全文获取类型
收费全文 | 34291篇 |
免费 | 1187篇 |
国内免费 | 11篇 |
专业分类
35489篇 |
出版年
2018年 | 460篇 |
2017年 | 515篇 |
2016年 | 563篇 |
2015年 | 404篇 |
2014年 | 504篇 |
2013年 | 2783篇 |
2012年 | 869篇 |
2011年 | 969篇 |
2010年 | 666篇 |
2009年 | 619篇 |
2008年 | 926篇 |
2007年 | 909篇 |
2006年 | 880篇 |
2005年 | 766篇 |
2004年 | 745篇 |
2003年 | 760篇 |
2002年 | 780篇 |
2001年 | 775篇 |
2000年 | 793篇 |
1999年 | 635篇 |
1998年 | 408篇 |
1997年 | 412篇 |
1996年 | 409篇 |
1995年 | 386篇 |
1992年 | 612篇 |
1991年 | 571篇 |
1990年 | 557篇 |
1989年 | 525篇 |
1988年 | 543篇 |
1987年 | 522篇 |
1986年 | 564篇 |
1985年 | 554篇 |
1984年 | 506篇 |
1983年 | 471篇 |
1982年 | 407篇 |
1981年 | 420篇 |
1979年 | 511篇 |
1978年 | 469篇 |
1977年 | 423篇 |
1976年 | 423篇 |
1975年 | 466篇 |
1974年 | 558篇 |
1973年 | 583篇 |
1972年 | 433篇 |
1971年 | 430篇 |
1970年 | 395篇 |
1969年 | 423篇 |
1968年 | 496篇 |
1967年 | 439篇 |
1966年 | 462篇 |
排序方式: 共有10000条查询结果,搜索用时 8 毫秒
891.
Testing a stochastic foraging model in an operant simulation: Agreement with qualitative but not quantitative predictions 下载免费PDF全文
Roberts WA 《Journal of the experimental analysis of behavior》1993,59(2):323-331
An operant simulation of foraging through baited and empty patches was studied with 4 pigeons. On a three-key panel, side keys were designated as patches, and successive opportunities to complete 16 fixed-ratio 10 schedules on side keys were defined as encounters with feeders. In a random half of the patches in any session, some of the fixed-ratio 10 schedules yielded reinforcement (baited feeders) and the other schedules yielded nonreinforcement (empty feeders). In the other half of the patches, all feeders were empty. Pigeons could travel between patches at any time by completing a fixed-ratio schedule on the center key. An optimal foraging model was tested in Experiments 1 and 2 by varying center-key travel time and number of baited feeders in baited patches. The ordinal predictions that number of feeders visited in empty patches would increase with travel time and decrease as number of baited feeders increased were supported, but pigeons visited far more feeders in empty patches than the optimal number predicted by the model to maximize energy/time. In Experiment 3, evidence was found to suggest that the number of empty feeders encountered before the first baited feeder in baited patches is an important factor controlling leaving empty patches. 相似文献
892.
893.
Unit price as a useful metric in analyzing effects of reinforcer magnitude. 总被引:7,自引:6,他引:1 下载免费PDF全文
R J DeGrandpre W K Bickel J R Hughes M P Layng G Badger 《Journal of the experimental analysis of behavior》1993,60(3):641-666
In this paper, we applied the behavioral-economic concept of unit price to the study of reinforcer magnitude in an attempt to provide a consistent account of the effects of reinforcer magnitude on behavior. Recent research in the experimental analysis of behavior and in behavioral pharmacology suggests that reinforcer magnitude interacts with the schedule of reinforcement to determine response rate and total consumption. The utility of the unit-price concept thus stems from its ability to quantify this interaction as a cost-benefit ratio (i.e., unit price = characteristics of the schedule of reinforcement divided by magnitude of reinforcement). Research employing the unit-price concept has shown that as unit price increases, a positively decelerating function exists for consumption (i.e., a function with an increasingly negative slope, when plotted on log coordinates) and a bitonic function exists for response rate. Based on these findings, the present analysis applied the unit-price concept to those studies of reinforcer magnitude and drug self-administration that examined the effects of reinforcer magnitude on response rate using simple schedules of reinforcement (e.g., fixed-ratio schedule). This resulted in three findings: (a) Reinforcer-magnitude manipulations and schedule manipulations interact in a manner that can be quantified in terms of unit price as benefit and cost factors, respectively; (b) different reinforcer-magnitude manipulations are functionally interchangeable as benefit factors in the unit-price ratio; and (c) these conclusions appear warranted despite the differences in reinforcers (food or drug), species (dogs, monkeys, or rats), and schedules (interval or ratio), and despite the fact that these studies were not designed for a unit-price analysis. In methodological terms, these results provide further evidence that employing the unit-price concept is a parsimonious method for examining the effects of reinforcer magnitude. In theoretical terms, these results suggest that a single process may underlie the effect of combined reinforcer-magnitude and schedule manipulations. 相似文献
894.
W. Alan Nicewander 《Psychometrika》1993,58(1):139-141
It is shown that IRTs information function for an item is functionally related to local versions of classical test theories' signal/noise ratio and reliability coefficient. 相似文献
895.
Daniel S. Shaw Ph.D. Robert E. Emery Michele D. Tuer 《Journal of abnormal child psychology》1993,21(1):119-134
This paper prospectively examined relations between marital status, predivorce parenting practices, and children's adjustment, using data from the New York Longitudinal Study (NYLS). Prospective analyses of children's predivorce adjustment indicated that neither boys nor girls showed more problematic behavior prior to parental separation, and only boys had more difficulties after divorce. However, parents of to-be-divorced families reported more difficulties in childcare practices before divorce than did parents of always-married families. Parenting difficulties in to-be-divorced families were found consistently for boys but not for girls. Results suggest that the difficulties found among boys after divorce may be linked with parenting problems that begin before divorce.The authors are indebted to Alexander Thomas and Stella Chess, the original investigators of the project. We also would like to thank Jacqueline and Richard Lerner, and the John D. and Catherine MacArthur Foundation for their efforts in preserving this data base. 相似文献
896.
The purpose of this research was to determine the role of syllabic stress in language processing during the early on-line processing of speech and later in the representation of a sentence in memory. Experiment 1 used a syllable monitoring task while Experiment 3 used a probe task in which subjects heard a sentence and then were asked to determine whether a probe syllable had occurred in the sentence. In the monitoring task, stressed syllables were detected more rapidly in word-initial position, but unstressed syllables were detected more rapidly in word-final position. Stress facilitation in initial syllables was strongly related to high relative F0, but not to changes in perceived vowel quality as assessed in Experiment 2. This pattern is interpreted as evidence that lexical stress is used on-line to guide lexical access and/or lexical segmentation. The probe task of Experiment 3 showed stress facilitation in both positions, indicating that stress is independently retained in the postperceptual representation of a sentence.The research reported in this paper was supported by grant 80-0416 to Harvard University (Peter C. Gordon, Principal Investigator) from the Air Force Office of Scientific Research Life Sciences Directorate. We thank Chris Thurber for his extensive and competent assistance in testing subjects and making acoustic measurements, and Jay Rueckl for comments on an earlier version of this paper 相似文献
897.
Robert F. Fagot 《Psychometrika》1993,58(2):357-370
A family of coefficients of relational agreement for numerical scales is proposed. The theory is a generalization to multiple judges of the Zegers and ten Berge theory of association coefficients for two variables and is based on the premise that the choice of a coefficient depends on the scale type of the variables, defined by the class of admissible transformations. Coefficients of relational agreement that denote agreement with respect to empirically meaningful relationships are derived for absolute, ratio, interval, and additive scales. The proposed theory is compared to intraclass correlation, and it is shown that the coefficient of additivity is identical to one measure of intraclass correlation.The author thanks the Editor and anonymous reviewers for helpful suggestions. 相似文献
898.
An experiment was conducted to examine the influence of the perceived extremity of a message and motivation to elaborate upon the process of persuasion. The first goal was to test a model of attitude change relating Social Judgment Theory to the Elaboration Likelihood Model. The second objective was to develop an instrument to measure attitude structure (latitudes of acceptance, non-commitment, and rejection) that allowed for a more refined assessment of the discrepancy between the position advocated in a message and the recipient's initial attitude. The main dependent variable was the attitude towards the use of automobiles in relation to environmental issues. Subjects were confronted with a message located in their own latitude of acceptance, rejection or non-commitment. Shortly after, a second measurement of attitude took place. The results showed that messages within the latitudes of non-commitment gave rise to the greatest attitude change. The data support the susceptibility hypothesis that subjects elaborate messages mainly in the latitude of non-commitment. 相似文献
899.
900.
Job Satisfaction Among Ethnic Minorities in The Netherlands 总被引:1,自引:0,他引:1