全文获取类型
收费全文 | 9575篇 |
免费 | 366篇 |
国内免费 | 4篇 |
出版年
2021年 | 97篇 |
2020年 | 149篇 |
2019年 | 133篇 |
2018年 | 206篇 |
2017年 | 209篇 |
2016年 | 257篇 |
2015年 | 184篇 |
2014年 | 225篇 |
2013年 | 976篇 |
2012年 | 402篇 |
2011年 | 411篇 |
2010年 | 259篇 |
2009年 | 251篇 |
2008年 | 356篇 |
2007年 | 366篇 |
2006年 | 325篇 |
2005年 | 351篇 |
2004年 | 324篇 |
2003年 | 304篇 |
2002年 | 312篇 |
2001年 | 156篇 |
2000年 | 113篇 |
1999年 | 160篇 |
1998年 | 153篇 |
1997年 | 139篇 |
1996年 | 126篇 |
1995年 | 115篇 |
1994年 | 108篇 |
1993年 | 114篇 |
1992年 | 118篇 |
1991年 | 117篇 |
1990年 | 102篇 |
1989年 | 93篇 |
1988年 | 83篇 |
1987年 | 89篇 |
1986年 | 89篇 |
1985年 | 96篇 |
1984年 | 108篇 |
1983年 | 103篇 |
1982年 | 108篇 |
1981年 | 111篇 |
1980年 | 108篇 |
1979年 | 104篇 |
1978年 | 113篇 |
1977年 | 105篇 |
1976年 | 103篇 |
1975年 | 88篇 |
1974年 | 102篇 |
1973年 | 73篇 |
1968年 | 66篇 |
排序方式: 共有9945条查询结果,搜索用时 15 毫秒
871.
872.
873.
874.
875.
A unified fielder theory is presented that explains how humans navigate to intercept targets that approach from either above
or below the horizon. Despite vastly different physical forces affecting airborne and ground-based moving targets, a common
set of invariant perception-action principles appears to guide pursuers. When intercepting airborne projectiles, fielders
keep the target image rising at a constant optical speed in a vertical image plane and moving in a constant optical direction
in an image plane that remains perpendicular to gaze direction. We confirm that fielders use the same strategies to intercept
grounders. Fielders maintained a cotangent of gaze angle that decreases linearly with time (accounting for 98.7% of variance
in ball speed) and a linear optical trajectory along an image plane that remains perpendicular to gaze direction (accounting
for 98.2% of variance in ball position). The universality of maintaining optical speed and direction for both airborne and
ground-based targets supports the theory that these mechanisms are domain independent. 相似文献
876.
Spatial updating relies on an egocentric representation of space: Effects of the number of objects 总被引:1,自引:0,他引:1
Wang RF Crowell JA Simons DJ Irwin DE Kramer AF Ambinder MS Thomas LE Gosney JL Levinthal BR Hsieh BB 《Psychonomic bulletin & review》2006,13(2):281-286
Models of spatial updating attempt to explain how representations of spatial relationships between the actor and objects in
the environment change as the actor moves. In allocentric models, object locations are encoded in an external reference frame,
and only the actor’s position and orientation in that reference frame need to be updated. Thus, spatial updating should be
independent of the number of objects in the environment (set size). In egocentric updating models, object locations are encoded
relative to the actor, so the location of each object relative to the actor must be updated as the actor moves. Thus, spatial
updating efficiency should depend on set size. We examined which model better accounts for human spatial updating by having
people reconstruct the locations of varying numbers of virtual objects either from the original study position or from a changed
viewing position. In consistency with the egocentric updating model, object localization following a viewpoint change was
affected by the number of objects in the environment. 相似文献
877.
878.
879.
OBJECTIVE: According to the American Psychiatric Association, 3% to 7% of the school-age population has ADHD and many children continue to display significant symptoms throughout adolescences and adulthood. Relative to the childhood literature, less is known about ADHD in adults, especially college students with ADHD. The principle purpose of this review articles is to summarize the major research findings concerning ADHD in the college student population with regard to prevalence of symptoms, neuropsychological and psychological functioning. Overall, findings suggest that college students with ADHD are at greater risk for academic and psychological difficulties, and they perform similar to non-ADHD controls on many neuropsychological tasks. These findings are preliminary, however, and are tempered by the small number of studies that have been conducted as well as the methodological limitations of these studies. CONCLUSION: Future research using larger sample sizes, rigorous assessment criteria, and a longitudinal design is needed to better understand the psychological, academic, and neuropsychological functioning of college students with ADHD. Studies are also needed to elucidate the effects of pharmacological and nonpharmacological effects of treatment on the functioning of college students with this disorder. 相似文献
880.
Treatment and rehabilitation of the cognitive, psychological, and motor sequelae of central nervous system dysfunction often relies on assessment instruments to inform diagnosis and to track changes in clinical status. Typically, these assessments employ paper-and-pencil psychometrics, hands-on analog/computer tests, and rating of behavior within the context of real-world functional environments. Virtual reality offers the option to produce and distribute identical "standard" simulation environments in which performance can be measured and rehabilitated. Within such digital scenarios, normative data can be accumulated for performance comparisons needed for assessment/diagnosis and for treatment/rehabilitation purposes. In this manner, reusable archetypic virtual environments constructed for one purpose can also be applied for applications addressing other clinical targets. This article will provide a review of such a retooling approach using a virtual classroom simulation that was originally developed as a controlled stimulus environment in which attention processes could be systematically assessed in children with attention-deficit/hyperactivity disorder. This system is now being applied to other clinical targets including the development of tests that address other cognitive functions, eye movement under distraction conditions, social anxiety disorder, and the creation of an earthquake safety training application for children with developmental and learning disabilities. 相似文献