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   567篇
  免费   15篇
  国内免费   15篇
儿科学   49篇
妇产科学   3篇
基础医学   36篇
口腔科学   6篇
临床医学   55篇
内科学   114篇
皮肤病学   4篇
神经病学   6篇
特种医学   128篇
外科学   23篇
综合类   49篇
预防医学   87篇
药学   22篇
肿瘤学   15篇
  2021年   4篇
  2020年   1篇
  2019年   5篇
  2018年   9篇
  2017年   2篇
  2016年   1篇
  2015年   4篇
  2014年   6篇
  2013年   14篇
  2012年   9篇
  2011年   8篇
  2010年   14篇
  2009年   22篇
  2008年   8篇
  2007年   19篇
  2006年   16篇
  2005年   19篇
  2004年   9篇
  2003年   11篇
  2002年   7篇
  2001年   11篇
  2000年   11篇
  1999年   16篇
  1998年   28篇
  1997年   41篇
  1996年   46篇
  1995年   23篇
  1994年   25篇
  1993年   26篇
  1992年   9篇
  1991年   8篇
  1990年   7篇
  1989年   17篇
  1988年   23篇
  1987年   17篇
  1986年   23篇
  1985年   8篇
  1984年   6篇
  1983年   7篇
  1982年   11篇
  1981年   5篇
  1980年   8篇
  1979年   2篇
  1978年   8篇
  1977年   6篇
  1976年   11篇
  1975年   6篇
排序方式: 共有597条查询结果,搜索用时 31 毫秒
31.
Knotting of intravascular catheters is an uncommon but a well‐recognized occurrence. The Swan–Ganz catheter (SGC) is the one that knots most commonly. A case of a knotted SGC is described in a patient with a persistent left‐sided superior vena cava, and we propose that the presence of a left‐sided superior vena cava is a risk factor for knot formation not previously reported. We review the published work on the risk factors for knot formation and on the techniques used to remove knotted SGC. We describe a technique using a gooseneck snare and Omni Flush catheter (Angiodynamics, Queensbury, NY, USA) to loosen and untie a knotted SGC.  相似文献   
32.
33.
BACKGROUND: Although many primary care patients are inactive, being able to classify even small amounts and intensities of activity and factors associated with these activity levels could be helpful for physicians who are trying to motivate their patients to become more physically active. METHODS: Sociodemographics, physical activity, fitness, other cardiovascular risk factors, and psychosocial measures were measured at baseline in the 874 patients in the Activity Counseling Trial. Patients were categorized into three groups: (1) no moderate-to-vigorous physical activity (MVPA), (2) some moderate but no vigorous activity, and (3) some vigorous activity. Multiple logistic regression was used to determine factors cross-sectionally associated with activity intensity. RESULTS: One or more cardiovascular risk factors in addition to physical inactivity were present in 84% of participants. Maximal oxygen uptake averaged 25.2 ml/kg/min; 85% had poor to fair aerobic fitness. Physical activity averaged 32.7 kcal/kg/day, with 13.5 min of MVPA/day; 26% engaged in some vigorous activity, 11% engaged in no MVPA. In unadjusted analyses, gender, age, race, education, income, employment, smoking, alcohol use, and exercise self-efficacy were associated with activity intensity (P = 0.05-0.001). A greater percentage engaged in moderate than in vigorous activity in all subgroups. In multiple logistic regression analyses, odds ratios (95% confidence intervals) for engaging in vigorous activity were 0. 39 (0.28, 0.56) for women, 0.38 (0.19, 0.75) for 65+ compared with 35- to 44-year-olds, and 1.14 (1.06, 1.22) for 10-unit increases in performance self-efficacy score. CONCLUSIONS: Most primary care patients who are physically inactive have additional cardiovascular risk factors, particularly overweight and obesity. All subgroups pursue moderate-intensity activity more often than vigorous activity. Women, older persons, and those with lower exercise self-efficacy are less likely to engage in vigorous activity.  相似文献   
34.
35.
36.
The purpose of the investigation was to determine if parent-teen discordance for parent-imposed restrictions on driving conditions, driving rules, and the consequences for driving rule violations were related to risky teen driving. A total of 579 parents and their newly licensed teens were interviewed by telephone, 1 month after teens obtained provisional licenses. In multiple regression analyses, the degree of disagreement with parent restrictions on driving conditions and parent-imposed consequences for driving rule violations were negatively associated with a composite measure of teen risky driving. Female parents were negatively associated and male teens were positively associated with risky driving, but discordance with restricted driving conditions was the most important predictor. Discordance may reflect poor parent–teen relations or inadequate communication about parental expectations. The findings suggest that increasing parent–teen concordance on parent-imposed driving restrictions may help reduce risky teen driving.  相似文献   
37.
38.
Background Patients with prostate cancer with a pre-operative prostate-specific antigen (PSA) τ;15ng/ml who undergo radical retropubic prostatectomy (RRP) generally do not have a good outcome, yet may have organ-confined cancer and should be offered the option of surgery. Aim To assess the outcome of patients who underwent RRP with a pre-operative PSA ≥ 15ng/ml. Methods Thirty-four patients, mean pre-operative PSA: 25.46ng/ml (15.03–76.6) and mean Gleason score: 6.4 (5–9) were assessed. Results Two groups were identified. Group I: 41% (14/34) have no biochemical recurrence to mean follow up of 58 months (30–106). Mean PSA: 18.8ng/ml (15.03–25.84). Mean Gleason score: 6.1 (5–7). Clinical stage: T1c in 80%. No patient had seminal vesicle or lymph node involvement. Group II: 59% (20/34) have biochemical recurrence or died (3) from their disease to mean follow up of 66 months (36–98). Mean PSA: 28.9ng/ml (15.28–76.6). Mean Gleason score: 6.7 (5–9). Clinical stage: T1c in 25%. Eleven patients had seminal vesicle (8) involvement or positive lymph nodes (3) or both (2). Conclusion RRP seems feasible in patients whose pre-operative PSA is between 15 and 25ng/ml with stage T1c, Gleason score ≤ 7 and negative lymph node frozen section.  相似文献   
39.
Early initiation of drinking increases the lifetime risk for substance abuse and other serious health and social problems. An understanding of the predictors of early initiation is needed if successful preventive interventions are to be developed. Surveys were completed by 1009 sixth grade students at the beginning (Time 1) and end (Time 2) of the school year in four schools in one suburban school district. At Time 1, 55/1009 (5.5%) reported drinking in the past 30 days. From Time 1 to Time 2, the percentage of drinkers increase to 127/1009 (10.9%) of whom 101 were new drinkers. In multiple logistic regression analyses, school engagement was negatively associated and peer influence and drinking expectancies were positively associated with drinking initiation. A significant interaction was found between drinking expectancies and parental expectations. Among sixth graders with high drinking expectancies, those with low parental expectations for their behavior were 2.6 times more likely to start drinking than those with parents with high expectations for their behavior. Positive drinking expectancies were significantly associated with drinking initiation only among teens who believed their parents did not hold strong expectations for them not to drink. This finding held for boys and girls, Blacks and Whites and was particularly strong for Black youth. This finding provides new information about the moderating effect of parental expectations on drinking expectancies among early adolescents.  相似文献   
40.
CONTEXT: Although violence among US youth is a current major concern, bullying is infrequently addressed and no national data on the prevalence of bullying are available. OBJECTIVES: To measure the prevalence of bullying behaviors among US youth and to determine the association of bullying and being bullied with indicators of psychosocial adjustment, including problem behavior, school adjustment, social/emotional adjustment, and parenting. DESIGN, SETTING, AND PARTICIPANTS: Analysis of data from a representative sample of 15 686 students in grades 6 through 10 in public and private schools throughout the United States who completed the World Health Organization's Health Behaviour in School-aged Children survey during the spring of 1998. MAIN OUTCOME MEASURE: Self-report of involvement in bullying and being bullied by others. RESULTS: A total of 29.9% of the sample reported moderate or frequent involvement in bullying, as a bully (13.0%), one who was bullied (10.6%), or both (6.3%). Males were more likely than females to be both perpetrators and targets of bullying. The frequency of bullying was higher among 6th- through 8th-grade students than among 9th- and 10th-grade students. Perpetrating and experiencing bullying were associated with poorer psychosocial adjustment (P<.001); however, different patterns of association occurred among bullies, those bullied, and those who both bullied others and were bullied themselves. CONCLUSIONS: The prevalence of bullying among US youth is substantial. Given the concurrent behavioral and emotional difficulties associated with bullying, as well as the potential long-term negative outcomes for these youth, the issue of bullying merits serious attention, both for future research and preventive intervention.  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