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   929篇
  免费   62篇
  国内免费   7篇
耳鼻咽喉   5篇
儿科学   37篇
妇产科学   10篇
基础医学   98篇
口腔科学   9篇
临床医学   100篇
内科学   154篇
皮肤病学   10篇
神经病学   46篇
特种医学   220篇
外科学   94篇
综合类   9篇
预防医学   131篇
眼科学   9篇
药学   49篇
肿瘤学   17篇
  2021年   12篇
  2020年   8篇
  2019年   15篇
  2018年   21篇
  2017年   7篇
  2016年   18篇
  2015年   9篇
  2014年   11篇
  2013年   33篇
  2012年   19篇
  2011年   37篇
  2010年   16篇
  2009年   17篇
  2008年   30篇
  2007年   31篇
  2006年   33篇
  2005年   33篇
  2004年   30篇
  2003年   22篇
  2002年   26篇
  2001年   21篇
  2000年   18篇
  1999年   28篇
  1998年   19篇
  1997年   30篇
  1996年   31篇
  1995年   17篇
  1994年   26篇
  1993年   16篇
  1992年   12篇
  1991年   24篇
  1990年   16篇
  1989年   37篇
  1988年   35篇
  1987年   21篇
  1986年   39篇
  1985年   23篇
  1984年   19篇
  1983年   9篇
  1982年   14篇
  1981年   10篇
  1980年   9篇
  1979年   7篇
  1978年   8篇
  1977年   12篇
  1976年   13篇
  1975年   8篇
  1973年   6篇
  1970年   8篇
  1968年   5篇
排序方式: 共有998条查询结果,搜索用时 48 毫秒
41.
INTRODUCTION/PURPOSE: To assess in men whether exercise affects the estimated age-related increase in adiposity, and contrariwise, whether age affects the estimated exercise-related decrease in adiposity. METHODS: Cross-sectional analyses of 64,911 male runners who provided data on their body mass index (97.6%) and waist circumference (91.1%). RESULTS: Between 18 and 55 yr old, the decline in BMI with weekly distance run (slope +/- SE) was significantly greater in men 25-55 yr old than in younger men (slope +/- SE: -0.036 +/- 0.001 vs -0.020 +/- 0.002 kg x m(-2) per km x wk(-1)). Declines in waist circumference with distance were also significantly greater in older than younger men (P < 10(-9)), that is, the slopes decreased progressively from -0.035 +/- 0.004 cm per km x wk(-1) in 18- to 25-yr-old men to -0.097 +/- 0.003 cm per km x wk(-1) in 50- to 55-yr-old men). Increases in BMI with age were greater for men who ran under 16 km.wk(-1) than for relatively longer distance runners. Waist circumference increased with age at all running distances, but the increase diminished by running further (0.259 +/- 0.015 cm x yr(-1) if running <8 km x wk(-1) and 0.154 +/- 0.003 cm x yr(-1) for >16 km x wk(-1)). In men 50-85 yr old, BMI declined -0.038 +/- 0.001 kg x m(-2) per km x wk(-1) run when adjusted for age and declined -0.054 +/- 0.003 kg x m(-2) (increased 0.021 +/- 0.007 cm) per year of age when adjusted for running distance. Their waist circumference declined -0.096 +/- 0.002 cm per km x wk(-1) run when adjusted for age and increased 0.021 +/- 0.007 cm per year of age when adjusted for running distance. CONCLUSIONS: These data suggest that age and vigorous exercise interact with each other in affecting men's adiposity and are consistent with the proposition that vigorous physical activity must increase with age to prevent middle-age weight gain.  相似文献   
42.
43.
Exercise physiology plays an important role in the practice of clinical sports medicine. Exercise physiology research has identified important effects of exercise on the body's systems, tissues, and cells. Ongoing research is investigating the role of exercise in subcellular, molecular, and chemical processes. Increasingly, sports medicine physicians and other practitioners are using the findings of this research to help athletes achieve peak performance, and nonathletes achieve better health through exercise. Many areas of sports medicine practice, including exercise testing, safety, performance evaluation, correction of training problems, and prevention of problems that affect specific populations (eg, older athletes, women, children), benefit from the application of exercise physiology theory and research. The continued demand for athletes at all levels to be better, faster, and stronger, combined with the national focus on getting all Americans involved in some form of physical activity, will require that sports medicine practitioners and exercise physiologists increasingly work together to optimize sports and exercise performance, health, and safety.  相似文献   
44.
45.
The presence of asbestos bodies (ABs) in lung parenchyma is considered a histopathologic hallmark of past exposure to asbestos fibers, of which there was a population of longer fibers. The mechanisms underlying AB formation are complex, involving inflammatory responses and iron (Fe) metabolism. Thus, the responsiveness to AB formation is variable, with some individuals appearing to be poor AB formers. The aim of this study was to disclose the possible role of genetic variants of genes encoding inflammasome and iron metabolism proteins in the ability to form ABs in a population of 81 individuals from North East Italy, who died after having developed malignant pleural mesothelioma (MPM). This study included 86 genetic variants distributed in 10 genes involved in Fe metabolism and 7 genetic variants in two genes encoding for inflammasome molecules. Genotypes/haplotypes were compared according to the number of lung ABs. Data showed that the NLRP1 rs12150220 missense variant (H155L) was significantly correlated with numbers of ABs in MPM patients. Specifically, a low number of ABs was detected in individuals carrying the NLRP1 rs12150220 A/T genotype. Our findings suggest that the NLRP1 inflammasome might contribute in the development of lung ABs. It is postulated that the NLRP1 missense variant may be considered as one of the possible host genetic factors contributing to individual variability in coating efficiency, which needs to be taken when assessing occupational exposure to asbestos.  相似文献   
46.
Objective. To evaluate student changes in self-directed learning (SDL) in a Pharmacists’ Patient Care Process (PPCP) course using adaptive learning technology (ALT).Methods. The Pharmacists’ Patient Care Process was delivered using traditional teaching methods in fall 2018 and ALT in spring 2019. First-year student pharmacists were surveyed three times throughout the academic year on SDL factors. Focus groups were conducted at the end of the spring semester to identify perceptions of course delivery. Multilevel linear modeling and qualitative content analysis were used to evaluate survey responses and focus group feedback, respectively.Results. Ninety-two of 106 students completed all three surveys. Scores on stress management and examination management increased from the beginning to the end of the academic year. Scores on seminar (lecture) learning proficiency, procrastination management, and time management decreased from the beginning to the end of the year. Assignment management and comprehension competence trends varied from the end of the first semesters to the end of the second semester. Themes identified from the focus groups were student learning preferences, semester comparisons, value, and technology.Conclusion. Student pharmacists struggled with the integration of ALT into their previously established study routines. Focus groups helped add context to students’ SDL scores. Although significant differences were found between some SDL factors, it was not possible to conclude that implementation of ALT improved SDL.  相似文献   
47.

Background

Patients under haemodialysis are considered at high risk to acquire hepatitis B virus (HBV) infection. Since few data are reported from Brazil, our aim was to assess the frequency and risk factors for HBV infection in haemodialysis patients from 22 Dialysis Centres from Santa Catarina State, south of Brazil.

Methods

This study includes 813 patients, 149 haemodialysis workers and 772 healthy controls matched by sex and age. Serum samples were assayed for HBV markers and viraemia was detected by nested PCR. HBV was genotyped by partial S gene sequencing. Univariate and multivariate statistical analyses with stepwise logistic regression analysis were carried out to analyse the relationship between HBV infection and the characteristics of patients and their Dialysis Units.

Results

Frequency of HBV infection was 10.0%, 2.7% and 2.7% among patients, haemodialysis workers and controls, respectively. Amidst patients, the most frequent HBV genotypes were A (30.6%), D (57.1%) and F (12.2%). Univariate analysis showed association between HBV infection and total time in haemodialysis, type of dialysis equipment, hygiene and sterilization of equipment, number of times reusing the dialysis lines and filters, number of patients per care-worker and current HCV infection. The logistic regression model showed that total time in haemodialysis, number of times of reusing the dialysis lines and filters, and number of patients per worker were significantly related to HBV infection.

Conclusions

Frequency of HBV infection among haemodialysis patients at Santa Catarina state is very high. The most frequent HBV genotypes were A, D and F. The risk for a patient to become HBV positive increase 1.47 times each month of haemodialysis; 1.96 times if the dialysis unit reuses the lines and filters ≥ 10 times compared with haemodialysis units which reuse < 10 times; 3.42 times if the number of patients per worker is more than five. Sequence similarity among the HBV S gene from isolates of different patients pointed out to nosocomial transmission.  相似文献   
48.
After-school hours are considered critical for children's physical activity (PA) and sedentary behaviors (SB); however, whether the after-school setting influences children's activity patterns is unknown. This study examined the influence of after-school setting (i.e., parent report of the child's usual after-school setting) on 5th grade children's PA and SB, and differences by race/ethnicity. Boys whose parents reported they usually attended an after-school program had higher PA than boys who usually went home after school. A significant interaction between race/ethnicity and after-school setting showed that minority girls whose parents reported they usually attended an after-school program had higher PA and engaged in less SB compared with those who usually went home, whereas the activity patterns of white girls did not differ by after-school setting. Children's usual after-school setting affects their activity patterns; after-school programs may potentially increase PA in boys and minority girls.  相似文献   
49.
Among women, there is an increased prevalence of sedentary lifestyle and less participation in physical activity at levels recommended by the Surgeon General. As a result, women have been identified as a target group in public health initiatives to increase physical activity. The health-related benefits of habitual, moderate intensity physical activity are well documented in the epidemiological literature, but less is known about the effect of such physical activity on cardiorespiratory fitness. Our hypothesis was that moderate and vigorous exercise training regimens of similar estimated energy expenditure would result in similar changes in cardiorespiratory fitness. Eighteen sedentary premenopausal women with the following baseline characteristics [x +/- SE]: maximal oxygen consumption (Vo2max) = 29.5+/-1.5 ml x kg(-1) x min(-1); age = 33+/-1 years; height = 162.6+/-0.9 cm; mass = 62.7+/-2.3 kg, were randomly assigned to either vigorous (HI, 80% Vo2max, n = 10) or moderate intensity (MOD, 40% Vo2max, n = 8) cycle ergometer training groups. Exercise training was conducted 3-4 (3.37+/-0.05) days/week for 12 weeks in a supervised and progressive manner, with estimated exercise energy expenditure equated across both training groups. Vo2max and time to exhaustion increased significantly in both groups (p<0.05), with no difference between groups. Both groups had lower (p<0.05) posttraining submaximal heart rates (HR), respiratory exchange ratios (RER), and ratings of perceived exertion (RPE) during graded exercise testing, with no significant differences between the groups in posttraining values. Women participating in moderate intensity exercise training as recommended in basic public health guidelines demonstrate an increase in cardiorespiratory fitness similar to that elicited by vigorous training.  相似文献   
50.
Adolescent health in the Caribbean: risk and protective factors   总被引:2,自引:0,他引:2       下载免费PDF全文
OBJECTIVES: This study sought to identify, among youths, factors associated with characteristics such as poor health status, substance use, and suicide risk and to explore the extent to which the risk and protective factors identified cut across health-compromising behaviors. METHODS: A survey was administered to representative samples of young people from 9 Caribbean countries. RESULTS: Physical/sexual abuse and having a friend or relative who had attempted suicide were associated with an increased prevalence of health-compromising behaviors. Connectedness with parents and school and attendance at religious services were associated with fewer health risk behaviors. CONCLUSIONS: When the identified risk and protective factors were compared with those seen among young people in the United States, similarities as well as important differences were found.  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