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   1704篇
  免费   65篇
  国内免费   78篇
耳鼻咽喉   7篇
儿科学   88篇
妇产科学   20篇
基础医学   136篇
口腔科学   32篇
临床医学   196篇
内科学   356篇
皮肤病学   38篇
神经病学   73篇
特种医学   267篇
外科学   295篇
综合类   35篇
一般理论   2篇
预防医学   96篇
眼科学   43篇
药学   67篇
中国医学   3篇
肿瘤学   93篇
  2023年   6篇
  2021年   8篇
  2020年   13篇
  2019年   20篇
  2018年   22篇
  2017年   15篇
  2016年   14篇
  2015年   20篇
  2014年   44篇
  2013年   35篇
  2012年   65篇
  2011年   51篇
  2010年   58篇
  2009年   70篇
  2008年   49篇
  2007年   106篇
  2006年   84篇
  2005年   72篇
  2004年   54篇
  2003年   53篇
  2002年   46篇
  2001年   44篇
  2000年   42篇
  1999年   22篇
  1998年   91篇
  1997年   72篇
  1996年   69篇
  1995年   62篇
  1994年   48篇
  1993年   47篇
  1992年   32篇
  1991年   28篇
  1990年   36篇
  1989年   40篇
  1988年   41篇
  1987年   29篇
  1986年   26篇
  1985年   32篇
  1984年   27篇
  1983年   14篇
  1982年   19篇
  1981年   11篇
  1980年   15篇
  1979年   7篇
  1978年   6篇
  1977年   19篇
  1976年   16篇
  1975年   14篇
  1974年   5篇
  1972年   3篇
排序方式: 共有1847条查询结果,搜索用时 15 毫秒
51.
52.
Some studies have reported associations between COMT and MAO genotypes and aggression, though results have been inconsistent. We examined the relationship between Overt aggression scale (OAS) scores, and both MAOA and MAOB polymorphisms in a well-powered sample of 346 subjects with schizophrenia. We also examined COMT in a Stage II replication sample of 150 individuals, and combined these results with our previously reported (Stage I) findings for COMT. We found no evidence of any associations between OAS ratings and any of the polymorphisms investigated under different genetic models. There was no evidence of epistatic interaction between MAOA and COMT on OAS scores. These results fail to support the theory that functional polymorphisms within the MAOA, MAOB, or COMT genes, as determinants of catecholamine enzymatic activity, are risk factors for aggressive behavior.  相似文献   
53.

Objectives

Identifying predictors of weight loss could help to triage people who will benefit most from programs and identify those who require additional support. The present research was designed to address statistical, conceptual and operational difficulties associated with the role of self-efficacy in predicting weight loss.

Methods

In Study 1, 115 dieting overweight/obese women at high risk of breast cancer were weighed and completed questionnaires assessing motivation, global self-efficacy and self-efficacy for temptations. The main outcome measure was weight, measured 3-months post-baseline. Study 2 was identical (n = 107), except changes in psychological variables were computed, and used to predict weight 6-months post-baseline.

Results

In Study 1, self-efficacy for temptations was a significant predictor of weight loss at 3-month follow-up. In Study 2, improved self-efficacy for temptations between baseline and four-weeks was predictive of lower weight at 6 months.

Conclusion

The key finding was that self-efficacy for temptations, as opposed to motivation and global self-efficacy, was predictive of subsequent weight loss.

Practice implications

The implication is that augmenting dieters’ capability for dealing with temptations might boost the impact of weight loss programs.  相似文献   
54.
Sensitivity of cervical cytology is suboptimal, especially in developing countries such as Mexico, despite available guidelines aimed at improving this. When obtaining cervical samples, whether the samples are taken from the transformation zone and whether abnormal cells are missing must be considered. Cervical secretions (CS) are always present in variable proportions, and when cleaning the cervix, better samples may be obtained. In this study, we analyzed samples obtained with or without cleaning the cervix, and compared their contents in order to determine the sensitivity and specificity of these two methods. Methods: Of 500 patients who underwent cytology and colposcopy, 271 (54.2%) required a second opinion due to a diagnosis of cervical intraepithelial neoplasia (CIN). CS was removed and compared with the clean, second sample (SS) using in both liquid-based cytology. The quality of samples according to the Bethesda System, the presence of CIN, and inflammatory reactions were recorded. The sensitivity and specificity were calculated using biopsy as the gold standard. Results: The SS resulted in a higher proportion of adequate samples being obtained (97.6% vs. 44.8%), and in increased sensitivity (88.2% vs. 58.8%). CIN was detected in the SS 26% more often than in the CS (34 vs. 27 samples), whereas inflammatory reactions were noted more often in the CS (91.4% vs. 74%). Conclusion: Cervical sampling including CS results in lower sensitivity and CIN detection rates, and in more inflammatory reactions. By excluding CS from cervical samples, the sensitivity could be improved and the false negative rate could be reduced.  相似文献   
55.
A pediatric cardiac intensive care unit (CICU) manages critically ill children and adults with congenital or acquired heart disease. These patients are at increased risk for arrhythmias. The purpose of this study was to prospectively evaluate the incidence of arrhythmias in a pediatric CICU patient population. All patients admitted to the CICU at the Cardiac Center at The Children's Hospital of Philadelphia between December 1, 1997, and November 30, 1998, were evaluated prospectively from CICU admission to hospital discharge via full disclosure telemetry reviewed every 24 hours. Arrhythmias reviewed included nonsustained and sustained ventricular tachycardia (VT), nonsustained and sustained supraventricular tachycardia (SVT), atrial flutter and fibrillation, junctional ectopic tachycardia, and complete heart block. We reviewed 789 admissions consisting of 629 patients (age range, 1 day–45.5 years; median, 8.1 months). Hospital stay ranged from 1 to 155 days (total of 8116 patient days). Surgical interventions (n = 602) included 482 utilizing cardiopulmonary bypass. During the study period, there were 44 deaths [44/629 patients (7.0%)], none of which were directly attributable to a primary arrhythmia. The operative mortality was 5.1%. Overall, 29.0% of admissions had one or more arrhythmias the most common arrhythmia was nonsustained VT (18.0% of admissions), followed by nonsustained SVT (12.9% of admissions). Patients admitted to a pediatric CICU have a high incidence of arrhythmias, most likely associated with their underlying pathophysiology and to the breadth of medical and surgical interventions conducted.  相似文献   
56.

Background

Leaving the median sternotomy wound open following cardiac surgery is employed to avoid cardiovascular compression. Horizontal struts can be used. Radiologists interpreting portable radiographs might be unaware of the open median sternotomy (OMS).

Objective

To describe the frequency of radiographic signs of OMS and to increase awareness among radiologists to prevent misdiagnosis of pneumothorax and pneumomediastinum.

Materials and methods

Radiographs of 41 infants (17 girls/24 boys) with OMS were studied (age range 2?days to 8?months, mean 33?days). Central lucency and sternal edges were noted. Interclavicular distances before and after sternotomy were compared.

Results

Central lucency was seen in 25/41 (61%) children. Sternal struts were apparent in 27 (66%). In 14 without struts, central lucency was present in 8 (57%). In 27 children with struts, central lucency was present in 17 (63%) and absent in 10 (37%). Split sternal centers were identified in 6/41 (15%). The mean interclavicular distance was 23.5?mm (SD?=?4.39) before sternotomy and 38.2?mm (SD?=?7.0?mm) after sternotomy (P?Conclusion OMS has characteristic signs in the majority of cases. Recognition of these findings is useful and can prevent misinterpretation.  相似文献   
57.
58.
This study assessed whether the accuracy of predicting maximal oxygen uptake (VO2max) from sub-maximal heart rate (HR) and ratings of perceived exertion (RPE) values was moderated by gender and habitual activity. In total, 27 men and 18 women completed two GXTs to determine VO2max and three perceptually-regulated GXTs, incremented by RPE 9, 11, 13, 15 and 17. The RPE and HR were individually regressed against VO2max (approximately 0.96) to enable predictions of VO2max. The VO2max was predicted from three RPE ranges (9-17, 9-15, 9-13). The RPE ranges were extrapolated to RPE(19), RPE(20) and age-predicted maximal HR (HRmax(pred)). ANOVA revealed no differences between measured and predicted VO2max (P > 0.05) when the RPE range 9-17 was extrapolated to RPE(19) and HRmax(pred). Extrapolation of RPE 9-17 to RPE(20) overestimated VO2max (P < 0.05), but no differences were observed when predicted from the RPE ranges 9-15 and 9-13. The prediction of VO2max was not moderated by gender or activity status. Hierarchical regression analysis revealed that HR explained additional variance in VO2max when added to the RPE (2%). Hierarchical multiple regression analysis also indicated that VO2max was significantly correlated with power output at sub-maximal RPE values of 13 and 15 (P < 0.01) in men and women. The addition of HRmax(pred) improved the accuracy of the prediction equation for men (P = 0.05) but not for women. The study confirmed the validity of estimating VO2max from perceptually-regulated, sub-maximal GXT and indicated the potential utility of regression analysis to gauge appropriate sub-maximal exercise intensities.  相似文献   
59.
60.
Aim: To examine the relevance of physical activity intensity when assessing the relationship between activity and psychological health in 9–10-year-old children.
Methods: Activity was assessed by accelerometry in 57 boys (n = 23) and girls (n = 34). Total activity and time spent in very light (≤1.9 METs) through to vigorous activity (≥6 METs) were recorded. Psychological health inventories to assess anxiety, depression and aspects of self-worth were completed.
Results: Time accumulated in very light activity had positive correlations with anxiety and depression (r > 0.30, p < 0.05) and negative correlations with aspects of physical self-worth (r > −0.29, p < 0.05). Time accumulated in vigorous activity had negative correlations with anxiety and behavioural conduct (r > −0.30, p < 0.05) and positive correlation with aspects of physical self-worth (r > 0.28, p < 0.05). Children spending over 4 h in very light intensity activity had more negative psychological profiles than children spending under 4 h at this intensity.
Conclusion: Aspects of psychological health were negatively correlated with very light intensity activity and positively correlated with vigorous intensity activity. Further research should investigate whether reducing time spent in very light intensity activity and increasing time spent in vigorous intensity activity improves psychological health in children.  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