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   3386311篇
  免费   269162篇
  国内免费   6057篇
耳鼻咽喉   48693篇
儿科学   108034篇
妇产科学   93356篇
基础医学   476366篇
口腔科学   99674篇
临床医学   308704篇
内科学   655233篇
皮肤病学   70556篇
神经病学   282046篇
特种医学   134739篇
外国民族医学   1247篇
外科学   508447篇
综合类   83232篇
现状与发展   4篇
一般理论   1460篇
预防医学   273991篇
眼科学   80013篇
药学   253317篇
  9篇
中国医学   6262篇
肿瘤学   176147篇
  2018年   33866篇
  2016年   29098篇
  2015年   33261篇
  2014年   47228篇
  2013年   72302篇
  2012年   97073篇
  2011年   102720篇
  2010年   60687篇
  2009年   57834篇
  2008年   97768篇
  2007年   103563篇
  2006年   104786篇
  2005年   101808篇
  2004年   98871篇
  2003年   95084篇
  2002年   93866篇
  2001年   153802篇
  2000年   159280篇
  1999年   135198篇
  1998年   39284篇
  1997年   35625篇
  1996年   35097篇
  1995年   34027篇
  1994年   32008篇
  1993年   29943篇
  1992年   109867篇
  1991年   106246篇
  1990年   103126篇
  1989年   99625篇
  1988年   92627篇
  1987年   91364篇
  1986年   86789篇
  1985年   83220篇
  1984年   63154篇
  1983年   54242篇
  1982年   32766篇
  1981年   29296篇
  1980年   27598篇
  1979年   59993篇
  1978年   42205篇
  1977年   35617篇
  1976年   33403篇
  1975年   35346篇
  1974年   43588篇
  1973年   41617篇
  1972年   38788篇
  1971年   36109篇
  1970年   33713篇
  1969年   31482篇
  1968年   28719篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
81.
The purpose of this study was to determine fixed cut-off points for forced expiratory volume in one second (FEV(1))/FEV(6) and FEV(6) as an alternative for FEV(1)/forced vital capacity (FVC) and FVC in the detection of obstructive and restrictive spirometric patterns, respectively. For the study, a total of 11,676 spirometric examinations, which took place on Caucasian subjects aged between 20-80 yrs, were analysed. Receiver-operator characteristic curves were used to determine the FEV(1)/FEV(6) ratio and FEV(6) value that corresponded to the optimal combination of sensitivity and specificity, compared with the commonly used fixed cut-off term for FEV(1)/FVC and FVC. The data from the current study indicate that FEV(1)/ FEV(6) <73% and FEV(6) <82% predicted can be used as a valid alternative for the FEV(1)/FVC <70% and FVC <80% pred cut-off points for the detection of obstruction and restriction, respectively. The statistical analysis demonstrated very good, overall, agreement between the two categorisation schemes. For the spirometric diagnosis of airway obstruction (prevalence of 45.9%), FEV(1)/FEV(6) sensitivity and specificity were 94.4 and 93.3%, respectively; the positive and negative predictive values were 92.2 and 95.2%, respectively. For the spirometric detection of a restrictive pattern (prevalence of 14.9%), FEV(6) sensitivity and specificity were 95.9 and 98.6%, respectively; the positive and negative predictive values were 92.2 and 99.3%, respectively. This study demonstrates that forced expiratory volume in one second/forced expiratory volume in six seconds <73% and forced expiratory volume in six seconds <82% predicted, can be used as valid alternatives to forced expiratory volume in one second/forced vital capacity <70% and forced vital capacity <80% predicted, as fixed cut-off terms for the detection of an obstructive or restrictive spirometric pattern in adults.  相似文献   
82.
83.
Bifid mandibular canal.   总被引:1,自引:0,他引:1  
PURPOSE: To determine the incidence and characteristics of bifid mandibular canals. METHODS: A retrospective study was performed using panoramic radiographs of 2012 patients subjected to dental treatment in the Dental Clinic of the Valencia University Dental School (Valencia, Spain) between 1996 and 1999. The goal was to investigate the presence of double mandibular canals. RESULTS: The extraoral panoramic radiographs revealed a total of 7 images suggestive of bifid canals. Mandibular computed tomography revealed the existence of this anatomic variant in 2 of 3 patients. An analysis was performed on the incidence of this type of image in extraoral panoramic radiography, its possible interpretations, and the clinical implications of bifid mandibular canals. CONCLUSIONS: In this study, 0.35% of canals were bifid. All cases were in women.  相似文献   
84.
Contour defects resulting in deformity caused by lack of tissue can be improved by conventional surgery using autologous tissue, but there is always a donor site morbidity. Integra has been available since the early 1980's for use in acute burns and more recently in reconstruction. It has been shown histologically to act as a tissue regeneration template. The regenerated dermis is buried under an autologous thin split-skin graft. In this study, the principle of burying Integra (without the silicone layer) has been applied to deep tissue defects in 12 reconstructive cases. Such regenerated tissues survive at least 3 years after burying. Modification to the technique to avoid visible edges are being developed.  相似文献   
85.
86.
87.
88.
89.
90.
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