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   32068篇
  免费   2172篇
  国内免费   733篇
耳鼻咽喉   203篇
儿科学   763篇
妇产科学   78篇
基础医学   1557篇
口腔科学   30篇
临床医学   5910篇
内科学   13836篇
皮肤病学   38篇
神经病学   569篇
特种医学   1082篇
外科学   3065篇
综合类   4403篇
现状与发展   2篇
一般理论   1篇
预防医学   463篇
眼科学   32篇
药学   2134篇
  10篇
中国医学   676篇
肿瘤学   121篇
  2024年   25篇
  2023年   513篇
  2022年   693篇
  2021年   1244篇
  2020年   1184篇
  2019年   1304篇
  2018年   1213篇
  2017年   795篇
  2016年   722篇
  2015年   926篇
  2014年   2089篇
  2013年   1897篇
  2012年   1390篇
  2011年   1644篇
  2010年   1461篇
  2009年   1373篇
  2008年   1567篇
  2007年   1604篇
  2006年   1367篇
  2005年   1280篇
  2004年   1050篇
  2003年   958篇
  2002年   817篇
  2001年   858篇
  2000年   682篇
  1999年   673篇
  1998年   620篇
  1997年   613篇
  1996年   502篇
  1995年   430篇
  1994年   403篇
  1993年   343篇
  1992年   335篇
  1991年   315篇
  1990年   265篇
  1989年   203篇
  1988年   204篇
  1987年   197篇
  1986年   181篇
  1985年   170篇
  1984年   181篇
  1983年   126篇
  1982年   123篇
  1981年   88篇
  1980年   72篇
  1979年   72篇
  1978年   55篇
  1977年   38篇
  1976年   37篇
  1973年   27篇
排序方式: 共有10000条查询结果,搜索用时 171 毫秒
991.

Objectives

The aim of this study was to assess the implications of concomitant tricuspid regurgitation (TR) in patients undergoing valve-in-valve (VIV) transcatheter aortic valve replacement.

Background

Patients undergoing VIV transcatheter aortic valve replacement with concomitant TR may have worse outcomes, and optimal management remains undetermined.

Methods

The multicenter PARTNER 2 (Placement of Aortic Transcatheter Valves) VIV trial enrolled patients with symptomatic degenerated surgical aortic bioprostheses who were at high risk for reoperation. Outcomes were assessed between patients with mild or no TR versus moderate or severe TR.

Results

A total of 237 patients underwent VIV procedures (mean age 78.7 ± 10.8 years, mean Society of Thoracic Surgeons score 9.1 ± 4.8%). In this cohort, 162 patients (68.4%) had mild or no TR, and 75 patients (31.6%) had moderate or severe TR. Although there was no difference in New York Heart Association functional class III or IV symptomatic status (89.3% vs. 91.4%; p = 0.62) or moderate or severe right ventricular dysfunction (9.4% vs. 16.9%; p = 0.11), patients with moderate or severe TR were more likely to be at high surgical risk, with a Society of Thoracic Surgeons score of >8 (62.7% vs 46.9%; p = 0.02). There was no difference in a composite endpoint of death and rehospitalization between moderate or severe TR and mild or no TR, either at 30 days (10.7% vs. 9.9%; p = 0.85) or at 1-year follow-up (24.1% vs. 23.2%; p = 0.80). There was a significant reduction in overall moderate or severe TR from baseline at 30 days (31.1% vs. 21.1%; p = 0.002), which was sustained at 1-year follow-up (38.0% vs. 22.8%; p = 0.004).

Conclusions

Despite higher predicted surgical risk, the presence of TR was not a predictor of long-term outcomes. Importantly, there was significant reduction in TR severity at both short- and long-term follow-up. In selected patients undergoing VIV transcatheter aortic valve replacement, it may be appropriate to conservatively manage concomitant TR.  相似文献   
992.
《JACC: Cardiovascular Imaging》2020,13(12):2561-2572
ObjectivesThe aim of this study was to investigate the relationship between extracellular volume fraction (ECV), a noninvasive parameter that quantifies the degree of diffuse myocardial fibrosis on cardiac magnetic resonance (CMR), and left ventricular diastolic dysfunction (LVDD) in patients with aortic stenosis (AS).BackgroundMyocardial fibrosis on invasive myocardial biopsy is associated with LVDD. However, there is a paucity of data on the association between noninvasively quantified diffuse myocardial fibrosis and the degree of LVDD and how these are related to symptoms and long-term prognosis in patients with AS.MethodsPatients with moderate or severe AS (n = 191; mean age 68.4 years) and 30 control subjects without cardiovascular risk factors underwent CMR. LVDD grade was evaluated using echocardiography according to the 2016 American Society of Echocardiography/European Association of Cardiovascular Imaging guidelines. Clinical outcomes were defined as a composite of all-cause mortality or hospitalization for heart failure aggravation.ResultsPatients in higher ECV quintiles had a significantly higher prevalence of LVDD. Higher ECV was particularly associated with decreased myocardial relaxation (septal e′ <7 cm/s) and increased LV filling pressure (E/e′ ratio ≥15). Although both impaired diastolic function and higher ECV were significantly associated with a worse degree of dyspnea, patients with higher ECV showed greater dyspnea within the same grade of LVDD. During a median follow-up period of 5.6 years, 37 clinical events occurred. Increased ECV, as well as lower septal e′ and higher E/septal e′ ratio, were independent predictors of clinical events, irrespective of age, AS severity, aortic valve replacement, and left ventricular (LV) ejection fraction. ECV provided incremental prognostic value on top of clinical factors and LV systolic and diastolic function.ConclusionsDiffuse myocardial fibrosis, assessed using ECV on CMR, was associated with LVDD in patients with AS, but both ECV and LV diastolic function parameters provided a complementary explanation for dyspnea and clinical outcomes. Concomitant assessment of both LVDD and diffuse myocardial fibrosis may further identify patients with AS with greater symptoms and worse prognosis.  相似文献   
993.
老年高血压患者胰岛素抵抗与左室结构改变的关系   总被引:1,自引:0,他引:1  
目的探讨老年原发性高血压患者胰岛素抵抗(IR)在高血压发生、发展过程中对左室结构的影响。方法72例高血压患肯依照左室质量指数(LVMI)和相对室壁厚度(RWT)分为左室正常构型组(34例)、向心性重构组(18例)、向心性肥厚组(11例)、离心性肥厚组(9例),并行口服葡萄糖耐量试验(OGTT)加同步胰岛素释放试验,计算胰岛素敏感性指数(ISI)、血糖曲线下面积(AG)、胰岛素曲线下面积(AI)、空腹血胰岛素/空腹血糖(FSI/FSG)比值、AI/AG比值。设健康对照组35例。应用单元和多元回归分析观察RWT和LVMI与各胰岛素敏感性指标的关系。结果高血压组的RWT与FSI、FSG无关(P〉0.05),与AI、AG呈正相关(r值分别为0.160、0.227,P〈0.05),与ISI呈负相关(r值为=0.266,P〈0.01);LVMI与各胰岛素敏感性指标无相关性(P〉0.05)。逐步回归分析显示RWT与ISI呈独立相关(r^2=0.071、P〈0.05)。结论高胰岛素血症(HIS)及IR存在于老年高血压患者各种左室几何构型中,其中与向心性重构关系最密切,与IR相关的HIS是参与和促进左心室向心性重构的重要影响因素。  相似文献   
994.
经皮冠状动脉介入治疗能够有效防止左室重构 ,改善左室功能 ,但其作用机制和实行时机尚不明确。通过对其作用机制及实行时机的研究 ,为及时、有效实行PCI提供理论依据。  相似文献   
995.
左室舒张功能障碍在心血管疾病中很常见,二尖瓣血流频谱是评价左室舒张功能障碍的经典方法,但存在不足。多普勒组织显像技术是一项应用多普勒原理分析心肌组织运动的新技术,包括心肌速度显像、定量组织速度显像、组织追踪以及应变/应变率,这些方法为评价左室舒张功能提供更多、更有益的信息。  相似文献   
996.
目的观察辛伐他汀对自发性高血压大鼠左心室肥厚作用及心肌转化生长因子-β1(TGF-β1)表达的的影响。方法实验用WKY大鼠做阴性对照组,SHR大鼠分为对照组和辛伐他汀治疗组。测量大鼠尾动脉收缩压(SBP)及左心室重量指数(LVMI)。应用HE、VG染色、免疫组织化学的方法,结合计算机图像分析技术,检测心肌细胞的直径(TDM)和面积(CA)、心肌组织胶原体积比例(CVF)、血管周围胶原面积和管腔面积比例(PVCA)以及左心室心肌TGF-β1表达。结果辛伐他汀组未能有效降低血压,但可以降低左心室肥厚;SHR辛伐他汀组与SHR对照组相比TDM、CA、CVF、PVCA明显降低,TGF-β1表达下调明显(均P<0.05)。结论应用辛伐他汀治疗可逆转高血压大鼠左心室肥厚形成,TGF-β1可能与辛伐他汀逆转左心室肥厚的机制有关。  相似文献   
997.
Overall, 133 patients underwent 170 procedures for the treatment of persistent ATa following an index cryoballoon pulmonary vein isolation (n = 715). After all the procedures, > 90% of the patients had a roof line, a mitral isthmus and/or septal line, and a cavotricuspid isthmus line. Ninety-two patients (69.2%) were in sinus rhythm after a median of 36 months since the index cryoballoon PVI. ATa: atrial tachyarrhythmia; cryo: cryoballoon; CTI: cavotricuspid isthmus; LSPV: left superior pulmonary vein; LIPV: left inferior pulmonary vein; PVI: pulmonary vein isolation; RF: radiofrequency; RSPV: right superior pulmonary vein; RIPV: right inferior pulmonary vein.
  相似文献   
998.
BACKGROUND: Plasma concentrations of atrial natriuretic peptides are correlated with atrial pressures, as are left ventricular ejection fraction and left ventricular filling abnormalities. AIMS: This study investigated the relation of atrial natriuretic peptides to both left ventricular systolic and diastolic function in heart failure. METHODS: Plasma concentrations of atrial natriuretic peptide and N-terminal pro-atrial natriuretic peptide were measured in 63 patients with chronic heart failure and left ventricular systolic dysfunction. According to Doppler transmitral flow measurements, 19 patients had a restrictive and 44 patients had a non-restrictive left ventricular filling pattern. RESULTS: Plasma concentrations of atrial natriuretic peptide and N-terminal pro-atrial natriuretic peptide were higher in patients with a restrictive filling pattern than in patients with a non-restrictive filling pattern (197 vs. 75 pmol/l, P<0.0001 and 1.14 vs. 0.45 nmol/l, P<0.0001). In univariate analysis, atrial natriuretic peptide and N-terminal pro-atrial natriuretic peptide correlated with deceleration time, E/A ratio and left ventricular ejection fraction. In multivariate analysis, both peptides appeared independently related to left ventricular ejection fraction and left ventricular filling pattern. CONCLUSION: In patients with chronic heart failure, atrial natriuretic peptides provide information on left ventricular systolic as well as diastolic function.  相似文献   
999.
为评价链激酶溶栓治疗急性心肌梗死(AMI)对左心室功能的影响,应用二维超声心动图对26例接受链激酶溶栓治疗的AMI患者和27例未溶栓的AMI患者,分别在急性期及6个月后随访时测量并计算左心室容积(EDV和ESV),射血分数(EF)以及室壁运动指数(GWMI和RWMI)。以上各项指标在急性期时比较各组无显著性差异;在随访期再通组EF值明显高于未通组和未溶栓组,再通组左室容量减小。急性期各组心功能无差异,随访时再通组心功能较未通组显著改善。提示:链激酶溶栓能明显减轻AMI患者的左心室扩张,改善左心室功能和长期预后  相似文献   
1000.
对19例劳力型心痛病人给予尼可地尔口服2周,通过卧位踏车试验观运动心电图二尖瓣口多普勒血流变化。用药后S-5段下降消失时间,运动持续时间及运动工作负荷明显改善,静息及运动工作后A/E比,E峰减时间及减速度明显改善,表明尼可地尔能改善冠心病人的左室舒张功能,提高运动耐力。  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