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   1049篇
  免费   78篇
  国内免费   17篇
耳鼻咽喉   3篇
儿科学   81篇
妇产科学   12篇
基础医学   88篇
口腔科学   26篇
临床医学   78篇
内科学   178篇
皮肤病学   27篇
神经病学   20篇
特种医学   132篇
外科学   114篇
综合类   134篇
预防医学   92篇
眼科学   4篇
药学   54篇
中国医学   39篇
肿瘤学   62篇
  2023年   8篇
  2022年   15篇
  2021年   23篇
  2020年   20篇
  2019年   16篇
  2018年   19篇
  2017年   14篇
  2016年   20篇
  2015年   28篇
  2014年   42篇
  2013年   37篇
  2012年   46篇
  2011年   46篇
  2010年   71篇
  2009年   60篇
  2008年   27篇
  2007年   29篇
  2006年   42篇
  2005年   31篇
  2004年   20篇
  2003年   24篇
  2002年   15篇
  2001年   15篇
  2000年   13篇
  1999年   18篇
  1998年   47篇
  1997年   59篇
  1996年   51篇
  1995年   38篇
  1994年   34篇
  1993年   31篇
  1992年   10篇
  1991年   8篇
  1990年   10篇
  1989年   23篇
  1988年   19篇
  1987年   17篇
  1986年   16篇
  1985年   10篇
  1984年   10篇
  1983年   2篇
  1982年   9篇
  1981年   8篇
  1980年   11篇
  1979年   3篇
  1977年   6篇
  1976年   6篇
  1975年   2篇
  1958年   4篇
  1957年   2篇
排序方式: 共有1144条查询结果,搜索用时 15 毫秒
151.
A survey was undertaken to examine the impact of Medicare's Prospective Payment System (PPS) and other recent changes in the health care environment on providers' decisions regarding acquisition of high-cost technologic equipment. The survey group included 199 hospitals and freestanding imaging centers known to have acquired magnetic resonance (MR) imaging units, as well as a random sample of 400 hospitals whose acquisition decisions were unknown to the authors. Fifty-eight percent of the known adopters and 61% of the randomly selected hospitals responded to the survey. Nonadopters' decisions were dominated by economic considerations, including the high cost of MR imagers and concerns about Medicare's reimbursement policies. Competition and a desire to provide the highest quality of care are counterbalancing the retardant effects of PPS, however, and are stimulating widespread diffusion of MR imagers.  相似文献   
152.
Synthesized and directly acquired spin-echo images were compared in order to assess the validity of magnetic resonance (MR) image synthesis as a method enabling retrospective formation of images by interactive manipulation of scan parameters. Synthetic images subjectively compared favorably in both accuracy and precision with acquired images when formed for the same values of echo (TE) and repetition times (TR) and for interpolated and extrapolated values of both TE and TR. Plots of synthetic and acquired signals within the same pixel sectors quantitatively showed comparable values for several regions of interest in the brain. Percent error and noise-normalized differences between acquired and synthetic images were tested as a quantitative measure of accuracy. Percent error was consistently less than 5% for brain parenchyma, and synthetic signals were accurate to within four times the noise level at acquisition. The apparent signal-to-noise ratio of synthetic images was comparable, superior, or inferior to similar acquired images, depending on the values of TE and TR. Total acquisition time required for synthetic formation of images for arbitrary values of TE and TR was equivalent to that of a single direct acquisition with a TR of 2,500 msec.  相似文献   
153.
154.
ABSTRACTS     
Myers SA 《分娩》1989,16(3):171-173
  相似文献   
155.

Introduction

To tailor local treatment in breast cancer patients there is a need for predicting ipsilateral recurrences after breast-conserving therapy. After adequate treatment (excision with free margins and radiotherapy), young age and incompletely excised extensive intraductal component are predictors for local recurrence, but many local recurrences can still not be predicted. Here we have used gene expression profiling by microarray analysis to identify gene expression profiles that can help to predict local recurrence in individual patients.

Methods

By using previously established gene expression profiles with proven value in predicting metastasis-free and overall survival (wound-response signature, 70-gene prognosis profile and hypoxia-induced profile) and training towards an optimal prediction of local recurrences in a training series, we establish a classifier for local recurrence after breast-conserving therapy.

Results

Validation of the different gene lists shows that the wound-response signature is able to separate patients with a high (29%) or low (5%) risk of a local recurrence at 10 years (sensitivity 87.5%, specificity 75%). In multivariable analysis the classifier is an independent predictor for local recurrence.

Conclusion

Our findings indicate that gene expression profiling can identify subgroups of patients at increased risk of developing a local recurrence after breast-conserving therapy.  相似文献   
156.
Youth risk behavior surveillance--United States, 2005   总被引:3,自引:0,他引:3  
In the United States, 71% of all deaths among persons aged 10-24 years result from 4 causes: motorvehicle crashes, other unintentional injuries, homicide, and suicide. Results from the 2005 national Youth Risk Behavior Survey (YRBS) indicated that during the 30 days preceding the survey, many high school students engaged in behaviors that increased their likelihood of death from these 4 causes: 9.9% had driven a car or other vehicle when they had been drinking alcohol, 18.5% had carried a weapon, 43.3% had drunk alcohol, and 20.2% had used marijuana. In addition, during the 12 months preceding the survey, 35.9% of high school students had been in a physical fight and 8.4% had attempted suicide. Substantial morbidity and social problems among youth also result from unintended pregnancies and sexually transmitted diseases, including human immunodeficiency virus infection. During 2005, a total of 46.8% of high school students had ever had sexual intercourse, 37.2% of sexually active high school students had not used a condom at last sexual intercourse, and 2.1% had ever injected an illegal drug. Among adults aged > or =25 years, 61% of all deaths result from 2 causes: cardiovascular disease and cancer. Results from the 2005 national YRBS indicated that risk behaviors associated with these 2 causes of death were initiated during adolescence. During 2005, a total of 23.0% of high school students had smoked cigarettes during the 30 days preceding the survey, 79.9% had not eaten > or =5 times/day of fruits and vegetables during the 7 days preceding the survey, 67.0% did not attend physical education classes daily, and 13.1% were overweight.  相似文献   
157.
158.
OBJECTIVE: To describe the prevalence of urinary incontinence during exercise in women, estimate whether exercise intensity is related to leakage severity, and report women's assessments of incontinence as a barrier to exercise. METHODS: Questionnaires were mailed to 5,130 women aged 18-60 years drawn from National Family Opinion research panels. Physical activity levels were assessed by the International Physical Activity Questionnaire. Urinary incontinence, defined as involuntary leakage in the last 30 days, was assessed with the Sandvik Severity Index and a global measure of bother. Prevalence estimates were adjusted via post-stratification weighting. RESULTS: A total of 3,364 eligible women responded (68%), of whom 34.6% were insufficiently active (95% confidence interval [CI] 32.7-36.5%), 29.7% were sufficiently active (95% CI 27.9-31.5%), and 35.7% were highly active (95% CI 33.8-37.6%). Urinary incontinence prevalence was 34.3% (95% CI 32.5-36.1%). One in seven women experienced urinary leakage during physical activity; this was more common among highly active (15.9%) than less active women (11.8%) (P = .01). After adjusting for age, comorbidities, education, and race, women with very severe incontinence were 2.64 times (95% CI 1.25-5.55) more likely to be insufficiently active than continent women. Incontinence was a moderate or substantial barrier to exercise for 9.8% (95% CI 8.8-10.9%) of women. Of incontinent women, the proportion for whom incontinence was a moderate or substantial barrier to exercise increased with each severity category: 9.2%, slight; 37.8%, moderate; 64.6%, severe; and 85.3%, very severe (P < .01). CONCLUSION: Urinary incontinence is perceived as a barrier to exercise, particularly by women with more severe leakage.  相似文献   
159.
160.
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