首页 | 官方网站   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   17698篇
  免费   1851篇
  国内免费   366篇
医药卫生   19915篇
  2024年   34篇
  2023年   202篇
  2022年   504篇
  2021年   747篇
  2020年   520篇
  2019年   663篇
  2018年   647篇
  2017年   576篇
  2016年   559篇
  2015年   698篇
  2014年   884篇
  2013年   1015篇
  2012年   1388篇
  2011年   1288篇
  2010年   868篇
  2009年   699篇
  2008年   973篇
  2007年   969篇
  2006年   866篇
  2005年   810篇
  2004年   708篇
  2003年   698篇
  2002年   583篇
  2001年   365篇
  2000年   372篇
  1999年   260篇
  1998年   143篇
  1997年   104篇
  1996年   104篇
  1995年   84篇
  1994年   72篇
  1993年   63篇
  1992年   138篇
  1991年   152篇
  1990年   148篇
  1989年   108篇
  1988年   107篇
  1987年   107篇
  1986年   74篇
  1985年   77篇
  1984年   64篇
  1983年   50篇
  1982年   38篇
  1981年   30篇
  1980年   36篇
  1979年   39篇
  1978年   32篇
  1976年   27篇
  1974年   28篇
  1973年   33篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
2.
3.
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   
4.
We report a reliable method for determining DOPA levels in plasma and cerebrospinal fluid. The method is based on complete conversion of DOPA to dopamine and quantification by HPLC-ECD of the dopamine formed. Lower limit of detection was 0.5 nmol/l. No differences in plasma DOPA levels were found between normal children (0-15 yr, n = 60), normal adults (n = 39) and patients with essential hypertension (n = 40) or Parkinson's disease (no DOPA therapy, n = 30). In normal individuals and in patients with essential hypertension venous plasma levels were higher than arterial levels (10.2 vs 9.3 nmol/l, p less than 0.001, V/A ratio 1.11 (SD 0.08), n = 15). Sympathetic stimuli (standing, tilting, bicycle exercise, tyramine) did not influence DOPA levels. In untreated depressed patients (n = 10) and in non-parkinsonian neurological patients (n = 12) cerebrospinal fluid levels of DOPA were 4.5 (SD 2.4) and 5.2 (SD 1.3) nmol/l respectively. A direct method for the measurement of DOPA by HPLC-ECD after deproteinization of plasma is also described and compared with the conversion method. Good agreement was found when plasma DOPA levels exceeded 0.25 mumol/l (y(conversion method) = 0.943x (direct method) + 0.118; n = 60; r = 0.985). The direct method, because of greater simplicity and the possibility of simultaneous measurement of the DOPA metabolite 3-O-methyldopa, is the method of choice with plasma samples from DOPA-treated patients. In non-DOPA treated individuals the conversion method is superior and has proved to be an accurate and sensitive method for the determination of DOPA levels in plasma and cerebrospinal fluid.  相似文献   
5.
6.
7.
8.
胰岛素瘤的超声诊断:与其他诊断方法比较   总被引:1,自引:0,他引:1  
目的:探讨超声等方法对胰岛素瘤的定位诊断价值。材料和方法:对42例经过手术和病理证实的胰岛素瘤患者术前定位诊断的各种方法进行回顾性分析,并与其他诊断方法对比分析其各自的定位符合率。结果:定位诊断符合率分别为B超31%(13/42)、EUS55.6%(5/9)、IOUS100%(10/10)、超声引导下PTPC100%(3/3)、CT59.5%(25/42)、MRI50%(6/12)、选择性DSA27.3%(3/11)及ASVS90%(9/10)。彩超(CDUS)对胰岛素瘤良、恶性有鉴别作用。结论:遵循循序渐进原则,先后选用B超(含CDUS)、EUS、CT等已可解决80%以上的定位诊断,然后再做MRI及ASVS;对仍未作出定位者,只要定性诊断明确即有手术探查指征,因为IOUS能提供可靠的定位信息。  相似文献   
9.
Goldenhar and cri-du-chat syndromes: a contiguous gene deletion syndrome?   总被引:2,自引:0,他引:2  
We report a full-term male infant born to nonconsanguinous parents who had clinical features of Goldenhar syndrome and cri du chat syndrome. At birth, the infant was noted to have dysmorphic features with bilateral preauricular tags, rotated ears, bilateral epicanthic folds, a left epibulbar lipodermoid, and an accessory left nipple. After he was assessed for feeding difficulty and tachypnea, he was found to have esophageal atresia with tracheoesophageal fistula. In addition, he had a high-pitched, cat-like cry, characteristic of cri-du-chat syndrome. He also failed a hearing test. Chromosomal analysis and fluorescence in situ hybridisation studies showed an unbalanced karyotype with a terminal deletion of the segment p14 on the short arm of chromosome 5, which is consistent with the cri-du-chat locus. The association of Goldenhar syndrome and cri-du-chat syndrome in this patient suggests that the chromosome 5p14 locus may harbor a gene implicated with Goldenhar syndrome.  相似文献   
10.
Selecting an appropriate working correlation structure is pertinent to clustered data analysis using generalized estimating equations (GEE) because an inappropriate choice will lead to inefficient parameter estimation. We investigate the well‐known criterion of QIC for selecting a working correlation structure, and have found that performance of the QIC is deteriorated by a term that is theoretically independent of the correlation structures but has to be estimated with an error. This leads us to propose a correlation information criterion (CIC) that substantially improves the QIC performance. Extensive simulation studies indicate that the CIC has remarkable improvement in selecting the correct correlation structures. We also illustrate our findings using a data set from the Madras Longitudinal Schizophrenia Study. Copyright © 2008 John Wiley & Sons, Ltd.  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-23

京公网安备 11010802026262号