全文获取类型
收费全文 | 2098篇 |
免费 | 28篇 |
国内免费 | 1篇 |
专业分类
教育 | 1479篇 |
科学研究 | 165篇 |
各国文化 | 19篇 |
体育 | 225篇 |
文化理论 | 53篇 |
信息传播 | 186篇 |
出版年
2023年 | 10篇 |
2022年 | 16篇 |
2021年 | 23篇 |
2020年 | 35篇 |
2019年 | 72篇 |
2018年 | 81篇 |
2017年 | 82篇 |
2016年 | 79篇 |
2015年 | 41篇 |
2014年 | 55篇 |
2013年 | 480篇 |
2012年 | 60篇 |
2011年 | 51篇 |
2010年 | 38篇 |
2009年 | 36篇 |
2008年 | 44篇 |
2007年 | 37篇 |
2006年 | 30篇 |
2005年 | 30篇 |
2004年 | 41篇 |
2003年 | 31篇 |
2002年 | 31篇 |
2001年 | 31篇 |
2000年 | 36篇 |
1999年 | 25篇 |
1998年 | 19篇 |
1997年 | 30篇 |
1996年 | 24篇 |
1995年 | 35篇 |
1994年 | 22篇 |
1993年 | 12篇 |
1992年 | 22篇 |
1991年 | 23篇 |
1990年 | 19篇 |
1989年 | 23篇 |
1987年 | 18篇 |
1986年 | 19篇 |
1985年 | 24篇 |
1984年 | 18篇 |
1983年 | 19篇 |
1982年 | 23篇 |
1981年 | 22篇 |
1980年 | 18篇 |
1979年 | 23篇 |
1978年 | 14篇 |
1977年 | 15篇 |
1976年 | 17篇 |
1973年 | 14篇 |
1971年 | 10篇 |
1889年 | 9篇 |
排序方式: 共有2127条查询结果,搜索用时 15 毫秒
51.
Kosuke Tamura Jeffrey S. Wilson Keith Goldfeld Robin C. Puett David B. Klenosky William A. Harper 《Research quarterly for exercise and sport》2013,84(3):395-402
ABSTRACTPurpose: Most built environment studies have quantified characteristics of the areas around participants’ homes. However, the environmental exposures for physical activity (PA) are spatially dynamic rather than static. Thus, merged accelerometer and global positioning system (GPS) data were utilized to estimate associations between the built environment and PA among adults. Methods: Participants (N = 142) were recruited on trails in Massachusetts and wore an accelerometer and GPS unit for 1–4 days. Two binary outcomes were created: moderate-to-vigorous PA (MVPA vs. light PA-to-sedentary); and light-to-vigorous PA (LVPA vs. sedentary). Five built environment variables were created within 50-meter buffers around GPS points: population density, street density, land use mix (LUM), greenness, and walkability index. Generalized linear mixed models were fit to examine associations between environmental variables and both outcomes, adjusting for demographic covariates. Results: Overall, in the fully adjusted models, greenness was positively associated with MVPA and LVPA (odds ratios [ORs] = 1.15, 95% confidence interval [CI] = 1.03, 1.30 and 1.25, 95% CI = 1.12, 1.41, respectively). In contrast, street density and LUM were negatively associated with MVPA (ORs = 0.69, 95% CI = 0.67, 0.71 and 0.87, 95% CI = 0.78, 0.97, respectively) and LVPA (ORs = 0.79, 95% CI = 0.77, 0.81 and 0.81, 95% CI = 0.74, 0.90, respectively). Negative associations of population density and walkability with both outcomes reached statistical significance, yet the effect sizes were small. Conclusions: Concurrent monitoring of activity with accelerometers and GPS units allowed us to investigate relationships between objectively measured built environment around GPS points and minute-by-minute PA. Negative relationships between street density and LUM and PA contrast evidence from most built environment studies in adults. However, direct comparisons should be made with caution since most previous studies have focused on spatially fixed buffers around home locations, rather than the precise locations where PA occurs. 相似文献
52.
Keith?KoenigEmail author Nan?Davis?Mitchell Thomas?E.?Hannigan J.?Keith?Clutter 《Sports Engineering》2004,7(2):105-117
The speed at which a player can swing a bat is central to the games of baseball and softball, determining, to a large extent,
the hit speed of the ball. Experimental and analytical studies of bat swing speed were conducted with particular emphasis
on the influence of bat moment of inertia on swing speed. Two distinct sets of experiments measured the swing speed of colege
baseball and fast-pitch softball players using weighted rods and modified bats. The swing targets included flexible targets,
balls on a tee and machine pitched balls. Internal mass alterations provided a range of inertial properties. The average measured
speeds, from 22 to 31 m s−1, are consistent with previous studies. Bat speed approximately correlates with the moment of inertia of the bat about a vertical
axis of rotation through the batter's body, the speed generally decreasing as this moment of inertia increases. The analytical
model assumes pure rotation of the batter/bat system about a vertical axis through the batter's body. Aerodynamic drag of
the batter's arms and the bat is included in the model. The independent variable is bat moment of inertia about the rotation
axis. There is reasonable agreement between the model and the measured speeds. Detailed differences between the two suggest
the importance of additional degrees of freedom in determining swing speed. 相似文献
53.
The aims of this study were: (1) to identify the exercise intensity that corresponds to the maximal lactate steady state in adolescent endurance-trained runners; (2) to identify any differences between the sexes; and (3) to compare the maximal lactate steady state with commonly cited fixed blood lactate reference parameters. Sixteen boys and nine girls volunteered to participate in the study. They were first tested using a stepwise incremental treadmill protocol to establish the blood lactate profile and peak oxygen uptake ([Vdot]O2). Running speeds corresponding to fixed whole blood lactate concentrations of 2.0, 2.5 and 4.0?mmol?·?l?1 were calculated using linear interpolation. The maximal lactate steady state was determined from four separate 20-min constant-speed treadmill runs. The maximal lactate steady state was defined as the fastest running speed, to the nearest 0.5?km?·?h?1, where the change in blood lactate concentration between 10 and 20?min was?<0.5?mmol?·?l?1. Although the boys had to run faster than the girls to elicit the maximal lactate steady state (15.7 vs 14.3?km?·?h?1, P?<0.01), once the data were expressed relative to percent peak [Vdot]O2 (85 and 85%, respectively) and percent peak heart rate (92 and 94%, respectively), there were no differences between the sexes (P?>0.05). The running speed and percent peak [Vdot]O2 at the maximal lactate steady state were not different to those corresponding to the fixed blood lactate concentrations of 2.0 and 2.5?mmol?·?l?1 (P?>0.05), but were both lower than those at the 4.0?mmol?·?l?1 concentration (P?<0.05). In conclusion, the maximal lactate steady state corresponded to a similar relative exercise intensity as that reported in adult athletes. The running speed, percent peak [Vdot]O2 and percent peak heart rate at the maximal lactate steady state are approximated by the fixed blood lactate concentration of 2.5?mmol?·?l?1 measured during an incremental treadmill test in boys and girls. 相似文献
54.
Luís Vilar Ricardo Duarte Pedro Silva Jia Yi Chow Keith Davids 《Journal of sports sciences》2013,31(19):1751-1759
AbstractThis study examined the influence of pitch dimensions in small-sided soccer games in shaping opportunities for performers to maintain ball possession, pass to teammates and shoot at goal. Fifteen amateur standard male participants (M = 21.87, σ = 1.96 years) played 5 v 5 small-sided soccer games in three varying pitch conditions (28 m × 14 m, 40 m × 20 m and 52 m × 26 m). Thirty sequences of play in each condition were selected for digitisation using TACTO software, allowing the capture of bi-dimensional displacement coordinate data of all players and the ball. The values of interpersonal distance between all attackers and immediate defenders and the relative distances of defenders to intercept a shot and a pass were computed as dependent variables. Results showed existence of fewer opportunities to maintain ball possession on smaller pitches, compared to medium and larger pitches. Conversely, the different dimensions set to the pitch did not influence opportunities for players to shoot at goal, or to perform passes to other teammates. By examining the specific spatial–temporal relationships of players and key-task constraints, the data from this study explain how effects of manipulating pitch dimensions of small-sided games might enhance opportunities for acquiring specific movement and decision-making skills. 相似文献
55.
The themes of love, loss and magic have been enduring themes in fairytales, myths, legends and fantasy within the genre of children's literature. These stories frequently depict young protagonists who have been ‘orphaned’ in some way—for example, through death, betrayal, absence, rejection or unexplained disappearance. In many of these narratives an important feature is the power of the story to grip and hold its readers through the intervention of magic in its most sinister and beneficent form as well as the love and loyalty of friends and creatures drawn from the world of fantasy. What is seldom examined is the way in which the author's own biography of loss and love both informs and provides a major impetus to the stories they have written. This article explores the way in which the themes of love, loss and magic interconnect with two phenomenally successful contemporary children's writers. Using selected extracts from the work of Philip Pullman and Michael Morpurgo, the article suggests a dynamic synergy with the authors and their stories. 相似文献
56.
Hannele Forsman Arto Gråstén Minna Blomqvist Keith Davids Jarmo Liukkonen Niilo Konttinen 《Journal of sports sciences》2016,34(14):1319-1327
ABSTRACTThe objective of this study was to create a valid, self-reported, game-specific soccer competence scale. A structural model of perceived competence, performance measures and motivation was tested as the basis for the scale. A total of 1321 soccer players (261 females, 1060 males) ranging from 12 to 15 years (13.4 ± 1.0 years) participated in the study. They completed the Perceived Game-Specific Soccer Competence Scale (PGSSCS), self-assessments of tactical skills and motivation, as well as technical and speed and agility tests. Results of factor analyses, tests of internal consistency and correlations between PGSSCS subscales, performance measures and motivation supported the reliability and validity of the PGSSCS. The scale can be considered a suitable instrument to assess perceived game-specific competence among young soccer players. 相似文献
57.
58.
Pedro Passos Duarte Araújo Keith Davids Luis Gouveia João Milho SidóNio Serpa 《Journal of sports sciences》2013,31(13):1421-1429
Abstract Previous work on dynamics of interpersonal interactions in 1 vs. 1 sub-phases of basketball has identified changes in interpersonal distance between an attacker and defender as a potential control parameter for influencing organizational states of attacker–defender dyads. Other studies have reported the constraining effect of relative velocity between an attacker and defender in 1 vs. 1 dyads. To evaluate the relationship between these candidate control parameters, we compared the impact of both interpersonal distance and relative velocity on the pattern-forming dynamics of attacker–defender dyads in the sport of rugby union. Results revealed that when interpersonal distance achieved a critical value of less than 4 m, and relative velocity values increased or were maintained above 1 m · s?1, a successful outcome (i.e. clean attempt) for an attacker was predicted. Alternatively, when values of relative velocity suddenly decreased below this threshold, at the same critical value of interpersonal distance, a successful outcome for the defender was predicted. Data demonstrated how the coupling of these two potential, nested control parameters moved the dyadic system to phase transitions, characterized as a try or a tackle. Observations suggested that relative velocity increased its influence on the organization of attacker–defender dyads in rugby union over time as spatial proximity to the try line increased. 相似文献
59.
Joel Blanchard Samuel Blais Philippe Chetaille Michele Bisson François P. Counil Thelma H. Girard 《Journal of sports sciences》2019,37(11):1265-1269
The purpose of this study was to identify which averaging methods most accurately measures peak cardiorespiratory fitness (CRF) parameters [peak O2 uptake (VO2), peak O2pulse and peak respiratory exchange ratio (RER)] in a sample of healthy children and adolescents. In this cross-sectional multicenter study, we recruited 278 healthy children aged 12–17 years. We compared the mean peak value of three CRF parameters using the recommended averaging methods (30-second block average) with alternative averaging methods such as moving averages or shorter smoothing periods. We also assessed averaging methods for accuracy by individually reviewing breath-by-breath scatter plots. The 30-second block average method resulted in a lower mean peak VO2 and in an increased proportion of underestimated peak values. Using a 30-second moving average significantly increased mean peak values which increased accuracy. Similar results were found for peak RER and peak O2pulse. In conclusion, the currently recommended averaging method (30-second block average) increased the risk of misinterpretation of peak CRF values in children. Using a moving average approach decreased misinterpretation and increased accuracy. 相似文献
60.