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   7740篇
  免费   597篇
  国内免费   45篇
耳鼻咽喉   101篇
儿科学   217篇
妇产科学   188篇
基础医学   952篇
口腔科学   127篇
临床医学   997篇
内科学   1528篇
皮肤病学   66篇
神经病学   698篇
特种医学   859篇
外科学   1034篇
综合类   95篇
一般理论   4篇
预防医学   486篇
眼科学   115篇
药学   437篇
中国医学   2篇
肿瘤学   476篇
  2023年   44篇
  2022年   61篇
  2021年   131篇
  2020年   101篇
  2019年   130篇
  2018年   153篇
  2017年   124篇
  2016年   132篇
  2015年   145篇
  2014年   198篇
  2013年   284篇
  2012年   371篇
  2011年   478篇
  2010年   288篇
  2009年   311篇
  2008年   425篇
  2007年   405篇
  2006年   410篇
  2005年   360篇
  2004年   335篇
  2003年   277篇
  2002年   262篇
  2001年   234篇
  2000年   211篇
  1999年   191篇
  1998年   112篇
  1997年   111篇
  1996年   94篇
  1995年   77篇
  1994年   72篇
  1993年   60篇
  1992年   123篇
  1991年   97篇
  1990年   116篇
  1989年   120篇
  1988年   109篇
  1987年   91篇
  1986年   82篇
  1985年   106篇
  1984年   80篇
  1983年   68篇
  1982年   65篇
  1981年   52篇
  1980年   51篇
  1979年   54篇
  1978年   47篇
  1977年   38篇
  1974年   36篇
  1973年   32篇
  1970年   34篇
排序方式: 共有8382条查询结果,搜索用时 312 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.
OBJECTIVE: Respiratory muscle endurance of able-bodied persons, assessed by normocapnic hyperpnoea at 70% of their maximal voluntary ventilation, usually ranges from 10 to 20 minutes. The aim of this study was to determine the level of ventilation that patients with paraplegia and tetraplegia can sustain for 10-20 minutes to later be used as the guideline for respiratory muscle endurance training. DESIGN: Pilot study; cross-over setting. SUBJECTS: Two groups, 8 patients with paraplegia and 6 with tetraplegia. METHODS: Respiratory muscle endurance tests were performed at 3 different intensities of normocapnic hyperpnoea, i.e. 20%, 40% and 60% maximal voluntary ventilation. Subjects performed partial re-breathing from a bag to assure normocapnia. Respiratory endurance was separately analysed for patients with paraplegia and tetraplegia. RESULTS: Mean respiratory endurance times were 46.0, 18.9 and 4.2 minutes at 20%, 40% and 60% maximal voluntary ventilation in patients with tetraplegia and 51.8, 38.8 and 12.2 minutes in patients with paraplegia. The duration differed significantly at 60% maximal voluntary ventilation between the groups. CONCLUSION: Minute ventilation to perform respiratory muscle endurance training can be set at around 40% of maximal voluntary ventilation for patients with tetraplegia and around 60% of maximal voluntary ventilation for patients with paraplegia, as these levels can be sustained for 10-20 minutes.  相似文献   
6.
7.
8.
Wir berichten über den ersten Fall von polyzystischer lipomembran?ser Osteodysplasie oder “brain, bone and fat disease” in Deutschland. Die nach dem Erstbeschreibern auch als Morbus J?rvi-Hakola-Nasu bezeichnete Erkrankung ist bisher vor allem in Japan und in Finnland beschrieben worden. Einzelne F?lle wurden aus Schweden, Norwegen, Italien, Südafrika, Belgien und den USA berichtet. Im deutschsprachigen Raum ist bisher ein Fall aus ? ver?ffentlicht worden.  相似文献   
9.
Secretory antibodies protect mucosal surfaces against transmission of many viruses. Human T-lymphotropic Virus, Type I (HTLV-I) is transmitted via blood products and via sexual contact across mucosal surfaces. We investigated the presence of HTLV-I-specific antibodies in whole saliva samples from 10 seronegative and 28 seropositive volunteers from a hospital in southern Japan. Antibodies directed to HTLV-I antigens were found in the salivas from 22 of 28 (79%) of the seropositive subjects. None of the seronegative individuals showed evidence of salivary antibodies. Antibodies directed to the envelope antigens of the virus were found in 21 of 22 positive saliva samples. Secretory antibodies may be important in preventing mucosal transmission.  相似文献   
10.
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