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   1212546篇
  免费   78824篇
  国内免费   1546篇
耳鼻咽喉   17193篇
儿科学   40015篇
妇产科学   32784篇
基础医学   172817篇
口腔科学   33639篇
临床医学   105977篇
内科学   229016篇
皮肤病学   28190篇
神经病学   93372篇
特种医学   49021篇
外国民族医学   232篇
外科学   184745篇
综合类   23108篇
现状与发展   1篇
一般理论   316篇
预防医学   82373篇
眼科学   28210篇
药学   95380篇
  7篇
中国医学   3089篇
肿瘤学   73431篇
  2019年   8761篇
  2018年   12999篇
  2017年   10409篇
  2016年   12071篇
  2015年   13137篇
  2014年   17581篇
  2013年   26153篇
  2012年   35552篇
  2011年   37770篇
  2010年   22056篇
  2009年   20311篇
  2008年   35381篇
  2007年   37915篇
  2006年   38378篇
  2005年   36717篇
  2004年   35253篇
  2003年   33977篇
  2002年   32894篇
  2001年   66779篇
  2000年   68553篇
  1999年   56318篇
  1998年   14076篇
  1997年   12543篇
  1996年   12295篇
  1995年   11483篇
  1994年   10428篇
  1993年   9954篇
  1992年   40919篇
  1991年   39255篇
  1990年   38687篇
  1989年   37150篇
  1988年   33370篇
  1987年   32483篇
  1986年   30642篇
  1985年   28795篇
  1984年   21004篇
  1983年   17589篇
  1982年   9772篇
  1979年   18669篇
  1978年   12641篇
  1977年   11286篇
  1976年   9771篇
  1975年   11170篇
  1974年   12768篇
  1973年   12387篇
  1972年   11678篇
  1971年   10964篇
  1970年   10030篇
  1969年   9683篇
  1968年   8626篇
排序方式: 共有10000条查询结果,搜索用时 19 毫秒
21.
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   
22.
23.
24.
25.
26.
27.
28.
29.
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   
30.
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