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   1198篇
  免费   16篇
教育   910篇
科学研究   66篇
各国文化   26篇
体育   98篇
综合类   1篇
文化理论   14篇
信息传播   99篇
  2023年   6篇
  2022年   9篇
  2020年   33篇
  2019年   24篇
  2018年   38篇
  2017年   40篇
  2016年   34篇
  2015年   26篇
  2014年   28篇
  2013年   274篇
  2012年   24篇
  2011年   32篇
  2010年   38篇
  2009年   27篇
  2008年   27篇
  2007年   25篇
  2006年   20篇
  2005年   18篇
  2004年   18篇
  2003年   21篇
  2002年   25篇
  2001年   13篇
  2000年   21篇
  1999年   14篇
  1998年   12篇
  1997年   10篇
  1996年   9篇
  1995年   14篇
  1994年   24篇
  1993年   7篇
  1992年   14篇
  1991年   13篇
  1990年   21篇
  1989年   14篇
  1987年   10篇
  1986年   9篇
  1985年   16篇
  1984年   16篇
  1983年   10篇
  1982年   11篇
  1981年   13篇
  1980年   13篇
  1979年   16篇
  1978年   11篇
  1977年   13篇
  1975年   6篇
  1974年   6篇
  1973年   8篇
  1971年   8篇
  1968年   10篇
排序方式: 共有1214条查询结果,搜索用时 15 毫秒
71.
How do public libraries develop their collections of high-demand materials for the “I want it now” generation? Ten public libraries’ holdings of fiction and nonfiction bestseller titles were observed over a four-week period. The number of copies rose fairly consistently, with the five fiction titles having roughly about twice the number of copies as the five nonfiction titles. The ratio of holds to copies averaged 2.7:1 and ranged from 0.8:1 to 6.5:1. Demand for e-books was consistently higher than the number of copies available, averaging more than 4:1 across all libraries.  相似文献   
72.
73.
74.
This study compares the instrumentation and analysis techniques used when determining the power expended pedalling a rope-braked ergometer manufactured by Monark (Sweden) during a low intensity test. Power values were generated by eight subjects. The instrumentation consisted of load cells to measure the rope brake forces, a tachometer to measure the flywheel velocity and instrumented pedal cranks manufactured by Schoberer Rad Messtechnik (SRM). The subjects pedalled a rope-braked ergometer at 60 rev min-1, against a resistance of 3 kg, for 5 minutes. Three different measurements of the mean power were recorded and these were compared with the value given by Monark. The SRM cranks provided two sets of results using different software packages supplied with the cranks. SRM standard software is used for taking measurements during training and cycle races over long time periods. An additional piece of software is provided by SRM called Ptnew, which gives readings of torque and pedal cadence over periods up to 30 seconds. Using the values supplied by Monark each subject generated 180 W of power. The mean power for the eight subjects, measured using the SRM cranks, was 170.36 W (SD 4.11) using the alternative SRM software (Ptnew) over a 30 second period and 173.68 W (SD 2.21) using the standard SRM software. From the direct measurement of the brake forces and flywheel velocity the mean power across the eight subjects was 148.90 W (SD 5.89). The SRM cranks measure the input power, whereas the direct measurement system measures the power output excluding mechanical losses. These values give a figure for the mechanical efficiency for the roped-braked ergometer of 88%. It was found that Monark overestimates the power generated by the subjects when compared with both the SRM systems and the direct measurement instrumentation.  相似文献   
75.
Measurement of ground reaction force (GRF) in running provides a direct indication of the loads to which the body is subjected at each foot-ground contact, and can provide an objective explanation for performance outcomes. Traditionally, the collection of three orthogonal component GRF data in running requires an athlete to complete a series of return loops along a laboratory based runway, within which a force platform is embedded, in order to collect data from a discrete footfall. The major disadvantages associated with this GRF data collection methodology include the inability to assess multiple consecutive foot contacts and the fact that measurements are typically confined to the laboratory. The objective of this research was to investigate the potential for wearable instrumentation to be employed, in conjunction with artificial neural network (ANN) and multiple linear regression (MLR) models, for the estimation of GRF in middle distance running. A modular wearable data acquisition system was developed to acquire in-shoe force (ISF) data. Matched data sets from wearable instrumentation (source data) and force plate (target data) records were collected from elite middle-distance runners under controlled laboratory conditions for the purposes of ANN and MLR model development (MD) and model validation (MV). In terms of statistical measures of prediction accuracy the MLR model was found to provide a superior level of accuracy for the prediction of the vertical and medio-lateral components of GRF and alternatively, the ANN model provided the most accurate predictions of the anterior-posterior component of GRF. The prediction accuracy of each component of GRF was found to be governed by the inherent signal variability, in which case the vertical and anterior-posterior components were more reliable and subsequently predicted significantly more accurately than the medio-lateral component. The emerging capability for obtaining continuous GRF records from wearable instrumentation has the potential to permit unprecedented quantification of training stress and competition demands in running.  相似文献   
76.
77.
Although the topic of research collaboration receives infrequent comment, a well functioning collaborative process is crucial to the substantive success of intercultural research enterprises. The present report addresses this topic and focuses on two major sets of collaborative issues, the personal/ personnel and the structural/organizational. The issues are organized around the phases of the project at which they optimally should be considered and resolved.  相似文献   
78.
79.
80.
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