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   4819篇
  免费   321篇
  国内免费   16篇
耳鼻咽喉   43篇
儿科学   158篇
妇产科学   140篇
基础医学   534篇
口腔科学   113篇
临床医学   565篇
内科学   842篇
皮肤病学   66篇
神经病学   372篇
特种医学   90篇
外科学   559篇
综合类   36篇
一般理论   5篇
预防医学   527篇
眼科学   105篇
药学   324篇
中国医学   7篇
肿瘤学   670篇
  2023年   24篇
  2022年   26篇
  2021年   104篇
  2020年   88篇
  2019年   102篇
  2018年   128篇
  2017年   109篇
  2016年   101篇
  2015年   137篇
  2014年   183篇
  2013年   269篇
  2012年   325篇
  2011年   350篇
  2010年   222篇
  2009年   172篇
  2008年   334篇
  2007年   310篇
  2006年   330篇
  2005年   279篇
  2004年   268篇
  2003年   253篇
  2002年   239篇
  2001年   63篇
  2000年   32篇
  1999年   48篇
  1998年   62篇
  1997年   58篇
  1996年   47篇
  1995年   46篇
  1994年   34篇
  1993年   35篇
  1992年   35篇
  1991年   45篇
  1990年   36篇
  1989年   26篇
  1988年   15篇
  1987年   20篇
  1986年   15篇
  1985年   20篇
  1984年   28篇
  1983年   21篇
  1982年   25篇
  1981年   17篇
  1980年   17篇
  1979年   7篇
  1978年   8篇
  1977年   6篇
  1976年   5篇
  1975年   5篇
  1968年   5篇
排序方式: 共有5156条查询结果,搜索用时 859 毫秒
101.
102.
This study examines trends and geographical differences in total and live birth prevalence of trisomies 21, 18 and 13 with regard to increasing maternal age and prenatal diagnosis in Europe. Twenty-one population-based EUROCAT registries covering 6.1 million births between 1990 and 2009 participated. Trisomy cases included live births, fetal deaths from 20 weeks gestational age and terminations of pregnancy for fetal anomaly. We present correction to 20 weeks gestational age (ie, correcting early terminations for the probability of fetal survival to 20 weeks) to allow for artefactual screening-related differences in total prevalence. Poisson regression was used. The proportion of births in the population to mothers aged 35+ years in the participating registries increased from 13% in 1990 to 19% in 2009. Total prevalence per 10 000 births was 22.0 (95% CI 21.7–22.4) for trisomy 21, 5.0 (95% CI 4.8–5.1) for trisomy 18 and 2.0 (95% CI 1.9–2.2) for trisomy 13; live birth prevalence was 11.2 (95% CI 10.9–11.5) for trisomy 21, 1.04 (95% CI 0.96–1.12) for trisomy 18 and 0.48 (95% CI 0.43–0.54) for trisomy 13. There was an increase in total and total corrected prevalence of all three trisomies over time, mainly explained by increasing maternal age. Live birth prevalence remained stable over time. For trisomy 21, there was a three-fold variation in live birth prevalence between countries. The rise in maternal age has led to an increase in the number of trisomy-affected pregnancies in Europe. Live birth prevalence has remained stable overall. Differences in prenatal screening and termination between countries lead to wide variation in live birth prevalence.  相似文献   
103.
Abstract

Media and politicians both influence public opinion and policy responses to illicit drug issues. This study examines the contribution each may have made in Australia in 2015 to the problem and politics streams of the policy process, as outlined in Kingdon’s ‘multiple streams’ heuristic, when a National Ice Taskforce responded to increased public, political and media concern about methamphetamine use. A retrospective content analysis compared the frequency and content of articles about methamphetamine in print media (N?=?639) and federal parliament speeches (N?=?158) in 2015. Peaks in the number of media articles and debates in parliament followed the establishment and interim findings of the Ice Taskforce. The findings showed that politicians more frequently framed methamphetamine use as a crisis or epidemic than the media. Both frequently portrayed cost to society as the consequence of methamphetamine use and often cited law enforcement sources. The media most frequently positioned methamphetamine users as criminal or deviant compared to politicians who did not position the user or positioned them as an addict or victim. This analysis highlights the convergence of the problem and politics streams and suggests they are not independent as first posited by Kingdon.  相似文献   
104.
105.
In this article, we report the prevalence of traumatic events (TEs), lifetime and 12‐month posttraumatic stress disorder (PTSD) among 148 women experiencing homelessness in 3 midsized cities in the United States (Omaha, NE, Pittsburgh, PA, and Portland, OR). The women ranged in age from 19 to 54 years with an average age of 38.89 years (SD = 10.18). The sample was 42.6% White/European American. We investigated the mediation of distal TEs (i.e., childhood maltreatment) by more proximal TEs associated with being homeless (i.e., homelessness‐related stressors) for meeting diagnostic criteria for 12‐month PTSD. Results indicated that 42.6% of the women met criteria for lifetime PTSD and 39.7% met criteria for past‐year PTSD. The number of TEs reported ranged from 0 to 16 in order of prevalence with a median of 6 TEs. The correlations between childhood maltreatment and 12‐month PTSD ranged from .16 to .20 and the correlations between homelessness‐related stressors and 12‐month PTSD ranged from .21 to .30. The mediation analysis was consistent with the association between childhood maltreatment and past‐year PTSD being fully mediated by homelessness‐related trauma.  相似文献   
106.

Background

Salla disease (SD) is a rare lysosomal storage disorder leading to severe intellectual disability. SD belongs to the Finnish disease heritage, and it is caused by mutations in the SLC17A5 gene. The aim of the study was to investigate the course of neurocognitive features of SD patients in a long-term follow-up.

Methods

Neuropsychological and neurological investigations were carried out on 24 SD patients, aged 16–65 years, 13 years after a similar examination.

Results

The survival analysis showed excess mortality among patients with SD after the age of 30 years. The course of the disease was progressive, but follow-up of SD patients revealed that motor skills improved till the age of 20 years, while mental abilities improved in most patients till 40 years of age. Verbal comprehension skills did not diminish during the follow-up, but productive speech deteriorated because of dyspraxia and dysarthria. Motor deficits were marked. Ataxia was prominent in childhood, but it was replaced by athetotic movements during the teens. Spasticity became more obvious with age especially in severely disabled SD patients.

Conclusions

Younger SD patients performed better in almost every task measuring mental abilities that then seem to remain fairly constant till early sixties. Thus, the results indicate better prognosis in cognitive skills than earlier assumed. There is an apparent decline in motor skills after the age of 20 years. The early neurocognitive development predicts the later course of motor and cognitive development.  相似文献   
107.
OBJECTIVE: To describe the secular changes in the prevalence, awareness, treatment and control of hypertension. DESIGN: Two independent cross-sectional population surveys using standardized methods conducted between the early 1980s and mid-1990s. SETTING: Twenty-four geographically defined populations of the WHO MONICA Project. PARTICIPANTS: Randomly selected men and women aged 35-64 years. The total number of participants was 69 907. MAIN OUTCOME MEASURES: Two definitions of hypertension were used: 160/95 mmHg or above and 140/90 mmHg or above for systolic or diastolic blood pressure. Subjects on antihypertensive drug treatment were considered to be hypertensive regardless of their blood pressure. Treated subjects whose measured blood pressure level was less than 160/95 or 140/90 mmHg according to the two definitions, respectively, were considered to be adequately treated. RESULTS: The age-adjusted prevalence of hypertension decreased in most and increased in only a few populations. For both definitions of hypertension, the proportion of hypertensive subjects who were aware of their condition increased in three-quarters of the male populations and in two-thirds of the female populations. Furthermore, the proportion of hypertensive individuals on antihypertensive drug treatment increased in three-quarters of the populations. In the final survey, hypertension tended to be better treated and controlled in women than in men. Nevertheless, a large proportion of patients receiving antihypertensive drug therapy still had inadequately controlled blood pressure levels. CONCLUSION: Although awareness and treatment of hypertension according to the data obtained during the late 1980s to the mid-1990s increased in several populations, the effectiveness of antihypertensive treatment showed the continuing need for improvements.  相似文献   
108.
We performed a genomewide scan with 904 microsatellite markers using 120 extended Icelandic families with 490 hypertensive patients. The families were identified by cross-matching a list of hypertensive patients from the Hypertension Clinic of the University Hospital (Landspitalinn) in Iceland with a genealogy database of the entire Icelandic nation. After adding 5 markers, we found linkage to chromosome 18q with an allele-sharing LOD score of 4.60 (P=2.1x 10(-6)). These results provide evidence for a novel susceptibility gene for essential hypertension on chromosome 18q and show that it is possible to study the genetics of essential hypertension without stratifying by subphenotypes.  相似文献   
109.
110.
Background and purpose — Previous studies have found different outcomes after revision of knee arthroplasties performed after high tibial osteotomy (HTO). We evaluated the risk of revision of total knee arthroplasty with or without previous HTO in a large registry material.Patients and methods — 31,077 primary TKAs were compared with 1,399 TKAs after HTO, using Kaplan-Meier 10-year survival percentages and adjusted Cox regression analysis.Results — The adjusted survival analyses showed similar survival in the 2 groups. The Kaplan-Meier 10-year survival was 93.8% in the primary TKA group and 92.6% in the TKA-post-HTO group. Adjusted RR was 0.97 (95% CI: 0.77–1.21; p = 0.8).Interpretation — In this registry-based study, previous high tibial osteotomy did not appear to compromise the results regarding risk of revision after total knee arthroplasty compared to primary knee arthroplasty.High tibial osteotomy (HTO) is a well-established joint preserving procedure for the treatment of medial knee osteoarthritis. The goal is to achieve unloading of the affected medial compartment of the knee to prevent or postpone the need for an artificial knee joint. This is performed by slightly overcorrecting the knee joint from varus malalignment to valgus or neutral position. Osteotomy was a standard treatment option for unicompartmental knee osteoarthritis in earlier years before knee arthroplasty was a surgical option, but osteotomy lost importance in the 1980s because of the success of knee replacement surgery (Smith et al. 2013). However, there has been an increase in osteotomies during the last 15 years, especially in younger patients in some countries (Seil et al. 2013). National arthroplasty registers have demonstrated higher risk of revision for knee arthroplasty in younger patients (under the age of 60) (NAR 2014, SKAR 2013). The 2 most commonly used methods for HTO are lateral closing wedge and medial opening wedge osteotomy. Both methods have shown improvement in knee pain and function (Naudie et al. 1999, van Raaij et al. 2008, Efe et al. 2011, W-Dahl et al. 2012). Nevertheless, some patients later require a second procedure, a total knee arthroplasty (Naudie et al. 1999), depending on the degree of osteoarthritis, their level of pain and function, and the degree of correction achieved. Although total knee arthroplasty appears to be technically more challenging after HTO in cases with severe overcorrection, bone stock loss, altered joint line (Figures 1 and and2),2), or patella infera, only a few studies have found inferior results compared to primary TKA (Windsor et al. 1988, Parvizi et al. 2004, Haslam et al. 2007, Farfalli et al. 2012). The aim of this study was to evaluate the risk of revision after TKA, comparing primary TKA with and without previous high tibial osteotomy using data from the Norwegian Arthroplasty Register (NAR).Open in a separate windowFigure 1.Example of extra-articular malalignment after high tibial osteotomy (HTO) with opening wedge technique. The red line on the left radiograph (a) indicates the mechanical axis lateral to the knee joint. The radiograph to the right (b) indicates the extra-articular angulation of the tibia in the osteotomy area.Open in a separate windowFigure 2.Example of intra-articular malalignment after high tibial osteotomy (WTO) with closing wedge technique. The solid red line indicates that the tibial plateau has been elevated medially and is not perpendicular to the tibial axis.  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