全文获取类型
收费全文 | 45092篇 |
免费 | 1782篇 |
国内免费 | 24篇 |
专业分类
46898篇 |
出版年
2020年 | 454篇 |
2019年 | 568篇 |
2018年 | 796篇 |
2017年 | 826篇 |
2016年 | 821篇 |
2015年 | 619篇 |
2014年 | 715篇 |
2013年 | 3414篇 |
2012年 | 1292篇 |
2011年 | 1359篇 |
2010年 | 901篇 |
2009年 | 877篇 |
2008年 | 1230篇 |
2007年 | 1194篇 |
2006年 | 1089篇 |
2005年 | 961篇 |
2004年 | 880篇 |
2003年 | 871篇 |
2002年 | 859篇 |
2001年 | 1713篇 |
2000年 | 1691篇 |
1999年 | 1207篇 |
1998年 | 515篇 |
1997年 | 448篇 |
1996年 | 435篇 |
1995年 | 419篇 |
1992年 | 1001篇 |
1991年 | 973篇 |
1990年 | 958篇 |
1989年 | 852篇 |
1988年 | 826篇 |
1987年 | 824篇 |
1986年 | 771篇 |
1985年 | 825篇 |
1984年 | 683篇 |
1983年 | 545篇 |
1982年 | 432篇 |
1979年 | 651篇 |
1978年 | 495篇 |
1977年 | 452篇 |
1975年 | 575篇 |
1974年 | 618篇 |
1973年 | 678篇 |
1972年 | 543篇 |
1971年 | 482篇 |
1970年 | 435篇 |
1969年 | 477篇 |
1968年 | 574篇 |
1967年 | 497篇 |
1966年 | 517篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
201.
High-resolution CRT displays are subject togeometric distortion: lines that are straight in the internal coordinates of the graphics software and hardware are curved when projected onto a plane in the observer’s line of sight. As the available resolution of CRT screens increases, it becomes more difficult to measure and correct for this distortion. We present a simple, highly accurate method for determining the mapping between internal coordinates and the viewing plane. It requires that an observer, using a calibration program, adjust triples of displayed points until they are collinear. A metal straightedge placed between the observer and the screen aids in this judgment. We describe the calibration of an IBM Enhanced Graphics Display in high-resolution mode (350 × 640 pixels), and illustrate how to use the estimated mapping to choose internal coordinates to draw undistorted figures that are accurate to within 0.5 pixel. The method can be used to assess or to correct the accuracy of visual displays. The method is relevant to experiments in spatial vision, spatial perception, perception of dot patterns, and any application in which geometrically accurate stimuli are required. 相似文献
202.
A computer-controlled system that detects spontaneous activity (locomotion and rearing) and diurnal activity rhythms in small animals is described. Automatic recording of subtotals during test periods provides data about habituation (nonassociative learning). The system is relatively inexpensive to construct. Fabricated from highly reliable circuit components, it provides replicable measures that enable comparisons between different experimental treatments to be made using parametric statistics. 相似文献
203.
Robert S. Burke 《Behavior research methods》1988,20(2):171-174
A technical issue in auditory spatial attention research is how best to provide low-cost, accurate control of the frequency, duration, and location of acoustic signals. Three solutions to the problem are compared: use of the internal oscillator of the Apple lIe, use of a Mountain A/D+D/A card, and use of an external oscillator chip. The unique advantages and drawbacks of each system are discussed. All share some common problems of external speaker interface, timing control, and interface with the software. Hardware and software solutions implemented on the Apple-Psych system are discussed, along with data that demonstrate the precision control achieved with the system. 相似文献
204.
Daniel S. Lordahl 《Behavior research methods》1988,20(2):221-223
Difficulties with the Microsoft BASIC function for generating random numbers (RND) are cited and new problems reported. Fixes are suggested that allow use of some of the speed of the original function and that produce greatly improved pseudorandom numbers. A published generator is combined with the RND function as a compromise solution. 相似文献
205.
206.
Maternal handling and motor development: an intracultural study 总被引:1,自引:0,他引:1
Citing a distinction between informal and formal routines used by mothers in handling their infants, we examined formal handling routines, in which the caregiver acts in a pedagogical manner; these routines are widespread in many non-Western countries. We hypothesised that formal handling serves to facilitate gross motor development during early infancy. To examine this hypothesis, the effects of a Jamaican formal handling routine on a broad range of developmental outcomes was examined. Results showed that the effects were specific to early gross motor development and in particular to postural control along the vertical axis of the body. Information is also provided on other aspects of Jamaican child care. It seems that the handling routine forms part of a folk (developmental) medicine system and may serve not only to promote child health but also as a sort of developmental neurological examination. 相似文献
207.
Two projective techniques were employed to explore the psychological characteristics of teenage mothers who were found, in a previous study, to have experienced more traumatic childhoods than the nonmother control group. Part I, presented here, investigated ego development using the Loevinger Sentence Completion Test. (Part II, responses to a set of TAT cards, will appear in a subsequent issue of Adolescence.) In comparison with the nonmothers, teenage mothers demonstrated more mature ego development. This is in distinct contrast with most reports in the literature, and the ramifications of these results are discussed. In addition, content analyses of the responses to the Sentence Completion Test confirm the highly involved mother-daughter and negative father-daughter relationships found in the previous study with this sample. 相似文献
208.
This paper deals with girls aged 13 to 21 who have run away from home. Social workers who work with such girls point out that they are not a homogeneous population and that their motives can be very different. This study divides their motives for running away into two types, "running from" and "running to," and describes the specific personality traits associated with each. Findings indicate that girls who "run to" are younger, more impulsive, have an internal locus of control and a history of more runaways and longer periods of staying away from home. Girls who "run from," on the other hand, are older, more reflective, have an external locus of control and a history of fewer runaways and shorter periods away from home. 相似文献
209.
210.