全文获取类型
收费全文 | 3308篇 |
免费 | 71篇 |
国内免费 | 1篇 |
专业分类
教育 | 2492篇 |
科学研究 | 164篇 |
各国文化 | 50篇 |
体育 | 242篇 |
文化理论 | 35篇 |
信息传播 | 397篇 |
出版年
2022年 | 36篇 |
2021年 | 32篇 |
2020年 | 72篇 |
2019年 | 123篇 |
2018年 | 133篇 |
2017年 | 162篇 |
2016年 | 148篇 |
2015年 | 92篇 |
2014年 | 114篇 |
2013年 | 756篇 |
2012年 | 95篇 |
2011年 | 84篇 |
2010年 | 77篇 |
2009年 | 77篇 |
2008年 | 81篇 |
2007年 | 80篇 |
2006年 | 59篇 |
2005年 | 62篇 |
2004年 | 57篇 |
2003年 | 68篇 |
2002年 | 59篇 |
2001年 | 48篇 |
2000年 | 65篇 |
1999年 | 56篇 |
1998年 | 29篇 |
1997年 | 25篇 |
1996年 | 25篇 |
1995年 | 30篇 |
1994年 | 21篇 |
1993年 | 36篇 |
1992年 | 41篇 |
1991年 | 38篇 |
1990年 | 33篇 |
1989年 | 25篇 |
1988年 | 22篇 |
1987年 | 27篇 |
1986年 | 19篇 |
1985年 | 28篇 |
1984年 | 18篇 |
1983年 | 17篇 |
1982年 | 29篇 |
1981年 | 26篇 |
1980年 | 16篇 |
1979年 | 24篇 |
1978年 | 22篇 |
1977年 | 12篇 |
1976年 | 18篇 |
1975年 | 10篇 |
1968年 | 9篇 |
1889年 | 9篇 |
排序方式: 共有3380条查询结果,搜索用时 0 毫秒
921.
We examined the effects of concomitant increases in crank rate and power output on incremental arm crank ergometry. Ten healthy males undertook three incremental upper body exercise tests to volitional exhaustion. The first test determined peak minute power. The subsequent tests involved arm cranking at an initial workload of 40% peak minute power with further increases of 10% peak minute power every 2 min. One involved a constant crank rate of 70 rev · min(-1), the other an initial crank rate of 50 rev · min(-1) increasing by 10 rev · min(-1) every 2 min. Fingertip capillary blood samples were analysed for blood lactate at rest and exhaustion. Local (working muscles) and cardiorespiratory ratings of perceived exertion (RPE) were recorded at the end of each exercise stage. Heart rate and expired gas were monitored continuously. No differences were observed in peak physiological responses or peak minute power achieved during either protocol. Blood lactate concentration tended to be greater for the constant crank rate protocol (P = 0.06). Test duration was shorter for the increasing than for the constant crank rate protocol. The relationship between local RPE and heart rate differed between tests. The results of this study show that increasing cadence during incremental arm crank ergometry provides a valid assessment of peak responses over a shorter duration but alters the heart rate-local RPE relationship. 相似文献
922.
A comparative study of baseball bat performance 总被引:2,自引:2,他引:0
Alan M. Nathan Joseph J. Crisco R. M. Greenwald D. A. Russell Lloyd V. Smith 《Sports Engineering》2011,13(4):153-162
The results of a comparative study of five aluminum and one wood baseball bats are presented. The study includes an analysis
of field data, high-speed laboratory testing, and modal analysis. It is found that field performance is strongly correlated
with the ball–bat coefficient of restitution (BBCOR) and only weakly correlated with other parameters of the bat, suggesting
that the BBCOR is the primary feature of a bat that determines its field performance. It is further found that the instantaneous
rotation axis of the bat at the moment of impact is very close to the knob of the bat and that the rotational velocity varies
inversely with the moment of inertia of the bat about the knob. A swing speed formula is derived from the field data and the
limits of its validity are discussed. The field and laboratory measurements of the collision efficiency are generally in good
agreement, as expected on theoretical grounds. Finally, the BBCOR is strongly correlated with the frequency of the lowest
hoop mode of the hollow bats, as predicted by models of the trampoline effect. 相似文献
923.
A method of examining the separation of the boundary layer of air from a sports ball, specifically a football, is presented. Using a ball launcher, a non-spinning football is fired into a dust cloud. A high-speed camera records the ball passing through the dust cloud. Unlike wind-tunnel methods, the dust method described here allows for the examination of the boundary-layer separation without a ball-supporting arrangement. Boundary-layer separation for speeds surrounding the drag crisis is studied. Though the general trend is for the boundary layer to separate farther back on the ball as the ball’s centre-of-mass speed increases, anomalous behaviour is seen just past the drag crisis, namely a rise in the separation angle, followed by an expected decrease. 相似文献
924.
925.
Purpose: An objective database for physical education (PE) is important for policy and practice decisions, and the System for Observing Fitness Instruction Time (SOFIT) has been identified as an appropriate surveillance tool for PE across the nation. The purpose of this review was to assess peer-reviewed studies using SOFIT to study K–12 PE in U.S. schools. Method: The Preferred Reporting Items for Systematic Reviews and Meta-Analyses informed the review, and 10 databases were searched for English-language articles published through 2016. A total of 704 records identifying SOFIT were located, and 137 full texts were read. Two authors reviewed full-text articles, and a data extraction tool was developed to select studies and main topics for synthesis. Results: Twenty-nine studies that included direct observations of 12,256 PE lessons met inclusion criteria; 17 were conducted in elementary schools, 9 in secondary schools, and 3 in combined-level schools. Inconsistent reporting among studies was evident, including not all identifying the number of classes and teachers involved. All studies reported student physical activity, but fewer reported observer reliabilities (88%), lesson context (76%), teacher behavior (38%), and PE dosage (34%). The most frequently analyzed independent variables were teacher preparation (48%), lesson location (38%), and student gender (31%). Conclusions: SOFIT can be used reliably in diverse settings. Inconsistent reporting about study procedures and variables analyzed, however, limited comparisons among studies. Adherence to an established protocol and more consistent reporting would more fully enable the development of a viable database for PE in U.S. schools. 相似文献
926.
Dave Smith 《Sport in History》2017,37(2):223-224
927.
928.
929.
930.