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   2033406篇
  免费   143902篇
  国内免费   3937篇
耳鼻咽喉   30082篇
儿科学   59526篇
妇产科学   56398篇
基础医学   288050篇
口腔科学   61982篇
临床医学   176131篇
内科学   393539篇
皮肤病学   44930篇
神经病学   160737篇
特种医学   80359篇
外国民族医学   501篇
外科学   318603篇
综合类   45174篇
现状与发展   7篇
一般理论   641篇
预防医学   142138篇
眼科学   48593篇
药学   154923篇
  7篇
中国医学   4519篇
肿瘤学   114405篇
  2018年   18730篇
  2016年   16634篇
  2015年   18727篇
  2014年   25919篇
  2013年   39045篇
  2012年   51980篇
  2011年   54836篇
  2010年   32527篇
  2009年   31421篇
  2008年   52921篇
  2007年   56697篇
  2006年   57662篇
  2005年   55781篇
  2004年   54214篇
  2003年   52247篇
  2002年   51444篇
  2001年   100678篇
  2000年   103645篇
  1999年   87438篇
  1998年   22653篇
  1997年   20460篇
  1996年   19999篇
  1995年   18880篇
  1994年   17564篇
  1993年   16305篇
  1992年   67636篇
  1991年   65415篇
  1990年   64059篇
  1989年   62332篇
  1988年   57761篇
  1987年   56656篇
  1986年   53730篇
  1985年   51407篇
  1984年   37905篇
  1983年   32392篇
  1982年   18582篇
  1981年   16810篇
  1979年   35944篇
  1978年   25294篇
  1977年   21991篇
  1976年   19675篇
  1975年   22163篇
  1974年   26438篇
  1973年   25548篇
  1972年   24295篇
  1971年   22774篇
  1970年   21685篇
  1969年   20636篇
  1968年   19226篇
  1967年   17279篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
71.
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   
72.
73.
74.
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   
75.
76.
77.
A new semi-empirical formula for the evaluation of (n,(3)He) reaction cross-sections at the energy of 14.6 and 20 MeV is presented. Formula was derived using the analytical expression for the evaluation of the (3)He spectrum within the frame of pre-equilibrium exciton model. The systematics obtained is compared with the empirical formula for the (n,(3)He) reaction cross-section.  相似文献   
78.
79.
This study was performed to evaluate the surgical strategy in patients with calvarial tumours, in order to design and modify a robot-assisted trepanation system. A total of 75 patients underwent craniectomy for the treatment of calvarial tumours during the 10-year period from 1993 to 2002. The patients' complaints, the size, location and histology of the tumour, and the various cranioplasty techniques used were analysed retrospectively. In a second procedure several craniectomies at typical locations according to the study's results were performed in a laboratory setting using a hexapod robotic tool, constructed at the Helmholtz-Institute, RWTH Aachen University, and plastic model heads. The workflow was documented and the reproducibility and the accuracy of the procedure were registered. A total of 83 surgical procedures were performed on 75 patients. The majority (87 %) of lesions treated surgically were located in the frontal, temporal and anterior parts of the parietal region. Histological examination revealed benign lesions in 66 % of the patients and dural involvement in 46 %. According to these results craniectomies were performed using the robotic system. Mean positioning accuracy of the robotic system while milling was 0.24 mm, with a standard deviation of 0.04 mm, and maximum error under 1 mm. Craniectomies leaving a 1-mm layer of the tabula interna intact to ensure a healthy dura were performed in several regions successfully. The majority of calvarial tumours, requiring surgical treatment in our patients, were located in cosmetically relevant areas in which drilling can be carried out with the robotic trepanation system. Consequently, the surgical approach had to be planned carefully in order to achieve a good cosmetic outcome.  相似文献   
80.
BG Aktuell     
This paper gives an overview of the changes in the sector of accident insurance companies over recent months and a prognosis for the changes that can still be expected, especially with reference to the election results.  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