首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   13771篇
  免费   311篇
  国内免费   194篇
  2015年   37篇
  2012年   1188篇
  2011年   1374篇
  2010年   338篇
  2009年   142篇
  2008年   1055篇
  2007年   1104篇
  2006年   986篇
  2005年   845篇
  2004年   764篇
  2003年   774篇
  2002年   704篇
  2001年   491篇
  2000年   543篇
  1999年   273篇
  1998年   92篇
  1997年   60篇
  1996年   79篇
  1995年   47篇
  1994年   96篇
  1993年   97篇
  1992年   111篇
  1991年   116篇
  1990年   100篇
  1989年   105篇
  1988年   117篇
  1987年   134篇
  1986年   92篇
  1985年   125篇
  1984年   118篇
  1983年   149篇
  1982年   103篇
  1981年   100篇
  1980年   87篇
  1979年   89篇
  1978年   77篇
  1966年   48篇
  1965年   132篇
  1964年   105篇
  1963年   127篇
  1962年   55篇
  1958年   155篇
  1957年   120篇
  1956年   99篇
  1955年   65篇
  1954年   59篇
  1953年   52篇
  1952年   46篇
  1951年   51篇
  1950年   48篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
921.
Practice effects in memory testing complicate the interpretation of score changes over repeated testings, particularly in clinical applications. Consequently, several alternative forms of the Auditory Verbal Learning Test (AVLT) have been developed. Studies of these typically indicate that the forms examined are equivalent. However, the implication that the forms in the literature are interchangeable must be tempered by several caveats. Few studies of equivalence have been undertaken; most are restricted to the comparison of single pairs of forms, and the pairings vary across studies. These limitations are exacerbated by the minimal overlapping across studies in variables reported, or in the analyses of equivalence undertaken. The data generated by these studies are nonetheless valuable, as significant practice effects result from serial use of the same form. The available data on alternative AVLT forms are summarized, and recommendations regarding form development and the determination of form equivalence are offered.  相似文献   
922.
Cortical reorganization in poststroke aphasia is not well understood. Few studies have investigated neural mechanisms underlying language recovery in severe aphasia patients, who are typically viewed as having a poor prognosis for language recovery. Although test-retest reliability is routinely demonstrated during collection of language data in single-subject aphasia research, this is rarely examined in fMRI studies investigating the underlying neural mechanisms in aphasia recovery. The purpose of this study was to acquire fMRI test-retest data examining semantic decisions both within and between two aphasia patients. Functional MRI was utilized to image individuals with chronic, moderate-severe nonfluent aphasia during nonverbal, yes/no button-box semantic judgments of iconic sentences presented in the Computer-assisted Visual Communication (C-ViC) program. We investigated the critical issue of intra-subject reliability by exploring similarities and differences in regions of activation during participants' performance of identical tasks twice on the same day. Each participant demonstrated high intra-subject reliability, with response decrements typical of task familiarity. Differences between participants included greater left hemisphere perilesional activation in the individual with better response to C-ViC training. This study provides fMRI reliability in chronic nonfluent aphasia, and adds to evidence supporting differences in individual cortical reorganization in aphasia recovery.  相似文献   
923.
A high percentage of Parkinson's disease (PD) patients show cognitive impairments in addition to the cardinal motor symptoms. These deficits primarily concern executive functions most probably linked to dysfunctions in prefrontal regions due to decreased dopaminergic transmission in fronto-striatal loops. To investigate possible associations between decision-making and executive functions in PD, we examined 20 non-demented PD patients and 20 healthy control subjects with a neuropsychological test battery and the Game of Dice Task. In this computerised decision-making task, the rules for gains and losses and the winning probabilities are obvious and stable. Thus, strategic components besides feedback processing might influence decision-making in this task. We found that PD patients were impaired in the Game of Dice task performance and that the frequency of disadvantageous choices correlated with both executive functions and feedback processing. We suggest that decision-making deficits of PD patients in explicit gambling situations might be associated with dysfunctions in two different fronto-striatal loops: the limbic-orbitofrontal-striatal loop, involved in feedback processing, and the dorsolateral prefrontal-striatal loop, involved in executive functions.  相似文献   
924.
Ambiguous visual information often produces unstable visual perception. In four psychophysical experiments, we found that unambiguous tactile information about the direction of rotation of a globe whose three-dimensional structure is ambiguous significantly influences visual perception of the globe. This disambiguation of vision by touch occurs only when the two modalities are stimulated concurrently, however. Using functional magnetic resonance imaging, we discovered that touching the rotating globe, even when not looking at it, reliably activates the middle temporal visual area (MT+), a brain region commonly thought to be crucially involved in registering structure from motion. Considered together, our results show that the brain draws on somatosensory information to resolve visual conflict.  相似文献   
925.
Our objective was to develop a personality profile of men who are violent toward their partners. A total of 52 experienced clinicians described either a current male patient who was violent toward his partner (and only toward his partner) or who was maritally distressed but nonviolent using the Shedler-Westen Assessment Procedure-200 (SWAP-200), a Q-sort instrument designed to harness the judgments of clinicians. Partner-violent patients showed significantly higher scores on the SWAP-200 antisocial and borderline personality disorder scales. In contrast, patients who were maritally distressed evidenced higher scores on the SWAP-200 obsessive, avoidant, and high-functioning depressive scales. The men who were violent toward their partners were more antisocial and emotionally dysregulated, which is consistent with theory, and less obsessive, which has not been theoretically explored. The groups did not differ on theoretically important dimensions of personality including paranoid, dependent, and hostile features.  相似文献   
926.
The purpose of this study was to assess the prevalence of each of the nine DSM criteria for borderline personality disorder and the prevalence of the disorder itself in the first-degree relatives of borderline probands and Axis II comparison subjects. Four hundred and forty-five inpatients were interviewed about familial borderline psychopathology using the Revised Family History Questionnaire--a semistructured interview of demonstrated reliability. Of these 445 subjects, 341 met both DIB-R and DSM-III-R criteria for BPD and 104 met DSM-III-R criteria for another type of personality disorder (and neither criteria set for BPD). The psychopathology of 1,580 first-degree relatives of borderline probands and 472 relatives of Axis II comparison subjects was assessed. Both DSM-III-R and DSM-IV BPD were found to be more common among the relatives of borderline than Axis II comparison probands. However, five of the criteria for BPD (inappropriate anger, affective instability, paranoia/dissociation, general impulsivity, and intense, unstable relationships) and all four sectors of borderline psychopathology (affect, cognition, impulsivity, and interpersonal relationships) were found to be both more common and discriminating than the BPD diagnosis itself. Taken together, the results of this study suggest that the subsyndromal phenomenology of BPD may be more common than the borderline diagnosis itself.  相似文献   
927.
The human voice was one of the more elusive acoustical phenomena to study in the 19th century and therefore a crucial test of Hermann von Helmholtz's new theory of sound. This article describes the origins of instruments used to study vowel sounds: synthesizers for production, resonators for detection, and manometric flames for visual display. Instrument maker Rudolph Koenig played a leading role in transforming Helmholtz's ideas into apparatus. In particular, he was the first to make the human voice visible for research and teaching. Koenig's work reveals the rich context of science, craft traditions, experiment, demonstration culture, and commerce in his Paris workshop.  相似文献   
928.
We investigated the effect of learning one category structure on the learning of a related category structure. Photograph-name combinations, called identifiers, were associated with values of four demographic attributes. Two problems were related by analogous demographic attributes, common identifiers, or both to examine the impact of common identifier, related general characteristics, and the interaction of the two variables in mediating learning transfer from one category structure to another. Problems sharing the same identifier information prompted greater positive transfer than those not sharing the same identifier information. In contrast, analogous defining characteristics in the two problems did not facilitate transfer. We computed correlations between responses to first-problem stimuli and responses to analogous second-problem stimuli for each participant. The analogous characteristics produced a tendency to respond in the same way to corresponding stimuli in the two problems. The results support an alignment between category structures related by analogous defining characteristics, which is facilitated by specific identifier information shared by two category structures.  相似文献   
929.
It is often intuitively assumed that disconnected image fragments result in a representation of separate objects. When objects are partly occluded, disconnected image fragments can still result in a representation of a single object, based on visual completion. In a simultaneous matching task, displays showing one object, partly occluded objects, or two objects were compared with each other. When only a translation was required to match pairs of displays, one-object displays were matched faster than both occluded-object and two-object displays, which did not differ significantly from each other. When mental rotation and translation were required, the one-object displays were again matched the fastest. In addition, an advantage for occluded-object displays compared with two-object displays was found. We conclude that when the generation of a mental representation is likely, object-based connectedness determines object matching. Mental rotation then seems to depend on the number of objects rather than on the number of image fragments.  相似文献   
930.
Hamel R  Panicola M 《America》2004,190(14):6-13
  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号