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   3470篇
  免费   215篇
  国内免费   4篇
耳鼻咽喉   16篇
儿科学   86篇
妇产科学   124篇
基础医学   446篇
口腔科学   25篇
临床医学   407篇
内科学   566篇
皮肤病学   63篇
神经病学   375篇
特种医学   46篇
外科学   492篇
综合类   22篇
一般理论   2篇
预防医学   487篇
眼科学   44篇
药学   205篇
中国医学   1篇
肿瘤学   282篇
  2024年   2篇
  2023年   49篇
  2022年   78篇
  2021年   146篇
  2020年   97篇
  2019年   142篇
  2018年   145篇
  2017年   95篇
  2016年   123篇
  2015年   104篇
  2014年   161篇
  2013年   224篇
  2012年   322篇
  2011年   317篇
  2010年   149篇
  2009年   114篇
  2008年   212篇
  2007年   223篇
  2006年   175篇
  2005年   201篇
  2004年   158篇
  2003年   134篇
  2002年   121篇
  2001年   19篇
  2000年   5篇
  1999年   13篇
  1998年   19篇
  1997年   11篇
  1996年   4篇
  1995年   15篇
  1994年   8篇
  1993年   13篇
  1992年   7篇
  1991年   14篇
  1990年   3篇
  1989年   5篇
  1988年   2篇
  1987年   4篇
  1986年   4篇
  1985年   4篇
  1984年   3篇
  1983年   9篇
  1982年   7篇
  1981年   4篇
  1980年   3篇
  1978年   6篇
  1975年   4篇
  1943年   1篇
  1942年   1篇
  1939年   1篇
排序方式: 共有3689条查询结果,搜索用时 0 毫秒
61.
62.
63.
64.

Background

Caffeine is frequently added to dietary supplements with claims it facilitates weight loss.

Objective

The purpose of this study was to test the hypothesis that caffeine administration reduces laboratory and free-living food intake by reducing appetite and that these effects vary by body mass index (BMI).

Participants/setting

Fifty adults aged 18 to 50 years completed the study (42% male). Exclusion criteria included no previous experience with caffeine, previous adverse event following caffeine consumption, taking any medications or having a medical condition contraindicating caffeine or stimulant consumption or affecting appetite or eating, and reported tobacco use within the past 6 months.

Design and intervention

Participants visited the laboratory on four separate occasions to complete a double-blind, placebo-controlled, randomized, crossover study. On the first three visits, participants consumed a beverage containing 0, 1, or 3 mg/kg caffeine (order randomized). Thirty minutes later, participants consumed a buffet breakfast, ad libitum. After leaving the laboratory, participants completed hourly appetite assessments and dietary habit books until midnight or bedtime. The fourth session consisted of questionnaires, debriefing, and compensation.

Main outcome measures

Total and macronutrient intake and appetite sensations in and out of the laboratory were measured.

Statistical analyses performed

Intake data were analyzed using mixed analysis of covariance (ANCOVA). Appetite sensations were analyzed using repeated measures mixed ANCOVA.

Results

Total laboratory energy intake was lower (~10%) after 1 mg/kg caffeine (650.4±52.2 kcal at 1 mg/kg; 721.2±63.2 at 0 mg/kg; 714.7±79.0 at 3 mg/kg) (P=0.046). In the laboratory, appetite sensations were not significantly different by caffeine treatment. Out of the laboratory, neither total intake nor appetite was significantly different by caffeine treatment. There were no significant interactions between caffeine treatment and BMI on intake and appetite sensations in or out of the laboratory.

Conclusions

These results suggest caffeine has weak, transient effects on energy intake and do not support caffeine as an effective appetite suppressant.  相似文献   
65.
66.
Several health-related agencies administer national and targeted public education campaigns to provide health information and change health-related behaviors. The trust the public has in these agencies as the source of the message impacts the effectiveness of their communication campaigns. In this study, we explore the perceived trust of agencies that communicate health messages in the tobacco control field. As part of a larger tobacco regulatory science study, we conducted six 90-min focus groups comprising 41 participants. Five main themes emerged pertinent to the agency: (1) its integrity, (2) its competence, (3) its motives, (4) how it is portrayed in the media, and (5) skepticism and mistrust about it. Given the significant resources spent on health messaging to the public and potential benefits offered by this communication, an understanding of public trust in the agencies as the source of health messages is important. Findings suggest health information may be ignored or discounted when there is mistrust in the agency sending those messages.  相似文献   
67.
68.
BackgroundEnhanced Recovery After Surgery (ERAS) is a global surgical quality-improvement initiative. Little is known about the economic effects of implementing multiple ERAS guidelines in both the short and long term.MethodsWe performed a return on investment (ROI) analysis of the implementation of multiple ERAS guidelines (for colorectal, pancreas, cystectomy, liver and gynecologic oncology procedures) across multiple sites (9 hospitals) in Alberta using 30-, 180- and 365-day time horizons. The effects of ERAS on health services utilization (length of stay of the primary admission, number of readmissions, length of stay of the readmissions, number of emergency department visits, number of outpatient clinic visits, number of specialist visits and number of general practitioner visits) were assessed by mixed-effect multilevel multivariate negative binomial regressions. Net benefits and ROI were estimated by a decision analytic modelling analysis. All costs were reported in 2019 Canadian dollars.ResultsThe net health system savings per patient ranged from $26.35 to $3606.44 and ROI ranged from 1.05 to 7.31, meaning that every dollar invested in ERAS bro-brought $1.05 to $7.31 in return. Probabilities for ERAS to be cost-saving were from 86.5% to 99.9%. The effects of ERAS were found to be larger in the longer time horizons, indicating that if only the 30-day time horizon had been used, the benefits of ERAS would have been underestimated.ConclusionThese results demonstrated that ERAS multiguideline implementation was cost-saving in Alberta. To produce a better ROI, it is important to consider a broad range of health service utilizations, long-term impact, economies of scale, productive efficiency and allocative efficiency for sustainability, scale and spread of ERAS implementations.  相似文献   
69.
Introduction

Obesity is associated with increased morbidity and mortality in abdominal trauma patients. The characteristics of abdominal trauma patients with poor outcomes related to obesity require evaluation. We hypothesize that obesity is related to increased mortality and length of stay (LOS) among abdominal trauma patients undergoing laparotomies.

Methods

Abdominal trauma patients were identified from the National Trauma Data Bank between 2013 and 2015. Patients who received laparotomies were analyzed using propensity score matching (PSM) to evaluate the mortality rate and LOS between obese and non-obese patients. Patients without laparotomies were analyzed as a control group using PSM cohort analysis.

Results

A total of 33,798 abdominal trauma patients were evaluated, 10,987 of them received laparotomies. Of these patients, the proportion of obesity in deceased patients was significantly higher when compared to the survivors (33.1% vs. 26.2%, p < 0.001). Elevation of one kg/m2 of body mass index independently resulted in 2.5% increased odds of mortality. After a well-balanced PSM, obese patients undergoing laparotomies had significantly higher mortality rates [3.7% vs. 2.4%, standardized difference (SD) = 0.241], longer hospital LOS (11.1 vs. 9.6 days, SD = 0.135), and longer intensive care unit LOS (3.5 vs. 2.3 days, SD = 0.171) than non-obese patients undergoing laparotomies.

Conclusions

Obesity is associated with increased mortality in abdominal trauma patients who received laparotomies versus those who did not. Obesity requires a careful evaluation of alternatives to laparotomy in injured patients.

  相似文献   
70.
Familial tumoral calcinosis is characterized by ectopic calcifications due to persistent hyperphosphatemia. The most common genetic cause of the disease is mutations in GALNT3, encoding a glycosyltransferase involved in a posttranslational modification of fibroblast growth factor 23 (FGF23). The Galnt3 knockout mouse we developed was hyperphosphatemic due to low intact Fgf23 levels, but did not develop any apparent calcifications on a standard rodent diet. We therefore tested the hypothesis that a further challenge with a high phosphate diet could induce ectopic calcifications in Galnt3 knockout mice. Mice were fed either normal (0.6%) or high (1.65%) phosphate diet for 20 weeks beginning from weaning at 3 weeks. The high phosphate diet did not affect serum phosphorus concentration. However, regardless of the dietary phosphate contents, serum phosphorus levels were consistently elevated in Galnt3 knockout mice. The mice on the high phosphate diet had slightly low serum calcium, but significantly high alkaline phosphatase, parathyroid hormone (PTH), and calcium in the kidney. Although none of Galnt3 knockout mice on the normal phosphate diet developed calcifications, calcifications appeared in approximately one‐half of the mice on the high phosphate diet by 12 weeks. Calcified masses were most often found around the neck and on the back and as large as 9.9 mm in length. These data indicate that dietary phosphate load has major impact on the development of ectopic calcifications in tumoral calcinosis. © 2014 American Society for Bone and Mineral Research.  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