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   2350027篇
  免费   171615篇
  国内免费   3331篇
耳鼻咽喉   32050篇
儿科学   75911篇
妇产科学   62686篇
基础医学   348184篇
口腔科学   63633篇
临床医学   211368篇
内科学   457318篇
皮肤病学   51727篇
神经病学   185306篇
特种医学   88018篇
外国民族医学   489篇
外科学   353930篇
综合类   47511篇
现状与发展   12篇
一般理论   848篇
预防医学   182730篇
眼科学   54327篇
药学   175121篇
  11篇
中国医学   4575篇
肿瘤学   129218篇
  2021年   18984篇
  2019年   19539篇
  2018年   27061篇
  2017年   20360篇
  2016年   22747篇
  2015年   25644篇
  2014年   36101篇
  2013年   53961篇
  2012年   74690篇
  2011年   79418篇
  2010年   47070篇
  2009年   44573篇
  2008年   74630篇
  2007年   79495篇
  2006年   80300篇
  2005年   77795篇
  2004年   74370篇
  2003年   71696篇
  2002年   69376篇
  2001年   108753篇
  2000年   111465篇
  1999年   93499篇
  1998年   26992篇
  1997年   23659篇
  1996年   24055篇
  1995年   22715篇
  1994年   20895篇
  1993年   19712篇
  1992年   72004篇
  1991年   70075篇
  1990年   68395篇
  1989年   65667篇
  1988年   60307篇
  1987年   59127篇
  1986年   55219篇
  1985年   53004篇
  1984年   39312篇
  1983年   33396篇
  1982年   19859篇
  1979年   35866篇
  1978年   25653篇
  1977年   21231篇
  1976年   20334篇
  1975年   21817篇
  1974年   26148篇
  1973年   24804篇
  1972年   23200篇
  1971年   22037篇
  1970年   20248篇
  1969年   19316篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
61.
BACKGROUND: Previous research has demonstrated that academic and neuropsychological functions are compromised in pediatric bipolar disorder (PBD). Investigation of the degree to which neuropsychological deficits might contribute to those academic problems is needed to aid in the recognition and intervention for school achievement difficulties in PBD. METHODS: A sample of 55 children and adolescents with PBD with and without attention-deficit/hyperactivity disorder (ADHD) (PBD group, n = 28; PBD+ADHD group, n = 27) were tested with a computerized neurocognitive battery and standardized neuropsychological tests. Age range of subjects was 7-17 years, with the mean age of 11.97 (3.18) years. Parents completed a structured questionnaire on school and academic functioning. RESULTS: Logistic regression analyses indicated that executive function, attention, working memory, and verbal memory scores were poorer in those with a history of reading/writing difficulties. A separate logistic regression analysis found that attentional dysfunction predicted math difficulties. These relationships between neuropsychological function and academic difficulties were not different in those with PBD+ADHD than in those with PBD alone. CONCLUSIONS: In PBD neuropsychological deficits in the areas of attention, working memory, and organization/problem solving skills all contribute to academic difficulties. Early identification and intervention for these difficulties might help prevent lower academic achievement in PBD.  相似文献   
62.
63.
64.
65.
66.
67.
68.
69.
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   
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