全文获取类型
收费全文 | 20515篇 |
免费 | 979篇 |
国内免费 | 18篇 |
专业分类
21512篇 |
出版年
2020年 | 277篇 |
2019年 | 297篇 |
2018年 | 450篇 |
2017年 | 466篇 |
2016年 | 472篇 |
2015年 | 344篇 |
2014年 | 398篇 |
2013年 | 1785篇 |
2012年 | 692篇 |
2011年 | 761篇 |
2010年 | 448篇 |
2009年 | 434篇 |
2008年 | 615篇 |
2007年 | 582篇 |
2006年 | 490篇 |
2005年 | 448篇 |
2004年 | 432篇 |
2003年 | 408篇 |
2002年 | 403篇 |
2001年 | 736篇 |
2000年 | 749篇 |
1999年 | 507篇 |
1998年 | 242篇 |
1997年 | 214篇 |
1996年 | 180篇 |
1995年 | 175篇 |
1992年 | 409篇 |
1991年 | 344篇 |
1990年 | 381篇 |
1989年 | 372篇 |
1988年 | 357篇 |
1987年 | 320篇 |
1986年 | 354篇 |
1985年 | 334篇 |
1984年 | 284篇 |
1983年 | 241篇 |
1979年 | 229篇 |
1978年 | 205篇 |
1977年 | 181篇 |
1976年 | 175篇 |
1975年 | 244篇 |
1974年 | 288篇 |
1973年 | 252篇 |
1972年 | 239篇 |
1971年 | 202篇 |
1970年 | 188篇 |
1969年 | 226篇 |
1968年 | 244篇 |
1967年 | 186篇 |
1966年 | 203篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
131.
S B Chapman K A Culhane H S Levin H Harward D Mendelsohn L Ewing-Cobbs J M Fletcher D Bruce 《Brain and language》1992,43(1):42-65
This study examined narrative discourse in 20 children and adolescents at least 1 year after sustaining a head injury. Narratives were analyzed along the dimensions of language structure, information structure, and flow of information. Severity of impaired consciousness was associated with a significant reduction in the amount of language and information. The most important finding which emerged was the disruption in information structure. This pattern confirms the impression of disorganized discourse in severely injured children. Explanations for the disruption in information structure are explored in terms of the role of vocabulary, memory, and localization of lesion according to magnetic resonance imaging. In view of recent evidence that frontal lobe damage is associated with discourse formulation deficits in adults and is the most common site of focal lesion in closed head injury, we examined discourse patterns in individual patients with frontal lobe lesions. Preliminary data from our single-case studies suggest discourse patterns similar to those reported for adults with frontal lobe injuries. 相似文献
132.
J E Cutting K Springer P A Braren S H Johnson 《Journal of experimental psychology. General》1992,121(1):41-72
People find their way through cluttered environments with ease and without injury. How do they do it? Two approaches to wayfinding are considered: Differential motion parallax (DMP) is a retinal motion invariant of near and far objects moving against fixation; the information in optical flow (IOF) is a radial pattern of vectors, relying on decomposition of retinal flow. Evidence is presented that DMP guides wayfinding during natural gait, accounting for errors as well as correct responses. Evidence against IOF is also presented, and a space-time aliasing artifact that can contaminate IOF displays is explored. Finally, DMP and IOF are separated, showing they can yield different results in different environments. Thus, it is concluded that (a) DMP and IOF are different, (b) DMP and not IOF is used for wayfinding, (c) moving observers do not usually decompose retinal flow, and (d) optical flow may be a mathematical fiction with no psychological reality. 相似文献
133.
Reminder treatments have been shown to facilitate the retrieval of a variety of conditioned responses. Whether or not similar results would occur with an experimental paradigm which involves primarily memory for a stimulus, i.e., where no particular response is specified, is unclear. Accordingly, using Sprague-Dawley rats, we employed a latent inhibition paradigm with a long (10 days) retention interval between sucrose (CS) preexposure and sucrose-illness pairing (training). The results demonstrated a loss of latent inhibition following the 10-day retention interval suggesting "forgetting" of the CS preexposure. However, placing a single reminder exposure to the CS within the preexposure-to-training interval reinstated the preexposure effect. Controls indicated that in the absence of the initial preexposure the reminder per se did not produce latent inhibition. Thus, a reminder can reinstate a stimulus attribute (flavor representation) and explicit conditioned responses. 相似文献
134.
Observers classified sine-wave and square-wave gratings on the basis of fundamental frequency (Are the bars wide or narrow?) or on the basis of higher harmonic frequencies (Are the bars sharp or fuzzy?). Stimuli were presented in either the left (LVF) or right (RVF) visual field. When the classification was made on the basis of the fundamental frequencies (1 or 3 c/deg), there was a LVF/right hemisphere advantage. However, when the classification was on the basis of a sharp/fuzzy distinction which involved searching for the higher harmonic frequencies, then a RVF/left hemisphere advantage was found. 相似文献
135.
Although visuoconstructive impairment has been reported in both Alzheimer's (DAT) and Huntington's (HD) disease, there is little knowledge concerning how this cognitive deficit differs quantitatively and qualitatively in these two progressive dementias. To address this issue, the present study compared performances on the Clock Drawing Test (CDT: command and copy) of 25 DAT patients, 25 equally demented HD patients, and 25 elderly normal controls (NC). In the command condition, both patients groups were significantly impaired compared to the NC group. Although there was no significant difference between DAT and HD patients' total quantitative scores, a qualitative error analysis revealed a number of dissociations between the two patient groups. Graphic difficulties, very common in HD patients, were virtually absent in DAT patients; in contrast, conceptual errors were almost exclusively seen in DAT patients and were related to the severity of their dementia. Perseveration and "stimulus-bound" responses were also more frequent in DAT patients, and both groups made visuospatial errors. In the copy condition, the DAT, but not the HD, patients evidenced a marked improvement in performance. These results indicate that while both DAT and HD patients have significant visuoconstructive difficulties even in the early stages of their disorders, the specific cognitive processes underlying their quantitative impairments are quite different. It is possible that the DAT patients' conceptual errors are yet another indicator of the deterioration of their semantic knowledge. 相似文献
136.
Remembering pictures: pleasure and arousal in memory. 总被引:17,自引:0,他引:17
M M Bradley M K Greenwald M C Petry P J Lang 《Journal of experimental psychology. Learning, memory, and cognition》1992,18(2):379-390
Incidental memory performance for pictures that varied along the affective dimensions of pleasantness and arousal was assessed. For both an immediate and delayed (1 year later) free-recall task, only the arousal dimension had a stable effect on memory performance: Pictures rated as highly arousing were remembered better than low-arousal stimuli. This effect was corroborated in a speeded recognition test, in which high-arousal materials encoded earlier in the experiment produced faster reaction times than their low-arousal counterparts. Pleasantness affected reaction time decisions only for pictures not encoded earlier. These results suggest that whereas both the dimensions of pleasantness and arousal are processed at initial encoding, long-term memory performance is mainly affected by arousal. 相似文献
137.
138.
I examined preweanling rats' (Rattus norvegicus) expression of ultrasounds and secretion of ACTH when exposed to unfamiliar adult male rats or to their mothers. Pups at 7 days of age produced similar levels of ultrasonic vocalization near both unfamiliar males and mothers. However, these pups could discriminate familiar from unfamiliar adults because ACTH was significantly higher in pups near adult males than in those near mothers. At 14 days of age, pups avoided adult males but not their mothers; therefore, adult males represented a significant threat. Importantly, 14-day-old rats significantly reduced ultrasound production only when near adult males. Pups at 21 days of age no longer emitted ultrasounds when socially isolated or when near conspecific adults. In addition, 14- and 21-day-old rats produced similar elevated ACTH levels across stimulus conditions. Results show significant changes in preweanling rats' responses to conspecific adults. 相似文献
139.
This study sought to investigate the effects of mild head injury on a particular type of cognitive ability, verbal analogical
reasoning. The performance of 19 individuals with head injuries was compared to a group of 30 control subjects matched for
age, education, and gender on 100 verbal analogies. Solution times and error rates were modeled. Unstandardized regression
weights for individual subjects were correlated with subjects’ performance on a number of standardized ability tests. Results
showed that compared to the control subjects, the head injured subjects: (a) were significantly slower to solve the analogies,
and were particularly slow to perform certain processes: encoding/inference and comparison; (b) tended to show greater variability
in performance; and (c) had data that had a poorer componential model fit. The data suggest that analogical reasoning is affected
by a head injury, and that certain information processes may be responsible for performance deficits. 相似文献
140.
Measures of spatial cognition, neighborhood knowledge, and neighborhood use from the research described by Walsh, Krauss, and Regnier (1981) were examined to determine if laboratory tests of spatial cognition were significant predictors of older adults' use of their neighborhoods. The overall results show that laboratory-based measures of spatial cognition and subjects' knowledge of their neighborhoods are both significant predictors of their use of neighborhood goods and services. The ability to learn and remember the location and orientation of objects, when contextual cues were not provided at test, was more predictive of the participants' neighborhood use than either the participants' number of years in the neighborhood or their mobility. Spatial memory as measured by the Educational Testing Service Building Memory task predicted neighborhood knowledge, which was predictive of neighborhood use. 相似文献