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   3031篇
  免费   316篇
  国内免费   24篇
耳鼻咽喉   54篇
儿科学   185篇
妇产科学   83篇
基础医学   412篇
口腔科学   91篇
临床医学   466篇
内科学   621篇
皮肤病学   27篇
神经病学   212篇
特种医学   153篇
外科学   343篇
综合类   115篇
一般理论   1篇
预防医学   233篇
眼科学   24篇
药学   214篇
中国医学   3篇
肿瘤学   134篇
  2021年   45篇
  2020年   47篇
  2019年   59篇
  2018年   62篇
  2017年   43篇
  2016年   64篇
  2015年   53篇
  2014年   89篇
  2013年   107篇
  2012年   173篇
  2011年   146篇
  2010年   88篇
  2009年   78篇
  2008年   122篇
  2007年   153篇
  2006年   130篇
  2005年   151篇
  2004年   115篇
  2003年   107篇
  2002年   117篇
  2001年   106篇
  2000年   94篇
  1999年   94篇
  1998年   38篇
  1997年   51篇
  1996年   45篇
  1995年   42篇
  1994年   38篇
  1993年   31篇
  1992年   55篇
  1991年   52篇
  1990年   59篇
  1989年   61篇
  1988年   44篇
  1987年   51篇
  1986年   43篇
  1985年   43篇
  1984年   26篇
  1983年   23篇
  1982年   20篇
  1979年   27篇
  1978年   19篇
  1977年   24篇
  1975年   23篇
  1974年   29篇
  1973年   23篇
  1972年   20篇
  1971年   29篇
  1970年   33篇
  1969年   23篇
排序方式: 共有3371条查询结果,搜索用时 19 毫秒
1.
2.

Background

The International Agency for Research on Cancer (IARC) has recently classified glyphosate as a Group 2A ‘probably carcinogenic to humans’. Due to this carcinogenic classification and resulting international debate, there is an increased demand for studies evaluating human health effects from glyphosate exposures. There is currently limited information on human exposures to glyphosate and a paucity of data regarding glyphosate's biological half-life in humans.

Objective

This study aims to estimate the human half-life of glyphosate from human urine samples collected from amenity horticulture workers using glyphosate based pesticide products.

Methods

Full void urine spot samples were collected over a period of approximately 24?h for eight work tasks involving seven workers. The elimination time and estimation of the half-life of glyphosate using three different measurement metrics: the unadjusted glyphosate concentrations, creatinine corrected concentrations and by using Urinary Excretion Rates (UER) (μg L?1, μmol/mol creatinine and UER μg L?1) was calculated by summary and linear interpolation using regression analysis.

Results

This study estimates the human biological half-life of glyphosate as approximately 5 ½, 10 and 7 ¼ hours for unadjusted samples, creatinine corrected concentrations and by using UER (μg L?1, μmol/mol creatinine, UER μg L?1), respectively. The approximated glyphosate half-life calculations seem to have less variability when using the UER compared to the other measuring metrics.

Conclusion

This study provides new information on the elimination rate of glyphosate and an approximate biological half-life range for humans. This information can help optimise the design of sampling strategies, as well as assisting in the interpretation of results for human biomonitoring studies involving this active ingredient. The data could also contribute to the development or refinement of Physiologically Based PharmacoKinetic (PBPK) models for glyphosate.  相似文献   
3.
4.
5.
6.
7.
The concept of an Ecological Approach to health and including Health in All Policies warrants inter-sectoral and transdisciplinary collaboration to improve health determinants and reduce health inequities. Agriculture policies, which greatly influence food production and its environmental impacts as well as food availability and dietary consumption, are therefore of interest to public health. Increasing rates of non-communicable diseases linked to diets containing high levels of processed foods, increasing numbers of households unable to access nutritious food and the environmental consequences of the food system are amongst the major health challenges of today, both globally and in Ireland. In 2010, Ireland’s Department of Agriculture, Food and Fisheries published Food Harvest 2020 a roadmap for Irish agriculture for the subsequent decade prepared against a backdrop of rising diet-related ill-health and increasing environmental concerns. This article critically analyses the process of consultation and stakeholder involvement in the development of Food Harvest 2020 from a public health perspective. Publically available documents including submissions to the Food Harvest 2020 consultation process were the primary source of data. This study highlights a distinct absence of public health representation in the process, an avoidance of some key public health challenges and the dominance of a ‘business as usual’ approach.  相似文献   
8.
ObjectivesOutpatient parenteral antimicrobial therapy (OPAT) is increasingly used to treat a wide range of infections. However, there is risk of hospital readmissions. The study aim was to develop a prediction model for the risk of 30-day unplanned hospitalization in patients receiving OPAT.MethodsUsing a retrospective cohort design, we retrieved data on 1073 patients who received OPAT over 2 years (January 2015 to January 2017) at a large teaching hospital in Sheffield, UK. We developed a multivariable logistic regression model for 30-day unplanned hospitalization, assessed its discrimination and calibration abilities, and internally them validated using bootstrap resampling.ResultsThe 30-day unplanned hospitalization rate was 11% (123/1073). The main indication for hospitalization was worsening or nonresponse of infection (52/123, 42%). The final regression model consisted of age (adjusted odds ratio (aOR), 1.18 per decade; 95% confidence interval (CI), 1.04–1.34), Charlson comorbidity score (aOR, 1.11 per unit increase; 95% CI, 1.00–1.23), prior hospitalizations in past 12 months (aOR, 1.30 per admission; 95% CI, 1.17–1.45), concurrent intravenous antimicrobial therapy (aOR, 1.89; 95% CI, 1.03–3.47) and endovascular infection (aOR, 3.51; 95% CI, 1.49–8.28). Mode of OPAT treatment was retained in the model as a confounder. The model had adequate concordance (c-statistic 0.72; 95% CI 0.67–0.77) and calibration (Hosmer-Lemeshow p 0.546; calibration slope 0.99; 95% CI 0.78–1.21), and low degree of optimism (bootstrap optimism corrected c-statistic, 0.70).ConclusionsWe identified a set of six important predictors of unplanned hospitalization based on readily available data. The prediction model may help improve OPAT outcomes through better identification of high-risk patients and provision of tailored care.  相似文献   
9.

Background

Fear of falling (FoF) is present in 20% to 85% of older adults and may be an early marker of decline in global cognitive functioning (GCF). We tested the hypothesis that FoF is associated with lower levels of GCF (cross-sectional) and greater decline in GCF (prospective) in adults aged 50 and older.

Design

Observational cohort study.

Setting

The Irish Longitudinal Study on Ageing, a population-based study.

Participants

Data were from 4931 participants (mean age 62.9 ± 9.1, range 50–98, 54.3% female).

Measurements

FoF was based on self-report in 2010. GCF was measured with the Montreal Cognitive Assessment (MoCA) and Mini Mental Status Examination (MMSE) in 2010 and 2014. The cross-sectional association was examined using linear regression unadjusted and after adjustment for demographic and health factors. The prospective association between FoF and the odds of >1-SD decline in GCF were examined using logistic regression. Interaction with age and mediation by social and physical activities were examined.

Results

In 2010, 21.9% of participants reported FoF. In the unadjusted cross-sectional models, those with FoF had lower scores on the MoCA (B ?1.15, 95% confidence interval [CI] ?1.40 to ?0.90) and MMSE (B ?0.52, CI ?0.67 to ?0.37). In the unadjusted prospective models, FoF was associated with a greater odds of decline in MoCA (odds ratio [OR] 1.60, CI 1.26–2.04) and MMSE (OR 1.64, CI 1.29–2.08). After adjustment for covariates, all associations attenuated and were no longer statistically significant, except the association with decline in MoCA (OR 1.32, CI 1.01–1.71). No statistically significant interaction with age was found (P > .37). Additional adjustment for social and physical activity did not change the results.

Conclusions

The findings provide weak evidence for FoF as a predictor of cognitive decline.  相似文献   
10.
Abstract –  This study employed novel topographic and histological techniques to assess remaining periodontal ligament (PDL) in a convenience sample of avulsed and intruded human permanent incisors and extracted premolars. Seventeen human teeth (eight avulsed, five severely intruded and four uninjured extracted) were evaluated for the distribution and physical characteristics of adherent root surface PDL. The topographic distribution of PDL was assessed by staining roots with malachite green and determining the proportion of remaining PDL within selected regions on four aspects of each tooth. In order to characterize mechanical damage to PDL, serial transverse sections of roots were stained with hematoxylin and eosin and examined at magnifications of 40× to 800×. The sections were photographed and imaging software was used to calculate the percentage of remaining PDL in the circumference of each root section. Topographic analysis demonstrated that 54% of the PDL remained on roots of avulsed and severely intruded incisors and 36% of the PDL remained on the extracted single-rooted premolars. Examination of serial transverse root sections revealed that 58% of the PDL remained on roots of avulsed or severely intruded incisors and 54% on extracted premolars. Avulsed and severely intruded incisors demonstrated similar amounts of retained PDL. In both injuries, almost half of the root surface was denuded of PDL.  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