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   1840754篇
  免费   135506篇
  国内免费   3066篇
耳鼻咽喉   26084篇
儿科学   62557篇
妇产科学   49248篇
基础医学   269353篇
口腔科学   50415篇
临床医学   163217篇
内科学   362088篇
皮肤病学   40969篇
神经病学   139689篇
特种医学   71584篇
外国民族医学   718篇
外科学   278979篇
综合类   39212篇
现状与发展   3篇
一般理论   515篇
预防医学   137569篇
眼科学   41540篇
药学   137964篇
  5篇
中国医学   4394篇
肿瘤学   103223篇
  2018年   19338篇
  2017年   14725篇
  2016年   16264篇
  2015年   18225篇
  2014年   25319篇
  2013年   38557篇
  2012年   52233篇
  2011年   55191篇
  2010年   32866篇
  2009年   31142篇
  2008年   52317篇
  2007年   56022篇
  2006年   56611篇
  2005年   54456篇
  2004年   53204篇
  2003年   51279篇
  2002年   50190篇
  2001年   91562篇
  2000年   94426篇
  1999年   79549篇
  1998年   21275篇
  1997年   18919篇
  1996年   19475篇
  1995年   18468篇
  1994年   17371篇
  1993年   16064篇
  1992年   62417篇
  1991年   61317篇
  1990年   59707篇
  1989年   57589篇
  1988年   52837篇
  1987年   51673篇
  1986年   48402篇
  1985年   46115篇
  1984年   34361篇
  1983年   28929篇
  1982年   16502篇
  1981年   14904篇
  1979年   30762篇
  1978年   21446篇
  1977年   18157篇
  1976年   17131篇
  1975年   18613篇
  1974年   21748篇
  1973年   20866篇
  1972年   19372篇
  1971年   17777篇
  1970年   16913篇
  1969年   15380篇
  1968年   14106篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
61.
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   
62.
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   
63.
Systems of care (SOCs) have been developed throughout the country to meet the needs of children with severe emotional disturbances (SED) and their families. In these SOCs, multiple agencies and disciplines are expected to work together with informal community supports to address families' needs (Stroul & Friedman, 1986a). A review of the literature on the impact of SOCs suggests: (a) communities' service delivery systems change; and (b) children experience modest improvements in symptomatology and functioning. At the same time, little is known about (a) which components of the SOC approach, at what levels, are necessary to impact child and family outcomes; (b) the degree to which SOCs affect other family members, beyond the target child; and (c) the impact of community contexts and supports in SOCs. Future research should improve measurement of key SOC constructs, examine the relation between specific levels of implementation and outcomes for the entire family, and investigate the impact of broader community systems and supports on families within SOCs. © 2004 Wiley Periodicals, Inc. J Comm Psychol 32: 655–674, 2004.  相似文献   
64.
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   
65.
For many parents stopping life-sustaining medical treatment on their dying infant is psychologically impossible. Dostoevsky's insights into human behavior, particularly the fact that individuals do not want the anxiety and guilt associated with responsibility for making difficult decisions, might change the way physicians approach parents for permission to withdraw life-prolonging medical interventions on dying infants.  相似文献   
66.
67.
68.
69.
Four clinical trials of porcine islet transplantation have been reported, and there are verbal reports that clinical trials on much larger scales are continuing in centers in China and Russia. The four reported trials are briefly reviewed and, in the light of the present status of experimental islet xenotransplantation, consideration is given to whether such trials are currently justified. The Ethics Committee of the International Xenotransplantation Association has (1) emphasized the need for encouraging studies in non-human primates before clinical trials should be undertaken, (2) mandatory monitoring for the transfer of porcine microorganisms, and (3) careful regulation and oversight by recognized bodies. Other aspects of the topic, such as the need for informed consent, are briefly discussed. We conclude that, at the present time, more data documenting convincing efficacy, focused on clinically applicable immunosuppressive regimens, are needed to justify the initiation of closely monitored clinical trials. A clinical trial may then be justified even though the potential risk to the patients, and possibly for society, will not be zero.  相似文献   
70.
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