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   29702篇
  免费   454篇
  国内免费   182篇
教育   20242篇
科学研究   3128篇
各国文化   294篇
体育   2764篇
综合类   401篇
文化理论   246篇
信息传播   3263篇
  2022年   176篇
  2021年   425篇
  2020年   492篇
  2019年   598篇
  2018年   804篇
  2017年   732篇
  2016年   723篇
  2015年   600篇
  2014年   835篇
  2013年   4575篇
  2012年   925篇
  2011年   1003篇
  2010年   842篇
  2009年   856篇
  2008年   848篇
  2007年   879篇
  2006年   834篇
  2005年   705篇
  2004年   612篇
  2003年   561篇
  2002年   627篇
  2001年   750篇
  2000年   671篇
  1999年   546篇
  1998年   337篇
  1997年   304篇
  1996年   357篇
  1995年   274篇
  1994年   292篇
  1993年   234篇
  1992年   368篇
  1991年   377篇
  1990年   342篇
  1989年   374篇
  1988年   340篇
  1987年   326篇
  1986年   329篇
  1985年   373篇
  1984年   300篇
  1983年   305篇
  1982年   240篇
  1981年   246篇
  1980年   259篇
  1979年   350篇
  1978年   258篇
  1977年   238篇
  1976年   199篇
  1975年   181篇
  1974年   182篇
  1973年   176篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
941.
The present study describes the development and validation of an instrument to measure volition in the exercise context. Volition describes an individual’s self-regulatory mental processes that are responsible for taking and maintaining a desirable action (e.g., exercising regularly). The scale structure was developed in an exploratory factor analysis which resulted in a reliable structure of the following six factors: Volitional Inhibition—Reasons, Volitional Inhibition—Postponing Training, Volitional Facilitation—Self-Confidence, Volitional Inhibition—Unrelated Thoughts, Volitional Inhibition—Approval From Others, and Volitional Facilitation—Coping with Failure. A sound theoretical explanation for these six factors is based on the Personal System Interaction Theory. This six-factor structure was also confirmed in a new sample in a confirmatory factor analysis, delivering an 18-item questionnaire with strong model fit and good internal consistency. In addition, the Volition in Exercise Questionnaire showed convergent validity because it was able to predict exercise participation. It showed incremental validity by explaining additional variance to the Sport Motivation Scale’s well-established predictors of exercise participation.  相似文献   
942.
Brain injury research in sport employs a variety of physical models equipped with accelerometers. These acceleration signals are commonly processed using filters. The purpose of this research was to determine the effect of applying filters with different cutoff frequencies to the acceleration signals used as input for finite element modeling of the brain. Signals were generated from reconstructions of concussion events from American football and ice hockey in the laboratory using a Hybrid III headform. The resulting acceleration signals were used as input for the University College Dublin Brain Trauma Model after being processed with filters. The results indicated that using a filter with a cutoff of 300 Hz or higher had little effect on the resulting strain measures. In some cases there was some effect of the filters on the peak linear (8–30g) and rotational measures (1000–4000 rad/s2), but little effect on the finite element strain result (approximately 2–6 %). The short duration and high magnitude accelerations, such as the puck impact, were most affected by the cutoff frequency of different filters.  相似文献   
943.
The forward skating start is a fundamental skill for male and female ice hockey players. However, performance differences by athlete’s sex cannot be fully explained by physiological variables; hence, other factors such as skating technique warrant examination. Therefore, the purpose of this study was to evaluate the body movement kinematics of ice hockey skating starts between elite male and female ice hockey participants. Male (n = 9) and female (n = 10) elite ice hockey players performed five forward skating start accelerations. An 18-camera motion capture system placed on the arena ice surface captured full-body kinematics during the first seven skating start steps within 15 meters. Males’ maximum skating speeds were greater than females. Skating technique sex differences were noted: in particular, females presented ~10° lower hip abduction throughout skating stance as well as ~10° greater knee extension at initial ice stance contact, conspicuously followed by a brief cessation in knee extension at the moment of ice contact, not evident in male skaters. Further study is warranted to explain why these skating technique differences exist in relation to factors such as differences in training, equipment, performance level, and anthropometrics.  相似文献   
944.
Background: The advent of technology use in physical education is upon us. But the implications of using exergames as a substitute for traditional physical education instruction for some students raise questions. Although exergames have the potential to increase energy expenditure and motivation in some children, it is less clear whether they can provide skill acquisition benefits that are similar to those found in traditional physical education.

Purpose: In a previous experiment from our laboratory, we found that deliberate practice can significantly reduce the planning time required for lateral arm movements. The purpose of this study was to determine if exergames can produce a similar effect, by reducing the processing time required for children to initiate arm movements to the contralateral and ipsilateral space.

Participants and setting: Thirty children (boys?=?15, girls?=?15), between the ages of 7 and 12 years, participated in a pre- and post-test each taking 30?min and one 30?min treatment session in a university laboratory.

Research design: A repeated measures design was employed to test the effects of deliberate laterality practice on processing speed. Children were randomly assigned (n?=?10) to either a Nintendo Wii tennis contralateral movement experimental group, Nintendo Wii bowling ipsilateral movement experimental group, or handheld video-game control group. Each child participated in one 30?min treatment session.

Data collection: Upper extremity choice reaction time (RT) was measured through 27 goal-directed aiming movements for each arm separately, during the pre-test and post-test. The stimulus–response trials occurred in three randomly presented directions (ipsilateral, contralateral, and midline).

Data analysis: A 3 (treatment group)?×?2 (age group)?×?2 (test)?×?3 (direction) mixed design analysis of variance with repeated measures on the last two factors was used to test for significant differences, with an alpha level set at 0.05.

Findings: There were no significant treatment effects on RT across all groups indicating that a short bout of exergame training was unsuccessful in improving lateral movement processing.

Conclusions: Deliberate laterality practice using exergames did not improve the motor processing speed of lateral arm movements in the same manner of traditional physical education as indicated by our previous research. Explanations as to why exergames do not exhibit the same positive transfer for skill acquisition as traditional physical education instruction are discussed within this paper.  相似文献   
945.
Tennis featured in every Olympics from 1896 to 1924, after which disagreements between the International Olympic Committee (IOC) and the International Lawn Tennis Federation (ILTF) on matters pertaining to organisational control and the amateur eligibility of players led to tennis being removed from the Olympic Games as a full-medal event until the 1988 Seoul Olympics. This paper traces the steps of the sport’s reinstatement, from when efforts commenced in the 1950s, setting this development in the contexts of: broader political movements, shifting IOC leadership, burgeoning commercialisation of Olympic sport, the concomitant push for professionalisation and the declining influence of amateur ideals within both the Olympic movement and international tennis. Under the leadership of the amateur stalwart Avery Brundage, the IOC stymied attempts to facilitate tennis’s re-entry, challenging both the ILTF on failing to deal with widespread ‘sham-amateur’ practices and the avaricious promoters luring amateur players toward the professional ranks. Brundage and the IOC also strongly condemned the move to ‘open’ tennis and an acceptance of full-blown professionalism. Only a change in leadership, firstly with Lord Killanin and then the progressive reformer Juan Antonio Samaranch, did the IOC recognise the value of tennis within the Olympic movement, which by then had itself become increasingly money-oriented.  相似文献   
946.
The aim of this study is to determine changes in sedentary behaviour in response to extensive aerobic exercise training. Participants included adults who self-selected to run a marathon. Sedentary behaviour, total activity counts and physical activity (PA) intensity were assessed (Actigraph GT3X) for seven consecutive days during seven assessment periods (?3, ?2, and ?1 month prior to the marathon, within 2 weeks of the marathon, and +1, +2, and +3 months after the marathon). Models were fitted with multiple imputation data using the STATA mi module. Random intercept generalized least squares (GLS) regression models were used to determine change in sedentary behaviour with seven waves of repeated measures. Results: Twenty-three individuals (mean?±?Sx: 34.4?±?2.1y, 23.0?±?1.9% fat, 15 women, 8 men) completed the study. Marathon finishing times ranged from 185 to 344 minutes (253.2?±?9.6 minutes). Total counts in the vertical axis were 1,729,414 lower one month after the race, compared with two months prior to the race (peak training). Furthermore, counts per minute decreased by 252.7 counts·minute?1 during that same time period. Daily sedentary behaviour did not change over the seven assessment periods, after accounting for age, gender, per cent body fat, wear time, marathon finishing time, and previous marathon experience. This prospective study supports the notion that PA and sedentary behaviours are distinct, showing that sedentary behaviour was not impacted by high levels of aerobic training.  相似文献   
947.
This study compared markers of muscle damage and inflammation elevated by a matched-intensity interval running session on soft sand and grass surfaces. In a counterbalanced, repeated-measures and crossover design, 10 well-trained female athletes completed 2 interval-based running sessions 1 week apart on either a grass or a sand surface. Exercise heart rate (HR) was fixed at 83–88% of HR maximum. Venous blood samples were collected pre-, post- and 24?h post-exercise, and analysed for myoglobin (Mb) and C-reactive protein (CRP). Perceptual ratings of exertion (RPE) and muscle soreness (DOMS) were recorded immediately post- and 24?h post-exercise. A significant time effect showed that Mb increased from pre- to post-exercise on grass (p?=?.008) but not on sand (p?=?.611). Furthermore, there was a greater relative increase in Mb on grass compared with that on sand (p?=?.026). No differences in CRP were reported between surfaces (p?>?.05). The HR, RPE and DOMS scores were not significantly different between conditions (p > .05). These results suggest that in response to a matched-intensity exercise bout, markers of post-exercise muscle damage may be reduced by running on softer ground surfaces. Such training strategy may be used to minimize musculoskeletal strain while still incurring an equivalent cardiovascular training stimulus.  相似文献   
948.
Purpose: There is a paucity of research investigating the expression of mitogen-activated protein kinases (MAPK) in chronically trained (CT) athletes. Thus, it is unclear how MAPK may contribute to performance and muscle adaptation in CT subjects. The purpose of this study was to determine MAPK total protein, and phosphorylated expression of extracellular signal-regulated kinases 1 and 2 (ERK1/2), c-Jun N-terminal kinase (JNK), and p38-MAPK (p38) between untrained, and chronically trained runners. Methods: Tissue samples were analysed from sedentary (SED; n?=?5) controls and chronically trained runners (CT; n?=?5). Resting muscle biopsy samples were analysed for total-MAPK – and ratio of phosphorylated/total (p-MAPK) – ERK1/2, JNK, and p38-MAPK via western blotting. Mann–Whitney U tests and effect sizes were utilized to determine differences in total MAPK protein content and phosphorylation status between SED and CT subjects. Results: There was no difference in total-MAPK expression between SED and CT (p?>?.05). p-p38-MAPK tended to be greater for CT compared to SED (p?=?.07). There were moderate effect sizes of decreased pERK/total-ERK (d?=??0.69) and increased pJNK/total-JNK (d?=?0.54) in CT compared to SED. There was a positive correlation between p-p38-MAPK/total-MAPK and the percentage of type I fibres (r?=?0.73, p?=?.016). Conclusion: Contrary to previous studies, chronic endurance training does not greatly influence total MAPK protein expression in chronically trained runners. However, resting phosphorylation of p38-MAPK may contribute to enhanced oxidative metabolism at chronically trained levels. These alterations are likely involved in the different physiological adaptations that occur following long-term training or at highly competitive levels.  相似文献   
949.
Considering the growth in research, examining the development of mainstream sport athletes over the past two decades, studies examining development of athletes with disabilities have been surprisingly limited. While similarities in developmental trajectories between the two cohorts may exist regarding factors such as the value of practice, which tend to be universal regardless of context, disability-related issues (e.g. whether the disability was congenital or acquired) may influence the course of development, affecting variables such as starting age, training and developmental milestones. Fifty-two male and female athletes training with the Wheelchair Basketball Canada National Academy provided detailed training histories. Athletes illustrated similar developmental patterns (e.g. milestones, training adjustments) as they progressed through their sporting career. However, athletes with congenital disabilities started participation in wheelchair basketball and unorganised practice at significantly younger ages (t49?=??4.35, p?<?.001, d =?1.32; t49?=??3.49, p?<?.001, d =?1.03, respectively). While athletes with congenital disabilities continued to reach a majority of the sporting milestones at younger ages, athletes with acquired disabilities were able to reach late career milestones (e.g. national debuts) at similar ages. Athletes’ disability severity did not influence their progress through the developmental milestones and time devoted to training throughout their sporting career. Future work may consider examining developmental trajectories and training histories of athletes in various parasports to extend our understanding of their development and skill acquisition.  相似文献   
950.
The aim of this study was to ascertain if gear ratio selection would have an effect on peak power and time to peak power production in elite Bicycle Motocross (BMX) cyclists. Eight male elite BMX riders volunteered for the study. Each rider performed three, 10-s maximal sprints on an Olympic standard indoor BMX track. The riders’ bicycles were fitted with a portable SRM power meter. Each rider performed the three sprints using gear ratios of 41/16, 43/16 and 45/16 tooth. The results from the 41/16 and 45/16 gear ratios were compared to the current standard 43/16 gear ratio. Statistically, significant differences were found between the gear ratios for peak power (F(2,14)?=?6.448; p?=?.010) and peak torque (F(2,14)?=?4.777; p?=?.026), but no significant difference was found for time to peak power (F(2,14)?=?0.200; p?=?.821). When comparing gear ratios, the results showed a 45/16 gear ratio elicited the highest peak power,1658?±?221?W, compared to 1436?±?129?W and 1380?±?56?W, for the 43/16 and 41/16 ratios, respectively. The time to peak power showed a 41/16 tooth gear ratio attained peak power in ?0.01?s and a 45/16 in 0.22?s compared to the 43/16. The findings of this study suggest that gear ratio choice has a significant effect on peak power production, though time to peak power output is not significantly affected. Therefore, selecting a higher gear ratio results in riders attaining higher power outputs without reducing their start time.  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