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   3373229篇
  免费   268297篇
  国内免费   6045篇
耳鼻咽喉   48525篇
儿科学   107563篇
妇产科学   93039篇
基础医学   475052篇
口腔科学   99431篇
临床医学   306647篇
内科学   653142篇
皮肤病学   70344篇
神经病学   280741篇
特种医学   134326篇
外国民族医学   1247篇
外科学   506990篇
综合类   82929篇
现状与发展   4篇
一般理论   1426篇
预防医学   272196篇
眼科学   79795篇
药学   252333篇
  7篇
中国医学   6250篇
肿瘤学   175584篇
  2018年   33607篇
  2016年   28900篇
  2015年   33036篇
  2014年   46911篇
  2013年   71743篇
  2012年   96444篇
  2011年   102002篇
  2010年   60266篇
  2009年   57530篇
  2008年   97127篇
  2007年   102874篇
  2006年   104030篇
  2005年   101176篇
  2004年   98202篇
  2003年   94525篇
  2002年   93310篇
  2001年   153520篇
  2000年   158982篇
  1999年   134988篇
  1998年   39144篇
  1997年   35491篇
  1996年   34992篇
  1995年   33937篇
  1994年   31923篇
  1993年   29858篇
  1992年   109691篇
  1991年   106061篇
  1990年   102953篇
  1989年   99465篇
  1988年   92454篇
  1987年   91219篇
  1986年   86624篇
  1985年   83055篇
  1984年   63001篇
  1983年   54074篇
  1982年   32662篇
  1981年   29178篇
  1980年   27491篇
  1979年   59838篇
  1978年   42092篇
  1977年   35522篇
  1976年   33313篇
  1975年   35267篇
  1974年   43490篇
  1973年   41540篇
  1972年   38704篇
  1971年   36030篇
  1970年   33644篇
  1969年   31418篇
  1968年   28657篇
排序方式: 共有10000条查询结果,搜索用时 15 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