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   8730篇
  免费   1218篇
  国内免费   43篇
耳鼻咽喉   34篇
儿科学   368篇
妇产科学   124篇
基础医学   1253篇
口腔科学   88篇
临床医学   1541篇
内科学   2259篇
皮肤病学   267篇
神经病学   797篇
特种医学   140篇
外科学   899篇
综合类   40篇
一般理论   2篇
预防医学   683篇
眼科学   83篇
药学   483篇
中国医学   20篇
肿瘤学   910篇
  2024年   22篇
  2023年   188篇
  2022年   142篇
  2021年   193篇
  2020年   290篇
  2019年   170篇
  2018年   345篇
  2017年   305篇
  2016年   337篇
  2015年   354篇
  2014年   398篇
  2013年   501篇
  2012年   522篇
  2011年   548篇
  2010年   416篇
  2009年   518篇
  2008年   516篇
  2007年   571篇
  2006年   512篇
  2005年   555篇
  2004年   496篇
  2003年   458篇
  2002年   419篇
  2001年   97篇
  2000年   73篇
  1999年   104篇
  1998年   113篇
  1997年   104篇
  1996年   96篇
  1995年   91篇
  1994年   72篇
  1993年   51篇
  1992年   29篇
  1991年   31篇
  1990年   27篇
  1989年   29篇
  1988年   32篇
  1987年   31篇
  1986年   17篇
  1985年   18篇
  1984年   19篇
  1983年   21篇
  1982年   24篇
  1981年   8篇
  1980年   19篇
  1975年   9篇
  1974年   9篇
  1973年   7篇
  1971年   8篇
  1968年   7篇
排序方式: 共有9991条查询结果,搜索用时 15 毫秒
1.
2.

Background

The purpose of the study was to evaluate the association between fetal echocardiographic measurements and the need for intervention (primary coarctation repair, staged coarctation repair, or catheter intervention) in prenatally diagnosed coarctation of the aorta.

Methods

A single-centre retrospective cohort study (2005-2015) of 107 fetuses diagnosed with suspected coarctation of the aorta in the setting of an apex-forming left ventricle and antegrade flow across the mitral and aortic valves.

Results

Median gestational age at diagnosis was 32 weeks (interquartile range, 23-35 weeks). Fifty-six (52%) did not require any neonatal intervention, 51 patients (48%) underwent a biventricular repair. In univariable analysis, an increase in ascending aorta (AAo) peak Doppler flow velocity (odds ratio [OR], 1.40 [95% confidence interval [CI], 1.05-1.91] per 20 cm/s; P = 0.03) was associated with intervention. No intervention was associated with larger isthmus size (OR, 0.23; P < 0.001), transverse arch diameter (OR, 0.23; P < 0.001), and aortic (OR, 0.72; P = 0.02), mitral (OR, 0.58; P = 0.001), and AAo (OR, 0.53; P < 0.001) z-scores. In multivariable analysis, higher peak AAo Doppler (OR, 2.51 [95% CI, 1.54-4.58] per 20 cm/s; P = 0.001) and younger gestational age at diagnosis (OR, 0.81 [95% CI, 0.70-0.93] per week; P = 0.005) were associated with intervention, whereas a higher AAo z-score (OR, 0.65 [95% CI, 0.43-0.94] per z; P = 0.029) and transverse arch dimension (OR, 0.44 [95% CI, 0.18-0.97]; P = 0.05) decreased the risk of intervention.

Conclusions

In prenatally suspected coarctation, the variables associated with intervention comprised smaller AAo and transverse arch size, earlier gestational age at diagnosis, and the additional finding of a higher peak AAo Doppler.  相似文献   
3.
4.
5.
6.
7.
Coinciding with the present period of unemployment, a corps of school assistants – assistants de vie scolaire (AVS) – has been created in order to meet the demand for in-school assistance raised by the development of schooling for children with special needs. This paper reports on a questionnaire-based survey carried out among 151 AVS working in the Seine Saint-Denis department. It aims at describing their working conditions considering the precariousness of their status (temporary jobs, poor pay) and the nature of their assignment. The main question bears on whether these conditions enable the assistants to develop the capabilities necessary for dealing with their tasks. Results could contribute to the present issue of reorienting government action in order to improve these jobs in terms of professional development. Notably, they reveal that AVS's training is usually brief and that their opportunities for developing workplace professional relationships are scant even though these are needed for them to collaborate with the other workers concerned by schooling children with special needs.  相似文献   
8.
Management of upper gastrointestinal bleeding because of erosion of vessels by esophageal cancer may be challenging. We present herein the angiographic images of a 49-year-old patient who was admitted with massive bleeding from a tumor-eroded inferior thyroid artery. Attempts to control the bleeding by means of flexible endoscopy and insertion of a Sengstaken–Blakemore tube had failed. The diagnosis was impressively demonstrated by multislice computed tomography with intravenous contrast in the arterial phase and multiplanar reconstructions (computed tomography angiography) and by digital subtraction angiography. The bleeding was successfully treated with superselective catheterization and coiling of the eroded vessel.  相似文献   
9.
10.
A cytomorphometric analysis of superficial vaginal cells inwomen in three groups of different types of hormonal concentrationwas made. There were 15 women in each group. Group I was studiedduring a natural cycle, group II under oral contraceptive therapyand group III during an in-vitro fertilization (IVF) stimulationprotocol. Morphometric parameters were measured on an imageanalyser. The area, perimeter and several form factors weremeasured separately for nuclei and cytoplasm. The nucleus:cytoplasmicratio was also determined. The cytoplasmic area was significantlyreduced in group II and was associated with a statisticallysignificant reduction of the nuclear area. The nucleus:cytoplasmicratio appeared significantly increased in group II and reducedin group III. Low oestradiol impregnation obtained with an oralminidosed contraceptive interfered with vaginal cell maturation.High oestradiol concentrations obtained during IVF protocolsinduced marked nuclear pycnosis but did not induce supra-physiologicalcell enlargement. Maximal cell size is genetically regulatedaccording to Driesch's law of volume invariance and hormonalover-stimulation has no effect on cell size. The nucleus:cytoplasmicratio appears to be a powerful parameter reflecting the oppositeeffects of hormones on cell compartments.  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