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   6533篇
  免费   457篇
  国内免费   23篇
耳鼻咽喉   27篇
儿科学   267篇
妇产科学   81篇
基础医学   881篇
口腔科学   164篇
临床医学   686篇
内科学   1392篇
皮肤病学   56篇
神经病学   633篇
特种医学   353篇
外科学   833篇
综合类   40篇
预防医学   455篇
眼科学   74篇
药学   676篇
中国医学   8篇
肿瘤学   387篇
  2023年   30篇
  2022年   40篇
  2021年   84篇
  2020年   75篇
  2019年   112篇
  2018年   122篇
  2017年   139篇
  2016年   127篇
  2015年   102篇
  2014年   137篇
  2013年   296篇
  2012年   323篇
  2011年   287篇
  2010年   207篇
  2009年   186篇
  2008年   328篇
  2007年   339篇
  2006年   287篇
  2005年   316篇
  2004年   294篇
  2003年   307篇
  2002年   255篇
  2001年   212篇
  2000年   185篇
  1999年   198篇
  1998年   90篇
  1997年   66篇
  1996年   78篇
  1995年   66篇
  1994年   57篇
  1993年   67篇
  1992年   141篇
  1991年   138篇
  1990年   126篇
  1989年   158篇
  1988年   124篇
  1987年   125篇
  1986年   115篇
  1985年   75篇
  1984年   78篇
  1983年   58篇
  1982年   40篇
  1981年   40篇
  1980年   30篇
  1979年   56篇
  1978年   35篇
  1977年   31篇
  1976年   27篇
  1975年   26篇
  1971年   33篇
排序方式: 共有7013条查询结果,搜索用时 15 毫秒
121.
High levels of cytokines are risk factors for type 2 diabetes. Therefore, we investigated whether the promoter polymorphisms of the tumor necrosis factor-alpha (TNF-alpha; G-308A) and interleukin 6 (IL-6; C-174G) genes predict the conversion from impaired glucose tolerance (IGT) to type 2 diabetes in the Finnish Diabetes Prevention Study. Altogether, 490 overweight subjects with IGT whose DNA was available were randomly divided into one of the two treatment assignments: the control group and the intensive, individualized diet and exercise intervention group. The -308A allele of the TNF-alpha gene was associated with an approximate twofold higher risk for type 2 diabetes compared with the G-308G genotype (odds ratio 1.80, 95% CI 1.05-3.09; P = 0.034). Subjects with both the A allele of the TNF-alpha gene and the C-174C genotype of the IL-6 gene had a 2.2-fold (CI 1.02-4.85, P = 0.045) higher risk of developing type 2 diabetes than subjects without the risk genotypes. We conclude that the -308A allele of the promoter polymorphism (G-308A) of the TNF-alpha gene is a predictor for the conversion from IGT to type 2 diabetes. Furthermore, this polymorphism seems to have a gene-gene interaction with the C-174C genotype of the IL-6 gene.  相似文献   
122.

Background

Robot-assisted radical cystectomy (RARC) with totally intracorporeal neobladder diversion is a complex procedure that has been reported with good outcomes in small series.

Objective

To present complications and oncologic and functional outcomes of this procedure.

Design, setting, and participants

Between 2003 and 2012 in a tertiary referral center, 70 patients were operated on by two experienced robotic surgeons. Data were collected prospectively and reviewed retrospectively.

Intervention

RARC with totally intracorporeal modified Studer ileal neobladder formation.

Outcome measurements and statistical analysis

The overall outcome of RARC with a totally intracorporeal neobladder was presented by assessing (1) surgical margins, (2) recurrence or cancer-specific death at 24 mo, (3) 30-d and 90-d complications graded according to the modified Clavien-Dindo system, (4) daytime and nighttime continence (no or one pad per day) at 6 and 12 mo, and (5) satisfactory sexual activity or potency at 6 mo and 12 mo. Survival rates were estimated by Kaplan-Meier plots.

Results and limitations

Median follow-up of the cohort was 30.3 mo (interquartile range: 12.7–35.6). We recorded negative margins in 69 of 70 patients (98.6%). Clavien 3–5 complications occurred in 22 of 70 patients (31.4%) at 30 d and 13 of 70 (18.6%) at >30 d. At 90 d, the overall complication rate was 58.5%. Clavien <3 and Clavien ≥3 complications were recorded in 15 of 70 patients (21.4%) and 26 of 70 (37.1%), respectively. Kaplan-Meier estimates for recurrence-free, cancer-specific, and overall survival at 24 mo were 80.7%, 88.9%, and 88.9%, respectively. Daytime continence and satisfactory sexual function or potency at 12 mo ranged between 70% and 90% in both men and women. Limitations of this study include its retrospective design, selection bias due to the learning curve phase, and missing data.

Conclusions

In this expert center for RARC, outcomes after RARC with totally intracorporeal neobladder diversion appear satisfactory and in line with contemporary open series.  相似文献   
123.
124.
125.
126.

Objectives

To assess the association between fatigue, cognition, domains of the EuroQol five-dimensional questionnaire (EQ-5D-3L), disability, and utilities estimated with several Western European value sets in patients with multiple sclerosis (MS).

Methods

Data from a multinational, cross-sectional, observational study of patients with MS (N = 16,808) conducted in 16 European countries were used. Health-related quality of life data were collected through the EQ-5D-3L, and fatigue and cognitive difficulties were self-assessed on a 10-point visual analogue scale. Associations were assessed using Pearson correlation and multivariate regression model.

Results

Symptoms of fatigue and cognitive difficulties were present in 90% and 70% of patients at all levels of disability, respectively, and thus only weakly correlated to disability. Problems in the EQ-5D-3L domains were common even at mild disability levels. Mobility, usual activities, and pain issues were experienced by 80% to 90% of patients with moderate and high levels of disability. Mobility, usual activities, and self-care were strongly correlated to disability. Disability, MS type, fatigue, and cognition were associated with utility in regression models, although the coefficients of fatigue and cognition were small.

Conclusions

The strong relationship of disability with utility was confirmed. Despite this, fatigue and cognitive difficulties were associated with utility estimated with different European value sets.  相似文献   
127.
Abstract

Background: Integration of research-based knowledge in health care is challenging. Occupational therapists (OTs) need to implement new research-based interventions in clinical practice. Therefore it is crucial to recognize and understand the factors of specific barriers and facilitators affecting the implementation process.

Aim: To identify the key factors important for OTs during the implementation process of a complex intervention.

Materials and methods: A cross-sectional study with a combination of qualitative and quantitative data in a mixed method design. Forty-one OTs and 23 managers from three county councils in Sweden, responded to a questionnaire one year after the OTs participation in a workshop to prepare for implementation of a client-centered activity of daily living intervention for persons with stroke.

Results: Over 70% of the OTs benefitted from reading and discussing articles in the workshop; 60% had faith in the intervention; 69% reported usability of the intervention. High level of support from managers was reported, but less from team members. The therapists’ interaction, perceptions of own efforts and contextual influence affected the implementation process.

Conclusion: The workshop context with facilitation and access to evidence, supportive organizations and teams, sufficient interaction with researchers and satisfying self-image were successful key factors when involved in research.  相似文献   
128.
BACKGROUND: Cytosolic aldehyde dehydrogenase, or ALDH1A1, functions in ethanol detoxification, metabolism of neurotransmitters, and synthesis of retinoic acid. Because the promoter region of a gene can influence gene expression, the ALDH1A1 promoter regions were studied to identify polymorphism, to assess their functional significance, and to determine whether they were associated with a risk for developing alcoholism. METHODS: Sequence analysis was performed in the promoter region by using Asian, Caucasian, and African American subjects. The resulting polymorphisms were assessed for frequency in Asian, Caucasian, Jewish, and African American populations and tested for associations with alcohol dependence in Asian and African American populations of alcoholics and controls. The functional significance of each polymorphism was determined through in vitro expression analysis by using HeLa and HepG2 cells. RESULTS: Two polymorphisms, a 17 base pair (bp) deletion (-416/-432) and a 3 bp insertion (-524), were discovered in the ALDH1A1 promoter region: ALDH1A1*2 and ALDH1A1*3, respectively. ALDH1A1*2 was observed at frequencies of 0.035, 0.023, 0.023, and 0.012 in the Asian, Caucasian, Jewish, and African American populations, respectively. ALDH1A1*3 was observed only in the African American population, at a frequency of 0.029. By using HeLa and HepG2 cells for in vitro expression, the activity of the luciferase reporter gene was significantly decreased after transient transfection of ALDH1A1*3-luciferase compared with the wild-type construct ALDH1A1*1-luciferase. In an African American population, a trend for higher frequencies of the ALDH1A1*2 and ALDH1A1*3 alleles was observed in a population of alcoholics (p = 0.03 and f = 0.12, respectively) compared with the control population. CONCLUSIONS: ALDH1A1*2 and ALDH1A1*3 may influence ALDH1A1 gene expression. Both ALDH1A1*2 and ALDH1A1*3 produce a trend in an African American population that may be indicative of an association with alcoholism; however, more samples are required to validate this observation. The underlying mechanisms contributing to these trends are still unknown.  相似文献   
129.
130.
OBJECTIVE: The combination of small birth size and the Pro12Pro variant of the peroxisome proliferator-activated receptor-gamma 2 (PPAR-gamma 2) gene has been shown to be associated with insulin resistance, which is linked to hypertension. We examined whether the association between small body size at birth and adult blood pressure is modulated by PPAR-gamma 2 gene polymorphism, and whether the use of any class of antihypertensive medication is related to birth size. DESIGN AND METHODS: A total of 500 subjects from an original epidemiological cohort of 7086 men and women aged 65-75 years attended a clinical study. Two hundred and eight of them (73 men and 135 women) were taking antihypertensive medication and are included in this study. The Pro12Ala polymorphism of the PPAR-gamma 2 gene was determined using the polymerase chain reaction single-strand conformation polymorphism method. RESULTS AND CONCLUSIONS: Hypertensive subjects with low birth weight or short length at birth and the Pro12Pro variant had raised systolic blood pressure. We suggest that insulin resistance enhances the regulatory responses of the renin-angiotensin system, leading to raised blood pressure levels. Those hypertensive subjects who had small birth size and the Pro12Pro variant tended to use angiotensin-converting enzyme inhibitors or angiotensin-receptor blockers (ACEI/ARB). This could be because insulin resistance interacts with the renin-angiotensin system in ways that make ACEI/ARB an effective therapy. Alternative explanations include more severe and treatment resistant hypertension, leading to application of ACEI/ARB, or co-morbid conditions, such as myocardial infarction and type 2 diabetes, known to be linked to low birth weight.  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