全文获取类型
收费全文 | 57229篇 |
免费 | 1065篇 |
国内免费 | 4篇 |
专业分类
58298篇 |
出版年
2020年 | 529篇 |
2019年 | 658篇 |
2018年 | 830篇 |
2017年 | 889篇 |
2016年 | 925篇 |
2015年 | 694篇 |
2014年 | 846篇 |
2013年 | 4104篇 |
2012年 | 1546篇 |
2011年 | 1606篇 |
2010年 | 997篇 |
2009年 | 996篇 |
2008年 | 1457篇 |
2007年 | 1367篇 |
2006年 | 1266篇 |
2005年 | 1192篇 |
2004年 | 1136篇 |
2003年 | 1077篇 |
2002年 | 1119篇 |
2001年 | 1615篇 |
2000年 | 1522篇 |
1999年 | 1121篇 |
1998年 | 608篇 |
1997年 | 521篇 |
1992年 | 942篇 |
1991年 | 968篇 |
1990年 | 939篇 |
1989年 | 937篇 |
1988年 | 908篇 |
1987年 | 865篇 |
1986年 | 923篇 |
1985年 | 1001篇 |
1984年 | 818篇 |
1983年 | 776篇 |
1982年 | 606篇 |
1981年 | 637篇 |
1979年 | 905篇 |
1978年 | 662篇 |
1977年 | 577篇 |
1976年 | 611篇 |
1975年 | 808篇 |
1974年 | 913篇 |
1973年 | 940篇 |
1972年 | 776篇 |
1971年 | 733篇 |
1970年 | 719篇 |
1969年 | 761篇 |
1968年 | 913篇 |
1967年 | 836篇 |
1966年 | 819篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
261.
Charles Flicker Steven H. Ferris Thomas Crook Raymond T. Bartus 《Brain and language》1987,31(2):187-200
Young normals, elderly normals, and patients with either mild-to-moderate or severe senile dementia of the Alzheimer type (SDAT) were administered several tests of language function and remote memory. On all of the language tests examined, elderly normals exhibited a mild, nonsignificant performance decrement relative to the young normals. Advanced SDAT patients were markedly impaired on all of the tests. Early dementia patients were most impaired, relative to aged normals, on tests of object naming, category instance fluency, and remote memory. The deficit was smaller on the WAIS vocabulary subtest, on selecting the name of a visually presented object, and on recalling the function of an object. Early SDAT patients were least impaired in selecting the picture of an object after its name had been provided and in selecting objects that belong to a specified functional category. The results are consistent with the notion that the language dysfunction in early SDAT is due to a deficit in semantic memory function in which general, categorical information remains available whereas information about specific attributes becomes less accessible. The object naming test might be useful in the assessment of treatment effects upon SDAT because of its sensitivity and specificity to dementia, its high face validity, and its independence of recent memory. 相似文献
262.
263.
Judgments on the subjective duration of simple and complex imagined situations are studied. Four facets, concerning the evaluation of the situation (pleasant/unpleasant) and the characteristics of its events (many/few, variable/monotonous, difficult/easy), are taken into account. These facets proved significant for duration judgments in previous studies in which subjects were exposed to situations varying with respect to one of them. In this paper, we study whether these time-perception facets have comparable effects on the symbolic temporal basis of duration judgments. that is, whether they allow one to account for differences in the beliefs about duration experience in imagined situations. Two approaches were chosen: (1) Three groups of subjects compared the durations of all possible pairs of situations characterized by facet elments x and y. The confusion probabilities could be scaled in one dimension for all groups. The facet elements defined intervals that were hierarchically nested. (2)The facets allowed us to distinguish 24 structuples. For each of them, a concrete situation was described in writing. Seventy-six subjects rated the subjective durations of the situations. The structuples led to a partial order that corresponded well to the duration ratings. Moreover, three of the facets showed significant main effects, and the fourth interacted significantly with two others. Finally, the facets were useful in explaining the similarity structure of the duration ratings. 相似文献
264.
Regional cerebral blood flow (rCBF) may be measured with inhalation techniques that use end-expired values of radioactivity to estimate the isotope concentration in arterial blood. These end-expired data are used as an input function in a mathematical equation to derive rCBF. End-expired air is assumed normally to be in equilibrium with the arterial blood at the alveolar surface of the lung during regular (passive) breathing; this assumption may not be valid during continuous phonation. We therefore have analyzed breathing (inhalation/exhalation) patterns and end-expired radioactivity (133Xe) during (1) speaking, (2) singing, and (3) humming of the national anthem, and also during (4) passive breathing. Statistically significant differences in breathing patterns were measured between a group of nonmusicians and two groups of musicians (singers) during the phonation tasks: The nonmusicians breathed more often (and more rapidly) and exhibited less variability in their breathing patterns than did the musicians. Notwithstanding these differences, the shapes of smoothed functions derived from the end-expired values were not influenced appreciably during phonation (except possibly during talking). The latter finding suggests that estimates of rCBF derived with these data should not be confounded seriously because of the continuous phonation. 相似文献
265.
Douglas Cullinan Kenneth D. Gadow Michael H. Epstein 《Journal of abnormal child psychology》1987,15(4):469-477
Psychotropic drug treatment in learning-disabled (LD), educable mentally retarded (EMR), and seriously emotionally disturbed (ED) children and adolescents receiving public school special education services was examined. The findings indicated that while treatment prevalence rates for EMR and ED groups were comparable, the rate for LD students was much lower. In the LD sample, pharmacotherapy was associated with higher ratings of behavioral deviance, longer placement in special education, less social integration, and greater peer rejection, which suggests that symptom severity is an important determiner of pharmacotherapy in this population. 相似文献
266.
Joseph M. Byrne Daphne J. Smith Joan E. Backman 《Journal of abnormal child psychology》1987,15(2):239-246
This study evaluated the clinical validity of the Intellectual Screening, Development, and Achievement scales of the Personality Inventory for Children-Revised (PIC-R), as well as the newly derived PIC-R Factor IV scale, in identifying cognitive impairment in a clinic-referred sample of preschoolers. The clinical validity of these PIC-R subscales was also compared to that of the Minnesota Child Development Inventory (MCDI). The results showed that the PIC-R scales and Factor IV were reasonably successful in identifying cognitively impaired preschoolers, but much less successful in identifying cognitively normal preschoolers. Overall, the MCDI was the most successful in correctly identifying the preschoolers' cognitive status. 相似文献
267.
Locational representation in imagery: The third dimension 总被引:1,自引:0,他引:1
Nancy H. Kerr 《Memory & cognition》1987,15(6):521-530
Six experiments were conducted to test the relative processing characteristics of picture-plane and three-dimensional imagery as indexed by tasks that required subjects to keep track of successive locations in multiunit visual displays. Subjects were shown symmetrical displays either drawn on cardboard or constructed with three-dimensional blocks. They then were required to imagine these matrices and follow pathways through a series of adjacent squares (blocks) within the matrices. The pathways were described by a series of verbal terms that indicated the direction of the next square (block) in the pathway. Subjects experienced difficulty in performing the task with picture-plane displays composed of as few as 16 squares (4×4), but they rarely made errors with a three-dimensional matrix of 27 blocks (3×3×3). Performance with the three-dimensional task dropped dramatically when the matrix size was increased to 4×4×4. The results replicated previous findings that the image processing capacity for location in two-dimensional imagery is about three units in each direction, and they indicate that adding the depth dimension increases the capacity for representation of spatial location in imagery. 相似文献
268.
F H de Jonge J Burger F van Haaren H Overdijk N E van de Poll 《Behavioral and neural biology》1987,47(3):369-383
The influence of sexual experience on preference behavior was investigated in adult female rats. In the first experiment, preference behavior for sexually active males versus estrous females was investigated in female rats who were experienced with mounting behavior. Preference of these mount experienced females was compared to preference of females who were naive in this respect. Mount experience with estrous females induced a female-directed preference in ovariectomized female rats, irrespective of whether the females were treated with OIL or with testosterone-propionate (500 micrograms TP, injected once 48 h prior to testing). Sexually naive, OIL-treated females did not show a preference for males or females, but TP induced a preference for a male. Individual differences in mount frequency were not correlated with preference behavior. In the second experiment, the influence of experience with feminine sexual responses on preference behavior was investigated. OIL-treated and TP-treated females oriented equally toward males and females when they had been given the opportunity to copulate with males prior to the preference tests. The results strongly suggest that prior sexual experience is an important determinant of preference behavior. The female's behavior during sexual interactions was, however, not predictive of later preference. 相似文献
269.
A long-term temporal component of working memory of rats trained on the radial maze has been shown to be susceptible to disruption by the protein synthesis inhibitor, anisomycin. It is not clear whether protein synthesis played a role in working memory because accurate performance on the radial maze required the storage of a large amount of information, or because the information was to be held in store for relatively long periods of time. This experiment tested these hypotheses by assessing the effect of anisomycin on choice accuracy in a comparatively simple spatial delayed alternation task. Results indicate that under the present training conditions, protein involvement in working memory is related more to the length of the retention interval than to the amount of information retained. 相似文献
270.
Mary L. Jasnoski David S. Cordray B. Kent Houston Wayne H. Osness 《Motivation and emotion》1987,11(1):1-17
This psychophysiological evaluation of an aerobic exercise program examined specifically whether aerobic training modified Pattern A for those individuals at behavioral risk for developing coronary heart disease, i.e., young Type A individuals. At pretest and posttest of this secondary prevention study, Type A and Type B subjects were assessed in three conditions: aerobic exercise program, nonaerobic activity (Aikido, a martial art) control, and notreatment control. After 10 weeks, Type A but not Type B subjects exhibited lower Pattern A behavior in the aerobic program than in control conditions. Average workout pulse rates and differentially reliable increases in aerobic capacity indicated that aerobic training was indeed aerobic, whereas aikido activity was not. Even though selected nonaerobic factors, such as locus of control and group participation, did not mediate the Pattern A decrease for Type A's when comparing aikido and aerobic conditions, changes in aerobic capacity may have been the mediator. Generalizability of the results and implications for theoretical development and clinical intervention are discussed. 相似文献