全文获取类型
收费全文 | 56039篇 |
免费 | 2272篇 |
国内免费 | 27篇 |
专业分类
58338篇 |
出版年
2020年 | 648篇 |
2019年 | 742篇 |
2018年 | 1080篇 |
2017年 | 1101篇 |
2016年 | 1124篇 |
2015年 | 775篇 |
2014年 | 998篇 |
2013年 | 4266篇 |
2012年 | 1780篇 |
2011年 | 1822篇 |
2010年 | 1117篇 |
2009年 | 1155篇 |
2008年 | 1631篇 |
2007年 | 1653篇 |
2006年 | 1479篇 |
2005年 | 1319篇 |
2004年 | 1214篇 |
2003年 | 1178篇 |
2002年 | 1165篇 |
2001年 | 1808篇 |
2000年 | 1757篇 |
1999年 | 1349篇 |
1998年 | 584篇 |
1997年 | 563篇 |
1996年 | 513篇 |
1995年 | 517篇 |
1992年 | 1138篇 |
1991年 | 999篇 |
1990年 | 1103篇 |
1989年 | 947篇 |
1988年 | 960篇 |
1987年 | 910篇 |
1986年 | 931篇 |
1985年 | 922篇 |
1984年 | 798篇 |
1983年 | 734篇 |
1982年 | 540篇 |
1979年 | 844篇 |
1978年 | 623篇 |
1977年 | 522篇 |
1975年 | 708篇 |
1974年 | 792篇 |
1973年 | 835篇 |
1972年 | 637篇 |
1971年 | 600篇 |
1970年 | 533篇 |
1969年 | 594篇 |
1968年 | 717篇 |
1967年 | 643篇 |
1966年 | 604篇 |
排序方式: 共有10000条查询结果,搜索用时 7 毫秒
871.
Preference for less segmented fixed-time components in concurrent-chain schedules of reinforcement 总被引:1,自引:1,他引:0 下载免费PDF全文
A concurrent-chain procedure was used to examine choice between segmented and less segmented response-independent schedules of reinforcement. A pair of independent, concurrent variable-interval 60-s schedules were presented in the initial link, along with a 1.5-s changeover delay. A chained fixed-interval fixed-time and its corresponding tandem schedule constituted the terminal links. The length of the fixed-interval schedule in the terminal link was varied between 5 s and 30 s while that of the fixed-time schedule was kept at 5 s over conditions. The first components of both terminal-link schedules were accompanied by the same stimulus. Except in the baseline condition, the onset of the second component of the terminal-link chained schedule was accompanied by either a localized (key color) or a nonlocalized (dark houselight) stimulus change. Stimulus conditions were constant during the terminal-link tandem schedule. With three exceptions, pigeons demonstrated a slight preference for the tandem over the chained schedule in the terminal link. Furthermore, this preference varied inversely with the length of the first component. In general, these results are consistent with previous studies that reported an adverse effect on choice by segmenting an interval schedule into two or more components, but they are inconsistent with studies that reported preference for signaled over unsignaled delay of reinforcement. 相似文献
872.
Deprivation and satiation: The interrelations between food and wheel running 总被引:2,自引:1,他引:1 下载免费PDF全文
Two experiments were designed to assess whether depriving rats of food would increase the reinforcement effectiveness of wheel running (Experiment 1) and whether satiation for wheel running would decrease the reinforcement effectiveness of food (Experiment 2). In Experiment 1, a progressive-ratio schedule was used to measure the reinforcement effectiveness of wheel running when rats were deprived or not deprived of food. Completion of a fixed number of lever presses released a brake on a running wheel for 60 s, and the response requirement was systematically increased until the rat stopped pressing or until 8 hr had elapsed. The ratio value reached (and the total number of lever presses) was an inverted-U function of food deprivation (percentage body weight). In Experiment 2, when wheel running preceded test sessions, fewer food-reinforced lever presses were maintained by the progressive-ratio schedule, and responding occurred at a lower rate on a variable-interval schedule. An interpretation of these results is that deprivation or satiation with respect to one event (such as food) alters the reinforcement effectiveness of a different event (such as access to wheel running). 相似文献
873.
Syntactic decoding reaction times of 20 learning disabled children comprising two groups of subjects (mean age of 8 and 13 yr., respectively) were compared to the responses of normal controls matched for age and sex. An analysis of variance procedure showed that the learning disabled children and their normal peers did not differ significantly in responses to the experimental stimuli. This held true regardless of linguistic complexity, suggesting that delays in processing elementary syntactic constructions are not a concomitant of learning disabilities. 相似文献
874.
In previous studies subjects who have learned a positioning response with kinesthetic feedback tended to make greater errors when visual feedback was provided during later trials. These subjects have always performed with both kinesthetic and visual feedback available. This study determined whether subjects with only visual feedback would produce errors similar to those who received kinesthetic plus visual feedback. Blindfolded subjects learned to move a handle to a criterion location with knowledge of results following each trial. Subjects then were assigned to one of three experimental groups, with only kinesthetic feedback, with kinesthetic plus visual feedback, or with only visual feedback. Subjects had 9 trials without knowledge of results in these feedback conditions. When visual feedback was available, subjects tended to make longer response errors. This finding replicates previous studies. Also, the similarity of performances from the conditions with visual feedback indicated the dominance of visual information in the condition with kinesthetic plus visual feedback. 相似文献
875.
L Zusne 《Perceptual and motor skills》1986,62(3):729-730
The count of publications on geometric-optical illusions and the bibliography of extant books on the topic are brought up to date. The number of publications now exceeds 1100 and the number of books is 35. 相似文献
876.
The comparable worth controversy has generated much discussion about the appropriate valuation of job worth. To date, academic inquiries into the measurement of job worth have focused primarily on job evaluation; however, recent court decisions suggest that market wages are a more compelling indicator of job worth than are job evaluation results. This paper examines the construct of "market wage" and the process by which it is measured (wage surveys). It is argued that both the construct and the measurement of the market wage have not been sufficiently examined by either academics or the courts. Implications for pay administration and future research are noted. 相似文献
877.
VALIDITY GENERALIZATION RESULTS FOR LAW ENFORCEMENT OCCUPATIONS 总被引:1,自引:0,他引:1
The Schmidt-Hunter interactive validity generalization procedure was applied to validity data for cognitive abilities tests for law enforcement occupations. Both assumed artifact distributions, and distributions of artifacts constructed from information contained in the current sample of studies were used to test the hypothesis of situational specificity and to estimate validity generalizability. Results for studies using a criterion of performance in training programs showed that validities ranged from .41 to .71, and for four test types the hypothesis of situational specificity could be rejected using the 75% decision rule. For the remaining test types, validity was generalizable, based on 90% credibility values ranging from .37 to .71. Results for studies using a criterion of performance on the job indicated that the hypothesis of situational specificity was not tenable for three test types, which had validities between .17 and .31. For the remaining test types, estimated mean true validities ranged from .10 to .26 and were generalizable to a majority of situations. Results for both groups of studies were essentially identical for the two types of artifact distribution. Possible reasons for the apparently lower validities and lesser generalizability for job performance criteria are discussed, including possible low validity of the criterion (due to lack of opportunity by supervisors to observe behavior) and the potential role of noncognitive factors in the determination of law enforcement job success. Suggestions for specifically targeted additional research are made. 相似文献
878.
G Sack H J Leubuscher B P?gelt N Roth 《Psychiatrie, Neurologie, und medizinische Psychologie》1986,38(5):246-254
The influence in 8 of our patients with ophthalmic migraine of photic driving with sine-like flashing lights on EEG background activity was checked and the visually evoked potentials following the application of diffused simple light stimuli were analyzed using the recovery cycle technique. The results indicate a slightly increased tonic activity of the structures of the mesencephalic formatio reticularis, such as may be produced by slight functional disturbances. Some vegetative secondary symptoms of migraine attacks and some of the changes in EEG observed in patients with ophthalmic migraine are explicable by such an abnormality. 相似文献
879.
P Leitner E Umann H Kulawik 《Psychiatrie, Neurologie, und medizinische Psychologie》1986,38(10):579-583
Hitherto it has not been usual to talk in the German language about the therapy-oriented concept of two forms of the progress of atypical depression (Type A and Type V). The characteristic symptom of Type A is angst, together with phobias, physical complaints, etc. In Type V there are vegetative symptoms, often towards evening (Hypersomnia, difficulty in getting to sleep, increased appetite, increased weight, increased libido), accompanied by hysterical extrovert personality traits, and of intermittent occurrence. These clinical pictures are amenable to psychopharmalogical therapy. In conformity with the assumption of "somatic accommodation" treatment with antidepressives is recommended in the case neurotic depression, too, at least in the initial stages of treatment. 相似文献
880.
E P Lester 《The Psychoanalytic quarterly》1986,55(3):452-473
Kris (1956) described the concept of the personal myth as an autobiographical story built around a family romance fantasy seen specifically in obsessive characters and serving a defensive function. In this paper the concept of the personal myth was expanded to include similar defensive constellations originating from within the grandiose self, built around omnipotent and omniscient fantasies and occurring in character formations with pregenital, narcissistic pathology. The case of a known author and poet, Nikos Kazantzakis, was used to illustrate the thesis of the paper. The available biographical material and the work of the author offer evidence to support the claim that the author's personal myth was a protective shield against anxiety originating in early narcissistic traumata. 相似文献