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   1732571篇
  免费   114924篇
  国内免费   3696篇
耳鼻咽喉   22248篇
儿科学   56677篇
妇产科学   46947篇
基础医学   244676篇
口腔科学   49471篇
临床医学   153697篇
内科学   339500篇
皮肤病学   39298篇
神经病学   133963篇
特种医学   64633篇
外国民族医学   244篇
外科学   260296篇
综合类   39362篇
现状与发展   4篇
一般理论   571篇
预防医学   126153篇
眼科学   40722篇
药学   125223篇
  47篇
中国医学   4490篇
肿瘤学   102969篇
  2021年   13450篇
  2019年   14354篇
  2018年   20394篇
  2017年   15592篇
  2016年   17008篇
  2015年   19305篇
  2014年   26697篇
  2013年   38707篇
  2012年   53707篇
  2011年   56463篇
  2010年   33397篇
  2009年   31236篇
  2008年   52489篇
  2007年   55820篇
  2006年   56258篇
  2005年   53486篇
  2004年   51694篇
  2003年   49029篇
  2002年   47328篇
  2001年   92445篇
  2000年   94315篇
  1999年   77585篇
  1998年   19987篇
  1997年   17492篇
  1996年   17631篇
  1995年   16947篇
  1994年   15490篇
  1993年   14317篇
  1992年   57944篇
  1991年   55786篇
  1990年   53426篇
  1989年   51228篇
  1988年   46581篇
  1987年   45369篇
  1986年   42648篇
  1985年   40416篇
  1984年   29710篇
  1983年   25224篇
  1982年   14114篇
  1979年   25827篇
  1978年   17778篇
  1977年   15084篇
  1976年   14072篇
  1975年   14733篇
  1974年   17822篇
  1973年   17140篇
  1972年   15854篇
  1971年   14636篇
  1970年   13584篇
  1969年   12654篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.

Background and aim

Given the contradictory results of previous randomized controlled trials (RCTs), we performed a systematic review and meta-analysis to quantify and summarize the effects of folic acid supplementation on C-reactive protein (CRP).

Methods and results

We performed a systematic search of all available RCTs conducted up to October 2018 in the following databases: PubMed, Scopus, and Cochrane. RCTs that investigated the effect of folate on CRP were included in the present study. Data were combined with the use of generic inverse-variance random-effects models. Statistical heterogeneity between studies was evaluated using Cochran's Q-test. Ten RCTs (1179 subjects) were included in the present meta-analysis. Pooled analysis results showed that folate supplementation significantly lowered the serum CRP level (weighted mean difference (WMD): ?0.685 mg/l, 95% CI: ?1.053, ?0.318, p < 0.001). However, heterogeneity was significant (I2 = 96.7%, p = 0.000). Stratified analyses indicated that sex, intervention period, and type of study population were sources of heterogeneity. Following analysis, results revealed that the greatest impact was observed in women (WMD: ?0.967 mg/l, 95% CI: ?1.101, ?0.833, p = 0.000), patients with type 2 diabetes mellitus (WMD: ?1.764 mg/l, 95% CI: ?2.002, ?1.526, p = 0.000), and intervention period less than 12 weeks (WMD: ?0.742 mg/l, 95% CI: ?0.834, ?0.650, p = 0.000).

Conclusion

This meta-analysis suggested that folic acid supplementation could significantly lower the serum CRP level. Folic acid leads to greater CRP lowering effect in women, patients with T2DM, and those with less than 12-week intervention.  相似文献   
22.

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   
23.

Aims

To examine the influence of pre-existing psychiatric disorder on the choice of treatment in patients with gynaecological cancer.

Materials and methods

The analyses were based on all patients who underwent surgical treatment for endometrial, ovarian or cervical cancer who were registered in the Danish Gynecological Cancer Database in the years 2007–2014 (3059 patients with ovarian cancer, 5100 patients with endometrial cancer and 1150 with cervical cancer). Logistic regression model and Cox regression model, adjusted for relevant confounders, were used to estimate the effect of pre-existing psychiatric disorder on the course of cancer treatment. Our outcomes were (i) presurgical oncological treatment, (ii) macroradical surgery for patients with ovarian cancer, (iii) radiation/chemotherapy within 30 days and 100 days after surgery and (iv) time from surgery to first oncological treatment.

Results

In the group of patients with ovarian cancer, more patients with a psychiatric disorder received macroradical surgery versus patients without a psychiatric disorder, corresponding to an adjusted odds ratio of 1.24 (95% confidence interval 0.62–2.41) and the chance for having oncological treatment within 100 days was odds ratio = 1.26 (95% confidence interval 0.77–2.10). As for patients with endometrial cancer, all outcome estimates were close to unity. The adjusted odds ratio for oncological treatment within 30 days after surgery in patients with cervical cancer with a history of psychiatric disorder was 0.20 (95% confidence interval 0.03–1.54).

Conclusions

We did not find any significant differences in the treatment of ovarian and endometrial cancer in patients with pre-existing psychiatric diagnoses. When it comes to oncological treatment, we suggest that increased attention should be paid to patients with cervical cancer having a pre-existing psychiatric diagnosis.  相似文献   
24.

Objective

To assess a 6-month nutritional and physical activity intervention program on the nutritional status of overweight or obese and not very active 8-14 years old children by means of a controlled pre-post design (ACTIVA’T program).

Method

Pre-post study in 8-14 years old overweight or obese and low active children from Vilafranca del Penedès (Barcelona, Spain) randomized in control group (n = 51, 47.1% girls, nutritional intervention and ≤3 h/wk physical activity) and ACTIVA’T group (n = 45, 37.8% girls, nutritional and physical activity ≥5 h/wk intervention). Body mass index, waist/height index, and diet quality by means of KIDMED test at the beginning and at the end of the program were assessed. During the intervention, each participant was accompanied by a relative (father or mother) who performed the same activities as the children.

Results

Dietary recommendations have positively changed the habits of both ACTIVA’T and control group. The reversion in the prevalence of overweight and obesity was 93.8% and 58.6%, respectively, in the ACTIVA’T group, compared to 25.0% and 35.8% in the control group. Abdominal obesity was decreased from 42.2% to 17.8% in the ACTIVA’T group and from 47.1% to 27.5% in the control group.

Conclusions

The program ACTIVA’T (nutritional education and physical activity promotion) improves the quality of diet and reverses the prevalence of overweight and obesity in the underactive child population.  相似文献   
25.

Introduction

There are limited randomized data comparing radical cystectomy (RC) with bladder-sparing tri-modality therapy (TMT) in the treatment of muscle-invasive bladder cancer (MIBC). Both strategies are thought to have similar survival outcomes with different morbidity profiles. We compare the effectiveness of TMT and RC using decision-analytic modeling and the endpoint of quality-adjusted life years (QALYs).

Patients and Methods

Using a Markov model, we simulated the lifetime outcomes after TMT versus RC ± neoadjuvant chemotherapy for 67-year-old patients with clinical stage T2-T4aN0M0 MIBC. Model probabilities and utilities were extracted from the literature. The incremental effectiveness was reported in QALYs and sensitivity analyses were performed.

Results

For all patients with MIBC, although the model showed identical survival, TMT was the most effective strategy with an incremental gain of 0.59 QALYs over RC (7.83 vs. 7.24 QALYs, respectively). When limiting the model to favorable, contemporary cohorts in both the TMT and RC strategies, TMT remained more effective with an incremental gain of 1.61 QALYs (9.37 vs. 7.76 QALYs, respectively). One-way sensitivity analyses demonstrated the model was sensitive to the quality of life parameters (ie, the utilities) for RC and TMT. When testing the 95% confidence interval of the RC utility parameter the model demonstrated an incremental gain with TMT from ?0.54 to 4.23 QALYs. Probabilistic sensitivity analysis demonstrated that TMT was more effective than RC for 63% of model iterations.

Conclusions

This modeling study found that treatment of MIBC with organ-sparing TMT in appropriately-selected patients may result in a gain of QALYs relative to RC.  相似文献   
26.

Background

Children have a statutory right to a smoke-free environment, and tobacco control advocates are now considering regulation of smoking behavior in the private sphere. The Norwegian Institute of Public Health has investigated the support for a ban on smoking in cars with children compared to other possible extensions of the tobacco act among the Norwegian public.

Material and methods

A nationwide representative survey (CAWI) of 5543 participants was conducted in 2014–2015. Respondents were asked to consider several possible new tobacco control measures, through selfreported ranking on 5-point scales for each measure. Multiple logistic regression models were applied to control for confounders (i.a. smoking behavior) for the tendency to state full support.

Results

A majority (78 % of all respondents, 61.8% of daily smokers) supported a proposal prohibiting smoking in cars when children are present. This proposal received substantially more support than bans on private balconies, in parks and at public transport stops and work entrances. Full support for the latter proposals varied between 39.9% and 58.1% (between 2.7% and 16.8% among smokers). Differences by smoking status were maintained after multiple controls.

Interpretation

The strong endorsement of the proposal (also provided by the majority of current smokers) suggests high legitimacy and compliance, which means that an implementation could be introduced without serious enforcement problems.  相似文献   
27.
Abstract

Public health crises, including pandemics, are associated with significant health risk and concomitant stress, fear, decreased sense of control, and uncertainty. Deleterious impact on both physical and mental health can result, including for healthcare professionals and health professions trainees. Changes in governmental policies and hospital protocols for healthcare professionals as well as disruption of educational formats and requirements for trainees can ensue. Difficult anxiety-provoking realities of public health crises including pandemics which involve caring for many seriously ill patients, moral distress including difficult care decisions, personal health risk, and/or potential risk to one’s family can take a dire toll on the mental health of healthcare professionals at all stages of the professional lifecycle. Educational disruptions can create significant anxiety for trainees about completing requirements and achieving competencies. Within this, coping skills may be challenged and strengths may be elucidated as well. Such crises create an imperative for medical educators to support trainees’ wellbeing through adaptive flexibility for curriculum innovation and culturally sensitive resilience and wellbeing interventions. Strategies (‘tips’) to optimize resilience and wellbeing with an integrative resilience approach of individual, learning environment, and organization/systems factors are presented.  相似文献   
28.
29.
Abstract

In light of a growing body of evidence demonstrating pervasive health disparities, medical schools are increasingly incorporating educational programs on social medicine in undergraduate and graduate medical curricula. In 2015, we significantly restructured the cultural competency instruction for medical students at our institution, focusing on achieving greater health equity through caring for vulnerable populations and acknowledging and addressing bias and stereotyping. In order to facilitate educational sustainability while students were immersed in clinical care, a key element of our approach included extending teaching into the clerkship year. The resulting longitudinal thread, Health Equity and Social Justice, empowers future physicians with the knowledge and skills to work towards greater health equity. This article discusses the lessons learned in the implementation of this novel educational program. Our approach can serve as a model for other institutions considering similar instructional reform.  相似文献   
30.
Graphical abstract summarizing the overall results of our study comparing reintervention for a main or central branch pulmonary artery reconstruction site and various patch materials. Autologous pericardium was associate with the lowest reintervention and was free. Multivariable analysis demonstrated lack of superiority of homograft branch patch, which clearly has a much higher cost.
  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