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   11060篇
  免费   1114篇
  国内免费   109篇
耳鼻咽喉   33篇
儿科学   908篇
妇产科学   25篇
基础医学   2961篇
口腔科学   143篇
临床医学   425篇
内科学   932篇
皮肤病学   281篇
神经病学   355篇
特种医学   47篇
外科学   113篇
综合类   676篇
一般理论   1篇
预防医学   4084篇
眼科学   19篇
药学   935篇
  4篇
中国医学   257篇
肿瘤学   84篇
  2024年   10篇
  2023年   160篇
  2022年   169篇
  2021年   683篇
  2020年   508篇
  2019年   491篇
  2018年   439篇
  2017年   442篇
  2016年   440篇
  2015年   502篇
  2014年   657篇
  2013年   1033篇
  2012年   606篇
  2011年   673篇
  2010年   465篇
  2009年   453篇
  2008年   475篇
  2007年   483篇
  2006年   364篇
  2005年   358篇
  2004年   318篇
  2003年   298篇
  2002年   264篇
  2001年   222篇
  2000年   181篇
  1999年   166篇
  1998年   155篇
  1997年   132篇
  1996年   127篇
  1995年   121篇
  1994年   92篇
  1993年   80篇
  1992年   81篇
  1991年   57篇
  1990年   61篇
  1989年   49篇
  1988年   61篇
  1987年   42篇
  1986年   38篇
  1985年   52篇
  1984年   33篇
  1983年   37篇
  1982年   38篇
  1981年   30篇
  1980年   30篇
  1979年   25篇
  1978年   31篇
  1977年   12篇
  1976年   16篇
  1975年   9篇
排序方式: 共有10000条查询结果,搜索用时 15 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.
BackgroundIn 2021, the National Salt and Sugar Reduction Initiative (NSSRI) released voluntary sugar reduction targets for packaged foods and drinks in the United States.ObjectiveThe objectives of this study were to describe trends in added sugar intake from NSSRI foods and beverages among children and youth and estimate possible reductions if industry were to meet the targets.DesignThis study consisted of cross-sectional and trend analyses of demographic and 24-hour dietary recall data from eight survey cycles (2003-2004 to 2017-2018) of the National Health and Nutrition Examination Survey.Participants/settingThe study sample included 23,248 children and youth (aged 2 to 19 years).Main outcome measuresThe main outcome measure was the percent of daily calories from added sugar for foods and beverages in NSSRI categories.Statistical analyses performedFoods and beverages reported by participants were mapped to one of the NSSRI’s categories or coded as a non-NSSRI item. Trends over time in added sugar intake were assessed using regression models. To assess possible reductions in added sugar intake if industry were to meet the targets, sales-weighted mean percent reductions for 2023 and 2026 targets were applied to NSSRI items in the 2017-2018 National Health and Nutrition Examination Suvey data. Results were examined overall and by demographic characteristics.ResultsFrom 2003-2004 to 2017-2018, added sugar intake from NSSRI foods and beverages declined, but consumption remained high. During 2017-2018, NSSRI categories accounted for 70% of US child and youth added sugar intake. If industry met the NSSRI targets, US children and youth would consume 7% (2023 targets) to 21% (2026 targets) less added sugar.ConclusionsAlthough added sugar intake from NSSRI foods and drinks has declined over the past decade, added sugar intake from all sources remains high and consumption of added sugar from certain NSSRI categories has remained steady over time. If met, the NSSRI targets are expected to result in meaningful reductions in added sugar intake for US children and youth.  相似文献   
3.
Food-grade titanium dioxide (E171) is widely used as a food additive, and it is known that after oral consumption, E171 is translocated into the bloodstream reaching the highest titanium level at 6 h. E171 is accumulated in some organs triggering toxicity, but the effects on the blood parameters after oral consumption have been less studied. Recently, evidence shows that oral exposure to E171 induces behavioral signs of anxiety and depression. The relation between blood alterations and psychiatric disorders has been previously demonstrated. However, the oral exposure to E171 effects on alterations in blood parameters and effects linked to alterations in animal behavior has not been explored. In this short communication, we aimed to investigate the effects of E171 on specific blood parameters (hematocrit, hemoglobin, number of erythrocytes, and leukocytes) and anxiety and compulsive-like behavior in males and females orally exposed to ~5 mg/kg for 4 weeks. The results showed that E171 decreased hematocrit and hemoglobin in male but not in female mice while leukocyte and erythrocyte count remained unaltered. Oral consumption of E171 decreased the levels of anxiety-like behavior in females but not in male mice, while compulsive-like behavior was increased in both male and female mice.  相似文献   
4.
刘蕤  陈紫雯  华桂丰  王立强  萨翼  刘昶 《中草药》2020,51(18):4829-4836
目的建立保健食品原料评价体系(Functional Food Crude Materials Evaluation System,FUFMES),为保健食品原料目录排名提供科学依据与技术保障。方法首先,利用文献调研和多轮专家访谈方法筛选FUFMES的指标并确定其层级关系;第二,使用层次分析法(Analytic Hierarchy Process,AHP)计算指标权重,具体方法是依据专家打分构建判断矩阵,利用R语言进行一致性检验与最大特征根检验,得出各级指标权重;第三,使用极值法计算原料的单个指标值;第四,利用线性加权综合法得到每种原料的评价指数并据此进行排名;最后,将获得的分析结果与专家评价结果进行比较。结果 FUFMES包括6个一级指标、39个二级指标、11个三级指标。利用FUFMES对9种保健食品原料进行评价,获得的评价指数依次是:西洋参(0.49)、人参(0.48)、银杏叶(0.21)、灵芝孢子粉(0.08)、鱼油(0.06)、螺旋藻(0.03)、辅酶Q10(0.02)、褪黑素(0.01)、大蒜油(-0.03)。基于该评价指数的排名结果与专家评价结果显示了较高一致性。结论构建了科学、完整的FUFMES,FUFMES将成为保健食品原料目录评价与排名的有力工具,为推进保健食品原料备案制提供科学依据与技术保障。  相似文献   
5.
Rosmarinus species are aromatic plants that mainly grow in the Mediterranean region. They are widely used in folk medicine, food, and flavor industries and represent a valuable source of biologically active compounds (e.g., terpenoids, flavonoids, and phenolic acids). The extraction of rosemary essential oil is being done using three main methods: carbon dioxide supercritical extraction, steam distillation, and hydrodistillation. Furthermore, interesting antioxidant, antibacterial, antifungal, antileishmanial, anthelmintic, anticancer, anti‐inflammatory, antidepressant, and antiamnesic effects have also been broadly recognized for rosemary plant extracts. Thus the present review summarized data on economically important Rosmarinus officinalis species, including isolation, extraction techniques, chemical composition, pharmaceutical, and food applications.  相似文献   
6.
7.
The objective of this paper was to assess the link between premature mortality and a combination of neighbourhood contextual (environmental and health) and compositional (socioeconomic and demographic) characteristics. We statistically and spatially examined six environmental variables (ultrafine particles, carcinogenic and non-carcinogenic pollutants, pollution released to air, tree cover, and walkability index), six health service indicators (number health providers, breast, colorectal and cervical cancer screening uptake rates, student nutrition program uptake rates, and healthy food index), and eight socioeconomic indicators (total income, Gini coefficient, two age categories – below and above 40 years, proportion of females to males, visible minorities, Indigenous peoples, education, less than grade 9) among 140 neighbourhoods of the City of Toronto in Ontario (Canada). We applied principal component analysis to identify patterns and to reduce the number of explanatory variables into combined component axes that represent unique variation in these confounded and overlapping factors. We then applied regression analysis to model the relationship between the indices of enviro-health and socioeconomics and their potential relationship with premature mortality. Residual spatial analysis was used to investigate any remaining spatial structure (such as neighbourhoods with higher residual premature mortality rates). Neighbourhood Equity Index was correlated with our enviro-health and socioeconomic indices. Premature mortality within neighbourhoods was predicted by poor cancer screenings, pollution, lack of tree canopy, increased uptake of student nutrition programs and high walkability index. A negative association between premature mortality and pollution was associated low walkability index and presence of visible minorities within neighbourhoods. There was some unexplained residual spatial variation in our model of premature mortality - especially along the shores of Lake Ontario and in neighbourhoods with major highways or road corridors: premature mortality in Toronto neighbourhoods was higher than expected along highway-corridor neighbourhoods and shorelines. Our analysis revealed a significant relationship between neighbourhood contextual features – both environmental and health – and premature mortality, suggesting that these contextual components of neighbourhoods can predict rates of urban premature mortality in Toronto.  相似文献   
8.
目的 分析一起由两种罕见血清型混合感染引起的副溶血性弧菌食物中毒病原学的检测结果,为食物中毒病原学检查途径提供依据。方法 对一起在龙门县人民医院就诊食物中毒事件的9例患者采集其肛拭子样本,参照《食品微生物学检验副溶血性弧菌检验》( GB 4789.7—2013) 等标准进行病原学分析鉴定。结果 本次事件出现临床症状者9例,其中≤20岁2例,20~<40岁1例,40~<60岁4例,≥60岁2例;9份肛拭子样本检出8株副溶血性弧菌,血清分型O2:K28构成比占25.00%(2/8);O8:K21构成比占75.00%(6/8);经PFGE分子分型,2株O2∶K28血清型(VP18171、VP18175)相似度为66.7%;3株O8∶K21血清型(VP18172、VP18173、VP18176)相似度为100.0%,与另外3株O8∶K21血清型(VP18177、VP18174、VP18170)相似度为88.4%~95.2%;药敏试验结果显示,除有1株菌株对氨苄西林、头孢唑林二重耐药、1株菌株对氨苄西林耐药、3株菌株对头孢唑林耐药外,其它菌株对所有测试药物均敏感,无多重耐药现象。结论 此次食物中毒是由O2:K28和O8:K21这两种罕见血清型的副溶血性弧菌混合感染引起的。  相似文献   
9.
消渴病与饮食关系密切,关于消渴病发病及治疗过程中的饮食、服药宜忌古已有之。其思想发源于《内经》,具体论述始于《伤寒杂病论》,在魏晋南北朝时期的诸多医籍中不断积累完善,到了唐代《外台秘要》和《医心方》时已经比较成熟,能够自成体系。通过系统总结唐以前医籍所载关于消渴病饮食及服药宜忌内容,分析其内在规律,有助于扩展和加深对糖尿病饮食宜忌相关的学术研究。  相似文献   
10.
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