全文获取类型
收费全文 | 3829篇 |
免费 | 203篇 |
出版年
2023年 | 39篇 |
2022年 | 41篇 |
2021年 | 74篇 |
2020年 | 81篇 |
2019年 | 114篇 |
2018年 | 151篇 |
2017年 | 150篇 |
2016年 | 168篇 |
2015年 | 116篇 |
2014年 | 133篇 |
2013年 | 470篇 |
2012年 | 207篇 |
2011年 | 229篇 |
2010年 | 135篇 |
2009年 | 136篇 |
2008年 | 187篇 |
2007年 | 152篇 |
2006年 | 136篇 |
2005年 | 103篇 |
2004年 | 123篇 |
2003年 | 128篇 |
2002年 | 98篇 |
2001年 | 79篇 |
2000年 | 83篇 |
1999年 | 56篇 |
1998年 | 41篇 |
1997年 | 38篇 |
1996年 | 22篇 |
1995年 | 24篇 |
1994年 | 21篇 |
1993年 | 15篇 |
1992年 | 37篇 |
1991年 | 27篇 |
1990年 | 46篇 |
1989年 | 44篇 |
1988年 | 37篇 |
1987年 | 21篇 |
1986年 | 30篇 |
1985年 | 29篇 |
1984年 | 22篇 |
1983年 | 21篇 |
1982年 | 16篇 |
1981年 | 10篇 |
1980年 | 8篇 |
1979年 | 17篇 |
1978年 | 12篇 |
1977年 | 7篇 |
1975年 | 7篇 |
1972年 | 12篇 |
1966年 | 7篇 |
排序方式: 共有4032条查询结果,搜索用时 0 毫秒
911.
A behavioral and genetic dissection of two forms of olfactory plasticity in Caenorhabditis elegans: adaptation and habituation 总被引:9,自引:0,他引:9
下载免费PDF全文
![点击此处可从《Learning & memory (Cold Spring Harbor, N.Y.)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Continuous presentation of an olfactory stimulus causes a decrement of the chemotaxis response in the nematode Caenorhabditis elegans. However, the differences between the learning process of habituation (a readily reversible decrease in behavioral response) and other types of olfactory plasticity such as adaptation (a decrement in response due to sensory fatigue, which cannot be dishabituated) have not been addressed. The volatile odorant diacetyl (DA) was used within a single paradigm to assess the distinct processes of olfactory adaptation and habituation. Preexposing and testing worms to 100% DA vapors caused a chemotaxis decrement that was not reversible despite the presentation of potentially dishabituating stimuli. This DA adaptation was abolished in worms with an odr-10 mutation (encoding a high-affinity DA receptor on the AWA neuron), even though naive chemotaxis remained unaffected. Conversely, DA adaptation remained intact in odr-1 mutants (defective in AWC neuron-mediated olfactory behavior), even though naive chemotaxis to DA decreased. Surprisingly, exposure to vapors of intermediate concentrations of DA (0.01% and 25%) did not cause worms to exhibit any response decrement. In contrast to preexposure to high DA concentrations, preexposure to low DA concentrations (0.001%) produced habituation of the chemotaxis response (a dishabituating stimulus could reverse the response decrement back to baseline levels). The distinct behavioral effects produced by DA preexposure highlight a concentration-dependent dissociation between two decremental olfactory processes: adaptation at high DA concentrations versus habituation at low DA concentrations. 相似文献
912.
913.
We present an illusory display in which a grid of outlined squares is positioned in front of a moving luminance gradient. Observers perceive a strong, illusory, 'wavelike' motion of the superimposed squares. We compared luminance effects on dynamic and static aspects of this illusion. The dynamic aspect was investigated by means of a temporal gradient, which induced an illusory pulsing of the outlined squares. The static aspect was investigated in two different ways. In one experiment, the outlined squares were positioned on a spatial gradient, which caused the squares to look like trapezoid shapes. In another experiment, the squares were positioned on different luminance fields, which affected their apparent size. In all experiments, luminance settings were the same, and observers were asked to indicate the direction and strength of the induced distortions. The overall results show large agreements between the dynamic distortion and the first-mentioned static distortion, whereas different tendencies emerged for the second static distortion. In a second series of experiments, we examined these distortions for various ranges of the luminance gradient and for border gradients as well. On the basis of these data, we explored how the directions of the perceived distortions of the single-gradient displays examined in this paper could be related to each other. 相似文献
914.
Focusing of attention is influenced by external features such as the presence of global or local target stimuli, but also by motivation and mood states. In the current study, we examined whether working on cognitively demanding tasks for 2 h, which induces mental fatigue, subsequently had a differential effect on global and local processing. The results showed that, compared to non-fatigued participants, fatigued participants particularly displayed compromised local processing. This indicates that mental fatigue may also manifest itself as effects on attentional focusing. The findings of this study are in line with recent ideas about the nature of fatigue-related cognitive deficits, implying disturbances in the control over attention and behaviour. 相似文献
915.
van den Brink D Brown CM Hagoort P 《Journal of experimental psychology. Learning, memory, and cognition》2006,32(2):364-372
An event-related brain potential experiment was carried out to investigate the temporal relationship between lexical selection and the semantic integration in auditory sentence processing. Participants were presented with spoken sentences that ended with a word that was either semantically congruent or anomalous. Information about the moment in which a sentence-final word could uniquely be identified, its isolation point (IP), was compared with the onset of the elicited N400 congruity effect, reflecting semantic integration processing. The results revealed that the onset of the N400 effect occurred prior to the IP of the sentence-final words. Moreover, the factor early or late IP did not affect the onset of the N400. These findings indicate that lexical selection and semantic integration are cascading processes, in that semantic integration processing can start before the acoustic information allows the selection of a unique candidate and seems to be attempted in parallel for multiple candidates that are still compatible with the bottom-up acoustic input. 相似文献
916.
The present study addressed the development of bimanual interference in children performing a dual motor task, in which each hand executes a different task simultaneously. Forty right-handed children (aged 4, 5-6, 7-8 and 9-11years, ten in each age group) were asked to perform a bimanual task in which they had to tap with a pen using the non-preferred hand and simultaneously trace a circle or a square with a pen using the preferred hand as quickly as possible. Tapping and tracing were also performed unimanually. Differences between unimanual and bimanual performance were assessed for number of taps, length of tap trace and mean tracing velocity. It was assumed that with increasing age, better bimanual coordination would result in better performance on the dual task showing less intermanual interference. The results showed that tapping and tracing performance increased with age, unimanually as well as bimanually, consistent with developmental advancement. However, the percentage of intermanual interference due to bimanual performance was not significantly different in the four age groups. Although performing the dual task resulted in mutual intermanual interference, all groups showed a significant effect of tracing shape. More specifically, all age groups showed a larger percentage decrease in tracing velocity when performing the circle compared to the square in the dual task. The present study reveals that children as young as four years are able to coordinate both hands when tapping and tracing bimanually. 相似文献
917.
Hagedoorn M Van Yperen NW Coyne JC van Jaarsveld CH Ranchor AV van Sonderen E Sanderman R 《Psychology and aging》2006,21(3):611-620
The association between marital status and distress was examined in a largely neglected group, namely older people (65 and older; N = 1,649). In this 2-wave study, married persons were less distressed than single persons, but perceived equity within the marriage and recency of bereavement qualified these findings. Married persons who felt inequitably treated were more distressed than persons who had always been single. Married persons reported less distress than recently (= 2 years ago) widowed persons, but only equitably treated married persons reported less distress than persons widowed for more than 2 years. Increased distress between the 2 waves occurred in recently widowed persons, and there was a decrease in distress in persons who were widowed shortly before the 1st wave. No gender effects were found. 相似文献
918.
People integrate the features of perceived events and of action plans, as well as of episodic stimulus—response relations,
intoevent files. We investigated whether the management of event files, and particularly the speed of updating the binding between the task-relevant
stimulus feature and the response, correlates with fluid intelligence. Indeed, the performance of participants scoring high
on Raven’s Standard Progressive Matrices test was less impaired by a mismatch between the stimulus—response relation in the
current and the previous trial. This result suggests that high intelligence is accompanied by a higher degree of flexibility
in handling event files—that is, by higher efficiency in updating episodic representations. 相似文献
919.
There is an ongoing debate about how best to conceptualize the unconscious. Early psychodynamic views employed theories influenced by physics to explain clinical material, while subsequent cognitivist views relied on computational models of the mind to explain laboratory data. More recently, advances in cognitive-affective neuroscience have provided new insights into the workings of unconscious cognition and affect. We briefly review some of this recent work and its clinical implications. 相似文献
920.
The authors show how the use of inequality constraints on parameters in structural equation models may affect the distribution of the likelihood ratio test. Inequality constraints are implicitly used in the testing of commonly applied structural equation models, such as the common factor model, the autoregressive model, and the latent growth curve model, although this is not commonly acknowledged. Such constraints are the result of the null hypothesis in which the parameter value or values are placed on the boundary of the parameter space. For instance, this occurs in testing whether the variance of a growth parameter is significantly different from 0. It is shown that in these cases, the asymptotic distribution of the chi-square difference cannot be treated as that of a central chi-square-distributed random variable with degrees of freedom equal to the number of constraints. The correct distribution for testing 1 or a few parameters at a time is inferred for the 3 structural equation models mentioned above. Subsequently, the authors describe and illustrate the steps that one should take to obtain this distribution. An important message is that using the correct distribution may lead to appreciably greater statistical power. 相似文献