现状与发展   5篇
一般理论   968篇
预防医学   196271篇
眼科学   56740篇
药学   188195篇
  8篇
中国医学   5338篇
肿瘤学   145521篇
  2021年   20028篇
  2019年   20658篇
  2018年   29337篇
  2017年   22641篇
  2016年   26273篇
  2015年   29571篇
  2014年   40514篇
  2013年   60488篇
  2012年   80344篇
  2011年   84610篇
  2010年   51086篇
  2009年   49225篇
  2008年   79155篇
  2007年   83966篇
  2006年   85709篇
  2005年   81891篇
  2004年   78874篇
  2003年   76185篇
  2002年   73465篇
  2001年   128475篇
  2000年   131406篇
  1999年   110571篇
  1998年   31300篇
  1997年   27953篇
  1996年   28251篇
  1995年   27411篇
  1994年   25102篇
  1993年   23450篇
  1992年   85223篇
  1991年   81632篇
  1990年   78847篇
  1989年   76112篇
  1988年   69525篇
  1987年   68053篇
  1986年   63582篇
  1985年   60545篇
  1984年   44970篇
  1983年   37962篇
  1982年   22470篇
  1981年   19999篇
  1979年   38988篇
  1978年   27458篇
  1977年   23267篇
  1976年   21512篇
  1975年   22821篇
  1974年   26807篇
  1973年   25392篇
  1972年   23773篇
  1971年   21977篇
  1970年   20201篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
Southgate  M. Therese 《JAMA》2006,296(13):1564
  相似文献   
92.
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   
93.
94.
95.
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   
96.
97.
98.
Effect of catalase supplementation in storage media for avulsed teeth   总被引:1,自引:0,他引:1  
Abstract – The type of liquid medium used to store avulsed teeth prior to replantation has been shown to affect the long‐term prognosis. One possibility is that some storage media contain hydrogen peroxide (H2O2) that may be toxic to periodontal ligament cells. Therefore, the aim of this study was to determine if the addition of catalase to storage media improved the prognosis of replanted dog teeth. Forty‐eight mongrel premolar roots were endodontically treated, extracted, randomly divided and placed into one of four storage media: Hank's balanced salt solution (HBSS), containing no antioxidant); Viaspan, containing the antioxidant, glutathione, or the same two media supplemented with catalase(100 U ml?1) for 1, 5, or 26 h prior to replantation. After 2 months, the dogs were euthanized and the roots histologically examined to evaluate the attachment tissues. Regardless of the storage medium used, overall healing was excellent and only 4% of the roots displayed inflammatory or replacement resorption. When roots from the different storage media were compared, those stored in HBSS were found to display the highest incidence of surface resorption (55.7%). Supplementation of HBSS with catalase resulted in a lower level of surface resorption (48.6%) that was statistically significant (P < 0.05). Roots stored in Viaspan – or + catalase displayed even lower levels of surface resorption (41.3 and 38.2%, respectively). The improvement observed with catalase‐supplemented HBSS was confined to the 45‐min incubation period; only Viaspan – or + catalase reduced surface resorption at the 5‐ and 26‐h incubations. Collectively, these data demonstrate that roots stored in media containing antioxidant activity undergo less surface resorption. These results suggest that low levels of H2O2 in storage media for avulsed teeth may adversely affect periodontal ligament cells.  相似文献   
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