全文获取类型
收费全文 | 497篇 |
免费 | 5篇 |
专业分类
教育 | 345篇 |
科学研究 | 35篇 |
各国文化 | 10篇 |
体育 | 32篇 |
文化理论 | 6篇 |
信息传播 | 74篇 |
出版年
2020年 | 10篇 |
2019年 | 10篇 |
2018年 | 10篇 |
2017年 | 10篇 |
2016年 | 18篇 |
2015年 | 13篇 |
2014年 | 12篇 |
2013年 | 142篇 |
2012年 | 13篇 |
2011年 | 12篇 |
2010年 | 9篇 |
2009年 | 12篇 |
2008年 | 5篇 |
2007年 | 12篇 |
2006年 | 12篇 |
2005年 | 9篇 |
2003年 | 7篇 |
2002年 | 8篇 |
2001年 | 5篇 |
2000年 | 11篇 |
1999年 | 4篇 |
1998年 | 5篇 |
1997年 | 7篇 |
1996年 | 6篇 |
1995年 | 3篇 |
1994年 | 7篇 |
1993年 | 10篇 |
1992年 | 4篇 |
1991年 | 5篇 |
1990年 | 5篇 |
1989年 | 5篇 |
1988年 | 5篇 |
1987年 | 3篇 |
1986年 | 3篇 |
1985年 | 4篇 |
1984年 | 13篇 |
1983年 | 4篇 |
1982年 | 3篇 |
1981年 | 3篇 |
1979年 | 4篇 |
1978年 | 5篇 |
1977年 | 5篇 |
1976年 | 4篇 |
1973年 | 3篇 |
1971年 | 3篇 |
1970年 | 3篇 |
1966年 | 3篇 |
1920年 | 2篇 |
1912年 | 2篇 |
1885年 | 2篇 |
排序方式: 共有502条查询结果,搜索用时 31 毫秒
21.
Christopher R. Phaneuf Nikita Pak D. Curtis Saunders Gregory L. Holst Joav Birjiniuk Nikita Nagpal Stephen Culpepper Emily Popler Andi L. Shane Robert Jerris Craig R. Forest 《Biomicrofluidics》2015,9(4)
Amplification of multiple unique genetic targets using the polymerase chain reaction (PCR) is commonly required in molecular biology laboratories. Such reactions are typically performed either serially or by multiplex PCR. Serial reactions are time consuming, and multiplex PCR, while powerful and widely used, can be prone to amplification bias, PCR drift, and primer-primer interactions. We present a new thermocycling method, termed thermal multiplexing, in which a single heat source is uniformly distributed and selectively modulated for independent temperature control of an array of PCR reactions. Thermal multiplexing allows amplification of multiple targets simultaneously—each reaction segregated and performed at optimal conditions. We demonstrate the method using a microfluidic system consisting of an infrared laser thermocycler, a polymer microchip featuring 1 μl, oil-encapsulated reactions, and closed-loop pulse-width modulation control. Heat transfer modeling is used to characterize thermal performance limitations of the system. We validate the model and perform two reactions simultaneously with widely varying annealing temperatures (48 °C and 68 °C), demonstrating excellent amplification. In addition, to demonstrate microfluidic infrared PCR using clinical specimens, we successfully amplified and detected both influenza A and B from human nasopharyngeal swabs. Thermal multiplexing is scalable and applicable to challenges such as pathogen detection where patients presenting non-specific symptoms need to be efficiently screened across a viral or bacterial panel. 相似文献
22.
John Andrew Sampson Hugh Head Kelsham Fullagar Tim Gabbett 《Journal of sports sciences》2015,33(1):85-98
This investigation examines pacing during intermittent team sports. Sixteen junior Rugby League players participated in eight different small-sided offside touch games. All games were 24 min, but bout durations differed in continuous (1 × 24 min) or repeated (2 × 12, 3 × 8, 4 × 6, 6 × 4, 8 × 3, 12 × 2 or 24 × 1 min) formats. Repeat bouts were interspersed by 2 min of passive rest, and participants were informed of the bout duration immediately prior to the game. Heart rates, ratings of perceived exertion and data gathered from global positioning system devices were used to investigate the pacing strategies employed within each game. No significant (P > 0.05) between-game differences were observed in total distance; however, during the 1-min bouts, high-speed movement was significantly (P < 0.05) increased, during the first and second quarters of the 24 × 1-min game compared to all other formats (effect size range: 0.75 ± 0.61–1.38 ± 0.47). Furthermore, the rate of decline in high-speed movement over-time was greatest during the 24 × 1-min game with large differences observed between the first and third quarters (effect size: 0.90 ± 0.58). Greater moderate-speed (effect size range: 0.62 ± 0.63–1.56 ± 0.40) and less low-speed (effect size range: 0.69 ± 0.62–1.54 ± 0.40) distances were also observed during the 1-min bouts, yet heart rates were higher during the continuous 1 × 24-min game. Pacing strategies during intermittent activities are influenced by the number and duration of exercise bouts. Practitioners should consider within-game bout durations when prescribing game-based activities to improve aerobic capacity. 相似文献
23.
The aim of the present study is to conduct a systematic review research which focuses on research studies into the school practicum. In order to identify the main issues and also to provide a contemporary picture of practicum, 114 studies published on the topic are reviewed and analysed in terms of: (i) aims, (ii) main participants, (iii) methodology used and (iv) the main outcomes emerging. Many of the reviewed studies take pre-service teachers as their main participants. The review also shows that many practicum studies are relatively small-scale studies since they are mainly qualitative focused and findings derived from a relatively small sample. This suggests that more large-scale studies are needed in the field in order to provide greater insight into teaching practicum. Finally, this systematic review provides some food for thought in the area of practicum research and promotes further studies in this complex field. 相似文献
24.
25.
Can we train people to detect deception? It is the contention of this article that communication scholars should learn how to train law enforcement professionals on how to detect high stake lies, like those faced by police, judges, customs officials, immigration officials, and so forth. It is proposed that in order to know whether we can train or should bother to train people to detect deception, each training study must meet 6 challenges: (1) relevance, (2) high stakes, (3) proper training, (4) proper testing, (5) generalizability across situations, and (6) generalizability over time. Our quantitative review of the literature suggests that training does significantly raise lie detection accuracy rates. Meta-analytic findings indicate a mean effect size of r = .20 across 20 (11 published studies) paired comparisons of lie detection training versus the control group (i.e., those without some type of training). It should be noted that the majority of the studies that attempt to train lie detectors fall short on many of the above challenges. Current research in lie detection training may actually underestimate the ability to train lie detectors due to the stimulus materials employed in most experiments. 相似文献
26.
27.
Kevin King N. C. Perkins Hugh Churchill Ryan McGinnis Ryan Doss Ron Hickland 《Sports Engineering》2011,13(2):95-104
This paper presents a novel sensor technology to deduce the dynamics of a bowling ball. The sensor, a miniature wireless inertial
measurement unit (IMU), incorporates MEMS accelerometers and angular rate gyros, a microcontroller, a low power RF transceiver,
and a rechargeable battery. When embedded in a bowling ball, the IMU transmits the acceleration and angular velocity data
that define the dynamics of the ball starting with the bowler’s delivery and its motion in the lane. Example results from
professional bowlers illustrate how this technology can be used to assess bowler skill and ball performance. For instance,
the IMU accurately measures the spin dynamics of the ball which are crucial to develop the ball “hook.” An analysis of ball
dynamics in the lane is distilled to a measurable “hook potential” metric for further assessing bowler skill. Finally, the
sensor presented herein is believed to be the world’s smallest, wireless IMU. This highly miniaturized and wireless design
will enable parallel training systems for many sports, including basketball, baseball, crew, cricket, golf, fly fishing, soccer,
softball, tennis, rowing, among others. 相似文献
28.
Jay A. Bostwick Isaac Wade Calvert Jenifer Francis Melissa Hawkley Curtis R. Henrie Frederick R. Hyatt Janeel Juncker Andrew S. Gibbons 《Educational technology research and development : ETR & D》2014,62(5):571-582
Some have argued for a common language in the field of instructional design in an effort to reduce misunderstandings and simplify a multitude of synonymous terms and concepts. Others feel that this goal is undesirable in that it precludes development and flexibility. In this article we propose an ontology-building process as a way for readers to compare and analyze terms and concepts across theories. This process entails the development of categories that emerge from the literature, and the comparison of theories across categories. Such a process can reveal broader concepts that exist beyond specific theoretical terminology, differences in meanings behind common terms used by theorists, a greater understanding of the theorists’ intent, and discontinuities and gaps within the theoretical literature. 相似文献
29.
30.