全文获取类型
收费全文 | 8393篇 |
免费 | 77篇 |
国内免费 | 20篇 |
专业分类
教育 | 5842篇 |
科学研究 | 1098篇 |
各国文化 | 29篇 |
体育 | 466篇 |
综合类 | 6篇 |
文化理论 | 137篇 |
信息传播 | 912篇 |
出版年
2022年 | 31篇 |
2021年 | 45篇 |
2020年 | 85篇 |
2019年 | 126篇 |
2018年 | 840篇 |
2017年 | 873篇 |
2016年 | 613篇 |
2015年 | 160篇 |
2014年 | 168篇 |
2013年 | 787篇 |
2012年 | 202篇 |
2011年 | 424篇 |
2010年 | 403篇 |
2009年 | 254篇 |
2008年 | 315篇 |
2007年 | 439篇 |
2006年 | 105篇 |
2005年 | 154篇 |
2004年 | 226篇 |
2003年 | 159篇 |
2002年 | 89篇 |
2001年 | 106篇 |
2000年 | 145篇 |
1999年 | 89篇 |
1998年 | 72篇 |
1997年 | 74篇 |
1996年 | 59篇 |
1995年 | 41篇 |
1994年 | 43篇 |
1993年 | 30篇 |
1992年 | 72篇 |
1991年 | 66篇 |
1990年 | 59篇 |
1989年 | 59篇 |
1988年 | 72篇 |
1987年 | 55篇 |
1986年 | 76篇 |
1985年 | 67篇 |
1984年 | 52篇 |
1983年 | 66篇 |
1982年 | 49篇 |
1981年 | 36篇 |
1980年 | 26篇 |
1979年 | 48篇 |
1978年 | 46篇 |
1977年 | 34篇 |
1976年 | 38篇 |
1975年 | 28篇 |
1974年 | 29篇 |
1973年 | 33篇 |
排序方式: 共有8490条查询结果,搜索用时 15 毫秒
71.
J. Santos-Concejero N. Tam D. R. Coetzee J. Oliván T. D. Noakes R. Tucker 《Journal of sports sciences》2017,35(6):531-538
The aim of this study was to determine whether gait cycle characteristics are associated with running economy in elite Kenyan runners. Fifteen elite Kenyan male runners completed two constant-speed running sets on a treadmill (12 km ·h?1 and 20 km ·h?1). VO2 and respiratory exchange ratio values were measured to calculate steady-state oxygen and energy cost of running. Gait cycle characteristics and ground contact forces were measured at each speed. Oxygen cost of running at different velocities was 192.2 ± 14.7 ml· kg?1· km?1 at 12 km· h?1 and 184.8 ± 9.9 ml· kg?1· km?1 at 20 km· h?1, which corresponded to a caloric cost of running of 0.94 ± 0.07 kcal ·kg?1·km?1 and 0.93 ± 0.07 kcal· kg?1· km?1. We found no significant correlations between oxygen and energy cost of running and biomechanical variables and ground reaction forces at either 12 or 20 km· h?1. However, ground contact times were ~10.0% shorter (very large effect) than in previously published literature in elite runners at similar speeds, alongside an 8.9% lower oxygen cost (very large effect). These results provide evidence to hypothesise that the short ground contact times may contribute to the exceptional running economy of Kenyan runners. 相似文献
72.
Andrew Post J. Michio Clark D. G. E. Robertson T. Blaine Hoshizaki Michael D. Gilchrist 《Sports Engineering》2017,20(2):111-119
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
73.
74.
75.
K. S. Yakovlev D. A. Makarov E. S. Baskin 《Scientific and Technical Information Processing》2015,42(5):347-358
In the article we solve path planning task for an agent being multirotor unmanned aerial vehicle (multicopter). We propose an approach of estimating path geometry constraints based on UAV flight dynamics model and control constraints. Than we introduce a new path finding method which takes into consideration those geometry constraints and study this method both theoretically and empirically. 相似文献
76.
77.
Chris Bishop Lucas A. Pereira Valter P. Reis Paul Read Anthony N. Turner Irineu Loturco 《Journal of sports sciences》2020,38(11-12):1296-1303
ABSTRACT The aims of the present study were to provide an in-depth comparison of inter-limb asymmetry and determine how consistently asymmetry favours the same limb during different vertical jump tests. Eighteen elite female under-17 soccer players conducted unilateral squat jumps (SJ), countermovement jumps (CMJ) and drop jumps (DJ) on a portable force platform, with jump height, peak force, concentric impulse and peak power as common metrics across tests. For the magnitude of asymmetry, concentric impulse was significantly greater during the SJ test compared to CMJ (p = 0.019) and DJ (p = 0.003). No other significant differences in magnitude were present. For the direction of asymmetry, Kappa coefficients revealed fair to substantial levels of agreement between the SJ and CMJ (Kappa = 0.35 to 0.61) tests, but only slight to fair levels of agreement between the SJ and DJ (Kappa = ?0.26 to 0.18) and CMJ and DJ (Kappa = ?0.13 to 0.26) tests. These results highlight that the mean asymmetry value may be a poor indicator of true variability of between-limb differences in healthy athletes. The direction of asymmetry may provide a useful monitoring tool for practitioners in healthy athletes, when no obvious between-limb deficit exists. 相似文献
78.
This paper analyzes the effects that the 2012 VAT rise in Spain had on household’ demand for cultural goods and services. Household’ demands are modeled as a two-stage QUAIDS. After estimating price and expenditure elasticities, and the pass-through parameter associated with the reform, our results show that the individual welfare loss and the increment in the tax bill increase, but less than proportionately, with income. Consequently, the reform can be considered as regressive. Relating the effects of the VAT reform to households’ incomes also implies a low quantitative effect, because of the low proportion of total household expenditure that cultural expenditure represents. From a social perspective, the size of the induced welfare loss would positively depend on society’s inequality aversion. Regardless of the latter, it cannot be concluded whether the reform would have increased or reduced inequality in the distribution of cultural spending. Our results prove qualitatively robust to alternative values of the pass-through parameter. 相似文献
79.
Adam E. Wyse Eric M. Stickney David Butz Amanda Beckler Catherine N. Close 《Educational Measurement》2020,39(3):60-64
There is no denying the impact that the coronravirus disease (COVID-19) outbreak has had on many aspects of our lives. This article looks at the potential impact of COVID-19 on student learning as schools abruptly morphed into virtual learning environments using data from several instructional, practice, and assessment solutions offered by Renaissance. First, three hypothetical learning scenarios are considered using normative data from Star assessments to explore the potential impact on reading and math test performace. Next, data on Focus Skills are used to highlight which grades may have missed the most foundational math and reading content if instruction was stopped or reduced. Last, data from two of Renaissance's practice tools are used to evaluate whether students were practicing key skills following school closures. The article concludes that academic decline will likely occur but may be tempered by the increased use of practice tools; effects may look different for math and reading; and may impact grades and schools differently. As such, schools may need to leverage decision-making frameworks, such as the Multi-tiered Systems of Support/Response-to-Intervention (MTSS/RTI) framework, more than ever to identify needs and target instruction where it matters most when school begins in fall 2020. 相似文献
80.
Data from surveys of parents of students in Russian schools of various types in the years 2006 to 2011 show a high level of desire to invest in their children's education. There has been a high degree of stability in aspirations and investment in spite of the economic problems caused by global recession. 相似文献