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   39095篇
  免费   3093篇
  国内免费   83篇
耳鼻咽喉   317篇
儿科学   1722篇
妇产科学   1190篇
基础医学   5283篇
口腔科学   477篇
临床医学   4732篇
内科学   7111篇
皮肤病学   681篇
神经病学   4567篇
特种医学   740篇
外科学   3907篇
综合类   360篇
现状与发展   1篇
一般理论   75篇
预防医学   5275篇
眼科学   601篇
药学   2538篇
中国医学   35篇
肿瘤学   2659篇
  2024年   81篇
  2023年   624篇
  2022年   994篇
  2021年   1964篇
  2020年   1163篇
  2019年   1683篇
  2018年   1890篇
  2017年   1279篇
  2016年   1445篇
  2015年   1505篇
  2014年   1983篇
  2013年   2490篇
  2012年   3593篇
  2011年   3478篇
  2010年   1734篇
  2009年   1497篇
  2008年   2304篇
  2007年   2392篇
  2006年   2014篇
  2005年   1857篇
  2004年   1596篇
  2003年   1327篇
  2002年   1181篇
  2001年   166篇
  2000年   127篇
  1999年   203篇
  1998年   239篇
  1997年   148篇
  1996年   121篇
  1995年   119篇
  1994年   112篇
  1993年   102篇
  1992年   69篇
  1991年   69篇
  1990年   63篇
  1989年   42篇
  1988年   41篇
  1987年   41篇
  1986年   49篇
  1985年   50篇
  1984年   44篇
  1983年   38篇
  1982年   29篇
  1981年   32篇
  1980年   33篇
  1979年   29篇
  1978年   20篇
  1977年   18篇
  1974年   19篇
  1972年   27篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
Mode of delivery and risk of developing allergic disease   总被引:3,自引:0,他引:3  
The aim of this study was to quantify the relationship between mode of delivery and subsequent incidence of allergic disease. The analysis is based on data derived from a birth cohort of 24,690 children who contributed data to the West Midlands General Practice Research Database. We found no convincing evidence to suggest that babies born by caesarean, forceps, or breech delivery had an increased risk of developing allergic disease.  相似文献   
102.
Summary The personnel in laboratories that utilize tissue and fluids from humans and other primates are at risk for infection with agents, including the viruses causing hepatitis, AIDS, and other infective agents such as mycobacteria tuberculosis. To minimize the chance of infection of laboratory personnel, carefully organized policies and procedures to minimize exposure to infective agents must be established in research laboratories. We outline some of the approaches of hospital clinical laboratories which have proved most effective in minimizing transmission of infections from samples to laboratory personnel. Also, we discuss simple considerations important in the use and in the selection of safety equipment. These guidelines and references to other safety information are provided to aid research laboratories in establishing safety procedures that will minimize chances of personnel contamination with infective agents from research samples.  相似文献   
103.
We have developed small-volume (50 or 250 μl)-format branched-DNA assays for human immunodeficiency virus type 1 (HIV-1) RNA for use with specimens in which the volume is limited and/or a high viral load is anticipated. These formats exhibited good correlation with the standard 1-ml format; high specificity, reproducibility, and linearity; and no significant difference in the quantification of HIV-1 subtypes.  相似文献   
104.
Polymorphonuclear leukocytes (PMNs; commonly known as neutrophils) play essential roles in innate immunity and inflammation. Although there are standardized methods for the isolation of human neutrophils, they are time consuming and demand considerable technical expertise, making them unfeasible for many clinical applications. Here, we describe a simple and time-efficient technique for the isolation of human neutrophils, which adapts a readily available commercial cell preparation tube (CPT) currently in use for isolation of peripheral blood mononuclear cells (PBMC) and plasma and is now adapted to also yield neutrophils. The total time required for neutrophil isolation was less than 1 hr. Neutrophils isolated by this method were highly purified (> or =97%) as assessed by surface expression of the neutrophil specific marker, CD66b. Neutrophils isolated by this method were functional as demonstrated by their ability to secrete interleukin-1 receptor antagonist (IL-1RA). Neutrophils isolated using this new technique secreted significant amounts of soluble IL-1RA (929.3+/-197 pg/10(6)cells/mL) in response to lipopolysaccharide (LPS). Use of this adapted CPT method allows simultaneous isolation of functional human neutrophils as well as PBMC and plasma. Adoption of this new method will allow the conduct of different neutrophil assays at any clinical site without requiring trained laboratory personnel or a large staff time commitment.  相似文献   
105.
106.
107.
108.
Understanding the regulation of immune responses is central for control of autoimmune and infectious disease. In murine models of autoimmunity and chronic inflammatory disease, potent regulatory T lymphocytes have recently been characterized. Despite an explosion of interest in these cells, their relevance to human disease has been uncertain. In a longitudinal study of malaria sporozoite infection via the natural route, we provide evidence that regulatory T cells have modifying effects on blood-stage infection in vivo in humans. Cells with the characteristics of regulatory T cells are rapidly induced following blood-stage infection and are associated with a burst of TGF-beta production, decreased proinflammatory cytokine production, and decreased antigen-specific immune responses. Both the production of TGF-beta and the presence of CD4+CD25+FOXP3+ regulatory T cells are associated with higher rates of parasite growth in vivo. P. falciparum-mediated induction of regulatory T cells may represent a parasite-specific virulence factor.  相似文献   
109.
The research evaluated an intervention strategy designed to prevent skin cancer in young adolescents. The intervention used parents as change agents to effectively communicate the risks of skin cancer and encourage their children to avoid high-risk sun-related behaviors while increasing positive sun-safe behaviors. Three hundred and forty parents in two regions of the United States were educated about the dangers of risky sun behaviors and how to convey information about skin cancer prevention to their children. Parents were then encouraged to talk with their children about these issues over a 1-month period prior to the onset of summer. Following this time period, children whose parents received and implemented the intervention materials were compared with a control sample of 129 children. These two groups were matched on age, gender, and school on number of sunburns and sunburn severity, attitudes and beliefs, and sunbathing behavior. Children in the treatment condition differed significantly from controls in the predicted directions on all outcome variables. The findings are discussed in terms of reducing skin cancer risk behaviors of children via parent-based intervention approaches.  相似文献   
110.
This goal of this study was to assess the initial feasibility and efficacy of a play-based intervention targeting executive functions (EF) and parent–child relationships in preschoolers compared with an active control group. Preschoolers with EF deficits (M age = 3.7 ± 0.47, predominantly White boys) and their parents were randomized to intervention (= 36) or active control (= 32) conditions. Child performance on EF tasks, parent and masked teacher ratings of EF and behavior, and masked clinician ratings of severity were collected at baseline and at 3 and 6 months postbaseline. Partial eta-squared effect sizes at .02 or higher comparing performance across the two groups was considered evidence of meaningful, albeit small, intervention effects. Intervention effects were observed for parent ratings of inattention, hyperactivity/impulsivity, and number/severity of problems experienced in various home situations, teacher ratings of severity of problems in various school situations, parent and teacher ratings of overall impairment, and clinician ratings of impairment. Intervention effects for functional improvements were maintained at the 6-month follow-up. No effect of the intervention was observed on the objective EF measures, although parent ratings of emotional control were improved for children in the intervention group. An intervention utilizing play-based activities targeting EF, when administered in a structured way by parents, is a promising approach for improving behavior in preschoolers with self-regulation deficits. More work is needed to investigate potential impact on EF and to disentangle mechanisms of action. It may be that the intervention’s focus on the structure and quality of parent–child interactions is a mediator of outcomes, rather than improved EFs.  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