全文获取类型
收费全文 | 73935篇 |
免费 | 2330篇 |
国内免费 | 21篇 |
专业分类
76286篇 |
出版年
2020年 | 675篇 |
2019年 | 791篇 |
2018年 | 4214篇 |
2017年 | 3638篇 |
2016年 | 3169篇 |
2015年 | 1028篇 |
2014年 | 1098篇 |
2013年 | 4878篇 |
2012年 | 2432篇 |
2011年 | 4034篇 |
2010年 | 3421篇 |
2009年 | 2527篇 |
2008年 | 3186篇 |
2007年 | 3584篇 |
2006年 | 1510篇 |
2005年 | 1431篇 |
2004年 | 1424篇 |
2003年 | 1321篇 |
2002年 | 1212篇 |
2001年 | 1942篇 |
2000年 | 1839篇 |
1999年 | 1353篇 |
1998年 | 633篇 |
1997年 | 543篇 |
1996年 | 613篇 |
1995年 | 549篇 |
1994年 | 542篇 |
1993年 | 526篇 |
1992年 | 1105篇 |
1991年 | 1016篇 |
1990年 | 1002篇 |
1989年 | 957篇 |
1988年 | 934篇 |
1987年 | 862篇 |
1986年 | 857篇 |
1985年 | 903篇 |
1984年 | 729篇 |
1983年 | 627篇 |
1979年 | 758篇 |
1978年 | 562篇 |
1975年 | 601篇 |
1974年 | 679篇 |
1973年 | 701篇 |
1972年 | 604篇 |
1971年 | 561篇 |
1970年 | 483篇 |
1969年 | 479篇 |
1968年 | 609篇 |
1967年 | 530篇 |
1966年 | 506篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
871.
872.
873.
Developmental trends in letter-printing skill 总被引:1,自引:0,他引:1
874.
875.
Evidence for successive serial exhaustive searches was found in a task requiring detection of repeated letters in visually presented lists of varying length. The time per comparison was 25 msec. Important differences in processing appeared between instances of adjacent repeated letters and instances of nonadjacent repeated letters. 相似文献
876.
Patricia M. Blough 《Attention, perception & psychophysics》1972,12(4):342-348
This three-part study describes wavelength generalization gradients around a series of training wavelengths ranging from 480 to 645 om. Luminance was controlled for the pigeon’s spectral sensitivity. The response measure was probability of keypecking during a 2-sec stimulus presentation. Both an extinction procedure, where stimulus wavelengths occurred in 15-nm steps, and a maintained discrimination procedure, where step size was 2 to 4 nm, were used to obtain gradients. During a portion of the maintained discrimination procedure, new luminances were introduced, so that the effect of luminance level on gradient slope could be examined. Comparison of the resulting functions across training wavelengths revealed: (1) consistent differences in gradient slope in different spectral regions and (2) an increase in slope with luminance increase. The findings are related to recent electroretinographic wavelength contrast data and to psychophysical measures of wavelength discriminability. 相似文献
877.
A signal detection analysis of the effects of hearing on the visual recognition of two-digit numbers
A signal detection measure of visual recognition was used to assess the visual recognition of two-digit numbers in three different conditions: (1) voicing of the number as it was presented visually; (2) voicing of a different number than the one presented; and (3) no voicing. The three treatment means were significantly different, with matched voicing resulting in the best performance and no voicing, in the worst. There was no evidence that the treatments differentially affected response criteria. 相似文献
878.
Letters were tachistoscopically presented in pairs to the left or right of fixation for 40 msec. The pair consisted of a target letter (B, D, P, or T) and a noise letter (all other letters of the alphabet except I), with the noise letter appearing either to the inside or the outside of the stimulus letter. S’s task was to report verbally the target letter as fast as possible. Reaction times and number of errors indicated that there was more interference when the noise letter occurred further from the fixation point than the target letter for both the left and right visual field. Since a reading scan cannot account for the results in the right visual field, an outside-toward-fixation scan is proposed. An analysis of the different kinds of errors indicated that the outside to fixation scan is more primitive than the reading scan in that it produces less detailed information about the letters than does the reading scan. 相似文献
879.
J. M. Warren 《Attention, perception & psychophysics》1972,12(6):449-452
Two sets of 32 cats each were matched for performance in learning to discriminate an open and a closed shape and were then trained on a transfer task. The consistent groups were rewarded for choosing the same class of shape (open or closed) in learning and transfer. The inconsistent groups were rewarded for choosing the open figure in one task and the closed figure in the second, or vice versa. After learning the transfer task, all of the Ss relearned the original discrimination task under the same conditions that prevailed in initial training. The inconsistent groups made more errors on both the transfer and retention problems; both these differences were significant at the 0.1% level of confidence. These results and those obtained on preference tests support the hypothesis that cats classify shapes as open or closed in terms of perimeter and number of sides. 相似文献
880.
Morgan MJ 《Journal of the experimental analysis of behavior》1972,17(1):95-98
Four rats were trained on a schedule in which completion of a fixed number of lever presses initiated a signalled delay period, at the end of which food was delivered. Lever presses made during the delay had no scheduled consequences. Delays of 12, 3, and 0.75 sec were used, and it was found that the latency of the first response after food (the post-reinforcement pause) increased with length of delay. There was, on the other hand, no consistent effect of delay upon rates of responding after the post-reinforcement pause. 相似文献