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   2889篇
  免费   245篇
  国内免费   97篇
儿科学   44篇
妇产科学   19篇
基础医学   188篇
口腔科学   20篇
临床医学   258篇
内科学   324篇
皮肤病学   7篇
神经病学   107篇
特种医学   90篇
外科学   61篇
综合类   543篇
一般理论   1篇
预防医学   1107篇
眼科学   6篇
药学   188篇
  4篇
中国医学   229篇
肿瘤学   35篇
  2024年   6篇
  2023年   70篇
  2022年   86篇
  2021年   195篇
  2020年   136篇
  2019年   142篇
  2018年   101篇
  2017年   131篇
  2016年   133篇
  2015年   107篇
  2014年   216篇
  2013年   280篇
  2012年   213篇
  2011年   251篇
  2010年   186篇
  2009年   160篇
  2008年   157篇
  2007年   143篇
  2006年   114篇
  2005年   77篇
  2004年   77篇
  2003年   46篇
  2002年   43篇
  2001年   26篇
  2000年   29篇
  1999年   16篇
  1998年   15篇
  1997年   11篇
  1996年   12篇
  1995年   6篇
  1994年   7篇
  1993年   9篇
  1992年   5篇
  1990年   6篇
  1989年   4篇
  1988年   3篇
  1987年   2篇
  1986年   3篇
  1985年   1篇
  1984年   1篇
  1982年   1篇
  1980年   1篇
  1979年   1篇
  1978年   1篇
  1974年   1篇
排序方式: 共有3231条查询结果,搜索用时 31 毫秒
1.
BackgroundVoices for Food was a longitudinal community, food pantry–based intervention informed by the social ecological model, and designed to improve food security, dietary intake, and quality among clients, which was carried out in 24 rural food pantries across 6 Midwestern states.ObjectiveOur objective was to evaluate changes in adult food security, dietary intake, and quality from baseline (2014) to follow-up (2016), and to assess the role of adult food security on dietary outcomes.DesignA multistate, longitudinal, quasi-experimental intervention with matched treatment and comparison design was used to evaluate treatment vs comparison group changes over time and changes in both groups over time.Participants/settingAdult food pantry clients (n = 617) completed a demographic food security survey, and up to three 24-hour dietary recalls at baseline (n = 590) and follow-up (n = 160).InterventionCommunity coaching served as the experimental component, which only “treatment” communities received, and a food council guide and food pantry toolkit were provided to both “treatment” and matched “comparison” communities.Main outcome measuresChange in adult food security status, mean usual intakes of nutrients and food groups, and Healthy Eating Index-2010 scores were the main outcome measures.Statistical analyses performedLinear mixed models estimated changes in outcomes by intervention group and by adult food security status over time.ResultsImprovements in adult food security score (–0.7 ± 0.3; P = .01), Healthy Eating Index-2010 total score (4.2 ± 1.1; P < .0001), and empty calories component score (3.4 ± 0.5; P <.0001) from baseline to follow-up were observed in treatment and comparison groups, but no statistically significant changes were found for adult food security status, dietary quality, and usual intakes of nutrients and food groups between the 2 groups over time. The intervention effect on dietary quality and usual intake changes over time by adult food security status were also not observed.ConclusionsFood pantry clients in treatment and comparison groups had higher food security and dietary quality at the follow-up evaluation of the Voices for Food intervention trial compared with baseline, despite the lack of difference among the groups as a result of the experimental coaching component.  相似文献   
2.
BackgroundUsing a mobile phone while performing a postural and locomotor tasks is a common, daily situation. Conversing or sending messages (SMS) while walking account for a significant share of accidental injuries. Therefore, understanding the consequences of using a mobile phone on balance and walking is important, all the more so when these postural and locomotor tasks are aggravated by a disease.Research questionOur objective was to conduct a scoping review on the influence of a dual-task situation – generated by the use of mobile phone – on users' postural and/or locomotor tasks.MethodsThe literature search was conducted in English on PubMed/Medline and CINHAL databases, using keywords associated with postural and locomotor tasks and with the use of mobile phone. Study location, population, number of subjects, experimental design, types of phone use, evaluated postural-locomotor tasks and expected effects were then analyzed.Results and significance46 studies were included in this work, 24 of which came from North America. All studies compared postural and locomotor tasks with and without the use of a smartphone. Ten studies also compared at least 2 groups with different characteristics. Only 4 studies included pathological subjects. Various modalities were tested, and most studies focused on walking. Results show that the use of smartphones slows down movement and induces a systematic imbalance, except when listening to music. The dual task of "using the smartphone during a postural or locomotor tasks" induces systematic disturbances of balance and movement, which must be taken into account in the rehabilitation approach. Future studies will have to extend the knowledge regarding pathological situations.  相似文献   
3.
4.
Immune defenses provide resistance against infectious disease that is critical to survival. But immune defenses are costly, and limited resources allocated to immunity are not available for other physiological or developmental processes. We propose a framework for explaining variation in patterns of investment in two important subsystems of anti-pathogen defense: innate (non-specific) and acquired (specific) immunity. The developmental costs of acquired immunity are high, but the costs of maintenance and activation are relatively low. Innate immunity imposes lower upfront developmental costs, but higher operating costs. Innate defenses are mobilized quickly and are effective against novel pathogens. Acquired responses are less effective against novel exposures, but more effective against secondary exposures due to immunological memory. Based on their distinct profiles of costs and effectiveness, we propose that the balance of investment in innate versus acquired immunity is variable, and that this balance is optimized in response to local ecological conditions early in development. Nutritional abundance, high pathogen exposure and low signals of extrinsic mortality risk during sensitive periods of immune development should all favor relatively higher levels of investment in acquired immunity. Undernutrition, low pathogen exposure, and high mortality risk should favor innate immune defenses. The hypothesis provides a framework for organizing prior empirical research on the impact of developmental environments on innate and acquired immunity, and suggests promising directions for future research in human ecological immunology.  相似文献   
5.
目的 针对中医药大数据平台传统的加密方案效率不高的问题,提出一种高效的基于属性的内积加密的数据脱敏算法。方法 Hash(哈希)算法是应用广泛的高效的数据加密方法,但传统的哈希算法基于单一的控制策略,效率不高。本文提出一种基于属性的内积加密的数据脱敏算法,把批量的敏感数据分割为不同长度数据颗粒度,与特定密文的哈希进行内积处理。结果 在面对中医药大数据平台的海量数据加密的场景,与传统的哈希加密算法相比,本文提供的加密算法具有很好的性能。结论 为了保障个人隐私数据不被泄露,中医药大数据平台中的个人医疗数据需要加密脱敏后,才能进行分析处理或对外发布。本文提出的算法具备灵活的数据颗粒度、策略和高效的性能表现,适用于海量的中医药数据脱敏。  相似文献   
6.
7.
加强基层微生物室生物安全防护   总被引:1,自引:0,他引:1  
近年来,尤其是2003年发生的SARS疫情以及新加坡、台北、北京陆续发生的SARS冠状病毒实验室感染传播事件,使实验室的安全管理隐患变成了巨大的现实危害。这给各类微生物或生物医学实验室的生物安全防护敲响了警钟。作为基层微生物室工作人员每天都在接触含有不同致病性的微生物标本,其中也不排除含有风险级别较高、传播途径不明的微生物样品,但是由于基层微生物实验室的结构和设施、安全操作规范、安全设备、防护措施以及试验人员的安全防护意识却相对薄弱,因此为了试验人员、实验室及生态环境安伞,消除实验室生物安全隐患,卫生行政部门应重视基层微生物室的生物安全问题。  相似文献   
8.
珠海市横琴岛嗜人按蚊生态习性研究   总被引:4,自引:2,他引:2  
目的:研究珠海市横琴岛嗜人按蚊的生态习性。方法:蚊媒调查方法。结果:横琴岛嗜人按蚊主要孳生于水质清凉、遮阴良好的淡水沟溪及有丰富水体的香蕉地和甘蔗地等。属人、牛血兼吸品种,趋吸人血比例为76、34%,吸血后外逸比例为92、77%,夜间吸血活动高峰在午夜后至次日清晨,全年高峰季节在8~10月。结论:该地嗜人按蚊有人、牛血兼吸,趋吸人血比例较大陆品种低,偏野栖,夜间吸血活动持续时间长,全年活动高峰季节长的生态特点。  相似文献   
9.
相比其他组织的就业人员,卫生行政部门公务员拥有事实上的和法律上的就职保障,这种保障对于保证国家卫生公共政策执行的连贯性、稳定性和激励高素质人才进入公务员队伍至关重要,但在现实中它对公务员的有效激励产生了一定的影响,该文从就职保障与在职激励之间的调适关系出发,就如何确保对卫生行政部门公务员的有效激励进行了多维度分析和探讨,解析了激励发生的深层次机理,并在方法和手段上提出了建议。  相似文献   
10.
首先介绍了VPN的基本概念及其应用,并对使用IPSec的VPN技术与传统VPN技术的特点及安全性做了分析和比较。通过对IPSec协议的深入研究,给出了一种基于IPSec组合SA的端-端VPN系统的设计方法,并对其安全性进行了分析。  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