全文获取类型
收费全文 | 8746篇 |
免费 | 165篇 |
国内免费 | 44篇 |
专业分类
8955篇 |
出版年
2018年 | 22篇 |
2014年 | 15篇 |
2013年 | 13篇 |
2012年 | 947篇 |
2011年 | 1048篇 |
2010年 | 253篇 |
2009年 | 132篇 |
2008年 | 805篇 |
2007年 | 799篇 |
2006年 | 776篇 |
2005年 | 581篇 |
2004年 | 553篇 |
2003年 | 568篇 |
2002年 | 432篇 |
2001年 | 307篇 |
2000年 | 377篇 |
1999年 | 170篇 |
1998年 | 43篇 |
1997年 | 25篇 |
1996年 | 28篇 |
1995年 | 35篇 |
1994年 | 36篇 |
1993年 | 26篇 |
1992年 | 32篇 |
1991年 | 48篇 |
1990年 | 40篇 |
1989年 | 43篇 |
1988年 | 41篇 |
1987年 | 38篇 |
1986年 | 37篇 |
1985年 | 35篇 |
1984年 | 24篇 |
1983年 | 29篇 |
1982年 | 27篇 |
1981年 | 25篇 |
1979年 | 13篇 |
1978年 | 24篇 |
1965年 | 17篇 |
1964年 | 18篇 |
1959年 | 19篇 |
1958年 | 55篇 |
1957年 | 53篇 |
1956年 | 32篇 |
1955年 | 34篇 |
1954年 | 20篇 |
1953年 | 22篇 |
1952年 | 27篇 |
1951年 | 25篇 |
1950年 | 22篇 |
1949年 | 19篇 |
排序方式: 共有8955条查询结果,搜索用时 10 毫秒
171.
Plasticity of the human auditory cortex induced by discrimination learning of non-native,mora-timed contrasts of the Japanese language 总被引:2,自引:0,他引:2 下载免费PDF全文
Menning H Imaizumi S Zwitserlood P Pantev C 《Learning & memory (Cold Spring Harbor, N.Y.)》2002,9(5):253-267
In this magnetoencephalographic (MEG) study, we examined with high temporal resolution the traces of learning in the speech-dominant left-hemispheric auditory cortex as a function of newly trained mora-timing. In Japanese, the “mora” is a temporal unit that divides words into almost isochronous segments (e.g., na-ka-mu-ra and to-o-kyo-o each comprises four mora). Changes in the brain responses of a group of German and Japanese subjects to differences in the mora structure of Japanese words were compared. German subjects performed a discrimination training in 10 sessions of 1.5 h each day. They learned to discriminate Japanese pairs of words (in a consonant, anni–ani; and a vowel, kiyo–kyo, condition), where the second word was shortened by one mora in eight steps of 15 msec each. A significant increase in learning performance, as reflected by behavioral measures, was observed, accompanied by a significant increase of the amplitude of the Mismatch Negativity Field (MMF). The German subjects' hit rate for detecting durational deviants increased by up to 35%. Reaction times and MMF latencies decreased significantly across training sessions. Japanese subjects showed a more sensitive MMF to smaller differences. Thus, even in young adults, perceptual learning of non-native mora-timing occurs rapidly and deeply. The enhanced behavioral and neurophysiological sensitivity found after training indicates a strong relationship between learning and (plastic) changes in the cortical substrate. 相似文献
172.
Posttraining glucocorticoid receptor agonist enhances memory in appetitive and aversive Pavlovian discrete-cue conditioning paradigms 总被引:1,自引:0,他引:1
Glucocorticoid modulation of emotional memory has repeatedly been shown in aversive learning paradigms, but has received little attention in appetitive tasks. It has also been suggested that it may be selective for contextual cues. In order to investigate if glucocorticoids can modulate memory in discrete-cue conditioning of both appetitive and aversive tasks, two experiments were carried out. Male Lister-Hooded rats received pairings of an auditory cue and either food-reward (experiment 1) or footshock (experiment 2), followed immediately by posttraining injections of the glucocorticoid receptor agonist dexamethasone (0.3, 0.6, and 1.2 mg/kg) or vehicle. Dexamethasone (1.2 mg/kg) led to significantly enhanced learning. These results give support to the notion that glucocorticoids play a role in the modulation of both appetitive and aversive emotional memories and show that their role in learning goes beyond the construction of context representations. The modulation of appetitive and aversive discrete-cue learning may be subserved by a common mechanism. 相似文献
173.
Hippocampal damage and exploratory preferences in rats: memory for objects, places, and contexts 总被引:8,自引:1,他引:7 下载免费PDF全文
Mumby DG Gaskin S Glenn MJ Schramek TE Lehmann H 《Learning & memory (Cold Spring Harbor, N.Y.)》2002,9(2):49-57
Rats have a natural tendency to spend more time exploring novel objects than familiar objects, and this preference can be used as an index of object recognition. Rats also show an exploratory preference for objects in locations where they have not previously encountered objects (an index of place memory) and for familiar objects in contexts different from those in which the objects were originally encountered (an index of context memory). In this experiment, rats with cytotoxic lesions of the hippocampal formation were tested on all three versions of the novelty-preference paradigm, with a 5-min retention interval between the familiarization and test phases. Rats with sham lesions displayed a novelty preference on all three trial types, whereas the rats with hippocampal lesions displayed a novelty preference on Object trials but did not discriminate between the objects on Place trials or Context trials. The findings indicate that hippocampal damage impairs memory for contextual or spatial aspects of an experience, whereas memory for objects that were part of the same experience are left relatively intact. 相似文献
174.
Mapping of olfactory memory circuits: region-specific c-fos activation after odor-reward associative learning or after its retrieval 总被引:4,自引:2,他引:2 下载免费PDF全文
Although there is growing knowledge about intracellular mechanisms underlying neuronal plasticity and memory consolidation and reconsolidation after retrieval, information concerning the interaction among brain areas during formation and retrieval of memory is relatively sparse and fragmented. Addressing this question requires simultaneous monitoring of activity in multiple brain regions during learning, the post-acquisition consolidation period, and retrieval and subsequent reconsolidation. Immunoreaction to the immediate early gene c-fos is a powerful tool to mark neuronal activation of specific populations of neurons. Using this method, we are able to report, for the first time, post-training activation of a network of closely related brain regions, particularly in the frontal cortex and the basolateral amygdala (BLA), that is specific to the learning of an odor-reward association. On the other hand, retrieval of a well-established associative memory trace does not seem to differentially activate the same regions. The amygdala, in particular, is not engaged after retrieval, whereas the lateral habenula (LHab) shows strong activation that is restricted to animals having previously learned the association. Although intracellular mechanisms may be similar during consolidation and reconsolidation, this study indicates that different brain circuits are involved in the two processes, at least with respect to a rapidly learned olfactory task. 相似文献
175.
Soto-Faraco S Spence C Fairbank K Kingstone A Hillstrom AP Shapiro K 《Psychonomic bulletin & review》2002,9(4):731-738
There is currently a great deal of interest regarding the possible existence of a crossmodal attentional blink (AB) between audition and vision. The majority of evidence now suggests that no such crossmodal deficit exists unless a task switch is introduced. We report two experiments designed to investigate the existence of a crossmodal AB between vision and touch. Two masked targets were presented successively at variable interstimulus intervals. Participants had to respond either to both targets (experimental condition) or to just the second target (control condition). In Experiment 1, the order of target modality was blocked, and an AB was demonstrated when visual targets preceded tactile targets, but not when tactile targets preceded visual targets. In Experiment 2, target modality was mixed randomly, and a significant crossmodal AB was demonstrated in both directions between vision and touch. The contrast between our visuotactile results and those of previous audiovisual studies is discussed, as are the implications for current theories of the AB. 相似文献
176.
Place learning in scopolamine-treated rats: the roles of distal cues and catecholaminergic mediation
Mogensen J Christensen LH Johansson A Wörtwein G Bang LE Holm S 《Neurobiology of learning and memory》2002,78(1):139-166
Experiments 1 and 2 tested the hypothesis that cholinergic receptor antagonists impair place learning in a water maze by interfering with the processing of distal, visual cues. Extramaze cues were offered to rats in the form of geometrical patterns arranged on the inner circumference of a curtain surrounding the water maze. In Experiment 1 the animals were offered both the distal cues and proximal cues in the form of pingpong balls in fixed positions on the surface of the water while only distal cues were present in Experiment 2. Animals were injected with either scopolamine (0.5 mg/kg body wt) or saline 20 min prior to the daily place learning sessions. Upon reaching criterion level performance the animals were tested on "rotation" sessions on which the distal cues were displaced. The outcome of such "rotations" demonstrated that-regardless of the presence or absence of proximal cues-scopolamine-treated rats relied at least as much as normal animals on the distal cues. The acquisition phase of both Experiments 1 and 2 demonstrated an almost complete lack of scopolamine-associated impairment in acquisition and performance of the place learning task. In Experiment 3 (when scopolamine was no longer administered) the subjects of Experiment 2 were exposed to a series of pharmacological "challenges" of their place learning performance and eventually to surgical ablation of the anteromedial prefrontal cortex. The outcome of the pharmacological challenges and the postoperative test of task performance demonstrated that the place learning performance of animals which had acquired the task under scopolamine was mediated by a neural substrate dissimilar to the substrate of task performance in normal animals. Rats acquiring the task while deprived of the cholinergic system demonstrated above-normal contributions to task mediation from catecholaminergic-probably dopaminergic-mechanisms and tentative results pointed to a "shift" toward prefrontal task mediation. 相似文献
177.
In the present study, the effects of spatial-frequency uncertainty and cuing on psychometric functions for contrast detection
of sinusoidal gratings are examined. For this purpose, psychometric functions were collected from 4 subjects under fixed-frequency,
randomized-frequency, and cued-frequency conditions. The experiment was conducted with a temporal two-alternative forced-choice
task, and five spatial frequencies in the range of 0.5 and 8.0 c/deg and seven contrast levels for each frequency were used.
The results showed that the psychometric functions for the randomized-frequency condition were shallower than those for the
fixed-frequency condition, supporting the single-band model for the uncertainty effects (Hübner, 1993a, 1993b). For the cued-frequency
condition, the slopes of the functions were not clearly different from those for the randomized condition. These results clearly
differ from those of Hübner (1996b), which showed, in the spatial two-alternative forced-choice task, steeper psychometric
functions for the randomized-frequency condition than those for the fixed- and cued-frequency conditions, supporting the multiple-band
model (Hübner, 1993a, 1993b). The difference suggests that the single-band model applies to the uncertainty effects in the
temporal forced-choice task, whereas the multiple-band model does so in the spatial forced-choice task. 相似文献
178.
Twenty-four adults (24 to 53 years old) with Attention-Deficit/Hyperactivity Disorder (ADHD), Combined Type, were studied in a double-blind, placebo-controlled, crossover study of Pycnogenol and methylphenidate. Pycnogenol is an antioxidant derived from the bark of the French maritime pine tree. Methylphenidate is a standard pharmaceutical intervention for ADHD. Anecdotal reports suggest that Pycnogenol improves concentration in adults with ADHD without adverse side effects. Participants received Pycnogenol, methylphenidate, and placebo, each for three weeks, in a randomized and counterbalanced order. Although ADHD symptoms improved during treatment, neither methylphenidate nor Pycnogenol outperformed the placebo control, as measured by self-report rating scales, rating scales completed by the individual's significant other, and a computerized continuous performance test. The conservative dosage levels and relatively brief length of treatment may have contributed to the absence of significant differences among treatment conditions. Implications for future research are noted. 相似文献
179.
180.
Williams JK Goebert D Hishinuma E Miyamoto R Anzai N Izutsu S Yanagida E Nishimura S Andrade N Baker FM 《Cultural diversity & ethnic minority psychology》2002,8(4):320-333
A model integrating Japanese ethnicity, cultural identity, and anxiety was developed and assessed in Japanese American and part-Japanese American high school seniors (N = 141). Using measures from the Hawaiian High Schools Health Survey, the model incorporated the State-Trait Anxiety Inventory, the Major Life Events Scale, and the Japanese Culture Scale (JCS). Japanese American adolescents scored higher on the JCS and reported fewer anxiety symptoms than part-Japanese American adolescents. Predictors for anxiety were being Japanese American versus part-Japanese American, income, and culturally intensified events. A significant interaction of behavior by self-identification was obtained. The model had good overall fit, suggesting that cultural identity formation may contribute to anxiety experienced particularly by adolescents of mixed heritage. 相似文献