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441.
442.
Two experiments used rats in a conditioned lick suppression preparation to investigate how the conditioned stimulus (CS)-duration
and partial-reinforcement effects (i.e., weakened responding due to conditioning with a CS of longer duration and presenting
nonreinforced CSs intermingled with CS—unconditioned stimulus [US] pairings, respectively) interact with overshadowing. Experiment
1 found that when overshadowing treatment was combined with either extended CS duration or partial reinforcement, the response
deficit was weaker than when either of these three treatments was administered alone. In Experiment 2, the generality of the
findings in Experiment 1 was investigated by replicating it with various US—US intervals. This time counteraction was observed
only when both the absolute duration of total CS exposure and the US—US interval were short. The results support neither the
view that the ratio between the total CS exposure and total time in the context determines the CS-duration and the partial-reinforcement
effects nor the view that these two effects arise from a loss of effectiveness of the excitatory CS—US association during
CS-alone exposures in partial reinforcement or early periods of CS exposure with long CSs. 相似文献
443.
Rats were used in a lick suppression preparation to assess the contribution of conditioned-stimulus (CS)–context and context–unconditioned-stimulus
(US) associations to experimental extinction. Experiment 1 investigated whether strengthening the CS–acquisition context association enhances extinction by determining whether stronger
extinction is observed when CS-alone trials (i.e., extinction treatment) are administered in the acquisition context (AAC
renewal), relative to a context that is neutral with respect to the US (ABC renewal). Less recovery of responding to the CS
was observed in the former than in the latter case, extending the finding that AAC renewal is weaker than ABC renewal to our
lick suppression preparation. Experiment 2 assessed the contribution of the acquisition context–US association to extinction of a CS by examining the effect of postextinction
exposure to the acquisition context on responding to the extinguished CS. This manipulation enhanced responding to the extinguished
CS in AAC, but not ABC, renewal. Experiment 3 addressed the contribution of the CS–acquisition context association by examining the potential of a neutral stimulus, presented
in compound with the target CS during extinction treatment, to overshadow the CS–acquisition context association. This manipulation
enhanced responding to the extinguished CS in AAC, but not ABC, renewal. The results stress the important role of contextual
association in extinction and renewal. 相似文献
444.
In two experiments with rats as subjects, the temporal characteristics of inhibition produced through extinction were investigated.
Each experiment established two independent signals for unconditioned stimulus presentation, one trace and one delay. Following
initial training, either the trace or the delay conditioned stimulus (CS) was massively extinguished. In Experiment 1, a summation
test established that an extinguished delay CS (but not a neutral CS) passed a summation test with a delay, but not with a
trace, transfer excitor, and an extinguished trace CS (but not a neutral CS) passed a summation test with a trace, but not
with a delay, transfer excitor. In Experiment 2, a retardation test showed retarded behavioral control by an extinguished
delay CS when the CS was retrained as a delay CS, but not as a trace CS, and by an extinguished trace CS when the CS was retrained
as a trace CS, but not as a delay CS. The results are discussed in terms of contemporary theories of extinction. 相似文献
445.
Water-deprived rats served in seven conditioned lick suppression experiments designed to assess the effects on responding to a target CS of a series of unsignaled USs given in the training context following completion of CS training. Such treatment has been hypothesized to increase (inflate) the associative strength of the background cues from training (putatively, the CS’s comparator stimuli), thereby reducing responding to excitatory CSs and increasing the inhibitory potential of inhibitory CSs. Although posttraining extinction (deflation) of the CS’s comparator stimuli usually decreases inhibitory potential and increases excitatory potential of the target CS, posttraining inflation of the comparator stimuli had no effect on either excitatory responding to the target CS or summation test performance indicative of conditioned inhibition. This outcome was consistently obtained across a number of training, inflation, and test conditions selected to maximize sensitivity to any possible effects of comparator inflation. Implications of these null results for the comparator hypothesis of conditionedresponse generationare discussed. 相似文献
446.
Ralph Samuelson 《广西师范大学学报(哲学社会科学版)》2002,(Z3)
In the course offerings to students in the Foreign Languages College here atGuangxi Teachers'University,I had noted what was in my opinion an overemphasis onprose at the expense of poetry;and also a dearth of courses thatwentdeeply into a singlesubject,period,or writer.In place of this,courses tended to be survey,background,criticism,or history.After discussing this with my colleague,Professor Zheng Shuning,here at the Uni-versity,I determined to take a different approach in my Fall Term,… 相似文献
447.
Contribution of conditioned opioid analgesia to the shock-induced associative US-preexposure deficit
The modulatory effect of conditioned opioid analgesia on learning in the US-preexposure paradigm was examined in three experiments using water-deprived rats. In Experiment 1, it was found that tailflick latencies increased immediately after the rats were exposed to a context in which footshock had previously been administered. Prolonged nonreinforced exposure to the context attenuated this analgesia. Experiment 2 tested the possibility that the effectiveness of CS-US pairings in an excitatory context might be reduced by a conditioned analgesic response that lessens the perceived intensity of the US. Administration of the opiate antagonist naloxone prior to CS-US pairings in the excitatory context reduced the US-preexposure deficit—that is, the retarded response to the CS—but did not eliminate it, suggesting that part of the observed deficit resulted from conditioned activation of the endogenous opioid system. In Experiment 3, it was found that exposure to the excitatory context immediately prior to a CS-US pairing in an associatively neutral context resulted in a conditioned response deficit, indicating that the analgesia elicited by the excitatory context was sufficient to reduce US effectiveness. In combination with other recent reports, these results suggest that the associative deficit resulting from preexposure to a shock US may, in certain instances, represent the sum of several different associative processes. 相似文献
448.
Conditioned lick suppression in rats was used to explore the role of timing in trace conditioning. In Experiment 1, two groups of rats were exposed to pairings of a CS (CS1) with a US, under conditions in which the interstimulus interval (ISI) that separated CS1 offset and US onset was either 0 or 5 sec. Two additional groups were also exposed to the same CS1→US pairings with either a 0 or a 5-sec ISI, and then received “backward” second-order conditioning in which CS1 was immediately followed by a novel CS2 (i.e., CS1→CS2). A trace conditioning deficit was observed in that the CS1 conditioned with the 5-sec gap supported less excitatory responding than the CS1 conditioned with the 0-sec gap. However, CS2 elicited more conditioned responding in the group trained with the 5-sec CS1-US gap than in the group trained with the 0-sec CS1-US gap. Thus, the CS1-US interval had inverse effects on first- and second-order conditioned responding. Experiment 2 was conducted as a sensory preconditioning analogue to Experiment 1. In Experiment 2, rats received the CS1?CS2 pairings prior to the CS1→US pairings (in which CS1 was again conditioned with either a 0 or a 5-sec ISI). Experiment 2 showed a dissociation between first- and second-order conditioned responding similar to that observed in Experiment 1. These outcomes are not compatible with the view that differences in responding to CSs conditioned with different ISIs are mediated exclusively by differences in associative value. The results are discussed in the framework of the temporal coding hypothesis, according to which temporal relationships between events are encoded in elementary associations. 相似文献
449.
Abstract The initiative ‘Offenes Deutsches Schul‐Netz’ (ODS) ‐ The Open German School Network ‐ sees itself as a joint cover for school networking in Germany. In this article, we give an insight into the very successful ideas on which ODS is based. Practically every computer‐mediated communication between schools in Germany and abroad is transmitted on the basis of agreements by the ODS with various servers. We describe, briefly, how we imagine networking between schools in future. 相似文献
450.