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   420篇
  免费   8篇
教育   269篇
科学研究   54篇
各国文化   4篇
体育   74篇
文化理论   10篇
信息传播   17篇
  2024年   1篇
  2023年   1篇
  2022年   3篇
  2021年   16篇
  2020年   14篇
  2019年   30篇
  2018年   32篇
  2017年   26篇
  2016年   22篇
  2015年   18篇
  2014年   22篇
  2013年   74篇
  2012年   14篇
  2011年   19篇
  2010年   13篇
  2009年   9篇
  2008年   9篇
  2007年   9篇
  2006年   4篇
  2005年   14篇
  2004年   8篇
  2003年   4篇
  2002年   8篇
  2000年   2篇
  1999年   1篇
  1998年   1篇
  1997年   6篇
  1996年   5篇
  1995年   4篇
  1994年   4篇
  1993年   1篇
  1991年   1篇
  1990年   1篇
  1989年   4篇
  1988年   3篇
  1987年   1篇
  1986年   1篇
  1985年   2篇
  1984年   1篇
  1982年   2篇
  1981年   2篇
  1980年   1篇
  1979年   3篇
  1978年   2篇
  1977年   3篇
  1974年   1篇
  1970年   3篇
  1969年   1篇
  1887年   2篇
排序方式: 共有428条查询结果,搜索用时 265 毫秒
401.
The development of local technology-intensive suppliers (t-suppliers) may contribute to both reinforcing the industrial base and supporting the competitiveness of primary production in developing countries. This article explores the role of t-suppliers in natural resource-based economies and outlines a theoretical framework for the analysis of the factors which foster or constrain their development and defines areas for an effective promotion. The proposed model of analysis distinguishes between factors influencing the development of t-suppliers on the level of the main industry, the level of supplier firms or firm-level and the level of external determinants with special reference to industrial policy factors.  相似文献   
402.
We conducted a three-arm cluster randomized controlled trial (n = 2491) to evaluate a teacher delivered intervention to reduce aggressive and antisocial behavior and increase prosocial behavior in the classroom. A second aim of this trial was to establish whether combining this intervention with an intervention for parents was better than the teacher-only intervention. This evaluation was conducted in a resource-poor setting (Pereira, Colombia). The findings show that both interventions prevented increases in aggressive and antisocial behavior. However, the teacher-only intervention also had a positive impact on increasing prosocial behavior.  相似文献   
403.
404.
405.
The first part of this article explores whether convergence has occurred in technology and income across EU regions during the period 1990-2002. The second part evaluates whether these two processes of convergence are related to each other. With respect to the first question, we find that all R&D indicators and patents have converged among regions during the 1990s and this has ran parallel to a real convergence in income per capita levels. Regarding the second question, we have identified a strong relationship between the distribution of technology indicators and the distribution of regional income in Europe. Our main result is that convergence in business R&D leads to convergence in patents, which in turn leads to convergence in income per capita. Although, we identify a role for government R&D and higher education spending in this process, the policy implications for these two variables are less clear.  相似文献   
406.
The optimal widely linear state estimation problem for quaternion systems with multiple sensors and mixed uncertainties in the observations is solved in a unified framework. For that, we devise a unified model to describe the mixed uncertainties of sensor delays, packet dropouts and uncertain observations by using three Bernoulli distributed quaternion random processes. The proposed model is valid for linear discrete-time quaternion stochastic systems measured by multiple sensors and it allows us to provide filtering, prediction and smoothing algorithms for estimating the quaternion state through a widely linear processing. Simulation results are employed to show the superior performance of such algorithms in comparison to standard widely linear methods when mixed uncertainties are present in the observations.  相似文献   
407.
408.
409.
There is interest in the accuracy and inter-unit reliability of position-tracking systems to monitor players. Research into this technology, although relatively recent, has grown exponentially in the last years, and it is difficult to find professional team sport that does not use Global Positioning System (GPS) technology at least. The aim of this study is to know the accuracy of both GPS-based and Ultra Wide Band (UWB)-based systems on a soccer field and their inter- and intra-unit reliability. A secondary aim is to compare them for practical applications in sport science. Following institutional ethical approval and familiarization, 10 healthy and well-trained former soccer players (20?±?1.6 years, 1.76?±?0.08?cm, and 69.5?±?9.8?kg) performed three course tests: (i) linear course, (ii) circular course, and (iii) a zig–zag course, all using UWB and GPS technologies. The average speed and distance covered were compared with timing gates and the real distance as references. The UWB technology showed better accuracy (bias: 0.57–5.85%), test–retest reliability (%TEM: 1.19), and inter-unit reliability (bias: 0.18) in determining distance covered than the GPS technology (bias: 0.69–6.05%; %TEM: 1.47; bias: 0.25) overall. Also, UWB showed better results (bias: 0.09; ICC: 0.979; bias: 0.01) for mean velocity measurement than GPS (bias: 0.18; ICC: 0.951; bias: 0.03).  相似文献   
410.
The aims of this study were: (1) to observe participation in moderate-to-vigorous physical activity (MVPA) during school recess periods; (2) to determine the relative importance of physical activity during recesses to overall daily physical activity; and (3) to examine differences in physical activity between the sexes during unstructured recess periods. The participants were 22 school children (10 boys, 12 girls) aged 8 - 10 years (mean = 8.9, s = 0.7) in the third and fourth grades. Daily totals for the physical activity variables were calculated by summing the values for each hour of 14 h of physical activity measurements (08:00 to 22:00 h). Recess times (minutes) were as follows: morning 10:30 to 11:00 h and afternoon 15:30 to 16:00 h. We did not differences between boys and girls in daily total accelerometer counts or the overall time spent in MVPA. However, girls were significantly (P < 0.05) more involved (38%) in MVPA during recess time than boys (31%). Participation in MVPA during recess contributes significantly more (P < 0.05) for girls (19%) than boys (15%) to the total amount of physical activity suggested by international health-related physical activity guidelines, while the percentage of time engaged in MVPA during recess time at school accounts for a small amount of the daily MVPA (6% for boys and 8% for girls). The results of this study suggest that school recess time is an important setting to promote MVPA and contributes to daily physical activity in young children, especially in girls.  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