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   223382篇
  免费   46657篇
  国内免费   4403篇
耳鼻咽喉   2262篇
儿科学   7043篇
妇产科学   1584篇
基础医学   36726篇
口腔科学   8449篇
临床医学   20167篇
内科学   39178篇
皮肤病学   6620篇
神经病学   28179篇
特种医学   7686篇
外国民族医学   9篇
外科学   22347篇
综合类   13536篇
现状与发展   5篇
一般理论   8篇
预防医学   14929篇
眼科学   2440篇
药学   35002篇
  22篇
中国医学   9849篇
肿瘤学   18401篇
  2024年   345篇
  2023年   1959篇
  2022年   3689篇
  2021年   5547篇
  2020年   9250篇
  2019年   14508篇
  2018年   13888篇
  2017年   15185篇
  2016年   14157篇
  2015年   14416篇
  2014年   16605篇
  2013年   18128篇
  2012年   15828篇
  2011年   16558篇
  2010年   13912篇
  2009年   10325篇
  2008年   11070篇
  2007年   9458篇
  2006年   8693篇
  2005年   7931篇
  2004年   7428篇
  2003年   6574篇
  2002年   5756篇
  2001年   4581篇
  2000年   3379篇
  1999年   2018篇
  1998年   1765篇
  1997年   1638篇
  1996年   1524篇
  1995年   1413篇
  1994年   1266篇
  1993年   1115篇
  1992年   1097篇
  1991年   1000篇
  1990年   942篇
  1989年   860篇
  1988年   774篇
  1987年   720篇
  1986年   719篇
  1985年   1214篇
  1984年   1247篇
  1983年   864篇
  1982年   928篇
  1981年   846篇
  1980年   767篇
  1979年   593篇
  1978年   487篇
  1977年   352篇
  1976年   314篇
  1975年   238篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
42.
43.

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   
44.
45.
46.
47.
In the “basic” approach, medical expenses are catastrophic if they exceed a prespecified percentage of consumption or income; the approach tells us if expenses cause a large percentage reduction in living standards. The ability‐to‐pay (ATP) approach defines expenses as catastrophic if they exceed a prespecified percentage of consumption less expenses on nonmedical necessities or an allowance for them. The paper argues that the ATP approach does not tell us whether expenses are large enough to undermine a household's ability to purchase nonmedical necessities. The paper compares the income‐based and consumption‐based variants of the basic approach, and shows that if the individual is a borrower after a health shock, the income‐based ratio will exceed the consumption‐based ratio, and both will exceed the more theoretically correct Flores et al. ratio; whereas if the individual continues to be a saver after a health shock, the ordering is reversed and the income‐based ratio may not overestimate Flores et al.'s ratio. Last, the paper proposes a lifetime money metric utility (LMMU) approach defining medical expenses as catastrophic in terms of their lifetime consequences. Under certain assumptions, the LMMU and Flores et al. approaches are identical, and neither requires data on how households finance their medical expenses.  相似文献   
48.
A pulmonary artery (PA) sling is a very rare congenital cardiovascular anomaly, and only a few studies have reported PA slings in fetuses. The relationship of the PA, aorta, ductus arteriosus, and trachea can be evaluated in the 3‐vessel and 3‐vessel and trachea views during fetal echocardiography. A PA sling can be detected by abnormal positioning of the left PA in relation to the trachea when sweeping from the 3‐vessel view cranially to the 3‐vessel and trachea view. Here we report 3 cases of fetal PA slings and their follow‐ups. Two cases were confirmed by postnatal echocardiography, and the other case was confirmed by a cardiovascular cast after pregnancy termination. We emphasize that the 3‐vessel and 3‐vessel and trachea views are of crucial importance in the prenatal diagnosis of a PA sling.  相似文献   
49.
50.
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