全文获取类型
收费全文 | 45983篇 |
免费 | 1748篇 |
国内免费 | 22篇 |
专业分类
47753篇 |
出版年
2019年 | 600篇 |
2018年 | 786篇 |
2017年 | 811篇 |
2016年 | 801篇 |
2015年 | 586篇 |
2014年 | 715篇 |
2013年 | 3577篇 |
2012年 | 1241篇 |
2011年 | 1399篇 |
2010年 | 881篇 |
2009年 | 904篇 |
2008年 | 1243篇 |
2007年 | 1209篇 |
2006年 | 1126篇 |
2005年 | 951篇 |
2004年 | 914篇 |
2003年 | 924篇 |
2002年 | 883篇 |
2001年 | 1562篇 |
2000年 | 1577篇 |
1999年 | 1127篇 |
1998年 | 554篇 |
1997年 | 441篇 |
1996年 | 446篇 |
1995年 | 439篇 |
1994年 | 437篇 |
1992年 | 945篇 |
1991年 | 930篇 |
1990年 | 915篇 |
1989年 | 854篇 |
1988年 | 801篇 |
1987年 | 784篇 |
1986年 | 760篇 |
1985年 | 834篇 |
1984年 | 640篇 |
1983年 | 558篇 |
1979年 | 681篇 |
1978年 | 537篇 |
1977年 | 469篇 |
1976年 | 439篇 |
1975年 | 605篇 |
1974年 | 640篇 |
1973年 | 715篇 |
1972年 | 588篇 |
1971年 | 515篇 |
1970年 | 452篇 |
1969年 | 511篇 |
1968年 | 610篇 |
1967年 | 564篇 |
1966年 | 583篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
881.
Factor analysis by generalized least squares 总被引:1,自引:0,他引:1
Aitken's generalized least squares (GLS) principle, with the inverse of the observed variance-covariance matrix as a weight matrix, is applied to estimate the factor analysis model in the exploratory (unrestricted) case. It is shown that the GLS estimates are seale free and asymptotically efficient. The estimates are computed by a rapidly converging Newton-Raphson procedure. A new technique is used to deal with Heywood cases effectively.The work on this project was done when the first author was Research Statistician at Educational Testing Service, Princeton, N. J. The second author was in part supported by a grant from the Research Committee of the University of Wisconsin Graduate School. The authors wish to thank Michael Browne for many helpful comments and Marielle van Thillo for valuable assistance in the numerical computations. 相似文献
882.
883.
884.
David S. Emmerich James L. Gray Charles S. Watson David C. Tanis 《Attention, perception & psychophysics》1972,11(1):65-72
Response latencies were obtained from 10 Ss in auditory signal-detection experiments. The response latencies were inversely related to certainty that a signal was (or was not) presented. The S’s decision criterion was found to have an influence on response latency, which was consistent with the hypothesis that stimuli close to the current criterion elicit longer response latencies than stimuli more distant from the criterion. Comparisons among receiver operating characteristics derived from binary decisions, from the latencies of binary decisions, and from confidence ratings show that response latencies and binary decisions together yield more information about the stimulus than does the binary decision alone. However, the increment in information gained from the measurement of response latencies is in general (though not for every S) smaller than that gained by shifting from yes-no responses to a confidence-rating procedure. 相似文献
885.
John S. Monahan 《Attention, perception & psychophysics》1972,12(4):349-353
The effect of saccades on visual localization was tested before, during, and after the eye movements. After saccades, localization errors were much less than the distance that the eyes had moved. It is argued that these results demonstrate that extraretinal feedback affects visual localization. The results also suggest that the feedback is related to acceleration rather than to position. Implications for inflow and outflow theories are discussed. 相似文献
886.
Herbert L. Meiselman Harry E. Bose William F. Nykvist 《Attention, perception & psychophysics》1972,12(2):249-252
Magnitude productions of sodium chloride (salty), quinine hydrochloride (bitter), and sucrose (sweet) yielded steeper psychophysical functions than those obtained with magnitude estimation. Hydrochloric acid (sour) produced the opposite effect. The results are discussed with respect to previous findings in taste intensity scaling and to general psychophysical considerations. 相似文献
887.
The yes-no signal detection procedure was applied to a single-response operant paradigm in which rats discriminated between a standard auditory intensity and attenuated comparison values. The payoff matrix was symmetrical (with reinforcing brain stimulation for correct detections and brief time-out for errors), but signal probability and intensity differences were varied to generate a family of isobias and isosensitivity functions. The d’ parameter remained fairly constant across a wide range of bias levels. Isobias functions deviated from a strict matching strategy as discrimination difficulty increased, although an orderly relation was maintained between signal probability value and the degree and direction of response bias. 相似文献
888.
Inverse relation between choice and local response rate with a schedule of response-produced blackouts 下载免费PDF全文
Arnett FB 《Journal of the experimental analysis of behavior》1972,17(1):37-43
Pigeons were exposed to a two-key concurrent chains schedule in which identical frequencies and distributions of food presentations generated different response rates in the terminal links. An inverse relation between local rate of response in the terminal links and relative frequency of response in the initial links was observed. The high response rate was produced in one terminal link by a second-order schedule in which responding produced brief blackouts of the response key. Responding under the same schedule in the other terminal link did not produce blackouts. Under initial training and after spatial reversal of the terminal-link schedules, two of three pigeons had lower relative frequencies of response in the initial member of the chain with the higher terminal link response rate. The third pigeon showed no change in preference at reversal. 相似文献
889.
890.
Rats were trained to press a lever under schedules of food postponement. In the absence of lever presses, food was delivered periodically (food-food interval). Responses initiated a second interval (response-food interval) that was reset by each additional response. Performance was first studied at different response-food intervals with the food-food interval fixed at 30 or 60 sec, or 10 min. Response-food intervals were examined in ascending order and then recovery was studied at shorter intervals. Finally, the food-food interval was manipulated with response-food interval fixed at 30 sec. At food-food intervals of 30 and 60 sec, responding first increased and then decreased as the response-food interval increased. At the 10-min food-food interval, responding decreased with increasing response-food interval. In general, very low rates of responding occurred when the response-food interval was 60 sec or more and when it equalled or exceeded the food-food interval. However, responding was maintained in one animal when the food-food interval was decreased from 120 to 15 sec with the response-food interval at 30 sec. Results, in terms of several dependent variables, are compared with data on shock avoidance. Effects of response-independent and response-produced food and shock are discussed. 相似文献