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   11184篇
  免费   368篇
  国内免费   72篇
耳鼻咽喉   49篇
儿科学   400篇
妇产科学   250篇
基础医学   739篇
口腔科学   174篇
临床医学   737篇
内科学   2716篇
皮肤病学   172篇
神经病学   542篇
特种医学   212篇
外科学   1589篇
综合类   804篇
一般理论   5篇
预防医学   1749篇
眼科学   210篇
药学   797篇
  2篇
中国医学   238篇
肿瘤学   239篇
  2023年   108篇
  2022年   207篇
  2021年   315篇
  2020年   307篇
  2019年   752篇
  2018年   644篇
  2017年   384篇
  2016年   208篇
  2015年   223篇
  2014年   442篇
  2013年   447篇
  2012年   384篇
  2011年   419篇
  2010年   331篇
  2009年   319篇
  2008年   308篇
  2007年   297篇
  2006年   244篇
  2005年   176篇
  2004年   107篇
  2003年   119篇
  2002年   87篇
  2001年   93篇
  2000年   93篇
  1999年   60篇
  1998年   54篇
  1997年   43篇
  1996年   41篇
  1995年   38篇
  1994年   39篇
  1993年   41篇
  1992年   27篇
  1991年   28篇
  1989年   17篇
  1988年   22篇
  1987年   19篇
  1986年   17篇
  1985年   285篇
  1984年   483篇
  1983年   401篇
  1982年   400篇
  1981年   340篇
  1980年   316篇
  1979年   390篇
  1978年   283篇
  1977年   195篇
  1976年   283篇
  1975年   249篇
  1974年   255篇
  1973年   243篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
992.

Objectives

This was a first-in-human study to assess the feasibility, safety, and exploratory efficacy of interatrial shunting for treating high-risk heart failure (HF) in patients with reduced and preserved ejection fraction.

Methods

A single-arm open-label study of patients with New York Heart Association functional class III or IV HF on optimal therapy was performed at 6 centers. The V-Wave shunt, an hourglass-shaped implant containing a 1-way bioprosthetic valve, was implanted by transseptal catheterization. Clinical, functional, echocardiographic, and hemodynamic evaluations were performed at baseline, 3 and 12 months, and annually (clinical follow-up) thereafter (median follow-up 28 months; interquartile range: 21 to 31 months).

Results

A total of 38 patients were enrolled (30 with HF with reduced ejection fraction and 8 with HF with preserved ejection fraction; mean age 66 ± 9 years; 97% and 3% in New York Heart Association functional classes III and IV, respectively), and the shunt device was successfully implanted in all cases without periprocedural mortality. The rate of major device- or procedure-related complications during the first 12 months was 2.6% (periprocedural cardiac tamponade in 1 patient). At 3- and 12-month follow-up, there were improvements in New York Heart Association functional class (classes I and II in 78% and 60% of patients, respectively), quality of life (improvements ≥5 points in 74% and 73% of patients, respectively), and 6-min walk distance (mean increases of 41 ± 63 m and 28 ± 83 m, respectively) (p < 0.02 for all, data available for 36 patients), without changes in objective measures of left- or right-sided function. All shunts were patent at 3 months, but 5 of 36 (14%) had occluded, and another 13 of 36 (36%) were stenotic at the valve by 12 months. Patients with widely patent shunts had lower long-term rates of death, left ventricular assist device placement or heart transplantation (p = 0.001), and HF hospitalization (p = 0.008), along with a reduction of pulmonary capillary wedge pressure (from 23.3 ± 5.4 mm Hg at baseline to 18.0 ± 4.0 mm Hg at 12 months; p = 0.011).

Conclusions

Interatrial shunting with the V-Wave system was feasible and safe in patients with HF with reduced and preserved ejection fraction. Improvements in clinical and functional status were observed early and at 12 months despite attenuation of shunt patency in one-half of the patients. Patients with preserved shunt patency tended to maintain clinical benefit during longer term follow-up. Device modification that improves the durability of patency is likely worthwhile before confirmation of these findings in a randomized trial.  相似文献   
993.
994.

Background

Transcatheter mitral valve replacement (TMVR) is a potential therapy for patients with symptomatic, severe mitral regurgitation (MR). The feasibility of this therapy remains to be defined.

Objectives

The authors report their early experience with TMVR using a new valve system.

Methods

The valve is a self-expanding, nitinol valve with bovine pericardial leaflets that is placed using a transapical delivery system. Patients with symptomatic MR who were deemed high or extreme risk by the local heart teams were enrolled in a global pilot study at 14 sites (United States, Australia, and Europe).

Results

Fifty consecutively enrolled patients (mean age: 73 ± 9 years; 58.0% men; 84% secondary MR) underwent TMVR with the valve. The mean Society for Thoracic Surgery score was 6.4 ± 5.5%; 86% of patients were New York Heart Association functional class III or IV, and the mean left ventricular ejection fraction was 43 ± 12%. Device implant was successful in 48 patients with a median deployment time of 14 min (interquartile range: 12 to 17 min). The 30-day mortality was 14%, with no disabling strokes, or repeat interventions. Median follow-up was 173 days (interquartile range: 54 to 342 days). At latest follow-up, echocardiography confirmed mild or no residual MR in all patients who received implants. Improvements in symptom class (79% in New York Heart Association functional class I or II at follow-up; p < 0.0001 vs. baseline) and Minnesota Heart Failure Questionnaire scores (56.2 ± 26.8 vs. 31.7 ± 22.1; p = 0.011) were observed.

Conclusions

TMVR with the valve was feasible in a study group at high or extreme risk for conventional mitral valve replacement. These results inform trial design of TMVR in lower-risk patients with severe mitral valve regurgitation (Evaluation of the Safety and Performance of the Twelve Intrepid Transcatheter Mitral Valve Replacement System in High Risk Patients with Severe, Symptomatic Mitral Regurgitation – The Twelve Intrepid TMVR Pilot Study; NCT02322840)  相似文献   
995.

Background

Electrical storm (ES), characterized by unrelenting recurrences of ventricular arrhythmias, is observed in approximately 30% of patients with implantable cardioverter-defibrillators (ICDs) and is associated with high mortality rates.

Objectives

Sympathetic blockade with β-blockers, usually in combination with intravenous (IV) amiodarone, have proved highly effective in the suppression of ES. In this study, we compared the efficacy of a nonselective β-blocker (propranolol) versus a β1-selective blocker (metoprolol) in the management of ES.

Methods

Between 2011 and 2016, 60 ICD patients (45 men, mean age 65.0 ± 8.5 years) with ES developed within 24 h from admission were randomly assigned to therapy with either propranolol (160 mg/24 h, Group A) or metoprolol (200 mg/24 h, Group B), combined with IV amiodarone for 48 h.

Results

Patients under propranolol therapy in comparison with metoprolol-treated individuals presented a 2.67 times decreased incidence rate (incidence rate ratio: 0.375; 95% confidence interval: 0.207 to 0.678; p = 0.001) of ventricular arrhythmic events (tachycardia or fibrillation) and a 2.34 times decreased rate of ICD discharges (incidence rate ratio: 0.428; 95% CI: 0.227 to 0.892; p = 0.004) during the intensive care unit (ICU) stay, after adjusting for age, sex, ejection fraction, New York Heart Association functional class, heart failure type, arrhythmia type, and arrhythmic events before ICU admission. At the end of the first 24-h treatment period, 27 of 30 (90.0%) patients in group A, while only 16 of 30 (53.3%) patients in group B were free of arrhythmic events (p = 0.03). The termination of arrhythmic events was 77.5% less likely in Group B compared with Group A (hazard ratio: 0.225; 95% CI: 0.112 to 0.453; p < 0.001). Time to arrhythmia termination and length of hospital stay were significantly shorter in the propranolol group (p < 0.05 for both).

Conclusions

The combination of IV amiodarone and oral propranolol is safe, effective, and superior to the combination of IV amiodarone and oral metoprolol in the management of ES in ICD patients.  相似文献   
996.

Background

Potent P2Y12 inhibitors might offer enhanced benefit against thrombotic events in complex percutaneous coronary intervention (PCI). We examined prasugrel use and outcomes according to PCI complexity, as well as analyzing treatment effects according to thienopyridine type.

Methods

PROMETHEUS was a multicentre observational study that compared clopidogrel vs prasugrel in acute coronary syndrome patients who underwent PCI (n = 19,914). Complex PCI was defined as PCI of the left main, bifurcation lesion, moderate-severely calcified lesion, or total stent length ≥ 30 mm. Major adverse cardiac events (MACE) were a composite of death, myocardial infarction, stroke, or unplanned revascularization. Outcomes were adjusted using multivariable Cox regression for effect of PCI complexity and propensity-stratified analysis for effect of thienopyridine type.

Results

The study cohort included 48.9% (n = 9735) complex and 51.1% (n = 10,179) noncomplex patients. Second generation drug-eluting stents were used in 70.1% complex and 66.2% noncomplex PCI patients (P < 0.0001). Complex PCI was associated with greater adjusted risk of 1-year MACE (hazard ratio [HR], 1.29; 95% confidence interval [CI], 1.20-1.39; P < 0.001). Prasugrel was prescribed in 20.7% of complex and 20.1% of noncomplex PCI patients (P = 0.30). Compared with clopidogrel, prasugrel significantly decreased adjusted risk for 1-year MACE in complex PCI (HR, 0.79; 95% CI, 0.68-0.92) but not noncomplex PCI (HR, 0.91; 95% CI, 0.77-1.08), albeit there was no evidence of interaction (P interaction = 0.281).

Conclusions

Despite the use of contemporary techniques, acute coronary syndrome patients who undergo complex PCI had significantly higher rates of 1-year MACE. Adjusted magnitude of treatment effects with prasugrel vs clopidogrel were consistent in complex and noncomplex PCI without evidence of interaction.  相似文献   
997.
Coronary artery disease in patients with diabetes mellitus (DM) is characterized by extensive atherosclerosis, longer lesions, and diffuse distal disease. Consequently, these patients have worse outcomes after coronary revascularization, regardless of the modality used. Traditionally, coronary artery bypass grafting (CABG) has been regarded as more effective than percutaneous coronary intervention (PCI) in patients with DM, likely because of more complete revascularization and protection against disease progression in the bypass segment. Revascularization with balloon angioplasty, bare-metal stents, and first-generation drug-eluting stents have all been shown to be inferior to CABG in patients with DM. Current professional society guidelines reflect these findings, strongly recommending CABG over PCI in this setting. Newer stent platforms, however, have challenged this notion. The use of thinner struts, biocompatible polymer coating, and newer antiproliferative agents have improved the rates of cardiovascular events in patients with DM revascularized percutaneously. Since the publication of current guidelines, new studies suggested acceptable outcomes in patients with DM revascularized with second-generation drug-eluting stents, even though these conclusions are drawn from small subgroup analyses or nonrandomized studies. Robust registry data suggest similar mortality with lower rates of stroke after PCI compared with surgery, at the expense of increased rates of repeat revascularization. If complete revascularization can be achieved, similar rates of myocardial infarction are also observed. Therefore, contemporary revascularization in patients with DM with multivessel coronary artery disease should involve a multidisciplinary approach, in which interventional cardiologists and cardiac surgeons involve their patients to individualize treatment choices, and balance the risks and effectiveness of each modality.  相似文献   
998.
999.

Background

Elevation in the serum immunoglobulin-G4 (IgG4) level has been used as a diagnostic marker to distinguish autoimmune pancreatitis (AIP) from pancreatic ductal adenocarcinoma (PDAC), but its true utility is ill-defined. This study evaluates the clinical utility of IgG4 in differentiating AIP from PDAC.

Methods

All patients evaluated in the hepatopancreaticobiliary surgery clinics with measured serum IgG4 were included. Patients were divided into normal IgG4 (<135 mg/dL) and elevated IgG4 (≥135 mg/dL) groups. The final diagnosis was determined by operative pathology when available or by clinical outcome. The sensitivity, specificity, PPV, and NPV of IgG4 for diagnosing AIP was assessed.

Results

Between 1997 and 2015, 298 patients were identified. Normal IgG4 levels were present in 85% of patients (254/298), while 15% (44/298) were elevated. The overall prevalence of AIP was 17% (52/298). The sensitivity and specificity of IgG4 for AIP was 67% and 96%, respectively; however, the PPV was only 80%, including a 9% occurrence of PDAC in patients with an elevated IgG4.

Conclusion

In this study of selected patients who underwent IgG4 testing, 9% of elevated IgG4 patients had PDAC. The overreliance on IgG4 as diagnostic for AIP may lead to mis-diagnosis and delayed treatment for PDAC.  相似文献   
1000.
Carbapenemases have great importance in the global epidemiological scenario since infections with carbapenemase-producing bacteria are associated with high mortality, especially in hospitalized patients in intensive care units. This study describes two microorganisms producers of the New Delhi Metallo-b-lactamase, Klebsiella pneumoniae and Citrobacter freundii, from two patients admitted to a public hospital in Salvador, Bahia. These are the first clinical cases of New Delhi Metallo-b-lactamase described in microorganisms in the north and northeast Brazil. The isolates were characterized by antimicrobial susceptibility test, with resistance to all β-lactams including carbapenems, negative Modified Hodge Test and the synergy test with Ethylenediaminetetraacetic acid, Phenylboronic Acid and Cloxacillin was positive only with Ethylenediaminetetraacetic acid (difference of >5 mm in the inhibition zone between the disk without and with the inhibitor). Analysis by multiplex PCR for blaIMP, blaVIM, blaNDM, blaKPC and blaOXA-48 enzymes confirmed the presence of blaNDM gene. This report of two different New Delhi Metallo-b-lactamase-producing microorganisms in a different region of Brazil confirms the risk of spreading resistance genes between different species and emphasizes the need for prevention and control of infections caused by these pathogens, which have limited treatment options and have been linked to high mortality rates.  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