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   52308篇
  免费   3526篇
  国内免费   1664篇
耳鼻咽喉   101篇
儿科学   1124篇
妇产科学   301篇
基础医学   2683篇
口腔科学   105篇
临床医学   8833篇
内科学   5672篇
皮肤病学   51篇
神经病学   13935篇
特种医学   2509篇
外科学   2599篇
综合类   9265篇
现状与发展   5篇
预防医学   2054篇
眼科学   418篇
药学   4074篇
  48篇
中国医学   3600篇
肿瘤学   121篇
  2024年   52篇
  2023年   713篇
  2022年   1236篇
  2021年   2062篇
  2020年   1951篇
  2019年   1719篇
  2018年   1815篇
  2017年   1919篇
  2016年   2141篇
  2015年   1887篇
  2014年   3774篇
  2013年   4203篇
  2012年   3296篇
  2011年   3232篇
  2010年   2736篇
  2009年   2535篇
  2008年   2555篇
  2007年   2541篇
  2006年   2306篇
  2005年   1873篇
  2004年   1640篇
  2003年   1400篇
  2002年   1392篇
  2001年   1177篇
  2000年   1011篇
  1999年   888篇
  1998年   662篇
  1997年   604篇
  1996年   476篇
  1995年   445篇
  1994年   383篇
  1993年   312篇
  1992年   302篇
  1991年   246篇
  1990年   234篇
  1989年   191篇
  1988年   188篇
  1987年   178篇
  1986年   140篇
  1985年   194篇
  1984年   133篇
  1983年   89篇
  1982年   124篇
  1981年   76篇
  1980年   89篇
  1979年   65篇
  1978年   59篇
  1977年   62篇
  1976年   46篇
  1972年   32篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
BackgroundIschemia reperfusion (I/R) play an imperative role in the expansion of cardiovascular disease. Sinomenine (SM) has been exhibited to possess antioxidant, anticancer, anti-inflammatory, antiviral and anticarcinogenic properties. The aim of the study was scrutinized the cardioprotective effect of SM against I/R injury in rat.MethodsRat were randomly divided into normal control (NC), I/R control and I/R + SM (5, 10 and 20 mg/kg), respectively. Ventricular arrhythmias, body weight and heart weight were estimated. Antioxidant, inflammatory cytokines, inflammatory mediators and plasmin system indicator were accessed.ResultsPre-treated SM group rats exhibited the reduction in the duration and incidence of ventricular fibrillation, ventricular ectopic beat (VEB) and ventricular tachycardia along with suppression of arrhythmia score during the ischemia (30 and 120 min). SM treated rats significantly (P < 0.001) altered the level of antioxidant parameters. SM treatment significantly (P < 0.001) repressed the level of creatine kinase MB (CK-MB), creatine kinase (CK) and troponin I (Tnl). SM treated rats significantly (P < 0.001) repressed the tissue factor (TF), thromboxane B2 (TXB2), plasminogen activator inhibitor 1 (PAI-1) and plasma fibrinogen (Fbg) and inflammatory cytokines and inflammatory mediators.ConclusionOur result clearly indicated that SM plays anti-arrhythmia effect in I/R injury in the rats via alteration of oxidative stress and inflammatory reaction.  相似文献   
2.
3.
4.
5.
BackgroundRecent guidelines for the treatment of moderate or severe ischemic mitral regurgitation (IMR) in patients undergoing coronary artery bypass grafting (CABG) have changed. This study assessed the real-world impact of changing guidelines on the management of IMR during CABG over time. We hypothesized that the utilization of mitral valve repair for IMR would decrease over time, whereas mitral valve replacement for severe IMR would increase.MethodsPatients undergoing CABG in a statewide collaborative database (2011-2020) were stratified by severity of IMR. Trends in mitral valve repair or replacement were evaluated. To account for differences of the patients, propensity score–matched analyses were used to compare patients with and without mitral intervention.ResultsA total of 11,676 patients met inclusion criteria, including 1355 (11.6%) with moderate IMR and 390 (3.3%) with severe IMR. The proportion of patients undergoing mitral intervention for moderate IMR decreased over time (2011, 17.7%; 2020, 7.5%; Ptrend = .001), whereas mitral replacement for severe IMR remained stable (2011, 11.1%; 2020, 13.3%; Ptrend = .14). Major morbidity was higher for patients with moderate IMR who underwent mitral intervention (29.1% vs 19.9%; P = .005). In a propensity analysis of 249 well-matched pairs, there was no difference in major morbidity (29.3% with mitral intervention vs 23.7% without; P = .16) or operative mortality (1.2% vs 2.4%; P = .5).ConclusionsConsistent with recent guideline updates, patients with moderate IMR were less likely to undergo mitral repair. However, the rate of replacement for severe IMR did not change. Mitral intervention during CABG did not increase operative mortality or morbidity.  相似文献   
6.
7.
目的 探讨我国弓形虫Chinese 1优势基因型感染对宿主脑组织铁代谢及脑损伤的影响。方法 将20只C57BL/6(体质量15~17 g)小鼠随机分为对照组和感染组,每组10只。感染组每只小鼠腹腔注射4 000个弓形虫Chinese 1优势基因型TgCtwh3虫株速殖子,对照组小鼠注射等量无菌PBS,饲养6 d后处死小鼠并取其脑组织。采用电感耦合等离子体质谱法(inductively coupled plasma mass spectrometry, ICP⁃MS)检测小鼠脑组织铁元素水平;采用RNA芯片检测两组小鼠脑组织差异基因数目并对功能基因表达情况进行基因本体论(Gene Ontology, GO)功能富集;采用实时荧光定量PCR(fluorescent quantitative real⁃time PCR, qPCR)技术检测小鼠脑组织中弓形虫表面抗原1(Toxoplasma gondii surface antigen 1,TgSAG1)基因及部分锌铁调控蛋白(Zrt⁃ and Irt⁃like protein, ZIP)家族mRNA表达水平;采用光镜和电镜观察小鼠脑组织海马齿轮回(dentate gyrus, DG)超微结构;采用Western blotting检测谷胱甘肽过氧化物酶4(glutathione peroxidase 4, GPx4)蛋白表达水平;采用硫代巴比妥酸(TBA)法检测丙二醛(malondialdehyde, MDA)水平;采用免疫组化检测血管内皮生长因子(vascular endothelial growth factor, VEGF)蛋白表达光密度(optical density, OD)值。结果 光镜下可见感染组小鼠脑组织海马DG区细胞坏死,电镜下见感染组小鼠脑组织海马区出现胞质空泡化、核皱缩坏死、线粒体嵴断裂消融、自噬小体增加等超微结构变化。与对照组相比,感染组小鼠脑组织中铁元素水平上调[(32.92 ± 0.90) µg/g vs.(37.72 ± 1.10) µg/g;t = 3.397, P < 0.01];RNA芯片检测感染组小鼠脑组织发现721个基因上调、276个基因下调,差异表达基因在金属离子结合能力上有明显富集。与对照组相比,感染组小鼠脑组织金属元素转运体ZIP2 mRNA表达水平上调(t = 8.659,P < 0.05)、GPx4表达下降[(1.046 ± 0.025) vs. (0.720 ± 0.101);t = 3.129,P < 0.01])、MDA水平升高[(4.37 ± 0.33) nmol/mgprot vs.(5.93 ± 0.54) nmol/mgprot;t = 2.451,P < 0.05)]、VEGF蛋白平均OD值上调[(0.348 3 ± 0.017 8) vs. (0.490 6 ± 0.010 5);t = 6.641,P < 0.01]。结论 Chinese 1优势基因型弓形虫感染后,小鼠脑组织中铁元素蓄积、抗氧化能力下调、氧化应激水平升高,提示弓形虫感染可影响宿主脑组织铁代谢而导致脑损伤。  相似文献   
8.
BackgroundGait classification systems (GCS) may enable clinicians to differentiate gait patterns into clinically significant categories that assist in clinical decision-making and assessment of outcomes. Davids and Bagley in 2014 [1] described a GCS for children with cerebral palsy (GCS-CP). The purpose of our study was to use the GCS-CP for the first time on a sample of patients with CP and to evaluate the reliability and utility of the classification system.MethodsThe gait of 131 children with CP was retrospectively reviewed and classified according to Davids and Bagley’s classification using two-dimensional (2D) video and three-dimensional (3D) lower limb kinematics and kinetics. Gross Motor Function Classification System (GMFCS) levels were determined, and the Gait Profile Scores (GPS) calculated to characterize the sample concerning gait classification. The comparison between the groups was performed using the Kruskal-Wallis test with respect to the non-normal distribution of the data. The intrarater and interrater reliability was determined using the Kappa index (k) statistics with 95% CI.ResultsAll GCS-CP groups were represented within the evaluated sample. Of the 131 cases evaluated, 127 (96.95%) were able to be classified with respect to sagittal plane stance phase gait deviations. All patients in the sample were able to be classified with respect to sagittal plane swing phase and transverse plane gait deviations. The interrater reliability was 0.596 and 0.485 for the first and second levels of the classification, respectively, according to the Fleiss’s Kappa statistics. Intrarater reliability was 0.776 and 0.714 for the raters one and two, respectively, according to the Cohen’s Kappa statistics.SignificanceThe GCS-CP exhibited clinical utility, successfully classifying almost all subjects with CP in two planes, based upon kinematic and kinetic data. The classification is valid and has moderate interrater and moderate to substantial intrarater reliability.  相似文献   
9.
Cadmium is a toxic metal that can damage the brain and other organs. This study aimed to explore the protective effects of Potentilla anserine L. polysaccharide (PAP) against CdCl2-induced neurotoxicity in N2a and SH-SY5Y cells and in the cerebral cortex of BALB/c mice. In addition, we aimed to identify the potential mechanisms underlying these protective effects. Relative to CdCl2 treatment alone, pretreatment with PAP prevented the reduction in cell viability evoked by CdCl2, decreased rates of apoptosis, promoted calcium homeostasis, decreased ROS accumulation, increased mitochondrial membrane potential, inhibited cytochrome C and AIF release, and prevented the cleavage of caspase-3 and PARP. In addition, PAP significantly decreased the CdCl2-induced phosphorylation of CaMKII, Akt, and mTOR. In conclusion, PAP represents a potential therapeutic agent for the treatment of Cd-induced neurotoxicity, functioning in part via attenuating the activation of the mitochondrial apoptosis pathway and the Ca2+-CaMKII-dependent Akt/mTOR pathway.  相似文献   
10.
The importance of the left atrial appendage (LAA) as the source of thromboembolism including stroke in patients with nonvalvular atrial fibrillation is well documented, with more than 90% of ischemic strokes related to a LAA thrombus. Although oral anticoagulation has been the standard of care, approximately 50% to 60% of patients either have contraindications to oral anticoagulation or do not continue the medication beyond the first year. This led to the development of local site-specific therapy to occlude the LAA by either surgical or transcatheter means. Despite marked advancements, incomplete LAA closure with surgical and transcatheter approaches remains frequent. The etiology of incomplete LAA closure and its clinical implications remain unclear. Multiple strategies are in development including changes in deployment techniques, a new device design, and alternative approaches to leak closure.  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