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   947篇
  免费   84篇
  国内免费   23篇
耳鼻咽喉   5篇
儿科学   30篇
妇产科学   27篇
基础医学   126篇
口腔科学   15篇
临床医学   91篇
内科学   216篇
皮肤病学   39篇
神经病学   43篇
特种医学   100篇
外科学   56篇
综合类   25篇
预防医学   145篇
眼科学   29篇
药学   51篇
肿瘤学   56篇
  2023年   5篇
  2021年   7篇
  2019年   12篇
  2018年   13篇
  2017年   15篇
  2016年   9篇
  2015年   22篇
  2014年   13篇
  2013年   30篇
  2012年   38篇
  2011年   32篇
  2010年   27篇
  2009年   29篇
  2008年   39篇
  2007年   53篇
  2006年   46篇
  2005年   42篇
  2004年   43篇
  2003年   37篇
  2002年   42篇
  2001年   45篇
  2000年   27篇
  1999年   22篇
  1998年   34篇
  1997年   19篇
  1996年   39篇
  1995年   9篇
  1994年   20篇
  1993年   12篇
  1992年   14篇
  1991年   16篇
  1990年   20篇
  1989年   17篇
  1988年   20篇
  1987年   15篇
  1986年   14篇
  1985年   28篇
  1984年   13篇
  1983年   11篇
  1982年   12篇
  1981年   9篇
  1980年   5篇
  1979年   6篇
  1978年   9篇
  1977年   6篇
  1976年   10篇
  1972年   7篇
  1971年   7篇
  1967年   5篇
  1966年   4篇
排序方式: 共有1054条查询结果,搜索用时 15 毫秒
61.
PURPOSE: To estimate levels of nonoccupational leisure-time physical activity (LTPA) by degree of urbanization and geographic region of the United States. METHODS: Participants were respondents to the Behavioral Risk Factor Surveillance System (BRFSS) in 2001 (N = 137,359). Moderate- and vigorous-intensity LTPA was categorized as meeting recommended levels, insufficient, or inactive. The U.S. Department of Agriculture rural-urban continuum codes were used to describe degrees of urbanization (metro, large urban, small urban, and rural). Geographic regions were defined by the U.S. Bureau of the Census (Northeast, Midwest, South, and West). Prevalence estimates were calculated using sample weights to account for the design of the BRFSS. Multivariate logistic regression analyses examined regional differences in the odds of physical inactivity (physically inactive vs insufficient or meets) by degree of urbanization after adjustment for sex, age, race, BMI, education, and occupational physical activity. RESULTS: Large urban areas (49.0%) and the western United States (49.0%) had the highest prevalence of recommended levels of LTPA. Rural areas (24.1%) and the southern United States (17.4%) had the highest prevalence of inactivity. Adults living in the four urbanization categories of the midwestern (metro (OR = 1.47, 95% CI = 1.31, 1.65), large urban (OR = 1.83, 95% CI = 1.51, 2.23), small urban (OR = 1.99, 95% CI = 1.65, 2.40), and rural (OR = 2.59, 95% CI = 1.35, 4.97)); and southern (metro (OR = 1.70, 95% CI = 1.53, 1.88), large urban (OR = 2.04, 95% CI = 1.72, 2.41), small urban (OR = 2.32, 95% CI = 2.02, 2.67), and rural (OR = 5.49, 95% CI = 2.82, 10.68)) U.S. regions were more likely to be inactive than adults living in similar areas of the western United States. Adults in northeast metro and large urban areas (OR = 1.62, 95% CI = 1.45, 1.81; and OR = 1.37, 95% CI = 1.08, 1.74, respectively) were more likely to be inactive than those residing in western metro and large urban areas. CONCLUSION: The prevalence of physical inactivity varies by degree of urbanization and geographic region of the United States.  相似文献   
62.
We evaluated perceived social and environmental supports for physical activity and walking using multivariable modeling. Perceptions were obtained on a sample of households in a southeastern county. Respondents were classified according to physical activity levels and walking behaviors. Respondents who had good street lighting; trusted their neighbors; and used private recreational facilities, parks, playgrounds, and sports fields were more likely to be regularly active. Perceiving neighbors as being active, having access to sidewalks, and using malls were associated with regular walking.  相似文献   
63.
BACKGROUND: Community trail development is an emerging strategy to increase physical activity (PA) among community residents. The purpose of this study was to assess awareness and use of trails and compare perceptions to objective data. METHODS: A telephone survey was administered to a stratified sample of adults (N = 1,112) in a southeastern county in the United States. Respondents' home addresses and the locations of trails were entered into a GIS database. A kappa statistic was used to measure agreement between awareness and presence of trails. Differences in reported trail use patterns by sex, race, education, and PA levels were evaluated. RESULTS: There was no agreement between the awareness and presence of trails (kappa = 0.07). Fifty-six percent of the respondents reported having trails; however, only 33% reported using the trails. Of the trail users, 42% reported being regularly active in moderate-to-vigorous PA (30+ min/day for 5+ days/week), and 51% reported being less active (P < 0.003). Among walkers (> or =30 min/day for > or =5 days/week), 49% of regular walkers and 35% of irregular walkers (< walkers) reported using the trails (P < 0.04). CONCLUSIONS: Awareness of existing trails in this community and levels of use were low. Marketing programs should promote awareness and use of trails among older adults and irregularly active adults.  相似文献   
64.
65.
The effect of cigarette smoking on the risk of breast cancer is controversial, although most studies show little or no effect. It has been suggested that smoking may reduce the risk of developing hereditary breast cancer. We completed a case-control study on 1,097 women with breast cancer who were BRCA1 or BRCA2 mutation carriers and 1,097 age-matched controls with a mutation in the same gene but without breast cancer. There were no statistically significant differences between the cases and controls in terms of the number of current and ex-smokers (41.2% and 40.4%, respectively) or the age at smoking commencement (18.2 years and 18.5 years, respectively). There were no statistically significant differences between cases and controls regarding beginning smoking within 5 years of menarche (OR = 1.03; 95% CI 0.83 to l.28) or before the first pregnancy (OR = 1.09; 95% CI = 0.90 to 1.33). In conclusion, contrary to our previous report, smoking does not appear to be a risk factor for breast cancer among carriers of BRCA mutations.  相似文献   
66.
67.
Dissociation comprises a range of psychological processes, which have largely been the subject of psychodynamic discussion. Dissociative phenomena are for the most part unaddressed by cognitive theorists. Current measures are atheoretical and our understanding of dissociation has been hampered by the absence of clear psychological models. This paper describes a new cognitive model of dissociation and the development and validation of a theoretically based measure-the Wessex Dissociation Scale (WDS). The WDS has adequate internal consistency, shows convergent validity with the Dissociative Experiences Scale (DES-II), and is equivalent to the DES-II in its associations with severe psychopathology. However, the WDS has some advantages over the DES-II, in that it is sensitive to milder manifestations of dissociation, demonstrating links to less severe pathologies. The findings described here provide preliminary support for the usefulness of the cognitive model, and the varied consequences of dissociative processes. The clinical and research utility of the model and the scale are discussed.  相似文献   
68.
Silicone particles have been demonstrated in the effluent from silicone intravenous (IV) tubing. It has been widely suspected that polyvinyl chloride (PVC) particles are also lost. We sought to clarify the situation in a carefully controlled laboratory setting using the apparatus and flow rates common in a paediatric setting, using scanning electron microscope techniques (SEM), we found that particles were indeed shed from IV tubing during use, but they were not PVC.  相似文献   
69.
PURPOSE: Accumulation of physical activity throughout the day is recommended to reduce health risks and enhance quality of life. Yet, many epidemiologic studies measure leisure activity only, without assessment of occupational activity. The purposes of this study were to describe occupational activity and to quantify the association between occupational and leisure activity in 2991 African American and 8566 White middle-aged adults. METHODS: Physical activity was measured by the Baecke questionnaire in 1987-89 for participants 45 to 64 years of age in the Atherosclerosis Risk in Communities Study. RESULTS: Reported occupational activity was greater among African American men and women compared to White men and women. Leisure activity was greater among White men and women compared to African American men and women. Work indices (range-1 (low) to 5 (high)) were highest among African American women (2.78) and men (2.72), followed by White men (2.55) and women (2.45), adjusted for age, study center, body mass index, and perceived health status. Those with the highest occupational activity had lower participation in any sport or exercise than those with lower occupational activity across race-gender groups. CONCLUSIONS: This data suggests that studies relying solely on leisure activity may miss important information provided by occupational physical activity.  相似文献   
70.
Four infants developed invasive Pseudomonas aeruginosa ophthalmic infections between 5 and 90 days of age. Three died from septicaemia, and the fourth required enucleation of one eye. Absent red reflexes or other eye signs in a septicaemic infant merit urgent ophthalmological assessment for endophthalmitis, in particular, Pseudomonas.  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