全文获取类型
收费全文 | 71719篇 |
免费 | 2758篇 |
国内免费 | 25篇 |
出版年
2019年 | 785篇 |
2018年 | 1155篇 |
2017年 | 1124篇 |
2016年 | 1262篇 |
2015年 | 928篇 |
2014年 | 1087篇 |
2013年 | 5996篇 |
2012年 | 1986篇 |
2011年 | 1956篇 |
2010年 | 1261篇 |
2009年 | 1212篇 |
2008年 | 1819篇 |
2007年 | 1727篇 |
2006年 | 1524篇 |
2005年 | 1378篇 |
2004年 | 1302篇 |
2003年 | 1245篇 |
2002年 | 1247篇 |
2001年 | 2223篇 |
2000年 | 2158篇 |
1999年 | 1607篇 |
1998年 | 748篇 |
1996年 | 784篇 |
1995年 | 730篇 |
1994年 | 740篇 |
1993年 | 718篇 |
1992年 | 1592篇 |
1991年 | 1458篇 |
1990年 | 1475篇 |
1989年 | 1298篇 |
1988年 | 1281篇 |
1987年 | 1266篇 |
1986年 | 1285篇 |
1985年 | 1322篇 |
1984年 | 1107篇 |
1983年 | 980篇 |
1981年 | 725篇 |
1979年 | 1149篇 |
1978年 | 791篇 |
1976年 | 732篇 |
1975年 | 1009篇 |
1974年 | 1097篇 |
1973年 | 1194篇 |
1972年 | 1074篇 |
1971年 | 979篇 |
1970年 | 927篇 |
1969年 | 898篇 |
1968年 | 1152篇 |
1967年 | 1023篇 |
1966年 | 930篇 |
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
871.
Six pigeons were trained with a chain variable-interval variable-interval schedule on the left key and with reinforcers available on the right key on a single variable-interval schedule arranged concurrently with both links of the chain. All three schedules were separately and systematically varied over a wide range of mean intervals. During these manipulations, the obtained reinforcer rates on constant arranged schedules also frequently changed systematically. Increasing reinforcer rates in Link 2 of the chain increased response rates in both links and decreased response rates in the variable-interval schedule concurrently available with Link 2. Increasing Link-1 reinforcer rates increased Link-1 response rates and decreased Link-2 response rates. Increasing reinforcer rates on the right-key schedule decreased response rates in Link 1 of the chain but did not affect the rate in Link 2. The results extend and amplify previous analyses of chain-schedule performance and help define the effects that a quantitative model must describe. However, the complexity of the results, and the fact that constant arranged reinforcer schedules did not necessarily lead to constant obtained reinforcer rates, precluded a quantitative analysis. 相似文献
872.
Pigeons were trained under a discrete-trials detection procedure in which one of a set of color stimuli was presented on the center key and a single response turned off the stimulus and illuminated two side keys. Single responses to one or the other side key produced occasional reinforcers depending on the value of the color stimulus. In Experiment 1, one color-stimulus set comprised 559, 564, 569, and 574 nm, and right-key pecks were occasionally reinforced following presentations of members of this set. The other stimulus set comprised 579, 584, 589, and 594 nm, and left-key pecks were occasionally reinforced following presentations of members of this set. Across seven experimental conditions, the left/(left + right) relative reinforcer frequency was varied from .1 to .9. In Experiment 2, one stimulus set contained only one member, 574 nm, and right-key responses were occasionally reinforced following its presentation. Over 12 experimental conditions, two manipulations were carried out. First, the number of stimuli comprising the other stimulus set was increased from one (579 nm) to two (579 and 584 nm) to three (579, 584, and 589 nm) and to four (579, 584, 589, and 594 nm), and left-key responses were reinforced occasionally following center-key presentations of members of this set. Second, for each stimulus combination, the left/(left + right) relative reinforcer frequency was varied from .1 to .5 to .9 across three experimental conditions. The principal finding of Experiments 1 and 2 was that reinforcers and stimuli interacted in their effects on behavior. In Experiment 3, pairs of adjacent stimuli (5 nm apart) in the range 559 to 594 nm were presented in each experimental condition, and the left/(left + right) relative reinforcer frequency was held constant at .5. The data from all three experiments were analyzed according to a detection model describing performance in multiple-stimulus two-response procedures. This model provided independent measures of stimulus discriminability, contingency discriminability, and bias. The analysis showed that (a) consistent with the color-naming function, pigeons were better able to discriminate between higher nanometer values than lower nanometer values; (b) their ability to discriminate between the stimuli was independent of the number of wavelengths comprising each stimulus set; (c) they allocated delivered reinforcers very accurately to the previously emitted response; and (d) no consistent biases emerged. 相似文献
873.
In two experiments, rats were trained to deposit ball bearings down a hole in the floor, using an algorithmic version of shaping. The experimenter coded responses expected to be precursors of the target response, ball bearing deposit; a computer program reinforced these responses, or not, according to an algorithm that mimicked the processes thought to occur in conventional shaping. In the first experiment, 8 of 10 rats were successfully shaped; in the second, 5 of 5 were successfully shaped, and the median number of sessions required was the same as for a control group trained using conventional shaping. In both experiments, “misbehavior,” that is, excessive handling and chewing of the ball bearings, was observed, and when the algorithmic shaping procedure was used, misbehavior could be shown to occur in spite of reduced reinforcement for the responses involved. 相似文献
874.
875.
Sidman M Wynne CK Maguire RW Barnes T 《Journal of the experimental analysis of behavior》1989,52(3):261-274
Three adult subjects were taught a set of two-choice simultaneous discriminations, with three positive and three negative stimuli; all possible combinations of positive and negative stimuli yielded nine different pairs. The discriminations were repeatedly reversed and rereversed, the former positive stimuli becoming negative and the former negative stimuli becoming positive. With all subjects, a reversal of the contingencies for one pair of stimuli became sufficient to change their responses to all of the other pairs. The reversals had produced functional stimulus classes. Then, all subjects showed conditional discriminations emerging between members of a functional class; given a sample from one class and comparisons from both classes, they selected the comparison that was in the same class as the sample. Next, 2 of the subjects showed that the within-class conditional relations possessed the symmetric and transitive properties of equivalence relations; after having been taught to relate new stimuli to existing class members, the subjects then matched other class members to the new stimuli. Subsequent tests of two-choice discriminations showed that the conditional discriminations had transferred functional class membership to the new stimuli. The 3rd subject, who did not show equivalence relations among functional class members, was also found to have lost the within-class conditional relations after the equivalence tests. 相似文献
876.
The purpose of this study was to determine whether backward walking represented a simple temporal reversal of forward walking and, hence, could be controlled by a reversed cycling of the same group of neurons. Electromyographic (EMG), joint angle, joint moment, and joint muscle power patterns were compared for forward and backward walking, in 6 subjects. The joint angle patterns with the time-base of the backward walking reversed were similar, with the exception of the ankle. The moment patterns were similar except for the knee, whereas the joint muscle powers were almost reversed-polarity images of each other. This suggests that somewhat similar muscle activation patterns could be used to produce both modes of locomotion, but the temporal cycling of muscle contraction would be reversed: Concentric muscle activity in forward walking would become eccentric activity in backward walking, and visa versa. The EMG results generally supported these findings. 相似文献
877.
878.
Ulrich BD 《Journal of motor behavior》1989,21(4):392-408
Upright locomotion has been, perhaps, the most studied of all human motor behaviors. The acquisition of this motor milestone has been of major interest to developmentalists from the motor as well as the cognitive domains. Until recently, developmentalists have chosen a nonexperimental approach, opting instead to describe the motor behaviors that precede walking, assigning them precursor status, and attributing the sequence solely to maturation of the nervous system. In this paper, I will discuss evidence that suggests that we may better understand this and other aspects of motor development by viewing them from the theoretical perspective of nonlinear and complex dynamical systems. Focus will be on the availability of a coordinated and alternating stepping pattern throughout much of the first year of life. Factors that influence the expression of and variability in this movement pattern will also be discussed. In addition, I will address the need to understand the development of control of pattern formations as well as their coordination, and I will discuss one approach that may provide some insight; that is, to study the modulations and patterns of muscle and other forces underlying limb movements. 相似文献
879.
D L Schacter J F Kihlstrom L C Kihlstrom M B Berren 《Journal of abnormal psychology》1989,98(4):508-514
Previous research on multiple personality disorder (MPD) has been concerned with between-personalities amnesia, and little attention has been paid to within-personality memory function. This study examined the autobiographical memory of a multiple personality patient, I.C., with cueing procedures that have proven useful in previous studies of normal and abnormal memory. Results indicated that I.C. was able to retrieve autobiographical episodes from the recent past, although her performance differed in several respects from that of matched controls. The study also revealed a striking deficit in I.C.'s autobiographical memory for childhood: She was unable to recall a single episode from prior to the age of 10 in response to various retrieval cues, whereas control subjects had no difficulty recalling numerous childhood episodes. This phenomenon of extended childhood amnesia has not been reported previously in studies of MPD. 相似文献
880.
R. NOLL 《The Journal of analytical psychology》1989,34(4):353-370
Jung's contributions to the study of 'dissociation' are outlined here for perhaps the first time. Jung is unique in recognising that the 'dissociability of the psyche' is a fundamental process that extends along the continuum from 'normal' mental functioning to 'abnormal' states. Dissociation is recognised by Jung as a universal and necessary psychic activity for the development of personality through the differentiation of functions. However, when the cohesion of consciousness is shattered by extreme childhood traumata, as it is in the development of multiple personality, this natural differentiation of function is intensified and the dissociative splits between autonomous forces in the psyche become more extreme. This increases the autonomy of these 'splinter psyches' from ego-consciousness and reveals their archetypal core. They then develop into the phenomenon of 'alternate personalities' in multiple personality. In a comparison of the major tenets of the complex theory with recent empirical research on multiple personality, it is demonstrated that essential characteristics of Jung's 'autonomous complexes' are congruent with the phenomenology of the 'alternate personalities' or 'personality states' of this disorder. This underscores the relevance of Jung's complex theory to present understanding of multiple personality. In addition, the phenomenon of multiple personality is, in turn, important for realising the central significance of dissociation in the complex theory and provides an excellent contemporary clinical example of the archetypal ground of the psyche. 相似文献