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   1116946篇
  免费   75665篇
  国内免费   2684篇
耳鼻咽喉   15408篇
儿科学   35710篇
妇产科学   29313篇
基础医学   157918篇
口腔科学   30412篇
临床医学   99289篇
内科学   211493篇
皮肤病学   25101篇
神经病学   84284篇
特种医学   44474篇
外国民族医学   206篇
外科学   168777篇
综合类   25691篇
现状与发展   6篇
一般理论   277篇
预防医学   77788篇
眼科学   25873篇
药学   89905篇
  18篇
中国医学   3977篇
肿瘤学   69375篇
  2021年   8778篇
  2019年   8932篇
  2018年   12577篇
  2017年   9937篇
  2016年   11314篇
  2015年   12727篇
  2014年   17148篇
  2013年   24348篇
  2012年   33624篇
  2011年   35522篇
  2010年   21159篇
  2009年   19749篇
  2008年   32435篇
  2007年   34478篇
  2006年   34937篇
  2005年   33093篇
  2004年   31824篇
  2003年   30582篇
  2002年   29371篇
  2001年   61337篇
  2000年   62499篇
  1999年   51735篇
  1998年   12832篇
  1997年   11322篇
  1996年   11246篇
  1995年   10538篇
  1994年   9540篇
  1993年   9014篇
  1992年   38159篇
  1991年   36640篇
  1990年   36035篇
  1989年   34563篇
  1988年   31125篇
  1987年   30225篇
  1986年   28443篇
  1985年   26692篇
  1984年   19345篇
  1983年   16253篇
  1982年   8926篇
  1979年   17139篇
  1978年   11465篇
  1977年   10309篇
  1976年   8895篇
  1975年   10120篇
  1974年   11710篇
  1973年   11329篇
  1972年   10799篇
  1971年   10136篇
  1970年   9276篇
  1969年   8976篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
22.
23.
Levels of the soluble form of the triggering receptor expressed on myeloid cells (sTREM)-1 are elevated in severe sepsis. However, it is not known whether sTREM-1 measurements can distinguish milder bacterial infections from noninfectious inflammation. The present authors studied whether serum sTREM-1 levels differ in community-acquired pneumonia, exacerbations of chronic obstructive pulmonary disease (COPD), asthma and controls, and whether sTREM-1 may be used as a surrogate marker for the need for antibiotics. Serum sTREM-1 levels in 150 patients with pneumonia, COPD and asthma exacerbations and 62 healthy controls were measured. Serum sTREM-1 levels were significantly elevated in pneumonia (median 295.2 ng x mL(-1)), COPD (280.3 ng x mL(-1)) and asthma exacerbations (184.0 ng x mL(-1)) compared with controls (83.1 ng x mL(-1)). Levels were higher in pneumonia and Anthonisen type 1 COPD exacerbations than in type 2 and 3 COPD and asthma exacerbations. The area under the receiver operating characteristics curve for sTREM-1 as a surrogate marker for the need for antibiotics was 0.77. Serum levels of the soluble form of the triggering receptor expressed on myeloid cells-1 were elevated predominantly in pneumonia and Anthonisen type 1 COPD exacerbations versus type 2 and 3 chronic obstructive pulmonary disease exacerbations, asthma and controls. Serum levels of the soluble form of the triggering receptor expressed on myeloid cells-1 has moderate but insufficient accuracy as a surrogate marker for the need for antibiotics in lower respiratory tract infections.  相似文献   
24.
25.
26.
27.
28.
29.
30.
OBJECTIVE: To establish reference intervals for the fetal right, left and total lung volumes and heart volume between 12 and 32 weeks of gestation. METHODS: Fetal lung and heart volumes were measured using three-dimensional (3D) ultrasound in 650 normal singleton pregnancies at 12-32 weeks. The VOCAL (Virtual Organ Computer-aided AnaLysis) technique was used to obtain a sequence of six sections of each lung and the heart around a fixed axis, each after a 30 degrees rotation from the previous one. The rotation axis for the lungs extended from the apex to the upper limit of the diaphragm dome, and the rotation axis for the heart extended from its apex to its connection to the great vessels. The contour of each of these organs was drawn manually in the six different rotation planes to obtain the 3D volume measurement. In 60 cases the fetal lungs and heart volumes were measured by the same sonographer twice and also by a second sonographer once in order to compare the measurements and calculate intra- and interobserver agreement. RESULTS: The total lung volume and heart volume increased with gestation, from respective mean values of 1.6 and 0.6 mL at 12 weeks to 10.9 and 4.3 mL at 20 weeks and 49.3 and 26.6 mL at 32 weeks. The right to left lung volume ratio did not change significantly with gestation (median, 0.7), whereas the heart to total lung volume ratio increased with gestation from about 0.3 at 12 weeks to 0.5 at 32 weeks. In the Bland-Altman plot, the difference between paired measurements by two sonographers was, in 95% of the cases, less than 0.05, 0.5 and 1.9 mL for each lung at 12-13, 19-22 and 29-32 weeks, respectively, and the corresponding values for the heart volumes were 0.04, 0.4 and 2.3 mL. CONCLUSIONS: In normal fetuses the lung and heart volumes increase between 12 and 32 weeks of gestation. The extent to which in pathological pregnancies possible deviations in these measurements from normal prove to be useful in the prediction of outcome remains to be determined.  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