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   378428篇
  免费   34714篇
  国内免费   15116篇
耳鼻咽喉   2749篇
儿科学   9213篇
妇产科学   6177篇
基础医学   60720篇
口腔科学   7726篇
临床医学   25764篇
内科学   56535篇
皮肤病学   6738篇
神经病学   33565篇
特种医学   7764篇
外国民族医学   96篇
外科学   28098篇
综合类   51059篇
现状与发展   52篇
预防医学   18374篇
眼科学   5958篇
药学   56583篇
  71篇
中国医学   17114篇
肿瘤学   33902篇
  2024年   382篇
  2023年   5295篇
  2022年   7239篇
  2021年   12979篇
  2020年   12429篇
  2019年   12685篇
  2018年   12372篇
  2017年   13081篇
  2016年   13414篇
  2015年   15207篇
  2014年   22997篇
  2013年   26929篇
  2012年   23133篇
  2011年   26484篇
  2010年   22030篇
  2009年   21185篇
  2008年   21029篇
  2007年   19846篇
  2006年   17814篇
  2005年   15482篇
  2004年   13521篇
  2003年   11718篇
  2002年   9345篇
  2001年   8131篇
  2000年   6966篇
  1999年   5928篇
  1998年   4986篇
  1997年   4607篇
  1996年   3999篇
  1995年   4005篇
  1994年   3589篇
  1993年   3094篇
  1992年   2613篇
  1991年   2392篇
  1990年   2067篇
  1989年   1831篇
  1988年   1580篇
  1987年   1379篇
  1986年   1396篇
  1985年   2127篇
  1984年   2026篇
  1983年   1418篇
  1982年   1579篇
  1981年   1317篇
  1980年   1104篇
  1979年   839篇
  1978年   664篇
  1977年   520篇
  1976年   461篇
  1975年   328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.
田玥  邹健 《现代肿瘤医学》2022,(23):4377-4382
胃癌作为临床最常见的肿瘤之一,常因确诊疾病较晚而影响治疗效果,胃镜活检后的病理虽然作为确诊的金标准,但是由于此方式过程痛苦,操作复杂,费用较高,且具有侵入性,可能会导致患者拒绝操作而难普及于临床,因此积极找寻胃癌有效的监测指标十分必要。近年来,很多学者研究维生素与胃癌的相关关系,并试图通过摄取某些维生素降低胃癌发生率,延缓病情及改善预后,也有通过检测血清中维生素的水平给早期胃癌的诊断提供帮助。本文就同型半胱氨酸、维生素D、维生素C、维生素E、维生素B12及叶酸在胃癌中的作用机制,及其在血清中水平与胃癌关系的相关研究进展进行简要综述,为临床胃癌诊疗提供新思路。  相似文献   
5.
BackgroundStenotrophomonas maltophilia, a species of highly genetic diversity, has emerged as an important nosocomial pathogen. S. maltophilia and Pseudomonas aeruginosa are often co-isolated from pneumonia patients. In our previous study, we have demonstrated that the pacIRA cluster present in some but not all clinical S. maltophilia isolates. Proteins encoded by pacIRA operon are an extracytoplasmic function (ECF) sigma factor, a transmembrane anti-sigma regulator, and a TonB-dependent receptor. This study aimed to elucidate PacIRA system function and its significance to S. maltophilia.MethodsThe pacI, pacR, and pacA genes were individually or totally deleted from the chromosome of KJΔEnt, a pacIRA-positive and siderophore-null strain. Growth promotion assay was performed to examine the implication of pacIRA system in iron utilization. Gene expression was quantified by quantitative real time PCR (qRT-PCR). Growth competition assay was executed to investigate the significance of pacIRA operon to S. maltophilia.ResultsPacIRA system contributed to utilize ferri-pyochelin of P. aeruginosa as iron sources for growth in an iron-depleted condition, but hardly utilized ferric citrate, hemin, ferri-stenobactin, and ferri-pyoverdine. PacIRA was founded to belong to Fur regulon and upregulated in response to iron-depleted stress. Growth competition assay demonstrated that pacIRA-positive S. maltophilia had a superiority over pacIRA-negative S. maltophilia in iron acquisition when they were co-cultured in P. aeruginosa ferri-pyochelin-supplemented medium.ConclusionsPacIRA system of S. maltophilia is a xenosiderophore uptake implement, involving in the acquisition of pyochelin of P. aeruginosa.  相似文献   
6.
7.
8.
目的 建立细叶亚菊的质量标准,为其质量控制和合理开发利用提供科学参考。方法 采用性状鉴别、显微鉴别、薄层色谱法(TLC)对细叶亚菊进行定性分析;参照《中国药典》(2020年版)通则方法对细叶亚菊水分、总灰分、酸不溶性灰分、水溶性浸出物进行含量检查;利用高效液相色谱法(HPLC)测定细叶亚菊中绿原酸、异绿原酸A的含量。结果 确定了细叶亚菊的药材性状及显微特征。TLC鉴别显示,供试品(细叶亚菊药材)与对照品(绿原酸、异绿原酸A)在相应位置上均显示相同颜色的荧光斑点。13批细叶亚菊水分、总灰分、酸不溶性灰分、浸出物的含量分别为8.55%-13.07%、6.81%-12.68%、1.11%-3.53%、8.41%-11.64%;绿原酸、异绿原酸A的含量范围分别为0.072%-0.440%、0.283%-1.324%(n=3)。结论 本研究建立的方法准确稳定,可为细叶亚菊的质量控制提供参考。暂规定细叶亚菊水分不得过12.0%,总灰分不得过10.0%,酸不溶性灰分不得过2.5%,水溶性浸出物不得少于8.0%,绿原酸不得少于0.2%,异绿原酸A不得少于0.6%。  相似文献   
9.
目的探讨乙肝相关性肝癌临床病理学特征与溶血磷脂酸(LPA)和高敏C反应蛋白(hs-CRP)表达的相关性。方法选取2019年1月至2020年1月间河南省驻马店市中心医院收治的198例乙肝相关性肝癌患者作为乙肝组,198例酒精相关性肝癌患者作为酒精组。两组患者都进行血清hs-CRP和LPA表达检测,调查患者的病理学特征并进行相关性分析。结果乙肝组患者血清hs-CRP和LPA含量均高于酒精组,差异均有统计学意义(均P <0.05)。两组患者血清ALP、AFP、ALT、AST和GGT含量比较,差异均无统计学意义(P> 0.05)。乙肝组不同临床分期和组织学分化患者的血清hs-CRP和LPA含量比较,差异均有统计学意义(均P <0.05)。乙肝组患者的临床分期和组织学分化与血清hs-CRP和LPA表达均存在相关性,差异均有统计学意义(均P <0.05)。患者的临床分期和组织学分化均为影响hs-CRP和LPA表达的重要因素,差异均有统计学意义(均P <0.05)。结论相对于酒精相关性肝癌,乙肝相关性肝癌的血清hs-CRP和LPA呈现高表达,与患者的临床病理学特征存在相关性。  相似文献   
10.
Whether the underlying mutations are homozygous, heterozygous, or co-inherited with other hemoglobinopathies, sickle cell disease is known to afflict the kidneys, leading to the clinical entity known as sickle cell nephropathy (SCN). Although common, SCN remains diagnostically elusive. Conventional studies performed in the context of renal disorders often fail to detect early stage SCN. This makes the quest for early diagnosis and treatment more challenging, and it increases the burden of chronic kidney disease-related morbidity among patients. Novel diagnostic tools have been employed to overcome this limitation. In this study, we discuss various biomarkers of SCN, including those employed in clinical practice and others recently identified in experimental settings, such as markers of vascular injury, endothelial dysfunction, tubulo-glomerular damage, and oxidative stress. These include kidney injury molecule-1, monocyte chemoattractant protein-1, N-acetyl-B-D-glucosaminidase, ceruloplasmin, orosomucoid, nephrin, and cation channels, among others. Furthermore, we explore the potential of novel biomarkers for refining diagnostic and therapeutic approaches and describe some obstacles that still need to be overcome. We highlight the importance of a collaborative approach to standardize the use of promising new biomarkers. Finally, we outline the limitations of conventional markers of renal damage as extensions of the pathogenic process occurring at the level of the organ and its functional subunits, with a discussion of the expected pattern of clinical and biochemical progression among patients with SCN.  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