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   14384篇
  免费   630篇
  国内免费   187篇
耳鼻咽喉   40篇
儿科学   361篇
妇产科学   214篇
基础医学   681篇
口腔科学   31篇
临床医学   1383篇
内科学   5501篇
皮肤病学   292篇
神经病学   673篇
特种医学   586篇
外科学   809篇
综合类   955篇
预防医学   1060篇
眼科学   471篇
药学   1527篇
中国医学   330篇
肿瘤学   287篇
  2024年   32篇
  2023年   497篇
  2022年   654篇
  2021年   1057篇
  2020年   929篇
  2019年   1081篇
  2018年   1020篇
  2017年   514篇
  2016年   263篇
  2015年   331篇
  2014年   956篇
  2013年   793篇
  2012年   471篇
  2011年   591篇
  2010年   476篇
  2009年   541篇
  2008年   610篇
  2007年   623篇
  2006年   420篇
  2005年   436篇
  2004年   360篇
  2003年   339篇
  2002年   293篇
  2001年   269篇
  2000年   243篇
  1999年   232篇
  1998年   184篇
  1997年   153篇
  1996年   96篇
  1995年   78篇
  1994年   61篇
  1993年   53篇
  1992年   65篇
  1991年   45篇
  1990年   57篇
  1989年   33篇
  1988年   37篇
  1987年   23篇
  1986年   27篇
  1985年   40篇
  1984年   31篇
  1983年   30篇
  1982年   29篇
  1981年   31篇
  1980年   19篇
  1979年   21篇
  1978年   12篇
  1977年   13篇
  1976年   6篇
  1973年   8篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.

Objective

Native aortic valve calcium and transcatheter aortic valve oversize have been reported to predict pacemaker implantation after transcatheter aortic valve insertion. We reviewed our experience to better understand the association.

Methods

We retrospectively reviewed the records of 300 patients with no prior permanent pacemaker implantation who underwent transcatheter aortic valve insertion from November 2008 to February 2015. Valve oversize was calculated using area. The end point of the study was 30-day postoperative pacemaker implantation.

Results

Patient data included age of 81.1 ± 8.4 years, female sex in 135 patients (45%), atrial fibrillation in 74 patients (24.7%), Society of Thoracic Surgeons predicted risk of mortality of 7.6% (interquartile range [IQR], 5.3-10.6), aortic valve calcium score of 2568 (IQR, 1775-3526) Agatston units, and annulus area of 471 ± 82 mm2. Balloon-expandable valves were inserted in 244 patients (81.3%). Transcatheter aortic valve oversize was 12.8% (IQR, 3.9-23.3). Pacemaker implantation was performed in 59 patients (19.7%). Aortic valve calcium score (adjusted P = .275) and transcatheter valve oversize (adjusted P = .833) were not independent risk factors for pacemaker implantation when controlling for preoperative right bundle branch block (adjusted odds ratio, 3.49; 95% confidence interval, 1.61-8.55; P = .002), implantation of self-expanding valve (adjusted odds ratio, 4.09; 95% confidence interval, 1.53-10.96; P = .005), left bundle branch block (adjusted P = .331), previous percutaneous coronary intervention (adjusted P = .053), or valve surgery (adjusted P = .111), and PR interval (adjusted P = .350).

Conclusions

Right bundle branch block and implantation of a self-expanding prosthesis were predictive of pacemaker implantation, but not native aortic valve score or transcatheter valve oversize.  相似文献   
62.

Objective

Donor blood transfusion has been identified as a potential risk factor for primary graft dysfunction and by extension early mortality. We sought to define the contributing risk of donor transfusion on early mortality for lung transplant.

Methods

Donor and recipient data were abstracted from the Organ Procurement and Transplantation Network database updated through June 30, 2014, which included 86,398 potential donors and 16,255 transplants. Using the United Network for Organ Sharing 4-level designation of transfusion (no blood, 1-5 units, 6-10 units, and >10 units, massive), we analyzed all-cause mortality at 30-days with the use of logistic regression adjusted for confounders (ischemic time, donor age, recipient diagnosis, lung allocation score and recipient age, and recipient body mass index). Secondary analyses assessed 90-day and 1-year mortality and hospital length of stay.

Results

Of the 16,255 recipients transplanted, 8835 (54.35%) donors received at least one transfusion. Among those transfused, 1016 (6.25%) received a massive transfusion, defined as >10 units. Those donors with massive transfusion were most commonly young trauma patients. After adjustment for confounding variables, donor massive transfusion was associated significantly with an increased risk in 30-day (P = .03) and 90-day recipient mortality (P = .01) but not 1-year mortality (P = .09). There was no significant difference in recipient length of stay or hospital-free days with respect to donor transfusion.

Conclusions

Massive donor blood transfusion (>10 units) was associated with early recipient mortality after lung transplantation. Conversely, submassive donor transfusion was not associated with increased recipient mortality. The mechanism of increased early mortality in recipients of lungs from massively transfused donors is unclear and needs further study but is consistent with excess mortality seen with primary graft dysfunction in the first 90 days posttransplant.  相似文献   
63.
目的探讨经皮椎体成形(PVP)术中骨水泥在椎体骨折线内弥散情况对疗效的影响。方法回顾性分析自2014-01—2016-11行PVP治疗的20例骨质疏松性胸腰椎压缩骨折,根据椎体骨折线内骨水泥弥散情况分为2组(各10例),A组骨水泥在椎体骨折线内充分弥散,B组骨水泥在椎体骨折线内弥散不均匀。比较2组术后4 d、3个月ODI指数、VAS评分、局部后凸Cobb角,以及并发症情况。结果20例均获得3~6(3.82±0.26)个月随访。术后3个月时,A组未出现并发症,B组出现1例椎体再骨折、2例椎体塌陷;B组并发症发生率高于A组,差异有统计学意义(P0.05)。2组术后4 d、3个月的ODI指数、VAS评分、局部后凸Cobb角均较术前明显改善,而且A组术后4 d的ODI指数、VAS评分、局部后凸Cobb角明显低于B组,差异有统计学意义(P0.05)。结论 PVP治疗骨质疏松性胸腰椎压缩骨折可明显改善功能障碍与缓解疼痛程度,但骨水泥在椎体骨折线内弥散不佳会对早期疗效造成影响,甚至可能导致后凸畸形。  相似文献   
64.
BackgroundCoronary artery bypass grafting (CABG) improves survival in patients with heart failure and severely reduced left ventricular systolic function (LVEF). Limited data exist regarding adverse cardiovascular event rates after CABG in patients with heart failure with midrange ejection fraction (HFmrEF; LVEF > 40% and < 55%).MethodsWe analyzed data on isolated CABG patients from the Veterans Affairs national database (2010-2019). We stratified patients into control (normal LVEF and no heart failure), HFmrEF, and heart failure with reduced LVEF (HFrEF) groups. We compared all-cause mortality and heart failure hospitalization rates between groups with a Cox model and recurrent events analysis, respectively.ResultsIn 6533 veterans, HFmrEF and HFrEF was present in 1715 (26.3%) and 566 (8.6%) respectively; the control group had 4252 (65.1%) patients. HFrEF patients were more likely to have diabetes mellitus (59%), insulin therapy (36%), and previous myocardial infarction (31%). Anemia was more prevalent in patients with HFrEF (49%) as was a lower serum albumin (mean, 3.6 mg/dL). Compared with the control group, a higher risk of death was observed in the HFmrEF (hazard ratio [HR], 1.3 [1.2-1.5)] and HFrEF (HR, 1.5 [1.2-1.7]) groups. HFmrEF patients had the higher risk of myocardial infarction (subdistribution HR, 1.2 [1-1.6]; P = .04). Risk of heart failure hospitalization was higher in patients with HFmrEF (HR, 4.1 [3.5-4.7]) and patients with HFrEF (HR, 7.2 [6.2-8.5]).ConclusionsHeart failure with midrange ejection fraction negatively affects survival after CABG. These patients also experience higher rates myocardial infarction and heart failure hospitalization.  相似文献   
65.
ObjectivesThe reduction of postoperative acute kidney injury in patients undergoing cardiopulmonary bypass surgery using an oxygen delivery-guided perfusion strategy (oxygen delivery strategy) for cardiopulmonary bypass management compared with a fixed flow perfusion (conventional strategy) remains controversial. The purpose of this study was to determine whether a oxygen delivery strategy would reduce the incidence of postoperative acute kidney injury in patients undergoing cardiopulmonary bypass surgery.MethodsWe randomly enrolled 300 patients undergoing cardiopulmonary bypass surgery. Patients were randomly assigned to a oxygen delivery strategy (maintaining a oxygen delivery index value >300 mL/min/m2 through pump flow adjustments during cardiopulmonary bypass) or a conventional strategy (a target pump flow was determined on the basis of the body surface area). The primary end point was the development of acute kidney injury. Secondary end points were the red blood cell transfusion rate and number of red blood cell units, intubation time, postoperative length of stay in the intensive care unit and the hospital, predischarge estimated glomerular filtration rate, and hospital mortality.ResultsAcute kidney injury occurred in 20 patients (14.6%) receiving the oxygen delivery strategy and in 42 patients (30.4%) receiving the conventional strategy (relative risk, 0.48; 95% confidence interval, 0.30-0.77; P = .002). The secondary end points were not significantly different between strategies. In a prespecified subgroup analysis of patients who had nadir hematocrit less than 23% or body surface area less than 1.40 m2, the oxygen delivery strategy seemed to be superior to the conventional strategy and the existence of quantitative interactions was suggested.ConclusionsAn oxygen delivery strategy for cardiopulmonary bypass management was superior to a conventional strategy with respect to preventing the development of acute kidney injury.  相似文献   
66.
ObjectiveDeterioration of the native aortic valve function by a late progression of rheumatic disease is not infrequent in patients who underwent rheumatic mitral valve surgery; however, this phenomenon has not been clearly quantified.MethodsA total of 1155 consecutive patients (age 52.0 ± 12.9 years; 807 female) who underwent rheumatic mitral valve surgery without concomitant aortic valve surgery from 1997 to 2015 were enrolled. The primary end point was the composite of progression to severe aortic valve dysfunction or a requirement of subsequent aortic valve replacements during follow-up. To determine the risk factors of the primary outcome, we performed the generalized linear mixed model.ResultsThe baseline severities of aortic valve were none to trivial in 880 patients (76.2%), mild in 256 patients (22.2%), and moderate in 19 patients (1.6%). The latest 1062 echocardiographic assessments (91.9%; median, 81.2 postoperative months; interquartile range, 37.3-132.1 months) demonstrated 26 cases (0.33%/patient-year) meeting the primary end point during follow-up. Cumulative incidence of the primary end point at 10 years was 0.4% ± 0.3% and 7.4% ± 2.5% depending on the presence of mild or greater aortic valve dysfunction at baseline (P < .01). In multivariable analyses, aortic valve peak pressure gradient (odds ratio, 1.14; 95% confidence interval, 1.10-1.20), aortic regurgitation degree (mild over none: odds ratio, 3.26; 95% confidence interval, 1.15-9.23), and time (odds ratio, 1.30; 95% confidence interval 1.19-1.41) were significantly associated with the occurrence of the primary end point.ConclusionsProgression of severe aortic valve dysfunction and the need for aortic valve replacement are uncommon in patients undergoing rheumatic mitral valve surgery. However, such events were relatively common among those with mild or greater aortic valve dysfunction at the time of mitral valve surgery.  相似文献   
67.
ObjectiveNew-onset postoperative atrial fibrillation (POAF) after cardiac surgery is common, with rates up to 60%. POAF has been associated with early and late stroke, but its association with other cardiovascular outcomes is less known. The objective was to perform a meta-analysis of the studies reporting the association of POAF with perioperative and long-term outcomes in patients with cardiac surgery.MethodsWe performed a systematic review and a meta-analysis of studies that presented outcomes for cardiac surgery on the basis of the presence or absence of POAF. MEDLINE, EMBASE, and the Cochrane Library were assessed; 57 studies (246,340 patients) were selected. Perioperative mortality was the primary outcome. Inverse variance method and random model were performed. Leave-one-out analysis, subgroup analyses, and metaregression were conducted.ResultsPOAF was associated with perioperative mortality (odds ratio [OR], 1.92; 95% confidence interval [CI], 1.58-2.33), perioperative stroke (OR, 2.17; 95% CI, 1.90-2.49), perioperative myocardial infarction (OR, 1.28; 95% CI, 1.06-1.54), perioperative acute renal failure (OR, 2.74; 95% CI, 2.42-3.11), hospital (standardized mean difference, 0.80; 95% CI, 0.53-1.07) and intensive care unit stay (standardized mean difference, 0.55; 95% CI, 0.24-0.86), long-term mortality (incidence rate ratio [IRR], 1.54; 95% CI, 1.40-1.69), long-term stroke (IRR, 1.33; 95% CI, 1.21-1.46), and longstanding persistent atrial fibrillation (IRR, 4.73; 95% CI, 3.36-6.66).ConclusionsThe results suggest that POAF after cardiac surgery is associated with an increased occurrence of most short- and long-term cardiovascular adverse events. However, the causality of this association remains to be established.  相似文献   
68.
ObjectivesGuidelines suggest aortic valve replacement (AVR) for low-risk asymptomatic patients. Indications for transcatheter AVR now include low-risk patients, making it imperative to understand state-of-the-art surgical AVR (SAVR) in this population. Therefore, we compared SAVR outcomes in low-risk patients with those expected from Society of Thoracic Surgeons (STS) models and assessed their intermediate-term survival.MethodsFrom January 2005 to January 2017, 3493 isolated SAVRs were performed in 3474 patients with STS predicted risk of mortality <4%. Observed operative mortality and composite major morbidity or mortality were compared with STS-expected outcomes according to calendar year of surgery. Logistic regression analysis was used to identify risk factors for these outcomes. Patients were followed for time-related mortality.ResultsWith 15 observed operative deaths (0.43%) compared with 55 expected (1.6%), the observed:expected ratio was 0.27 for mortality (95% confidence interval [CI], 0.14-0.42), stroke 0.65 (95% CI, 0.41-0.89), and reoperation 0.50 (95% CI, 0.42-0.60). Major morbidity or mortality steadily declined, with probabilities of 8.6%, 6.7%, and 5.2% in 2006, 2011, and 2016, respectively, while STS-expected risk remained at approximately 12%. Mitral valve regurgitation, ventricular hypertrophy, pulmonary, renal, and hepatic failure, coronary artery disease, and earlier surgery date were residual risk factors. Survival was 98%, 91%, and 82% at 1, 5, and 9 years, respectively, superior to that predicted for the US age-race-sex–matched population.ConclusionsSTS risk models overestimate contemporary SAVR risk at a high-volume center, supporting efforts to create a more agile quality assessment program. SAVR in low-risk patients provides durable survival benefit, supporting early surgery and providing a benchmark for transcatheter AVR.  相似文献   
69.
BackgroundBilateral Wilms tumor (BWT) is a rare entity. The goal of this study is to report outcomes (overall and event-free survival, OS/EFS) of BWT in a large cohort representative of the Canadian population since 2000. We focused on the occurrence of late events (relapse or death beyond 18 months), as well as outcomes of patients treated following the only protocol specifically designed for BWT to date, AREN0534, compared to patients treated following other therapeutic schemes.MethodsData was obtained for patients diagnosed with BWT between 2001 and 2018 from the Cancer in Young People in Canada (CYP-C) database. Demographics, treatment protocols, and dates for events were collected. Specifically, we examined outcomes of patients treated according to the Children's Oncology Group (COG) protocol AREN0534 since 2009. Survival analysis was performed.Results57/816 (7%) of patients with Wilms tumor had BWT during the study period. Median age at diagnosis was 2.74 years (IQR 1.37–4.48) and 35 (64%) were female; 8/57 (15%) had metastatic disease. After a median follow-up of 4.8 years (IQR 2.8–5.7 years, range 0.2–18 years), OS and EFS were 86% (CI 73–93%) and 80% (CI 66–89%), respectively. Less than 5 events were recorded after 18 months from diagnosis. Since 2009, patients treated according to the AREN0534 protocol had a statistically significant higher OS compared to patients treated with other protocols.ConclusionsIn this large Canadian cohort of patients with BWT, OS and EFS compared favorably to the published literature. Late events were rare. Patients treated according to a disease-specific protocol (AREN0534) had improved overall survival.Type of studyOriginal article.Level of evidenceLevel IV.  相似文献   
70.
PurposeThe majority of patients with an anorectal malformation (ARM) have associated congenital anomalies. It is well established that all patients diagnosed with an ARM should undergo systematic screening, including renal, spinal, and cardiac imaging. This study aimed to evaluate the findings and completeness of screening, following local implementation of standardized protocols.MethodsA retrospective cohort study was performed assessing all patients with an ARM managed at our tertiary pediatric surgical center, following a standardized protocol implementation for VACTERL screening (January 2016–December 2021). Cohort demographics, medical characteristics, and screening investigations were analyzed. Findings were compared with our previously published data (2000–2015), conducted prior to protocol implementation.ResultsOne hundred twenty-seven (64 male, 50.4%) children were eligible for inclusion. Complete screening was performed in 107/127 (84.3%) children. Of these, one or more associated anomalies were diagnosed in 85/107 (79.4%), whilst the VACTERL association was demonstrated in 57/107 (53.3%). The proportion of children that underwent complete screening increased significantly in comparison with those assessed prior to protocol implementation (RR 0.43 [CI 0.27–0.66]; p < 0.001). Children with less complex ARM types were significantly less likely to receive complete screening (p = 0.028). Neither presence of an associated anomaly, nor prevalence of the VACTERL association, differed significantly by ARM type complexity.ConclusionScreening for associated VACTERL anomalies in children with ARM was significantly improved following standardized protocol implementation. The prevalence of associated anomalies in our cohort supports the value of routine VACTERL screening in all children with ARM, regardless of malformation type.Level of EvidenceII.  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