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   2178979篇
  免费   168516篇
  国内免费   5187篇
耳鼻咽喉   28913篇
儿科学   73428篇
妇产科学   62075篇
基础医学   312873篇
口腔科学   60036篇
临床医学   197263篇
内科学   427648篇
皮肤病学   50426篇
神经病学   177308篇
特种医学   83034篇
外国民族医学   752篇
外科学   324578篇
综合类   51735篇
现状与发展   3篇
一般理论   820篇
预防医学   172530篇
眼科学   49925篇
药学   155072篇
  4篇
中国医学   4864篇
肿瘤学   119395篇
  2019年   17098篇
  2018年   24282篇
  2017年   18665篇
  2016年   21169篇
  2015年   23722篇
  2014年   33241篇
  2013年   50132篇
  2012年   67159篇
  2011年   71383篇
  2010年   42220篇
  2009年   40144篇
  2008年   66300篇
  2007年   70206篇
  2006年   71131篇
  2005年   68693篇
  2004年   66177篇
  2003年   63279篇
  2002年   61100篇
  2001年   105598篇
  2000年   108223篇
  1999年   90165篇
  1998年   25503篇
  1997年   23019篇
  1996年   23053篇
  1995年   22041篇
  1994年   20211篇
  1993年   18920篇
  1992年   69438篇
  1991年   66948篇
  1990年   64915篇
  1989年   62167篇
  1988年   56755篇
  1987年   56285篇
  1986年   52563篇
  1985年   50375篇
  1984年   38163篇
  1983年   32202篇
  1982年   19562篇
  1981年   17461篇
  1979年   34402篇
  1978年   24481篇
  1977年   20491篇
  1976年   19333篇
  1975年   20068篇
  1974年   24330篇
  1973年   23435篇
  1972年   21735篇
  1971年   19993篇
  1970年   18888篇
  1969年   17491篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
42.
43.
44.
45.
Abstract: Background: Fetal pulse oximetry improves the assessment of fetal well‐being during labor. The objective of this study was to evaluate women's satisfaction with their experience with this additional technology. Methods: We surveyed women participating in the FOREMOST trial, a randomized controlled trial comparing the addition of fetal pulse oximetry (FPO) to conventional cardiotocograph (CTG) monitoring (intervention group), versus CTG‐only (control group), in the presence of nonreassuring fetal status during labor. Our survey evaluated 3 aspects of women's experience: labor, fetal monitoring, and participation in the research. The survey was administered within a few days of giving birth and repeated 3 months later. Results: No differences were found between the intervention and control groups for women's evaluations of their labor, fetal monitoring, research, or overall experiences when surveyed on both occasions. Within each study group, a small but statistically significant decline occurred in women's scores for their experience of labor and overall experience from the initial survey close to the time of giving birth, to 3 months later. The magnitude of differences in responses over time was similar for the both groups. Women were more satisfied after a spontaneous or assisted vaginal birth than after cesarean section. Length of time the research midwife was present had a significant positive effect on women's ratings of their experience several days after giving birth (p = 0.006), but no effect at 3 months. Conclusions: The addition of fetal pulse oximetry for the assessment of fetal well‐being during labor did not affect childbearing women's perceptions of fetal monitoring or their labor. Women evaluated their experience in the research process positively overall. Small changes occurred in women's perception of their satisfaction over time. (BIRTH 33:2 June 2006)  相似文献   
46.
B.  Greg  Brown  John  Growley  宋善俊 《美国医学会杂志》2006,25(2):124-126
过去15年来,有关动脉粥样硬化的流行病学、基础生物学和实验研究均支持下述假设:抗氧化剂可通过抑制动脉壁低密度脂蛋白的氧化而抑制动脉粥样硬化的发生。这种作用机制可抑制胆固醇酯通过巨噬细胞清除受体在动脉斑块内发生病理性沉积。胆固醇酯病理沉积是一种可引起斑块破裂及心血管事件的过程。同样,生物机制亦已确定,癌基因可被抗氧化剂阻断。  相似文献   
47.
48.
49.
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   
50.
OBJECTIVE: To explore the impact of timing and type of ultrasound, particularly three-dimensional (3D), exposure on maternal-fetal attachment and maternal health behavior during pregnancy. METHODS: Subjects were 68 women aged 18 years or older expecting their first child who presented for a routine ultrasound scan at around either 12 or 18 weeks' gestation in Nepean Hospital, Western Sydney. Women completed questionnaires assessing maternal-fetal attachment and health behavior, and were then allocated arbitrarily to either two-dimensional (2D) or 3D ultrasound examination. Repeat questionnaires were completed 1 week later. RESULTS: Maternal-fetal attachment increased after both 2D and 3D ultrasound exposure, and the effect was moderated by the timing of exposure, with women receiving their first ultrasound examination at around 12 weeks showing the greatest change. Alcohol consumption was the only behavior to show significant change following ultrasound exposure, with a reduction in the reported average number of drinks per week. There was no significant difference in the pattern of change for 2D compared with 3D ultrasound exposure, and no effect of ultrasound exposure on maternal perception of the fetus. CONCLUSIONS: Ultrasound has a positive impact on maternal-fetal attachment, particularly in the first trimester. 3D ultrasound did not offer enhanced benefits. Associations between ultrasound exposure and alcohol consumption warrant further investigation. Larger samples are needed to clarify the moderating effects of gestational age and type of ultrasound exposure.  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