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   69163篇
  免费   5071篇
  国内免费   444篇
耳鼻咽喉   881篇
儿科学   1787篇
妇产科学   1421篇
基础医学   8633篇
口腔科学   1029篇
临床医学   7370篇
内科学   14490篇
皮肤病学   1249篇
神经病学   5376篇
特种医学   2514篇
外科学   10474篇
综合类   1552篇
一般理论   72篇
预防医学   4975篇
眼科学   2094篇
药学   5224篇
中国医学   335篇
肿瘤学   5202篇
  2023年   462篇
  2022年   831篇
  2021年   2027篇
  2020年   1242篇
  2019年   1742篇
  2018年   2156篇
  2017年   1558篇
  2016年   1686篇
  2015年   2013篇
  2014年   2813篇
  2013年   3560篇
  2012年   5078篇
  2011年   5277篇
  2010年   2885篇
  2009年   2613篇
  2008年   4289篇
  2007年   4315篇
  2006年   4123篇
  2005年   4088篇
  2004年   3734篇
  2003年   3396篇
  2002年   3088篇
  2001年   1302篇
  2000年   1216篇
  1999年   1119篇
  1998年   666篇
  1997年   497篇
  1996年   475篇
  1995年   356篇
  1994年   353篇
  1993年   326篇
  1992年   537篇
  1991年   516篇
  1990年   486篇
  1989年   459篇
  1988年   406篇
  1987年   410篇
  1986年   353篇
  1985年   311篇
  1984年   257篇
  1983年   203篇
  1982年   163篇
  1981年   129篇
  1980年   122篇
  1979年   159篇
  1978年   109篇
  1977年   89篇
  1976年   88篇
  1975年   90篇
  1972年   75篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
12.
13.
14.
15.
16.
17.

Background

Persistent iatrogenic atrial septal defect (iASD) is a common but poorly characterized complication after cryoballoon (CB) pulmonary vein isolation (PVI) procedures. We therefore investigate its prevalence, evolution, risk factors, and clinical outcomes in a prospective longitudinal study.

Methods

A total of 108 patients (41 women, mean age 57 ± 11.3) underwent CB PVI for AF. Serial transesophageal echocardiography (TEE) was performed 9 months and then annually until 6 years after the procedure to study the characteristics of persistent iASD.

Results

Persistent iASD occurred in 33 (30.6%) patients 9 months after CB PVI. Spontaneous closure of iASD was found in 6 (22.2%) and 3 (15.8%) patients 2 and 3 years after the procedures, respectively. No spontaneous closure was observed on 4, 5, and 6-year TEE follow-up. The projected long-term persistence rate of iASD after CB PVI was therefore 20% (30.6% × 0.778 × 0.842). Using multivariate logistic regression, a higher number of cryoapplications (≥ 2 minutes) was the only independent predictor of persistent iASD 9 months after CB PVI (odds ratio [OR] 1.207; 95% confidence interval [CI], 1.033-1.411, P = 0.018). Two (1.9%) patients with significantly larger iASD size than the others (long diameter 12.6 ± 0.8 vs 3.7 ± 1.5 mm, P < 0.001; short diameter 10.9 ± 0.2 vs 3 ± 1.1 mm, P < 0.001) required percutaneous closure because of exertional dyspnea and right ventricular enlargement. Over 129.7 patient-years follow-up, during which iASD persisted, there was no occurrence of neurologic events.

Conclusions

Approximately one fifth of patients undergoing CB PVI will have permanently persistent iASD. Patients with defect sizes of greater than 10 mm may need percutaneous closure due to significant left-to-right shunting.  相似文献   
18.
A pathological feature in atherosclerosis is the dysfunction and death of vascular endothelial cells (EC). Oxidized low‐density lipoprotein (LDL), known to accumulate in the atherosclerotic arterial walls, impairs endothelium‐dependent relaxation and causes EC apoptosis. A major bioactive ingredient of the oxidized LDL is lysophosphatidylcholine (LPC), which at higher concentrations causes apoptosis and necrosis in various EC. There is hitherto no report on LPC‐induced cytotoxicity in brain EC. In this work, we found that LPC caused cytosolic Ca2+ overload, mitochondrial membrane potential decrease, p38 activation, caspase 3 activation and eventually apoptotic death in mouse cerebral bEND.3 EC. In contrast to reported reactive oxygen species (ROS) generation by LPC in other EC, LPC did not trigger ROS formation in bEND.3 cells. Pharmacological inhibition of p38 alleviated LPC‐inflicted cell death. We examined whether heparin could be cytoprotective: although it could not suppress LPC‐triggered Ca2+ signal, p38 activation and mitochondrial membrane potential drop, it did suppress LPC‐induced caspase 3 activation and alleviate LPC‐inflicted cytotoxicity. Our data suggest LPC apoptotic death mechanisms in bEND.3 might involve mitochondrial membrane potential decrease and p38 activation. Heparin is protective against LPC cytotoxicity and might intervene steps between mitochondrial membrane potential drop/p38 activation and caspase 3 activation.  相似文献   
19.
In the present review, we updated current information on the chemistry, contents, and anticancer properties of matrine (MT), oxymatrine (OMT), and compound Kushen injection (CKI). The anticancer properties were focused on lung, breast, and liver cancer cells because they are most susceptible. Sources of information were from Google, Google Scholar, PubMed, PubMed Central, Science Direct, PubChem, J-Stage, Directory of Open Access Journals (DOAJ), and China National Knowledge Infrastructure (CNKI). Reference was also made on botanical websites, such as Flora of China and World Flora Online. MT and OMT are dominant quinolizidine alkaloids from the roots of Sophora flavescens (Kushen) of the family Fabaceae. Against lung, breast, and liver cancer cells, MT and OMT inhibit cell proliferation; induce cell cycle arrest, apoptosis, and autophagy; restrict angiogenesis; and inhibit cell metastasis, invasion, and migration. The processes involve various molecular targets and signaling pathways. CKI is a traditional Chinese medicine (TCM) composed of root extracts of S. flavescens and Smilax glabra (Baituling) of the family Smilacaceae. With MT and OMT as major components, CKI has been approved for the treatment of cancer in China more than 20 years ago. In recent years, systematic reviews and meta-analysis have been undertaken to evaluate the anticancer effects of CKI. When CKI is used alone and in combination with chemotherapy of western medicine, there is much to be learned concerning their interactions besides their individual and integrated efficacy. Some perspectives of MT, OMT, and CKI are discussed, and their suggestions for future research are provided.  相似文献   
20.
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