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   34885篇
  免费   2035篇
  国内免费   740篇
耳鼻咽喉   183篇
儿科学   618篇
妇产科学   484篇
基础医学   2359篇
口腔科学   362篇
临床医学   3720篇
内科学   4424篇
皮肤病学   159篇
神经病学   549篇
特种医学   1039篇
外科学   12919篇
综合类   4535篇
预防医学   1782篇
眼科学   68篇
药学   2521篇
  35篇
中国医学   1148篇
肿瘤学   755篇
  2024年   48篇
  2023年   769篇
  2022年   1252篇
  2021年   2002篇
  2020年   1974篇
  2019年   1641篇
  2018年   1651篇
  2017年   1442篇
  2016年   1164篇
  2015年   1161篇
  2014年   2617篇
  2013年   2642篇
  2012年   2028篇
  2011年   2219篇
  2010年   1743篇
  2009年   1708篇
  2008年   1566篇
  2007年   1567篇
  2006年   1256篇
  2005年   1112篇
  2004年   941篇
  2003年   729篇
  2002年   621篇
  2001年   510篇
  2000年   462篇
  1999年   349篇
  1998年   318篇
  1997年   266篇
  1996年   218篇
  1995年   217篇
  1994年   149篇
  1993年   147篇
  1992年   137篇
  1991年   99篇
  1990年   81篇
  1989年   76篇
  1988年   89篇
  1987年   93篇
  1986年   62篇
  1985年   53篇
  1984年   70篇
  1983年   87篇
  1982年   71篇
  1981年   54篇
  1980年   43篇
  1979年   43篇
  1978年   25篇
  1977年   24篇
  1976年   21篇
  1975年   18篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
991.

Objectives

This study sought to evaluate whether frailty improves mortality prediction in combination with the conventional scores.

Background

European System for Cardiac Operative Risk Evaluation (EuroSCORE) or Society of Thoracic Surgeons (STS) score have not been evaluated in combined models with frailty for mortality prediction after transcatheter aortic valve replacement (TAVR).

Methods

This prospective cohort comprised 330 consecutive TAVR patients ≥70 years of age. Conventional scores and a frailty index (based on assessment of cognition, mobility, nutrition, and activities of daily living) were evaluated to predict 1-year all-cause mortality using Cox proportional hazards regression (providing hazard ratios [HRs] with confidence intervals [CIs]) and measures of test performance (providing likelihood ratio [LR] chi-square test statistic and C-statistic [CS]).

Results

All risk scores were predictive of the outcome (EuroSCORE, HR: 1.90 [95% CI: 1.45 to 2.48], LR chi-square test statistic 19.29, C-statistic 0.67; STS score, HR: 1.51 [95% CI: 1.21 to 1.88], LR chi-square test statistic 11.05, C-statistic 0.64; frailty index, HR: 3.29 [95% CI: 1.98 to 5.47], LR chi-square test statistic 22.28, C-statistic 0.66). A combination of the frailty index with either EuroSCORE (LR chi-square test statistic 38.27, C-statistic 0.72) or STS score (LR chi-square test statistic 28.71, C-statistic 0.68) improved mortality prediction. The frailty index accounted for 58.2% and 77.6% of the predictive information in the combined model with EuroSCORE and STS score, respectively. Net reclassification improvement and integrated discrimination improvement confirmed that the added frailty index improved risk prediction.

Conclusions

This is the first study showing that the assessment of frailty significantly enhances prediction of 1-year mortality after TAVR in combined risk models with conventional risk scores and relevantly contributes to this improvement.  相似文献   
992.
Transcatheter aortic valve replacement (TAVR) is approved for all patient risk profiles and is an option for all patients irrespective of age. However, patients enrolled in the low- and intermediate-risk trials were in their 70s, and those in the high-risk trials were in their 80s. TAVR has never been systematically tested in young (<65 years), low-risk patients. Unanswered questions remain, including the safety and effectiveness of TAVR in patients with bicuspid aortic valves; future coronary access; durability of transcatheter heart valves; technical considerations for surgical transcatheter heart valve explantation; management of concomitant conditions such as aortopathy, mitral valve disease, and coronary artery disease; and the safety and feasibility of future TAVR-in-TAVR. The authors predict that balancing these questions with patients’ clear preference for less invasive treatment will become common. In this paper, the authors consider each of these questions and discuss risks and benefits of theoretical treatment strategies in the lifetime management of young patients with severe aortic stenosis.  相似文献   
993.
Twenty-three patients who had undergone aortic valve replacementwith a mechanical aortic vlave prosthesis (ball-valve: 17, tilting-disc:6) were investigated by retrograde left ventricular catheterizationusing a 6 F pigtail catheter. Tweleve of these 23 patients alsohad combined aortic and mitral valve replacement. To assessthe magnitude of the catheter-induced aortic regurgitation andits effect on left ventricular and mitral valve function, 10patients (group 1) were simultaneously investigated by the transseptalroute (8 patients) or direct left ventricular puncture. The13 other patients (group 2) were studied only by the retrogradecrossing of the aortic valve prosthesis. In group 1, placementof the catheter across the valve induced an increase in heartrate (+ 12%), in left ventricular end-diastolic pressure (from17.2±9.6 to 33.3±12.0 mmHg), a decrease om aorticsystolic (–19%) and diastolic (–25%) pressures,and left ventricular systolic pressure (–10%). Transvalvularaortic pressure gradient increased from 15.4±8.2 to 23±12.1mmHg. Pre- and post-crossing pressure gradients were linearlycorrelated (r=0.98). Hence, the magnitude of catheter-inducedaortic regurgitation averaged 27% whether or not a pre-crossingregurgitation was noted. In group 2, retrograde crossing ofthe aortic valve prosthesis induced similar hemodynamic changes.There were no catheterization-related complications.On the basisof catheterizations studies, re-operation was contraindicatedin 2 patients because of severe left ventricular depression,and recommended in 18: aortic valve dysfunction in 14 patients,mitral valve incompetence in 4 patients. In 3 patients, thehemodynamic study ruled out any aortic valve prosthesis dysfunction,associated mitral valve disease and depressed left ventricularfunction. Intraoperative findings (15 patients) and postmortemexamination (7 patients) were consistent with catheterizationdata. Left ventricular retrograde catheterization is an alternativetechnique of investigation for patients with mechanical valvesin both mitral and aortic positions or in centers where theusual approach (transseptal catheterization or direct LV puncture)are not performed.  相似文献   
994.

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   
995.
Objectives. The aim of this study was to clarify the prevalence and the predictive factors for undergoing total knee arthroplasty (TKA) among patients with rheumatoid arthritis (RA).

Methods. The data of 1,134 patients with RA who were enrolled in the Japanese nationwide cohort database NinJa in 2003 and consecutively followed up until 2009 were analyzed.

Results. Seventy-six patients underwent TKA during the observation period. The yearly progression of the modified Health Assessment Questionnaire or mHAQ score from 2003 to 2004, but not the yearly progression of the Disease Activity Score in 28 Joints or DAS28 or patient visual analog scale (VAS) score, was significantly higher in the patients who underwent TKA than those who did not.

Multivariate analysis showed that knee involvement in the disease, high Steinbrocker stage (III or IV), and high patient VAS score at the time of enrollment were powerful predictive factors, with hazard ratios of 4.01, 3.71, and 1.20, respectively.

According to survival analysis with TKA as an endpoint, patients with knee involvement in the disease at the time of enrollment had a significantly worse 5-year survival rate than did those without knee involvement (83.5% vs. 97.0%, respectively).

Conclusion. Several factors were elucidated as predictive factors for undergoing TKA among patients with RA.  相似文献   
996.
ObjectivesThe aim of this study was to investigate the risk of coronary obstruction during redo–transcatheter aortic valve replacement (TAVR) within a previously implanted self-expanding valve in bicuspid aortic valve (BAV) versus tricuspid aortic valve (TAV) stenosis.BackgroundThe prevalence of BAV in TAVR patients is expected to increase as the indication expands; however, no study has investigated the risk of coronary obstruction for future redo-TAVR in these patients.MethodsComputed tomography (CT) simulation analysis was performed in 86 type 0 BAV, 70 type 1 BAV, and 132 TAV patients who underwent TAVR with 1 VenusA-Valve (Venus Medtech) between January 2014 and December 2019.ResultsCT-identified risk of coronary obstruction during redo-TAVR was observed in 36.1% of patients for the left coronary ostium (LCO) and 27.8% of patients for the right coronary ostium (RCO); however, the incidences were significantly lower in the type 0 BAV group than in the type 1 BAV or TAV group (for LCO: OR: 1.00 [reference] vs OR: 2.49; 95% CI: 1.24-5.01 vs OR: 2.60; 95% CI: 1.40-4.81; for RCO: OR: 1.00 [reference] vs OR: 2.14; 95% CI: 1.02-4.48 vs OR: 1.97; 95% CI: 1.02-3.80). The leaflet laceration technique may be unfeasible to improve coronary flow in 61.5% of the threatened LCOs and 58.8% of the threatened RCOs during redo-TAVR. The percentages were significantly or numerically lower in the type 0 BAV group than other groups (for LCO: 26.3% vs 62.1% vs 73.2%; P overall = 0.001; for RCO: 43.8% vs 65.2% vs 61.0%; P overall = 0.374).ConclusionsDifferences in anatomical features may impact the feasibility of future redo-TAVR. Type 0 BAV anatomy was associated with the lower incidence of CT-identified risk of coronary obstruction during redo-TAVR, and the leaflet laceration technique may be more feasible to ensure coronary flow in this population.  相似文献   
997.
ObjectivesThe aim of this study was to compare the incidence and prognostic significance of prosthesis-patient mismatch (PPM) after transcatheter aortic valve replacement (TAVR) according to racial groups.BackgroundPPM after TAVR may be of more concern in Asian populations considering their relatively small annular and valve sizes compared with Western populations.MethodsTP-TAVR (Transpacific TAVR Registry) was an international multicenter cohort study of patients with severe aortic stenosis who underwent TAVR in the United States and South Korea from January 2015 to November 2019. PPM was defined as moderate (0.65-0.85 cm2/m2) or severe (<0.65 cm2/m2) at the indexed effective orifice area. The primary outcome was a composite of death, stroke, or rehospitalization at 1 year.ResultsAmong 1,101 eligible patients (533 Asian and 569 non-Asian), the incidence of PPM was significantly lower in the Asian population (33.6%; moderate, 26.5%; severe, 7.1%) than in the non-Asian population (54.5%; moderate, 29.8%; severe, 24.7%). The 1-year rate of the primary outcome was similar between the PPM and non-PPM groups (27.5% vs 28.1%; P = 0.69); this pattern was consistent between Asian (25.4% vs 25.2%; P = 0.31) and non-Asian (28.7% vs 32.1%; P = 0.97) patients. After multivariable adjustment, the risk for the primary outcome did not significantly differ between the PPM and non-PPM groups in the overall population (HR: 0.95; 95% CI: 0.74-1.21), in Asian patients (HR: 1.07; 95% CI: 0.74-1.55), and in non-Asian patients (HR: 0.86; 95% CI: 0.63-1.19).ConclusionsIn this study of patients with severe aortic stenosis who underwent TAVR, the incidence of PPM was significantly lower in Asian patients than in non-Asian patients. The 1-year risk for the primary composite outcome was similar between the PPM and non-PPM groups regardless of racial group. (Transpacific TAVR Registry [TP-TAVR]; NCT03826264)  相似文献   
998.
BackgroundThe implications and potential challenges of coronary access after redo transcatheter aortic valve replacement (TAVR) are unknown.ObjectivesThe authors sought to evaluate the impact of different transcatheter heart valve (THV) designs, neoskirt height, implant technique, and cell misalignment on coronary access after redo TAVR.MethodsDifferent THV designs (Sapien 3 [Edwards Lifesciences LLC], Evolut Pro [Medtronic], ACURATE neo [Boston Scientific Corporation], and Portico [Abbott Structural Heart]) and sizes were implanted inside Sapien XT (Edwards Lifesciences LLC) and Evolut R (Medtronic) THVs, which were modeled as the “failed” THVs, at different implant depths. Valve combinations underwent micro–computed tomography to determine the neoskirt height and dimensions of the lowest accessible cell for potential coronary access. This was compared with dimensions of 6-F/7-F/8-F coronary guiding catheters.ResultsRedo TAVR combinations resulted in a wide range of neoskirt heights (15.4-31.6 mm) and a variable diameter of the lowest accessible cell (1.9-21.8 mm). An ACURATE neo implanted in a Sapien XT resulted in the largest accessible cells, whereas a Portico implanted in a Sapien XT resulted in the lowest neoskirt heights. The smallest accessible cell was observed in the Evolut Pro–in–Evolut R configuration with higher neoskirt heights. Redo TAVR in a tall frame valve with supra-annular leaflets caused a taller neoskirt height. In Evolut-in-Evolut combinations, misalignment of the cells of the 2 THVs reduced the cell area by 30% to 50% compared with an aligned configuration.ConclusionsThis study demonstrates that different redo TAVR combinations are not equivalent in terms of future coronary access. Redo TAVR using a tall frame valve in a failed tall frame valve and misaligned cells may lead to potentially challenging coronary access.  相似文献   
999.
ObjectivesThe aim of this study was to define predictors of prosthesis-patient mismatch (PPM) and its impact on mortality after transcatheter aortic valve replacement (TAVR) with self-expandable valves (SEVs) in patients with small annuli.BackgroundTAVR seems to reduce the risk for PPM compared with surgical aortic valve replacement, especially in patients with small aortic annuli. Nevertheless, predictors and impact of PPM in this population have not been clarified yet.MethodsPredictors of PPM and all-cause mortality were investigated using multivariable logistic regression analysis from the cohort of the TAVI-SMALL (International Multicenter Registry to Evaluate the Performance of Self-Expandable Valves in Small Aortic Annuli) registry, which included patients with severe aortic stenosis and small annuli (annular perimeter <72 mm or area <400 mm2 on computed tomography) treated with transcatheter SEVs: 445 patients with (n = 129) and without (n = 316) PPM were enrolled.ResultsIntra-annular valves conferred increased risk for PPM (odds ratio [OR]: 2.36; 95% confidence interval [CI]: 1.16 to 4.81), while post-dilation (OR: 0.46; 95% CI: 0.25–0.84) and valve oversizing (OR: 0.53; 95% CI: 0.28–1.00) seemed to protect against PPM occurrence. At a median follow-up of 354 days, patients with severe PPM, but not those with moderate PPM, had a higher all-cause mortality rate compared with those without PPM (log-rank p = 0.008). Multivariable Cox regression confirmed severe PPM as an independent predictor of all-cause mortality (hazard ratio: 4.27; 95% CI: 1.34 to 13.6).ConclusionsAmong patients with aortic stenosis and small aortic annuli undergoing transcatheter SEV implantation, use of intra-annular valves yielded higher risk for PPM; conversely, post-dilation and valve oversizing protected against PPM occurrence. Severe PPM was independently associated with all-cause mortality.  相似文献   
1000.
As transcatheter aortic valve replacement becomes a more dominant treatment option across all risk profiles, the frequency of encountering patients with multivalvular disease will increase. Furthermore, percutaneous interventions to treat other valvular lesions are also evolving. Understanding the clinical implications and treatment options for a second valvular lesion is becoming increasingly important to guide heart team decisions, and this paper aims to review the evidence around these situations. Diagnosis of multivalvular disease can be challenging because of changes in physiology. There are little randomized data to guide therapy in multivalvular disease. Multidisciplinary heart team decisions can be invaluable in integrating the plethora of clinical, hemodynamic, and imaging data on which an optimal management strategy can be planned. Prospective studies to assess the role of structural valve interventions in the transcatheter aortic valve replacement era would greatly help improve outcomes for structural heart patients.  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