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   44163篇
  免费   7111篇
  国内免费   2550篇
耳鼻咽喉   965篇
儿科学   1130篇
妇产科学   590篇
基础医学   2981篇
口腔科学   1325篇
临床医学   7015篇
内科学   7007篇
皮肤病学   329篇
神经病学   3847篇
特种医学   1508篇
外国民族医学   6篇
外科学   4358篇
综合类   10507篇
现状与发展   13篇
一般理论   1篇
预防医学   2871篇
眼科学   2458篇
药学   2910篇
  505篇
中国医学   1903篇
肿瘤学   1595篇
  2024年   166篇
  2023年   1193篇
  2022年   2516篇
  2021年   3061篇
  2020年   3054篇
  2019年   1847篇
  2018年   1894篇
  2017年   1382篇
  2016年   1720篇
  2015年   2252篇
  2014年   4376篇
  2013年   3704篇
  2012年   4606篇
  2011年   4436篇
  2010年   3410篇
  2009年   2525篇
  2008年   2026篇
  2007年   2247篇
  2006年   1813篇
  2005年   1130篇
  2004年   1001篇
  2003年   746篇
  2002年   592篇
  2001年   493篇
  2000年   381篇
  1999年   316篇
  1998年   270篇
  1997年   221篇
  1996年   133篇
  1995年   64篇
  1994年   41篇
  1993年   27篇
  1992年   16篇
  1991年   25篇
  1990年   22篇
  1989年   16篇
  1988年   28篇
  1987年   30篇
  1986年   23篇
  1985年   7篇
  1984年   3篇
  1983年   2篇
  1982年   2篇
  1980年   3篇
  1979年   4篇
排序方式: 共有10000条查询结果,搜索用时 62 毫秒
991.
BackgroundPrimary percutaneous coronary intervention (PPCI) is the preferred method of reperfusion in ST-elevation myocardial infarction. However, microvascular perfusion is often impaired due to distal embolization of thrombus. Intracoronary (IC) thrombolysis may attenuate thrombotic burden. We conducted a meta-analysis comparing the benefits and risks of IC thrombolytic therapy as an adjunct to PPCI.MethodsRandomized controlled trials (RCTs) were identified through search of Medline, EMBASE, Scopus, Web of Science, Cochrane Library (Cochrane Reviews and Cochrane Protocols), PROSPERO, and clinicaltrials.gov from 1946 to January 2019. Studies included patients with ST-elevation myocardial infarction undergoing primary PCI receiving IC thrombolytic agents. Both safety and efficacy outcomes were explored. Data were combined using a fixed-effects model.ResultsOf 1278 citations identified, 6 RCTs (890 patients; 519 IC thrombolytic and 371 IC placebo) were included. Post-PCI thrombolysis in myocardial infarction (TIMI) flow grade 2/3 occurred in 97.1% of the IC thrombolytic group vs 95.1% of the IC placebo group (odds ratio [OR], 0.57; 95% confidence interval [CI], 0.28-1.17; P = 0.13). Complete ST-segment resolution was more common with IC thrombolysis (OR, 0.29; 95% CI, 0.15-0.57; P = 0.0003). There was a strong trend favouring fewer in-hospital major adverse cardiac events with IC thrombolysis when compared with IC placebo (OR, 0.64; 95% CI, 0.41-1.01; P = 0.05). There was no difference in bleeding (TIMI major, TIMI minor, and Bleeding Academic Research Consortium [BARC] 3-5 bleeds) between the 2 groups (OR, 1.36; 95% CI, 0.38-3.54; P = 4.84).ConclusionsGiven the limited studies to date, our meta-analysis suggests that a targeted IC thrombolytic approach is safe and potentially effective to augment PPCI. However, these findings deserve confirmation in a larger RCT.  相似文献   
992.
BackgroundHeart failure with midrange ejection fraction (HFmrEF) has been recently acknowledged as a separate phenotype, but metabolomics evaluation of this subtype remains largely unexamined.MethodsA quantitative metabolomics study on amino acids and acylcarnitines was performed to characterize different states of heart failure (HF) in 628 participants. Both multivariate orthogonal partial least squares- discriminant analysis and univariate Mann-Whitney U test were used to explore reliable metabolic profiles associated with different HF states. The resulting metabolites were further refined to obtain diagnostic metabolite scores (DMSs) with the use of ordinal logistic regression. Lasso-penalized regression was applied to produce a survival-associated prognostic metabolite score (PMS). The Cox proportional hazards model, Kaplan-Meier curves, and time-dependent receiver operating characteristics were used for a comprehensive assessment of prognostic value using PMS versus traditional clinical biomarkers.ResultsThe optimized models identified a panel of 15 differential metabolites that were shared across different HF states, whereas some metabolites were associated with a specific state. PMS consisting of 9 metabolites demonstrated an appreciably better prognostic value (hazard ratio [HR] 1.62, 95% confidence interval [CI] 1.25-2.1) vs the natural logarithm of N-terminal pro–B-type natriuretic peptide (Ln[NT-proBNP]; HR 1.23, 95% CI 0.94-1.61; P < 0.001). The overall area under the receiver operating characteristic curve value of PMS was superior to that of Ln(NT-proBNP) in risk prediction for patients with HFmrEF and HF with reduced ejection fraction (HFrEF) subtypes (P < 0.001).ConclusionsTargeted metabolomics has provided a novel understanding of the molecular mechanism underlying HF. Both DMS and PMS clearly demonstrated HFmrEF as a distinct phenotype between a mild HF with preserved ejection fraction state and a severe HFrEF state. PMS exhibited superior prognostic value than Ln(NT-proBNP). Further investigation is needed with independent large-scale validation.  相似文献   
993.
目的: 研究结核性脊膜炎MRI表现、治疗后演变及患者预后情况,以提高临床认识。方法: 通过《首都医科大学附属北京胸科医院病案电子化管理系统》和《图像获取及传输系统》(PACS),收集2012年1月1日至2016年12月31日确诊并有完整MRI资料的31例结核性脊膜炎患者,记录脊膜、蛛网膜下腔及脊髓改变。 结果: 96.8%(30/31)的患者有脊膜增厚和强化。48.4%(15/31)的患者蛛网膜下腔不规则或狭窄,12.9%(4/31)的患者蛛网膜下腔闭塞,6.5%(2/31)的患者有髓外硬膜内结核瘤。脊髓炎见于51.6%(16/31)的患者,而髓内结核瘤见于9.7%(3/31)的患者。58.3%(7/12)的患者在随访MRI中显示病情缓解,25.0%(3/12)的患者有进展,16.7%(2/12)患者的MRI表现无变化。71.0%(22/31)的结核性脊膜炎患者预后不良,包括13例死亡及9例残疾。结论: MRI增强扫描能发现增厚强化的脊膜、脊髓及蛛网膜下腔改变,并且能观察抗结核治疗后的疗效,可以作为结核性脊膜炎患者首选的影像检查方法。  相似文献   
994.
目的: 评价基于基因芯片的miRNA表达差异在结核性脑膜炎(tuberculous meningitis,TBM)与病毒性脑膜炎(viral meningitis,VM)诊断中的价值。方法: 选取2017年12月至2019年9月在首都医科大学附属北京胸科医院和首都医科大学附属北京天坛医院治疗的TBM患者28例和VM患者27例作为验证样本进行实时荧光定量逆转录PCR(qRT-PCR)验证。选取前期收集的8例TBM患者和5例VM患者作为基因芯片样本进行全基因组miRNA微阵列分析,通过预测差异性miRNA的靶基因、基因本体(GO)富集分析、京都基因与基因组百科全书(KEGG)信号通路分析、构建蛋白质-蛋白质相互作用(PPI)网络筛选出两病间前10个差异性miRNA枢纽基因。再采用qRT-PCR对患者间表达差异明显的miR-21-5p进行验证,并通过受试者工作特征曲线(ROC)下面积(AUC)分析miRNA的诊断价值。结果: 通过miRNA微阵列分析初步筛选出26个差异表达的miRNA(14个表达上调,12个表达下调)和对应的靶基因3217个。经GO富集分析、KEGG信号通路分析筛选出190个相关靶基因,对其进行PPI网络分析,筛选出前10个靶基因作为核心靶基因。对基因芯片检测样本的hsa-miR-21-5p相对表达量进行qRT-PCR验证,发现TBM患者hsa-miR-21-5p的表达水平[15.890(3.423,25.581)]较VM患者[0.807(0.614,0.955)]明显上调(Z=-2.355,P=0.019),差异倍数(TBM/VM)在基因芯片和qRT-PCR中分别是4.817和4.660,两种检测方法结果基本一致;对28例TBM和27例VM患者的hsa-miR-21-5p进行qRT-PCR结果比较,发现hsa-miR-21-5p在TBM患者的相对表达量为4.825(2.433,21.362),明显高于VM患者[0.204(0.112,0.711)],差异有统计学意义(Z=-5.000,P=0.000),且ROC曲线区分TBM与VM患者的AUC为0.893(0.806~0.980),敏感度为85.7%,特异度为88.9%。结论: 相较于VM患者,作为基因芯片检测中表达差异明显的miR-21-5p在TBM患者中表达明显上调,可作为鉴别TBM与VM的潜在生物标志物。  相似文献   
995.
肺结核的影像学形态往往呈多样性,因此,如何鉴别诊断肺结核一直以来是常规影像学研究的重点与难点。近年来,深度学习在辅助影像诊断方面有了飞快发展。深度学习擅长识别大量图像数据中的复杂模式,可大大提高医师的诊断准确性及工作效率。笔者将对深度学习在影像诊断及肺结核影像诊断中的应用、不足及展望进行综述。  相似文献   
996.
目的:研究药物性肝损伤临床特点及病因,为临床防治提供资料。方法:回顾性分析我院儿童药物性肝损伤患儿服药史、临床表现、服药基础疾病、治疗及转归等。结果:29例患儿中,男21例,女8例,以纳差、恶心呕吐、尿黄、乏力等为主要临床表现,有48.27%患儿仅以肝功能异常就诊。分型以肝细胞损伤型为主20例,混合型5例,胆汁淤积型4例;肝细胞损伤组ALT值最高,胆汁淤积组AST和TB值最高。导致肝损伤的药物类别主要有抗感染药(38.77%)、抗肿瘤药(28.57%)、中药(10.2%)、激素(8.16%)等;服药基础疾病为肿瘤11例、感染性疾病10例、发热3例、腹泻2例、感冒2例、抽动症1例。经治疗19例治愈,8例好转,1例进行肝移植,1例自动出院。结论:儿童药物性肝损伤仅肝功能指标异常者比例较大,需警惕误诊漏诊;引起儿童肝损伤药物以抗肿瘤药和抗感染药为主,其中布洛芬引起后果较严重,需关注其安全性;患者多数转归较好。  相似文献   
997.
Cardiovascular Drugs and Therapy - This meta-analysis compared the efficacy and safety of oral anticoagulation (OAC) therapy alone versus OAC plus single antiplatelet therapy (SAPT) in patients...  相似文献   
998.
BackgroundThe association of antihypertensive drugs with the risk and severity of COVID-19 remains unknown.Methods and ResultsWe systematically searched PubMed, MEDLINE, The Cochrane Library, Cochrane Central Register of Controlled Trials (CENTRAL), ClinicalTrials.gov, and medRxiv for publications before July 13, 2020. Cohort studies and case-control studies that contain information on the association of antihypertensive agents including angiotensin-converting enzyme inhibitors (ACEIs), angiotensin II receptor blockers (ARBs), calcium-channel blockers (CCBs), β-blockers, and diuretics with the risk and severity of COVID-19 were selected. The random or fixed-effects models were used to pool the odds ratio (OR) with 95% confidence interval (CI) for the outcomes.The literature search yielded 53 studies that satisfied our inclusion criteria, which comprised 39 cohort studies and 14 case-control studies. These studies included a total of 2,100,587 participants. We observed no association between prior usage of antihypertensive medications including ACEIs/ARBs, CCBs, β-blockers, or diuretics and the risk and severity of COVID-19. Additionally, when only hypertensive patients were included, the severity and mortality were lower with prior usage of ACEIs/ARBs (overall OR of 0.81, 95% CI 0.66?0.99, p < 0.05 and overall OR of 0.77, 95% CI 0.66?0.91, p < 0.01).ConclusionsTaken together, usage of antihypertensive drugs is not associated with the risk and severity of COVID-19. Based on the current available literature, it is not recommended to abstain from the usage of these drugs in COVID-19 patients.RegistrationThe meta-analysis was registered on OSF (https://osf.io/ynd5g).  相似文献   
999.
2014年FDA批准了41个新分子实体和新的治疗生物制品。本文介绍和评价感染和传染病治疗领域新药。  相似文献   
1000.
目的分析单纯慢性阻塞性肺疾病(简称慢阻肺)患者与慢阻肺合并阻塞性睡眠呼吸暂停低通气综合征(OSAHS)患者的临床特征,研究合并OSAHS对慢阻肺患者心功能的影响。方法本研究回顾性纳入2016年9月至2018年10月就诊于北京大学第三医院呼吸与危重症医学科门诊的稳定期慢阻肺患者126例,其中男112例,女14例,年龄48~89岁,中位年龄67岁。以呼吸暂停低通气指数(AHI)5次/h为界值,分为单纯慢阻肺组(31例)和慢阻肺合并OSAHS组(95例),比较患者的人口学特征、呼吸道症状、肺功能、心血管事件发生率和反映患者的患者心功能的超声心动图E/e′比率、左心房前后径(LAD)及左心室射血分数(LVEF)等指标,采用独立样本t检验、卡方检验等对数据进行统计学分析。结果单纯慢阻肺患者与慢阻肺合并OSAHS患者的人口学特征、呼吸道症状、肺功能差异均无统计学意义,各项夜间血氧饱和度水平指标差异均有统计学意义(均P<0.05),两组患者左心室质量指数(LVMI)差异有统计学意义(P=0.047),而心血管事件发生率差异无统计学意义。AHI≥30次/h的合并严重OSAHS的患者与AHI<30次/h的非严重OSAHS的患者相比,超声心动图指标E/e′(P=0.013)、LAD(P=0.006)、LVMI(P=0.051)、LVEF(P=0.030)差异均有统计学意义,冠心病及充血性心力衰竭病史差异有统计学意义(P=0.025,P<0.001)。按轻中重度对慢阻肺合并OSAHS患者严重程度进行分组后,E/e′及LAD与严重程度明显相关(P=0.045,P=0.011)。夜间血氧饱和度水平方面,夜间平均血氧饱和度和E/e′、LAD、LVMI均有显著相关性(r=-0.195,P=0.033;r=-0.197,P=0.030;r=-0.195,P=0.044);血氧饱和度≤90%的比例与LAD有显著相关性(r=0.209,P=0.021)。多元线性回归模型中,AHI每增加一个单位时E/e′平均增加0.070,氧减指数每增加一个单位时E/e′平均增加0.084。结论慢阻肺合并重度OSAHS的患者与慢阻肺合并非重度OSAHS患者相比,左心舒张功能显著降低且发生充血性心力衰竭和冠心病的风险显著增加,且慢阻肺合并OSAHS的严重程度与左心舒张功能受限的严重程度相关,AHI越高、氧减指数越高,左心舒张功能受限及结构改变越严重。  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