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   633465篇
  免费   39774篇
  国内免费   19299篇
耳鼻咽喉   8332篇
儿科学   18267篇
妇产科学   8887篇
基础医学   74679篇
口腔科学   16119篇
临床医学   57427篇
内科学   108120篇
皮肤病学   11595篇
神经病学   32446篇
特种医学   24982篇
外国民族医学   229篇
外科学   88854篇
综合类   67059篇
现状与发展   84篇
一般理论   4篇
预防医学   32086篇
眼科学   11741篇
药学   55052篇
  138篇
中国医学   17380篇
肿瘤学   59057篇
  2023年   8322篇
  2022年   17587篇
  2021年   23413篇
  2020年   15985篇
  2019年   29047篇
  2018年   25671篇
  2017年   18655篇
  2016年   16792篇
  2015年   21248篇
  2014年   34529篇
  2013年   33537篇
  2012年   33754篇
  2011年   34247篇
  2010年   28368篇
  2009年   27815篇
  2008年   27541篇
  2007年   28710篇
  2006年   25876篇
  2005年   21740篇
  2004年   16321篇
  2003年   14224篇
  2002年   12600篇
  2001年   11889篇
  2000年   11614篇
  1999年   10388篇
  1998年   10236篇
  1997年   8530篇
  1996年   7515篇
  1995年   7039篇
  1994年   6610篇
  1993年   5176篇
  1992年   4635篇
  1991年   4315篇
  1990年   3755篇
  1989年   3332篇
  1988年   3245篇
  1987年   2729篇
  1985年   7479篇
  1984年   9134篇
  1983年   7134篇
  1982年   7752篇
  1981年   7054篇
  1980年   6103篇
  1979年   5865篇
  1978年   4729篇
  1977年   3714篇
  1976年   3980篇
  1975年   2945篇
  1974年   2755篇
  1973年   2472篇
排序方式: 共有10000条查询结果,搜索用时 10 毫秒
1.
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   
2.
Background/PurposeA small number of Hirschsprung disease (HD) patients develop inflammatory bowel disease (IBD)-like symptoms after pullthrough surgery. The etiology and pathophysiology of Hirschsprung-associated IBD (HD-IBD) remains unknown. This study aims to further characterize HD-IBD, to identify potential risk factors and to evaluate response to treatment in a large group of patients.MethodsRetrospective study of patients diagnosed with IBD after pullthrough surgery between 2000 and 2021 at 17 institutions. Data regarding clinical presentation and course of HD and IBD were reviewed. Effectiveness of medical therapy for IBD was recorded using a Likert scale.ResultsThere were 55 patients (78% male). 50% (n = 28) had long segment disease. Hirschsprung-associated enterocolitis (HAEC) was reported in 68% (n = 36). Ten patients (18%) had Trisomy 21. IBD was diagnosed after age 5 in 63% (n = 34). IBD presentation consisted of colonic or small bowel inflammation resembling IBD in 69% (n = 38), unexplained or persistent fistula in 18% (n = 10) and unexplained HAEC >5 years old or unresponsive to standard treatment in 13% (n = 7). Biological agents were the most effective (80%) medications. A third of patients required a surgical procedure for IBD.ConclusionMore than half of the patients were diagnosed with HD-IBD after 5 years old. Long segment disease, HAEC after pull through operation and trisomy 21 may represent risk factors for this condition. Investigation for possible IBD should be considered in children with unexplained fistulae, HAEC beyond the age of 5 or unresponsive to standard therapy, and symptoms suggestive of IBD. Biological agents were the most effective medical treatment.Level of EvidenceLevel 4  相似文献   
3.

Background

Purulent bacterial pericarditis is a rare and potentially fatal disease. The course may be fulminant, and the presentation may pose a diagnostic challenge.

Case report

An otherwise healthy 75-year-old male was brought to the emergency department in a state of general deterioration, confusion, and shock. Bedside ultrasound showed a significant pericardial effusion. His condition quickly deteriorated and the resuscitation included emergent bedside pericardiocentesis. The drainage was purulent and later cultures grew out Streptococcus pneumoniae.

Why should an emergency physician be aware of this?

Purulent pericarditis is extremely rare but should be considered in the patient with a fulminant infectious process (particularly pneumonia) and signs of pericardial effusion. Treatment should include appropriate antibiotics and early drainage.  相似文献   
4.
Objective: To determine whether packed red blood cell (PRBC) transfusion affects post-prandial superior mesenteric artery blood flow velocities (SMA BFVs) in very-low birth weight (VLBW) neonates and if so, at what time point after transfusion restoration of previous SMA BFV patterns occurs.

Design/Methods: VLBW pre-term neonates, older than 14 days and tolerating bolus enteral feedings administered every 3?h were enrolled in this prospective observational study. Pulsed Doppler ultrasound was used to measure pre- and post-prandial (at 45?min) time-averaged mean, peak and end diastolic velocities (TAMV, PSV, EDV) immediately before and after 15?ml/kg of PRBC transfusion was given over 3?h; patent ductus arteriosus (PDA) status was also evaluated. Subsequent pre- and post-prandial SMA BFVs were recorded 24 and 48?h after the transfusion.

Results: Pre- and post-prandial measurements were obtained for 21 out of 25 enrolled infants. Post-prandial SMA BFVs were attenuated during the feedings immediately after transfusion; at 24 and 48?h after transfusion, changes in post-prandial SMA BFVs were similar to those measured prior to transfusion; the presence of the PDA did not affect results.

Conclusions: PRBC transfusion blunted SMA BFV responses to feedings immediately after the transfusion with normalization observed 24?h post-transfusion.  相似文献   
5.
6.
PurposeTo examine predictors of midterm occlusion in portal and hepatic veins within or adjacent to the ablation zone after irreversible electroporation (IRE) of liver tumors.Materials and MethodsThis retrospective cohort analysis included 39 patients who underwent CT-guided IRE of liver tumors. Vessels within or adjacent to the ablation zone were identified on CT images acquired immediately after the procedure, and the positional relationships with the ablation zone (within/adjacent), locations (proximal/distal), and diameters (< 4 mm or ≥ 4 mm) were evaluated. Using contrast-enhanced follow-up scans, each vessel was classified as patent, stenosed, or occluded. Associations between vessel occlusion and each variable were investigated.ResultsOverall, 33 portal veins and 64 hepatic veins were analyzed. Follow-up scans showed occlusion in 12/33 (36.7%) portal veins and 17/64 (26.6%) hepatic veins. Vessels within the ablation zone were occluded significantly more frequently than vessels adjacent to the ablation zone (portal: 55.6% [10/18] vs 13.3% [2/15], P = .04; hepatic: 45.4% [15/33] vs 6.4% [2/31], P = .011). Vessels with a diameter < 4 mm were also occluded significantly more frequently than vessels with a diameter ≥ 4 mm (portal: 72.7% [8/11] vs 18.1% [4/22], P = .011; hepatic: 54.8% [17/31] vs 0% [0/33], P < .001). The respective positive and negative predictive values for occlusion of vessels categorized as both within and < 4 mm were 88% (7/8) and 82% (20/25) for portal veins and 79% (15/19) and 96% (43/45) for hepatic veins.ConclusionsMidterm vessel occlusion after liver IRE could be predicted with relatively high accuracy by assessing ablation location and vessel diameter.  相似文献   
7.
PurposeTo assess the feasibility, safety, and efficacy of balloon-assisted delivery of ethylene vinyl alcohol copolymer (EVOH) for a range of peripheral arterial applications.Materials and MethodsSix academic medical centers entered retrospective data on 46 consecutive patients (27 men, 19 women; ages, 11–94 y; mean age, 50.3 y) who underwent 60 balloon-assisted EVOH procedures. The cohort was restricted to procedures involving peripheral, nonneural arteries 1–5.5 mm in diameter. Clinical indications included a wide range of vascular pathologic conditions (most commonly arteriovenous malformations [n = 20], renal angiomyolipomas [n = 8], and acute hemorrhage [n = 9]) and targeted visceral and musculoskeletal peripheral arteries. Data collected included sex, age, clinical indication, arterial pathology, arteries embolized, type of occlusion balloon microcatheter, type and concentration of EVOH agent, effectiveness as an embolic backstop, vessels protected, adequacy of EVOH cast penetration, catheter extraction, nontarget embolization, and complications.ResultsBalloon occlusion prevented EVOH reflux in 59 of 60 procedures (98.3%). Nontarget EVOH embolization occurred in 2 procedures (3.3%). Adequate EVOH cast penetration and complete filling of the target pathologic structure were seen in 57 of 60 procedures (95%). Balloon deflation and uneventful extraction occurred in all procedures; small EVOH fragments detached into target arteries in 2 cases. One major (1.7%) and 2 minor (3.3%) complications occurred.ConclusionsBalloon-assisted EVOH embolization of peripheral arteries is feasible, safe, effective, and versatile. The primary advantage of balloon-assisted EVOH embolization is the ability to apply more injection pressure to advance the EVOH cast assertively into the pathologic structure(s).  相似文献   
8.
PurposeTo explore the safety and effectiveness of bronchial artery (BA) embolization (BAE) in children with pulmonary hemorrhage.Materials and MethodsBetween February 2016 and February 2019, 41 patients (median age, 4 y; interquartile range, 2.3-8 y; median weight, 17.6 kg; interquartile range, 12.3–23.6 kg) underwent BAE. The indication of BAE included massive hemoptysis in 10 patients (24.4%), recurrent hemoptysis in 18 patients (43.9%), and refractory anemia in 13 patients (31.7%). The main etiology of pulmonary hemorrhage included pulmonary hemosiderosis (58.5%), congenital heart disease (17.1%), and infection (14.6%). A retrospective review was conducted of clinical outcomes of BAE.ResultsThere were 44 embolization sessions, with a total of 137 embolized vessels. Pulmonary hemorrhage was caused by BAs in 30 cases, nonbronchial systemic arteries plus BAs in 10, and nonbronchial systemic arteries in 1. Embolic particles were used in 30 cases (24 polyvinyl alcohol [PVA] and 6 microsphere), coils in 9 cases, and particles plus coils in 5 cases (4 PVA and 1 microsphere). Technical success (ability to embolize abnormal vessel) was achieved in 97.6% of patients (40 of 41), and clinical success (complete or partial resolution of hemoptysis within 30 days of embolization) was achieved in 90.2% (37 of 41). There was 1 procedure-related complication (2.4%) of cerebral infarction and 1 death from multiple-organ dysfunction (2.4%). Bleeding-free survival rates at 6, 12, 24, and 36 months were 92.5%, 83.9%, 83.9%, and 70.8%, respectively.ConclusionsBAE is a safe and effective procedure in children with pulmonary hemorrhage.  相似文献   
9.
《Vaccine》2020,38(3):570-577
IntroductionPediatric pneumococcal pneumonia complicated by parapneumonic pleural effusion/empyema (PPE/PE) remains a major concern despite general immunization with pneumococcal conjugate vaccines (PCVs).MethodsIn a nationwide pediatric hospital surveillance study in Germany we identified 584 children <18 years of age with bacteriologically confirmed PPE/PE from October 2010 to June 2018. Streptococcus pneumoniae was identified by culture and/or PCR of blood samples and/or pleural fluid and serotyped.ResultsS. pneumoniae was identified in 256 of 584 (43.8%) children by culture (n = 122) and/or PCR (n = 207). The following pneumococcal serotypes were detected in 114 children: serotype 3 (42.1%), 1 (25.4%), 7F (12.3%), 19A (7.9%), other PCV13 serotypes (4.4%) and non-PCV13 serotypes (7.9%). Between October 2010 and June 2014 serotype 1 (38.1%) and serotype 3 (25.4%) were most prevalent, whereas between July 2014 and June 2018 serotype 3 (62.7%) and non-PCV13 serotypes (15.7%) were dominant. Compared to children with other pneumococcal serotypes, children with serotype 3 associated PPE/PE were younger (median 3.2 years [IQR 2.1–4.3 years] vs. median 5.6 years [IQR 3.8–8.2 years]; p < 0.001) and more frequently admitted to intensive care (43 [89.6%] vs. 48 [73.8%]; p = 0.04). Seventy-six of 114 (66.7%) children with pneumococcal PPE/PE had been vaccinated with pneumococcal vaccines. Thirty-nine of 76 (51.3%) had received a vaccine covering the serotype detected. Thirty of these 39 breakthrough cases were age-appropriately vaccinated with PCV13 and considered vaccine failures, including 26 children with serotype 3, three children with serotype 19A and one child with serotype 1.ConclusionFollowing the introduction of PCV13 in general childhood vaccination we observed a strong emergence of serotype 3 associated PPE/PE in the German pediatric population, including a considerable number of younger children with serotype 3 vaccine breakthrough cases and failures. Future PCVs should not only cover newly emerging serotypes, but also include a more effective component against serotype 3.  相似文献   
10.
Central illustration: cumulative major adverse cardiac events (MACE) and bioresorbable vascular scaffold (BVS) thrombosis rates after 1, 2, 3, 4 and 5 years.
  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