全文获取类型
收费全文 | 13423篇 |
免费 | 177篇 |
国内免费 | 21篇 |
专业分类
教育 | 9344篇 |
科学研究 | 1524篇 |
各国文化 | 125篇 |
体育 | 1150篇 |
综合类 | 6篇 |
文化理论 | 98篇 |
信息传播 | 1374篇 |
出版年
2021年 | 138篇 |
2020年 | 195篇 |
2019年 | 267篇 |
2018年 | 367篇 |
2017年 | 350篇 |
2016年 | 356篇 |
2015年 | 238篇 |
2014年 | 314篇 |
2013年 | 2305篇 |
2012年 | 291篇 |
2011年 | 315篇 |
2010年 | 278篇 |
2009年 | 218篇 |
2008年 | 268篇 |
2007年 | 238篇 |
2006年 | 232篇 |
2005年 | 207篇 |
2004年 | 227篇 |
2003年 | 204篇 |
2002年 | 175篇 |
2001年 | 444篇 |
2000年 | 291篇 |
1999年 | 253篇 |
1998年 | 117篇 |
1997年 | 155篇 |
1996年 | 132篇 |
1995年 | 123篇 |
1994年 | 144篇 |
1993年 | 110篇 |
1992年 | 181篇 |
1991年 | 191篇 |
1990年 | 192篇 |
1989年 | 198篇 |
1988年 | 165篇 |
1987年 | 158篇 |
1986年 | 167篇 |
1985年 | 205篇 |
1984年 | 160篇 |
1983年 | 148篇 |
1982年 | 128篇 |
1981年 | 121篇 |
1980年 | 115篇 |
1979年 | 163篇 |
1978年 | 131篇 |
1977年 | 116篇 |
1976年 | 92篇 |
1975年 | 112篇 |
1974年 | 100篇 |
1973年 | 107篇 |
1971年 | 98篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
941.
942.
943.
944.
C.D. Tuska 《Journal of The Franklin Institute》1944,237(2):83-102
The foregoing notes trace the history of the measurement of the propagation times of radio waves as a means for determining distance. While the reader may feel that undue emphasis has been placed upon the KHL height measurements, a survey of the literature will show that only a small proportion of the reported observations have been cited here. Out of the hundreds of published articles on KHL height measurements, the writer has endeavored to select those which present the step-by-step improvements in the methods and apparatus. In the period just prior to the War, the United States Patents offered the principal means for tracing the development of the art. In the war period the notes are necessarily incomplete because of the scarcity of publications; this is no doubt due to secrecy conditions. 相似文献
945.
946.
Abstract A study was made of the relationship of physique and developmental level, determined by use of the Wetzel Grid, to performance of junior high boys on four fitness tests: pull-ups, 50-yd. dash, standing broad jump, and softball throw. Subjects of different physique groups (heavy, medium, and thin) who were alike developmentally (accelerated, normal, and retarded) differed more markedly in performance than did subjects of different developmental levels who were alike with regard to physique. Subjects who were medium in physique and normal in development were the best performers. Subjects of heavy physique (many overweight) were the poorest performers. This would seem to indicate the need for a restudy of classification methods, particularly when norms are to be used for evaluating performance. 相似文献
947.
948.
Abstract Four sprint starting positions—the bunch, medium, elongated, and hyperextended—were compared on mean elapsed times at distances of 10 and 30 yd. Averages of three starts for each of 30 inexperienced college undergraduate males on each type of start were derived from electronically-controlled measures, the times for both distances being recorded from the same start. Statistical analyses indicated significantly lower elapsed times with the hyperextended starting position. 相似文献
949.
Joanne DiFrancisco-Donoghue William G. Werner Peter C. Douris Hallie Zwibel 《运动与健康科学(英文)》2022,11(6):725
BackgroundEsports players, like traditional athletes, practice for long hours and, thus, are vulnerable to the negative health effects of prolonged sitting. There is a lack of research on the physical activity and the health ramifications of prolonged sitting by competitive players. The purpose of this study was to investigate activity levels, body mass index (BMI), and body composition in collegiate esports players as compared to age-matched controls.MethodsTwenty-four male collegiate esports players and non-esports players between 18 and 25 years of age signed a written consent to participate. Physical activity was examined using daily activity (step count) with a wrist-worn activity tracker. A questionnaire assessing physical activity was also administered. Secondary outcomes included body-fat percentage, lean-body mass, BMI, and bone mineral content measured using dual X-ray absorptiometry.ResultsThe step count in the esports players was significantly lower than the age-matched controls (6040.2 ± 3028.6 vs. 12843.8 ± 5661.1; p = 0.004). Esports players exhibited greater body-fat percentage (p = 0.05), less lean body mass (p = 0.003), and less bone mineral content (p = 0.03), despite no difference in BMI between the esports and non-esports players.ConclusionAs compared to non-esports players, collegiate esports players were significantly less active and had a higher body-fat percentage, with lower lean body mass and bone mineral content. The BMIs showed no difference between the 2 groups. Esports athletes displayed significantly less activity and poor body composition, which are all correlated with potential health issues and risk of injury. BMI did not capture this difference and should not be considered as an accurate measure of health in competitive esports players. 相似文献
950.