全文获取类型
收费全文 | 2665篇 |
免费 | 192篇 |
国内免费 | 339篇 |
专业分类
3196篇 |
出版年
2023年 | 24篇 |
2022年 | 39篇 |
2021年 | 67篇 |
2020年 | 72篇 |
2019年 | 62篇 |
2018年 | 96篇 |
2017年 | 89篇 |
2016年 | 91篇 |
2015年 | 63篇 |
2014年 | 78篇 |
2013年 | 271篇 |
2012年 | 129篇 |
2011年 | 155篇 |
2010年 | 125篇 |
2009年 | 124篇 |
2008年 | 143篇 |
2007年 | 196篇 |
2006年 | 187篇 |
2005年 | 136篇 |
2004年 | 100篇 |
2003年 | 85篇 |
2002年 | 71篇 |
2001年 | 73篇 |
2000年 | 70篇 |
1999年 | 66篇 |
1998年 | 45篇 |
1997年 | 26篇 |
1996年 | 14篇 |
1995年 | 22篇 |
1993年 | 17篇 |
1992年 | 20篇 |
1991年 | 28篇 |
1990年 | 28篇 |
1989年 | 26篇 |
1988年 | 19篇 |
1987年 | 21篇 |
1986年 | 23篇 |
1985年 | 20篇 |
1984年 | 13篇 |
1983年 | 12篇 |
1982年 | 14篇 |
1979年 | 12篇 |
1978年 | 14篇 |
1976年 | 12篇 |
1975年 | 13篇 |
1973年 | 16篇 |
1972年 | 11篇 |
1970年 | 14篇 |
1969年 | 11篇 |
1968年 | 14篇 |
排序方式: 共有3196条查询结果,搜索用时 15 毫秒
101.
This article examines the usefulness of the Family Assessment Device(FAD) in assessing family functioning with school-aged children (under 12 years of age) compared to children 12 and older and mothers. FAD reports from 194 children with asthma (132 under 12 years; 62 12 years and older) were evaluated in comparison to mothers' FAD reports as well as mothers' reports on two other family functioning measures: the Family Inventory of Life Events (FILE) and the Impact on Family (IOF) scale, both relevant to functioning in families with children with asthma. Although FAD scale reliabilities were lowest in younger children (alpha = 48-.79), good concurrent validity was found with mothers' reports on the three different measures of family functioning. Older childrens' FAD scales showed good reliability (> .70) but poorer agreement with the various maternal measures. With modifications to make items more structured and simplified, the FAD could be tried with younger children, although documentation of improved reliability is needed before more widespread use with school-aged children is advocated. The measure already shows good agreement with maternal report in this younger age group, which likely would be strengthened with improved reliability. FAD reports in older children correlated less well with maternal measures, but may represent nonredundant information on family health from an independent perspective and are worth considering in addition to mothers' perspectives. 相似文献
102.
Working and long-term memory deficits in schizophrenia: is there a common prefrontal mechanism? 总被引:3,自引:0,他引:3
This study tested the hypothesis that dorsolateral prefrontal cortex deficits contribute to both working memory and long-term memory disturbances in schizophrenia. It also examined whether such deficits were more severe for verbal than nonverbal stimuli. Functional magnetic resonance imaging was used to assess cortical activation during performance of verbal and nonverbal versions of a working memory task and both encoding and recognition tasks in 38 individuals with schizophrenia and 48 healthy controls. Performance of both working memory and long-term memory tasks revealed disturbed dorsolateral prefrontal cortex activation in schizophrenia, although medial temporal deficits were also present. Some evidence was found for more severe cognitive and functional deficits with verbal than nonverbal stimuli, although these results were mixed. 相似文献
103.
The goal of this study was to test the response styles theory of depression in a sample of 3rd- and 7th-grade children. In addition, we examined whether the relationship between rumination and increases in depressive symptoms is mediated by hopelessness and low self-esteem. The procedure involved an initial assessment in which depressive symptoms, response styles, hopelessness, and self-esteem were assessed. The procedure also involved a follow-up assessment, 6 weeks later, in which depressive symptoms, hopelessness, and self-esteem were reassessed. Children with a ruminative response style exhibited increases in depressive symptoms over the 6-week period. In addition, the relationship between rumination and increases in depressive symptoms was mediated by both hopelessness and low self-esteem. Last, contrary to our hypotheses, neither distraction nor problem-solving response styles predicted decreases in depressive symptoms over the course of the study. 相似文献
104.
Unimanual left-right responses to up-down stimuli show a stimulus-response compatibility (SRC) effect for which the preferred mapping varies as a function of response eccentricity. Responses made in the right hemispace and, to a lesser extent, at a midline position, are faster with the up-right/down-left mapping than with the up-left/down-right mapping, but responses made in the left hemispace are faster with the up-left/down-right mapping. Also, for responses at the midline position, the preferred mapping switches when the hand is placed in a supine posture instead of the more usual prone posture. The response eccentricity effect can be explained in terms of correspondence of asymmetrically coded stimulus and response features, but it is not obvious whether the hand posture effect can be explained in a similar manner. The present study tested the implications of a hypothesis that the body of the hand provides a frame of reference with respect to which the response switch is coded as left or right. As was predicted by this hand referent hypothesis, Experiment 1 showed that the influence of hand posture (prone and supine) on orthogonal SRC was additive with that of response location. In Experiment 2, the location of the switch relative to the hand was varied by having subjects use either a normal grip in which the switch was held between the thumb and the index finger or a grip in which it was held between the little and the ring fingers. The magnitudes of the mapping preferences varied as a function of the grip and hand posture in a manner consistent with the hand referent hypothesis. 相似文献
105.
The motion of objects that are both translating and rotating can be decomposed into an infinite number of translational and rotational combinations. How, then, do such stimuli routinely elicit specific percepts and behavioral responses that are usually appropriate? A possible answer is that motion percepts are fully determined by the probability distributions of all the possible correspondences and differences in the stimulus sequence. To test the merits of this conceptual framework, we investigated the perceived motion elicited by a line that is both translating and rotating behind an aperture. When stimuli are presented such that a particular sequence of appearance and disappearance occurs at the aperture boundary, subjects report that the line is rotating only; furthermore, the perceived centers of rotation appear to describe a cycloidal trajectory, even when one aperture shape is replaced by another. These and other perceptual effects elicited by translating and rotating stimuli are all accurately predicted by the probability distribution of the possible sources of the physical movements, supporting the conclusion that motion perception is indeed generated by a wholly probabilistic strategy. 相似文献
106.
We extended perceptual studies of the Brodatz set of textured materials. In the experiments, texture perception for different texture sets, viewing distances, or lighting intensities was examined. Subjects compared one pair of textures at a time. The main task was to rapidly rate all of the texture pairs on a number scale for their overall dissimilarities first and then for their dissimilarities according to six specified attributes (e.g., texture contrast). The implied dimensionality of perceptual texture space was usually at least four, rather than three. All six attributes proved to be useful predictors of overall dissimilarity, especially coarseness and regularity. The novel attribute texture lightness, an assessment of mean surface reflectance, was important when viewing conditions were wide-ranging. We were impressed by the general validity of texture judgments across subject, texture set, and comfortable viewing distances or lighting intensities. The attributes are nonorthogonal directions in four-dimensional perceptual space and are probably not narrow linear axes. In a supplementary experiment, we studied a completely different task: identifying textures from a distance. The dimensionality for this more refined task is similar to that for rating judgments, so our findings may have general application. 相似文献
107.
A common research problem is the estimation of the population correlation between x and y from an observed correlation rxy obtained from a sample that has been restricted because of some sample selection process. Methods of correcting sample correlations for range restriction in a limited set of conditions are well-known. An expanded classification scheme for range-restriction scenarios is developed that conceptualizes range-restriction scenarios from various combinations of the following facets: (a) the variable(s) on which selection occurs (x, y and/or a 3rd variable z), (b) whether unrestricted variances for the relevant variables are known, and (c) whether a 3rd variable, if involved, is measured or unmeasured. On the basis of these facets, the authors describe potential solutions for 11 different range-restriction scenarios and summarize research to date on these techniques. 相似文献
108.
In a sample of 18 industrialized nations, measures of national character did not improve the power of socioeconomic variables in predicting unemployment rates. 相似文献
109.
George MS Nahas Z Bohning DE Lomarev M Denslow S Osenbach R Ballenger JC 《CNS spectrums》2000,5(11):43-52
Although the vagus nerve has traditionally been considered to perform efferent functions, in reality it performs significant afferent functions as well, carrying information from the body, head, and neck to the brain. Preliminary studies examining this afferent activity led to the theory that vagus nerve stimulation (VNS) could successfully control seizure activity in persons who are refractory to antiepileptic medications. Unlike other forms of brain stimulation, VNS is unable to directly stimulate multiple discrete areas of the brain; however, through several pathways, it is able to relay sensory information to higher brain regions. An implantable VNS device known as the VNSTM NeuroCybernetic Prosthesis (NCP) System has been used in approximately 9,000 epilepsy patients in Europe and the United States since 1994. The implant has reduced seizure frequency by an average of 25% to 30%, with minimal side effects. Studies underway are also showing some degree of success in the management of treatment-refractory depression. The future efficacy of the implantable system in other disorders may depend on whether the implant can be more precisely focused to affect different brain regions. Research in this area is underway. 相似文献
110.
Mean response times, variability, and skew in the responding of ADHD children: a response time distributional approach 总被引:7,自引:0,他引:7
Response time (RT) distributions from three fixed foreperiod conditions (2, 4, and 8 s) in a warned four-choice RT task were obtained for a group of boys with attention-deficit/hyperactivity disorder, combined type (ADHD; n = 17) and for two groups of normal control boys (age-matched, n = 18, and younger-aged, n = 10). Quantitative measures of distributional shape were derived by fitting the ex-Gaussian distributional model to the individual RT data. Statistical results indicate that the ADHD distributions differ from the age-matched control distributions with respect to the size of the tail (larger for the ADHD boys), but differ from the younger control distributions with respect to the location of the leading edge (slower for the younger control boys). Receiver operating characteristic (ROC) results reveal that the ex-Gaussian exponential component is highly diagnostic of the ADHD boys. 相似文献