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   2439篇
  免费   177篇
  国内免费   5篇
耳鼻咽喉   14篇
儿科学   42篇
妇产科学   19篇
基础医学   269篇
口腔科学   45篇
临床医学   139篇
内科学   765篇
皮肤病学   24篇
神经病学   231篇
特种医学   69篇
外科学   501篇
综合类   7篇
预防医学   55篇
眼科学   58篇
药学   91篇
中国医学   4篇
肿瘤学   288篇
  2023年   28篇
  2022年   42篇
  2021年   92篇
  2020年   63篇
  2019年   66篇
  2018年   95篇
  2017年   63篇
  2016年   67篇
  2015年   83篇
  2014年   102篇
  2013年   105篇
  2012年   187篇
  2011年   185篇
  2010年   100篇
  2009年   91篇
  2008年   139篇
  2007年   149篇
  2006年   132篇
  2005年   149篇
  2004年   144篇
  2003年   121篇
  2002年   124篇
  2001年   24篇
  2000年   25篇
  1999年   25篇
  1998年   27篇
  1997年   14篇
  1996年   23篇
  1995年   17篇
  1994年   14篇
  1993年   18篇
  1992年   16篇
  1991年   11篇
  1990年   6篇
  1989年   8篇
  1988年   7篇
  1987年   7篇
  1986年   9篇
  1985年   3篇
  1984年   5篇
  1983年   2篇
  1982年   5篇
  1981年   4篇
  1980年   6篇
  1979年   2篇
  1978年   4篇
  1977年   5篇
  1976年   3篇
  1975年   2篇
  1969年   1篇
排序方式: 共有2621条查询结果,搜索用时 15 毫秒
41.
Summary The chronic effects of the oral administration of OPC-8212 (3,4-DIHYDRO-6-[4-(3,4-dimethoxybenzoyl)-1-piperazinyl]-2(1H)-quinolinone) on resting hemodynamics and exercise capacity were assessed in 15 patients with congestive heart failure (NYHA II–IV). Doses of 30 or 60 mg per day were given per os over 3.0 weeks on average (range 2–6 weeks). Multigated radionuclide ventriculography and multistage exercise testing were performed before and during OPC-8212 therapy to assess the changes in left ventricular volume and exercise capacity respectively. Systolic blood pressure showed a slight increase (from 123±3 to 129±4 mmHg) during OPC-8212 therapy, while heart rate was unchanged (69±3 vs 67±3 beats/min). The left ventricular end-diastolic volume index decreased from 127±9 to 107±7 ml/m2, and ejection fraction and the P/V index (the ratio of peak systolic pressure to left ventricular end-systolic volume index) increased during OPC-8212 therapy (from 27%±3% to 30%±4% and from 1.5±0.2 to 2.0±0.3 mmHg/ml/m2 respectively). NYHA functional class was improved in 9 of 15 patients, and the average peak work load achieved during exercise testing increased from 27±6 to 47±7 W. No significant adverse effect was observed in any patient. These results indicate that OPC-8212 enhances the inotropic state and, hence, reduces heart size with no change in heart rate. Moreover, it increases exercise capacity. Thus, OPC-8212 is an inotropic agent with promise for application in the long-term treatment of congestive heart failure.  相似文献   
42.
RATIONALE: Adrenomedullin, a potent vasodilator peptide, regulates cell growth and survival. However, whether adrenomedullin contributes to lung regeneration remains unknown. OBJECTIVES: To investigate whether adrenomedullin influences the kinetics of bone marrow cells, and whether adrenomedullin promotes regeneration of alveoli and vasculature and thereby improves lung structure and function in elastase-induced emphysema in mice. METHODS: Adrenomedullin or vehicle was randomly administered to C57BL/6 mice for 5 days. We counted the numbers of mononuclear cells and stem cell antigen-1-positive cells in circulating blood. After intratracheal injection of elastase or saline, mice were randomized to receive continuous infusion of adrenomedullin or vehicle for 14 days. Functional and histologic analyses were performed 28 days after treatment. RESULTS: Twenty-eight days after elastase injection, destruction of the alveolar walls was observed. However, adrenomedullin infusion significantly inhibited the increase in lung volume, static lung compliance, and mean linear intercept in mice given elastase. Adrenomedullin increased the numbers of mononuclear cells and stem cell antigen-1-positive cells in circulating blood. Adrenomedullin significantly increased the number of bone marrow-derived cells incorporated into the elastase-treated lung. Some of these cells were positive for cytokeratin or von Willebrand factor. Infusion of adrenomedullin after the establishment of emphysema also had beneficial effects on lung structure and function. In vitro, addition of adrenomedullin attenuates elastase-induced cell death in alveolar epithelial cells and endothelial cells. CONCLUSIONS: Adrenomedullin improved elastase-induced emphysema at least in part through mobilization of bone marrow cells and the direct protective effects on alveolar epithelial cells and endothelial cells.  相似文献   
43.
BACKGROUND: To investigate the activation patterns and conduction velocity (CV) in the posterolateral right atrial (RA) wall during typical counterclockwise atrial flutter (AFL) using an electroanatomic mapping system. METHODS AND RESULTS: During typical AFL in 25 patients, the transverse conduction pattern and CV were classified and calculated. The line blocking transverse conduction was defined by the conduction pattern and double potentials recorded during mapping. There were 3 types (including 2 subtypes) of transverse conduction pattern based on the conduction blocks across the posterolateral RA in a line between the superior and inferior venae cava. Trans-cristal conduction activation in a horizontal direction was seen in all but 4 patients. The CV in the gap area was 0.59+/-0.21 m/s. CONCLUSIONS: Three types of transverse conduction pattern were observed during trans-ctristal conduction and the trans-ctristal CV was relatively slower than that in other parts of the RA, except for the isthmus.  相似文献   
44.
45.
Asymptomatic dural arteriovenous fistulas (DAVFs) with cortical venous reflux (CVR) are now more commonly encountered. However, patients with an incidental onset may have a less aggressive clinical course. It is desirable to explore methods and indicators to predict the clinical outcomes. This study investigates whether the relative signal intensity (rSI) of the draining vessels on the time-of-flight magnetic resonance angiography is related to clinical behavior in patients with intracranial DAVFs. We retrospectively reviewed 36 intracranial DAVFs. The patients were categorized as those with either aggressive-presentation or non-aggressive-presentation (n = 16 and 20, respectively). The rSIs of the shunt points, affected sinuses, and veins with CVR were compared between the two groups. The two groups were not significantly different in terms of rSIs of the shunt points and affected sinuses (p = 0.37 and 0.41, respectively). However, a significant positive correlation was observed in the rSI of the veins with CVR between the aggressive and non-aggressive behavior groups (p < 0.0001). The rSI of the veins with CVR could serve as a reliable indicator of aggressive behavior in intracranial DAVFs, and its optimal cutoff value was 1.63 with high sensitivity and specificity for predicting aggressive behavior (area under the curve, 0.909).  相似文献   
46.
European Journal of Clinical Microbiology & Infectious Diseases - The aim of this study is to clarify the characteristics of gram-negative bacteremia (GNB), including extended-spectrum...  相似文献   
47.
48.
A 5-year-old girl presented with headache and vomiting. Head computed tomography and magnetic resonance imaging showed a right frontal lobe tumor with marked calcification. The patient underwent resection surgery with suspicion of anaplastic ependymoma, and the tumor was gross totally removed. Pathological examination revealed areas of dense tumor cells with a high nucleocytoplasmic ratio and myxoid areas consisting of tumor cells with a round-shaped nucleus and eosinophilic cytoplasm. Perivascular pseudorosette, necrosis, circumscribed growth, and microcalcification were also observed. Immunohistochemistry demonstrated negative staining for glial fibrillary protein and epithelial membrane antigen. Diagnosis of a high-grade neuroepithelial tumor (HGNET) with BCL6 corepressor (BCOR) alteration was made based on pathological findings and internal tandem duplication in the exon 15 of BCOR. Although calcification on radiological and pathological examination is not typical, it would be essential to recognize that calcification could appear in HGNET-BCOR.  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