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   2461篇
  免费   199篇
  国内免费   87篇
耳鼻咽喉   3篇
儿科学   78篇
妇产科学   24篇
基础医学   555篇
口腔科学   54篇
临床医学   196篇
内科学   485篇
皮肤病学   18篇
神经病学   74篇
特种医学   45篇
外科学   75篇
综合类   177篇
一般理论   3篇
预防医学   412篇
眼科学   5篇
药学   165篇
中国医学   334篇
肿瘤学   44篇
  2024年   16篇
  2023年   99篇
  2022年   141篇
  2021年   204篇
  2020年   124篇
  2019年   128篇
  2018年   116篇
  2017年   102篇
  2016年   92篇
  2015年   134篇
  2014年   162篇
  2013年   234篇
  2012年   150篇
  2011年   153篇
  2010年   90篇
  2009年   129篇
  2008年   102篇
  2007年   91篇
  2006年   104篇
  2005年   70篇
  2004年   55篇
  2003年   38篇
  2002年   32篇
  2001年   25篇
  2000年   27篇
  1999年   16篇
  1998年   21篇
  1997年   16篇
  1996年   14篇
  1995年   14篇
  1994年   10篇
  1993年   4篇
  1992年   5篇
  1991年   4篇
  1990年   6篇
  1989年   1篇
  1987年   4篇
  1986年   3篇
  1985年   2篇
  1984年   1篇
  1983年   4篇
  1982年   2篇
  1981年   1篇
  1977年   1篇
排序方式: 共有2747条查询结果,搜索用时 31 毫秒
101.
The Hypertension Cardiovascular Outcome Prevention and Evidence in Asia (HOPE Asia) Network was set up to improve the management of hypertension in Asia with the ultimate goal of achieving “zero” cardiovascular events. Asia is a diverse continent, and the prevalence of hypertension has increased over the last 30 years. There are a number of Asia‐specific features of hypertension and hypertension‐related cardiovascular complications, which means that a region‐specific approach is needed. White‐coat hypertension will become more of an issue over time as Asian populations age, and masked hypertension is more prevalent in Asian than in Western countries. Identifying and treating masked hypertension is important to reduce cardiovascular risk. Abnormal patterns of blood pressure (BP) variability common in Asia include exaggerated early morning BP surge and nocturnal hypertension. These are also important cardiovascular risk factors that need to be managed. Home blood pressure monitoring (HBPM) is an important tool for detecting white‐coat and masked hypertension, and monitoring BP variability, and practices in Asia are variable. Use of HBPM is important given the Asia‐specific features of hypertension, and strategies are needed to improve and standardize HBPM usage. Development of HBPM devices capable of measuring nocturnal BP along with other information and communication technology‐based strategies are key developments in the widespread implementation of anticipation medicine strategies to detect and prevent cardiovascular events in patients with hypertension. Region‐wide differences in hypertension prevalence, control, and management practices in Asia highlight the importance of information sharing to facilitate best practices.  相似文献   
102.
目的 了解间日疟原虫传播阻断疫苗候选抗原Pvs48/45在中缅边境地区的基因多态性和自然选择特点。方法 提取39例来自中缅边境主要流行区(Laiza)的间日疟原虫基因组DNA,采用巢式PCR(nest-PCR)扩增Pvs48/45基因开放阅读区(Open reading frame, ORF);通过MEGA 4.0、DnaSP v5.10和NETWORK 4.6对Pvs48/45基因多态性和自然选择特点进行分析。结果 研究发现了6个突变位点,均为非同义突变(E35K ,H211N ,K250N ,D335Y,A376T,K418R),导致了5种单倍型;Pvs48/45基因的核苷酸多态性水平极低(π=0.00064),CRDⅢ区最高(π=0.00163);多种中性检验均表明Pvs48/45基因处于平衡选择;种群进化分析和单倍型网络图显示Pvs48/45具有较强的地理分化,且H2型为中缅边境地区频率最高的单倍型。结论 Pvs48/45在中缅边境地区遗传多样性很低,且在进化过程中经历平衡选择,提示其可作为传播阻断疫苗候选靶点;Pvs48/45在全球具有较强的地理分化,应根据地区遗传特点开发更加有效的传播阻断疫苗。  相似文献   
103.
The gene encoding the small subunit rRNA serves as a prominent tool for the phylogenetic analysis and classification of Bacteria and Archaea owing to its high degree of conservation and its fundamental function in living organisms. Here we show that the 16S rRNA genes of not-yet-cultivated large sulfur bacteria, among them the largest known bacterium Thiomargarita namibiensis, regularly contain numerous self-splicing introns of variable length. The 16S rRNA genes can thus be enlarged to up to 3.5 kb. Remarkably, introns have never been identified in bacterial 16S rRNA genes before, although they are the most frequently sequenced genes today. This may be caused in part by a bias during the PCR amplification step that discriminates against longer homologs, as we show experimentally. Such length heterogeneity of 16S rRNA genes has so far never been considered when constructing 16S rRNA-based clone libraries, even though an elongation of rRNA genes due to intervening sequences has been reported previously. The detection of elongated 16S rRNA genes has profound implications for common methods in molecular ecology and may cause systematic biases in several techniques. In this study, catalyzed reporter deposition-fluorescence in situ hybridization on both ribosomes and rRNA precursor molecules as well as in vitro splicing experiments were performed and confirmed self-splicing of the introns. Accordingly, the introns do not inhibit the formation of functional ribosomes.  相似文献   
104.
Oral Diseases (2011) 18 , 85–95 Objective: Oral infection is considered to play a critical role in the pathogenesis of bisphosphonate‐related osteonecrosis of the jaw (BRONJ), and antibiotic therapy has become a mainstay of BRONJ therapy. This study was aimed to investigate the effect of antibiotics on bacterial diversity in BRONJ tissues. Materials and methods: The bacterial profile from soft tissues associated with the BRONJ lesion was determined using 16S rRNA‐based denaturing gradient gel electrophoresis (DGGE) and sequencing. Twenty BRONJ subjects classified as stage 0–2 were enrolled in this study, and patient groups were divided into an antibiotic cohort (n = 10) treated with systemic antibiotic and a non‐antibiotic cohort (n = 10) with no prior antibiotic therapy. Results: The DGGE fingerprints indicated no significant differences in bacterial diversity of BRONJ tissue samples. Patients on antibiotics had higher relative abundance of phylum Firmicutes with bacterial species, Streptococcus intermedius, Lactobacillus gasseri, Mogibacterium timidum, and Solobacterium moorei, whereas patients without antibiotics had greater amounts of Parvimonas micra and Streptococcus anginosus. Thirty percent of bacterial populations were uncultured (yet‐to be cultured) phylotypes. Conclusion: This study using limited sample size indicated that oral antibiotic therapy may have a limited efficacy on the bacterial population associated with BRONJ lesions.  相似文献   
105.
目的:应用PCR-变性梯度凝胶电泳技术(denaturing gradient gel electrophoresis,DGGE)技术检测早期儿童龋治疗前后唾液中微生物多样性的变化。方法:选取北京大学燕东幼儿园22名3~5岁儿童进行口腔检查,在龋齿治疗前和治疗后2周分别取样,采用PCR-DGGE技术检测受试儿童唾液样本,分析治疗前后唾液微生物多样性的变化。结果:治疗前唾液样本DGGE条带数为23±2.9,治疗后唾液样本DGGE条带数为28±4.1,差异有显著性(P<0.01);在同一时期内各唾液样本DGGE图谱的相似性高于不同时期样本之间。结论:PCR-DGGE技术可用于与龋病相关细菌的生物多样性的研究以及监测微生物群落组成的动态变化。  相似文献   
106.
This paper draws upon recent feminist and gay scholarship in arguing that sexuality is an inherently political realm of thinking and activity. Sexology1 is a profession which claims special expertise in relation to sexuality and might, at first glance, be thought to have a key role to play within sexuality education, particularly in the face of the global pandemic of HIV infection. It is argued that the potential contribution of sexology is ultimately compromised by its reluctance to acknowledge the inherently political nature of its activity.  相似文献   
107.
Abstract

Objective: The purpose of this paper is to provide an overview of helpful clinical practices when working with transgender adult individuals. Method: While the number of openly transgender individuals appears to be growing with society’s increased acceptance and awareness, many neuropsychologists have had few opportunities to gain experience with this patient population. In this article, we review the existing literature as it relates to clinical neuropsychological practice. Results: We describe important terminology, ideals for creating an environment of respect, and how existing clinical guidelines for transgender individuals may apply to neuropsychology. In addition, we review the primary steps in the assessment process and provide a set of principles and recommendations for conducting neuropsychological assessments with transgender patients. Conclusions: There is a paucity of guidance in the field for working with transgender individuals. This article represents a step forward in the dialog and we look forward to future research that develops appropriate normative information, increases understanding of psychosocial factors, and better appreciates the range of hormonal influences for transgender individuals.  相似文献   
108.
Abstract

This article is an exploration of the feeling state engendered in the art psychotherapist when working with a child who had been emotionally and sexually abused. It attempts to discover the meaning of what happened in a therapy when no verbal or thinking interaction could initially take place. It describes the difficulty of finding a way to articulate the fragmented information available, both to bring to consciousness the snippets of memory presented, and to structure them into an organised story.

Thinking appeared to be what the child was desperate to avoid. It was far too painful for her, so anger and abuse were used as a defence. Noise was produced during therapy, so that the artwork, the games and in particular the experience of projective identification could not be thought about. The noise often led to the art psychotherapist being silenced and also unable to think.

Countertransference feelings were communicated, including shame, hatred, love and fear. These were explored to help find meaning, which led to understanding that the child needed to experience attachment to a constant and non-retaliatory Other. This made the experience of both merging and separation from the therapist an enabling space in which to find symbol and thought.  相似文献   
109.
110.
目的通过叶绿体基因psb A-trn H序列分析,探讨我国忽地笑种质资源的系统进化关系及分子鉴定方法。方法分别提取15省(市)52个忽地笑居群的DNA,经PCR扩增叶绿体基因psb A-trn H序列及测序,并用Mega5.0等软件对测序结果进行分析。结果 52条psb A-trn H序列长度为544~656 bp,GC含量为35.8%~37.0%,遗传距离为0.000 00~0.009 47;核苷酸变异(多态性)位点数共33个,其中简约信息位点9个,单一突变位点18个,插入/缺失片段6个;单倍型数量(H)10个,单倍型多态性水平(Hd)0.749,核苷酸多态性(π)0.002 63,收集的忽地笑资源具有较高的遗传多样性。最大简约法(maximum parsimony,MP)系统树中52个居群聚为4类,并且该聚类结果与其地理分布基本一致。结论不同产地忽地笑居群的遗传变异较大,psb A-trn H序列可作为忽地笑种源分子鉴定的依据;我国忽地笑种质资源在进化上具有明显的地域性特征。  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