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   970996篇
  免费   78769篇
  国内免费   2333篇
耳鼻咽喉   13983篇
儿科学   27946篇
妇产科学   26992篇
基础医学   138800篇
口腔科学   27397篇
临床医学   86265篇
内科学   187457篇
皮肤病学   18342篇
神经病学   80793篇
特种医学   38617篇
外国民族医学   172篇
外科学   151821篇
综合类   26092篇
现状与发展   3篇
一般理论   413篇
预防医学   76706篇
眼科学   23562篇
药学   72484篇
  1篇
中国医学   1841篇
肿瘤学   52411篇
  2018年   9870篇
  2016年   8657篇
  2015年   10142篇
  2014年   14608篇
  2013年   21807篇
  2012年   30256篇
  2011年   31929篇
  2010年   18278篇
  2009年   17196篇
  2008年   29715篇
  2007年   32145篇
  2006年   31673篇
  2005年   31305篇
  2004年   30478篇
  2003年   29152篇
  2002年   27984篇
  2001年   36887篇
  2000年   37267篇
  1999年   32024篇
  1998年   10520篇
  1997年   9640篇
  1996年   9319篇
  1995年   8856篇
  1994年   8447篇
  1992年   27259篇
  1991年   26634篇
  1990年   26081篇
  1989年   25128篇
  1988年   23677篇
  1987年   23320篇
  1986年   22102篇
  1985年   21541篇
  1984年   16884篇
  1983年   14465篇
  1982年   9481篇
  1981年   8745篇
  1980年   8158篇
  1979年   17059篇
  1978年   12425篇
  1977年   10478篇
  1976年   9585篇
  1975年   10382篇
  1974年   12886篇
  1973年   12370篇
  1972年   11711篇
  1971年   10825篇
  1970年   10342篇
  1969年   10032篇
  1968年   9010篇
  1967年   8333篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
Porocarcinoma is an unusual, locally aggressive and potentially fatal neoplasm. Several cutaneous malignancies have been described in association with porocarcinoma, including squamous cell carcinoma, basal cell carcinoma and tricholemmal carcinoma. Previous reports have indicated that the occurrence of malignant tumours in combination with porocarcinoma is extremely rare, in particular with regard to Bowen disease (BD). We report an uncommon case of porocarcinoma occurring synchronously in a single BD lesion in a 63‐year‐old woman with multiple BD lesions. The clinical and histological findings confirmed this diagnosis.  相似文献   
42.
43.
DNA methylation at CpG dinucleotides is an important epigenetic regulator common to virtually all mammalian cell types, but recent evidence indicates that during early postnatal development neuronal genomes also accumulate uniquely high levels of two alternative forms of methylation, non-CpG methylation and hydroxymethylation. Here we discuss the distinct landscape of DNA methylation in neurons, how it is established, and how it might affect the binding and function of protein readers of DNA methylation. We review studies of one critical reader of DNA methylation in the brain, the Rett syndrome protein methyl CpG-binding protein 2 (MeCP2), and discuss how differential binding affinity of MeCP2 for non-CpG and hydroxymethylation may affect the function of this methyl-binding protein in the nervous system.  相似文献   
44.
We present a patient with both dynamic left ventricular outflow tract obstruction and valvular aortic stenosis. The aortic valve was calcified, and velocities and gradients measured by continuous‐wave Doppler met standard criteria for severe aortic stenosis. The increased subvalvular velocities invalidated assumptions of the simplified Bernoulli equation; correction using the longer form of the Bernoulli equation suggested a lower but still significant gradient. The complex shape of the subvalvular spectral Doppler envelope indicated supranormal systolic function and dynamic left ventricular outflow obstruction. Left heart catheterization with an end‐hole catheter was required to determine the subvalvular and valvular components of the obstruction.  相似文献   
45.
46.
47.
48.
49.
50.

Objective

Arch obstruction after the Norwood procedure is common and contributes to mortality. We determined the prevalence, associated factors, and practice variability of arch reintervention and assessed whether arch reintervention is associated with mortality.

Methods

From 2005 to 2017, 593 neonates in the Congenital Heart Surgeons' Society Critical Left Heart Obstruction cohort underwent a Norwood procedure. Median follow-up was 3.7 years. Multivariable parametric models, including a modulated renewal analysis, were performed.

Results

Of the 593 neonates, 146 (25%) underwent 218 reinterventions for arch obstruction after the Norwood procedure: catheter-based (n = 168) or surgical (n = 50) at a median age of 4.3 months (quartile 1-quartile 3, 2.6-5.7). Interdigitation of the distal aortic anastomosis was protective against arch reintervention. Development of ≥ moderate tricuspid valve regurgitation and right ventricular dysfunction at any point was associated with arch reintervention. Nonsignificant variables for arch reintervention included shunt type and preoperative aortic measurements. Surgical arch reintervention was protective against arch reintervention, but transcatheter reintervention was associated with increased reintervention. Arch reintervention was not associated with increased mortality. There was wide institutional variation in incidence of arch reintervention (range, 0-40 reinterventions per 100 years patient follow-up) and in preintervention gradient (range, 0-64 mm Hg).

Conclusions

Interdigitation of the distal aortic anastomosis during the Norwood procedure decreased the risk of arch reintervention. Surgical arch reintervention is more definitive than transcatheter. Arch reintervention after the Norwood procedure is not associated with increased mortality. Serial surveillance for arch obstruction, integrated with changes in right ventricular function and tricuspid valve regurgitation, is recommended after the Norwood procedure to improve outcomes.  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