全文获取类型
收费全文 | 167265篇 |
免费 | 7714篇 |
国内免费 | 155篇 |
出版年
2021年 | 1513篇 |
2020年 | 2808篇 |
2019年 | 3480篇 |
2018年 | 3500篇 |
2017年 | 3950篇 |
2016年 | 4635篇 |
2015年 | 3934篇 |
2014年 | 4816篇 |
2013年 | 23491篇 |
2012年 | 4451篇 |
2011年 | 3501篇 |
2010年 | 3816篇 |
2009年 | 4748篇 |
2008年 | 3647篇 |
2007年 | 3173篇 |
2006年 | 3842篇 |
2005年 | 3811篇 |
2004年 | 3350篇 |
2003年 | 2957篇 |
2002年 | 2764篇 |
2001年 | 3146篇 |
2000年 | 3013篇 |
1999年 | 3018篇 |
1998年 | 2804篇 |
1997年 | 2648篇 |
1996年 | 2561篇 |
1995年 | 2405篇 |
1994年 | 2362篇 |
1993年 | 2328篇 |
1992年 | 2470篇 |
1991年 | 2305篇 |
1990年 | 2164篇 |
1989年 | 2108篇 |
1988年 | 2079篇 |
1987年 | 2099篇 |
1986年 | 2089篇 |
1985年 | 2285篇 |
1984年 | 2417篇 |
1983年 | 2230篇 |
1982年 | 2332篇 |
1981年 | 2303篇 |
1980年 | 2136篇 |
1979年 | 2047篇 |
1978年 | 2113篇 |
1977年 | 2097篇 |
1976年 | 1876篇 |
1975年 | 1891篇 |
1974年 | 1950篇 |
1973年 | 1756篇 |
1972年 | 1407篇 |
排序方式: 共有10000条查询结果,搜索用时 109 毫秒
901.
Three experiments were performed to examine the role that central and peripheral vision play in the perception of the direction of translational self-motion, or heading, from optical flow. When the focus of radial outflow was in central vision, heading accuracy was slightly higher with central circular displays (10 degrees-25 degrees diameter) than with peripheral annular displays (40 degrees diameter), indicating that central vision is somewhat more sensitive to this information. Performance dropped rapidly as the eccentricity of the focus of outflow increased, indicating that the periphery does not accurately extract radial flow patterns. Together with recent research on vection and postural adjustments, these results contradict the peripheral dominance hypothesis that peripheral vision is specialized for perception of self-motion. We propose a functional sensitivity hypothesis--that self-motion is perceived on the basis of optical information rather than the retinal locus of stimulation, but that central and peripheral vision are differentially sensitive to the information characteristic of each retinal region. 相似文献
902.
Variation of amplitude envelope at stimulus onset has been considered to be of primary importance for distinguishing voiceless affricates from fricatives (e.g., [symbol: see text]). In earlier perceptual experiments, however, variation in amplitude rise time was confounded with variation in frication duration. In two experiments, these variables were independently manipulated, and their individual and combined effects for perception of magnitude of [symbol: see text] were examined. Variation in amplitude rise time alone was not sufficient to signal the voiceless affricate/fricative contrast in these experiments, but variation in frication duration alone was sufficient. 相似文献
903.
This investigation was conducted to examine whether older adults would improve their performance when given statements intended to make them feel important to a research study as well as statements concerning their over-all well-being. Women (n = 14) and men (n = 15) with mean ages of 76.0 yr. and 75.1 yr., respectively, were randomly assigned into a control group, a positive reinforcement group, and a group given statements of personal importance. Dependent measures on a rotary pursuit task, screw-and-nut assembly task, and an interest questionnaire were obtained during three separate visits. Data were analyzed with a 3 x 3 (Groups x Days) analysis of variance. While no significant group effects were found on any measure, a significant main effect was obtained for days, indicative of learning. 相似文献
904.
A soft contact-lens system for achieving unilateral visual stimulation in a free vision format is described. Initial testing with light transmittance and visual perimetry indicated that the lenses created artificial visual-field deficits. The efficacy of the lenses as a technique for lateralizing visual input was evaluated by examining within-subject differences in performance on two visuospatial tasks. Speed and accuracy of performance were greater with visual input directed to the right hemisphere. These data support the lens design as a useful alternative to tachistoscopic procedures and previous lens systems. 相似文献
905.
The purpose of this study was to investigate differences in function of the tactile sensory system between groups of normal-speaking children and children with articulation problems. This task was accomplished by studying possible tactile threshold shifts occurring during magnitude-estimation scaling of vibratory stimuli presented to the dorsal surface of the tongue. 10 normal-speaking children (M age = 7.8 yr.) and 9 children with articulation problems (M age = 7.5 yr.) participated. The normal-speaking children and articulatory defective children performed differently on the magnitude-estimation scaling task in which threshold was allowed to return to baseline after each stimulus presentation. These two groups of children also showed dissimilar threshold shifts for the suprathreshold intensities employed in the magnitude-estimation scaling. 相似文献
906.
The Profile of Mood States was printed on four different colors of paper (yellow, red, green, blue) and white to test whether the color of paper would influence mood state scores of 246 college students. Univariate analyses of variance identified color effects only on the Fatigue scale. 相似文献
907.
This paper suggests a method to supplant missing categorical data by reasonable replacements. These replacements will maximize the consistency of the completed data as measured by Guttman's squared correlation ratio. The text outlines a solution of the optimization problem, describes relationships with the relevant psychometric theory, and studies some properties of the method in detail. The main result is that the average correlation should be at least 0.50 before the method becomes practical. At that point, the technique gives reasonable results up to 10–15% missing data.We thank Anneke Bloemhoff of NIPG-TNO for compiling and making the Dutch Life Style Survey data available to use, and Chantal Houée and Thérèse Bardaine, IUT, Vannes, France, exchange students under the COMETT program of the EC, for computational assistance. We also thank Donald Rubin, the Editors and several anonymous reviewers for constructive suggestions. 相似文献
908.
909.
910.
Deborah G. Mayo 《Synthese》1992,90(2):233-262
I document some of the main evidence showing that E. S. Pearson rejected the key features of the behavioral-decision philosophy that became associated with the Neyman-Pearson Theory of statistics (NPT). I argue that NPT principles arose not out of behavioral aims, where the concern is solely with behaving correctly sufficiently often in some long run, but out of the epistemological aim of learning about causes of experimental results (e.g., distinguishing genuine from spurious effects). The view Pearson did hold gives a deeper understanding of NPT tests than their typical formulation as accept-reject routines, against which criticisms of NPT are really directed. The Pearsonian view that emerges suggests how NPT tests may avoid these criticisms while still retaining what is central to these methods: the control of error probabilities.A portion of this research was carried out during tenure of a National Endowment for the Humanities Summer Stipend Fellowship; I gratefully acknowledge that support. A version of this paper was presented at the 1987 meeting of the Society for Exact Philosophy. This paper benefited from discussions and communications with George Barnard and Isaac Levi. I thank Harlan Miller for helpful comments on earlier drafts. 相似文献