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   900篇
  免费   24篇
教育   684篇
科学研究   42篇
各国文化   25篇
体育   60篇
综合类   1篇
文化理论   8篇
信息传播   104篇
  2022年   5篇
  2021年   8篇
  2020年   18篇
  2019年   22篇
  2018年   26篇
  2017年   28篇
  2016年   29篇
  2015年   21篇
  2014年   35篇
  2013年   216篇
  2012年   22篇
  2011年   23篇
  2010年   16篇
  2009年   21篇
  2008年   22篇
  2007年   17篇
  2006年   21篇
  2005年   22篇
  2004年   17篇
  2003年   18篇
  2002年   20篇
  2001年   7篇
  1999年   10篇
  1998年   6篇
  1997年   8篇
  1996年   10篇
  1995年   14篇
  1994年   4篇
  1993年   12篇
  1992年   9篇
  1991年   11篇
  1990年   14篇
  1989年   18篇
  1988年   21篇
  1987年   9篇
  1986年   10篇
  1985年   10篇
  1984年   13篇
  1983年   6篇
  1982年   8篇
  1981年   8篇
  1980年   12篇
  1979年   8篇
  1978年   13篇
  1977年   7篇
  1976年   9篇
  1975年   6篇
  1974年   8篇
  1971年   3篇
  1969年   4篇
排序方式: 共有924条查询结果,搜索用时 312 毫秒
151.
Abstract

To characterize hypertrophy and quantify seasonal changes in cardiac structure and function of women collegiate basketball (BB) athletes (n = 15), echocardiography (echo) measurements were made in the fall (FALL1), winter (WIN), and spring (SPR), then again during the subsequent fall (FALL2; n = 10). Comparisons were made to age-matched nonathletes (NA) measured during FALL1 (n = 22) and SPR (n = 5). Left ventricular (LV) internal dimension–diastole (LVIDd), LV end-diastolic volume (LVEDV), stroke volume (SV), LV mass (LVM), septal thickness (IVS), LV posterior wall thickness (LVPW), right ventricular (RV) internal dimension-diastole (RVIDd), and aortic root diameter (AOD) were significantly larger (12–70%) in the athletes; RVIDd-, LVEDV-, SV-, and LVM-index were also significantly greater (8–46%). From FALL1 to SPR measurement periods, LVWd, RVWd, LVEDV, SV, IVS, and LVM-index increased significantly (7–18%) in the athletes. Over the same period of time, LVIDd, LAD, AOD, LVEDV, and SV measured in the five NA subjects increased significantly. In the athletes, LVIDs, RVIDd, IVS, LVPW, and LVM decreased significantly (5–30%) from the SPR to FALL2 measurement period. These data characterize the general nature of the cardiac hypertrophy noted in women BB athletes compared to NA controls and show that distinct changes in heart structure corresponding to different periods of the competitive season can occur in these athletes.  相似文献   
152.
Purpose: Even though physical education (PE) is an evidence-based strategy for providing and promoting physical activity, alternative programs such as the Junior Reserve Officer Training Corps (JROTC) are commonly substituted for PE in many states. The purpose of this study was to compare student physical activity and lesson contexts during high school PE and JROTC sessions. Method: The System for Observing Fitness Instruction Time was used to assess PE and JROTC sessions (N = 38 each) in 4 high schools that provided both programs. Data were analyzed using t tests, negative binomial regression, and logistic regression. Results: Students engaged in significantly more moderate-to-vigorous physical activity during PE than during JROTC sessions and they were significantly less sedentary. Significant differences between the 2 program types were also found among lesson contexts. Conclusions: PE and JROTC provide substantially different content and contexts, and students in these programs engage in substantially different amounts of moderate-to-vigorous physical activity. Students in JROTC, and perhaps other alternative programs, are less likely to accrue health-supporting physical activity and engage in fewer opportunities to be physically fit and motorically skilled. Policies and practices for providing substitutions for PE should be carefully examined.  相似文献   
153.
154.

P. Arnaud (ed.), Les Athlètes de la République: gymnastique, sport et idéologic republicaine 1870–1914 (Toulouse: Editions Privat, 1987). Pp.423. FF175. ISBN 2–7089–532330.

P. Arnaud and J. Camy (eds.), La naissance du mouvement sportif associatif en France: sociabilitiés et formes de pratiques sportives (Lyons: Presses Universitaires de Lyon, 1986). Pp.422. FF 128. ISBN 2–7297–02938.  相似文献   
155.
Carbohydrate ingestion before and during endurance exercise delays the onset of fatigue (reduced power output). Therefore, endurance athletes are recommended to ingest diets high in carbohydrate (70% of total energy) during competition and training. However, increasing the availability of plasma free fatty acids has been shown to slow the rate of muscle and liver glycogen depletion by promoting the utilization of fat. Ingested fat, in the form of long-chain (C 16-22 ) triacylglycerols, is largely unavailable during acute exercise, but medium-chain (C 8-10 ) triacylglycerols are rapidly absorbed and oxidized. We have shown that the ingestion of medium-chain triacylglycerols in combination with carbohydrate spares muscle carbohydrate stores during 2 h of submaximal (< 70% VO 2 peak) cycling exercise, and improves 40 km time-trial performance. These data suggest that by combining carbohydrate and medium-chain triacylglycerols as a pre-exercise supplement and as a nutritional supplement during exercise, fat oxidation will be enhanced, and endogenous carbohydrate will be spared. We have also examined the chronic metabolic adaptations and effects on substrate utilization and endurance performance when athletes ingest a diet that is high in fat (> 70% by energy). Dietary fat adaptation for a period of at least 2-4 weeks has resulted in a nearly two-fold increase in resistance to fatigue during prolonged, low- to moderate-intensity cycling (< 70% VO 2 peak). Moreover, preliminary studies suggest that mean cycling 20 km time-trial performance following prolonged submaximal exercise is enhanced by 80 s after dietary fat adaptation and 3 days of carbohydrate loading. Thus the relative contribution of fuel substrate to prolonged endurance activity may be modified by training, pre-exercise feeding, habitual diet, or by artificially altering the hormonal milieu or the availability of circulating fuels. The time course and dose-response of these effects on maximizing the oxidative contribution of fat for exercise metabolism and in exercise performance have not been systematically studied during moderate- to high-intensity exercise in humans.  相似文献   
156.
Qualitative data often need analysis using log-linear models, as pointed out by Liu and Sanders. In this article, references to the state-of-the-art literature and software packages for analyzing such data are presented. We also illustrate the two types of log-linear models and present procedures for investigating both types.  相似文献   
157.
This study examines an emerging trend in state higher education finance policy: the use of an index to establish tuition and fee levels at public institutions. Based on a national survey of tuition-setting policies, this study documents the increasing use of an indexing formula to determine tuition levels. Factors encouraging this trend are examined, and questions that must be addressed by state and institutional policymakers in adopting such a formula are discussed. Policy implications for states and institutions are also considered.  相似文献   
158.
This paper examines the key impact that technology is having on shaping and, indeed, fusing the worlds of work both outside and inside tertiary institutions. The transformation of organisations by technology creates key challenges for tertiary institutions which are identified. One tertiary institution's attempts to engage with these challenges is illuminated through case study research. The institution in question, Deakin University, is a major open and distance education organisation in Australia. In grappling with the technological imperative, issues of leadership, management and organisational change come to the fore. Leadership in dynamically evolving organisations committed to the use of educational technologies in a range of diverse teaching‐learning contexts is an enormously complex and difficult task. The complexities, ambiguities and difficulties of leadership in such an environment are illuminated in this paper through the presentation of a set of eight interconnected issues which reveal some of the experiences of people within the University who are attempting to manage educational change and technological innovation.  相似文献   
159.
To assess the impact of economic hardship on 111 European American and 167 Mexican American families and their 5th-grade (M age=11.4 years) children, a family stress model was evaluated. Structural equation analyses revealed that economic hardship was linked to indexes of economic pressure that were related to depressive symptoms for mothers and fathers of both ethnicities. Depressive symptoms were linked to marital problems and hostile parenting. Paternal hostile parenting was related to child adjustment problems for European Americans, whereas marital problems were linked to child adjustment problems for Mexican Americans. Maternal acculturation was associated with both higher marital problems and lower hostile parenting. The utility of the model for describing the effects of economic hardship in Mexican Americans is noted.  相似文献   
160.
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