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   2207篇
  免费   122篇
  2329篇
  2023年   14篇
  2022年   20篇
  2021年   19篇
  2020年   46篇
  2019年   69篇
  2018年   78篇
  2017年   76篇
  2016年   74篇
  2015年   76篇
  2014年   83篇
  2013年   255篇
  2012年   150篇
  2011年   152篇
  2010年   86篇
  2009年   85篇
  2008年   105篇
  2007年   124篇
  2006年   85篇
  2005年   90篇
  2004年   90篇
  2003年   92篇
  2002年   90篇
  2001年   30篇
  2000年   28篇
  1999年   36篇
  1998年   31篇
  1997年   26篇
  1996年   25篇
  1995年   23篇
  1994年   25篇
  1993年   25篇
  1992年   8篇
  1991年   14篇
  1990年   7篇
  1989年   14篇
  1988年   7篇
  1987年   7篇
  1986年   9篇
  1985年   9篇
  1984年   5篇
  1983年   4篇
  1982年   5篇
  1981年   6篇
  1979年   3篇
  1978年   3篇
  1977年   4篇
  1976年   2篇
  1975年   4篇
  1974年   4篇
  1973年   2篇
排序方式: 共有2329条查询结果,搜索用时 0 毫秒
71.
Prior exposure to drugs of abuse has been shown to occlude the structural plasticity associated with living in a complex environment. Amphetamine treatment may also occlude some cognitive advantages normally associated with living in a complex environment. To test this hypothesis we examined the influence of prior exposure to amphetamine on fear conditioning in rats housed in either a standard or complex environment. Housing in a complex environment facilitated fear learning to an auditory conditioned stimulus (CS), but not to the training context, relative to animals housed singly or in a social group. Prior treatment with amphetamine eliminated this effect. These results indicate that living in a complex environment facilitates conditional freezing to an auditory CS, and that this effect is abolished by pretreatment with amphetamine.  相似文献   
72.
We previously showed that dietary cytidine (5')-diphosphocholine (CDP-choline) supplementation could protect against the development of memory deficits in aging rats. In the present study, younger rats exposed to impoverished environmental conditions and manifesting hippocampal-dependent memory impairments similar to those observed in the aging rodents were given CDP-choline, and its effects on this cognitive deficit were assessed. Male Sprague-Dawley rats reared for 3 mo in impoverished (IC) or enriched environmental (EC) conditions concurrently received either a control diet or a diet supplemented with CDP-choline (approximately 500 mg/kg/d). After 3 mo, rats were trained to perform spatial and cued versions of the Morris water maze, and their rates of acquisition and retention were compared. Impoverished rats exhibited a selective deficit in hippocampal-dependent spatial memory which could be ameliorated by feeding them CDP-choline. The CDP-choline had no memory-enhancing effect in enriched rats, nor did it prevent the memory impairment of impoverished rats if the animals consumed it for the initial or final months instead of for the entire 3-mo period. These findings indicate that long-term dietary CDP-choline supplementation can ameliorate the hippocampal-dependent memory impairment caused by impoverished environmental conditions in rats, and suggest that its actions result, in part, from a long-term effect such as enhanced membrane phosphatide synthesis, an effect shown to require long-term dietary supplementation with CDP-choline.  相似文献   
73.
Research examining the neuroanatomical bases of memory in mammals suggests that the hippocampus and dorsal striatum are parts of independent memory systems that mediate "cognitive" and stimulus-response "habit" memory, respectively. At the molecular level, increasing evidence indicates a role for immediate early gene (IEG) expression in memory formation. The present experiment examined whether acquisition of cognitive and habit memory result in differential patterns of IEG protein product expression in these two brain structures. Adult male Long-Evans rats were trained in either a hippocampal-dependent spatial water maze task, or a dorsal striatal-dependent cued water maze task. Ninety minutes after task acquisition, brains were removed and processed for immunocytochemical procedures, and the number of cells expressing Fos-like immunoreactivity (Fos-like-IR) and c-Jun-IR in sections from the dorsal hippocampus and the dorsal striatum were counted. In the dorsal hippocampus of rats trained in the spatial task, there were significantly more c-Jun-IR pyramidal cells in the CA1 and CA3 regions, relative to rats that had acquired the cued task, yoked controls (free-swim), or na?ve (home cage) rats. Relative to rats receiving cued task training and control conditions, increases in Fos-like IR were also observed in the CA1 region of rats trained in the spatial task. In rats that had acquired the cued task, patches of c-Jun-IR were observed in the posteroventral striatum; no such patches were evident in rats trained in the spatial task, yoked-control rats, or na?ve rats. The results demonstrate that IEG protein product expression is up-regulated in a task-dependent and brain structure-specific manner shortly after acquisition of cognitive and habit memory tasks.  相似文献   
74.
The development of the 42-item Asian American Values Scale-Multidimensional (AAVS-M) is presented. In Study 1, data from 163 Asian American respondents were subjected to a principal components analysis, which reduced the initial set of 180 items to 42 items divided into 5 components: collectivism, conformity to norms, emotional self-control, family recognition through achievement, and humility. The data also revealed initial evidence of the AAVS-M total and subscale scores' reliability and validity. In Study 2, data from 189 Asian American respondents were subjected to a confirmatory factor analysis, which supported a hierarchical factor structure underlying the AAVS-M. Additional reliability and validity evidence of AAVS-M total and subscale scores were found. In Study 3, data from 38 Asian American respondents yielded evidence of AAVS-M total and subscale scores' test-retest reliability.  相似文献   
75.
In 2 studies, the authors examined the degree to which implicit self-attitudes predicted people's spontaneous affective experiences in daily life. Across both studies, implicit attitudes toward the self (as measured by Implicit Association Tests) strongly predicted negative feeling states (as measured by computerized experience-sampling procedures), suggesting that implicit self-attitudes may be linked to changes in undifferentiated negative affect. Explicit attitudes toward the self generally did not account for these relations. Findings extend understanding of the factors that contribute to experienced affect and are the first to empirically link implicit self-attitudes with phenomenological affective experience in real-life settings over time.  相似文献   
76.
77.
Stressors external to the marriage frequently affect the way spouses evaluate their marital quality. To date, however, understanding of the interplay between external stress and internal relationship processes has been limited in two ways. First, research has generally examined only the short-term consequences of stress. Second, the mechanisms through which external stressors influence relationship outcomes are unclear. This study addressed both limitations by examining relationship cognitions that may mediate the effects of external stress throughout 4 years of marriage. Analyses confirmed that stressful experiences were associated with the trajectory of marital quality overtime. Furthermore, both the content and the organization of spouses' specific relationship cognitions mediated this effect. That is, stress negatively influenced the nature of spouses' marital perceptions as well as the way spouses interpreted and processed those perceptions. These findings draw attention to ways that the context of relationships shapes and constrains relationship processes.  相似文献   
78.
Although there is some understanding of the shared characteristics and predictors of psychological distress of women participating in hereditary breast and ovarian cancer registries, these same characteristics are only beginning to be identified in research on community women seeking genetic testing for BRCA1/BRCA2 gene mutations. This study provides an initial exploration of characteristics associated with family environments for 51 community women waiting to receive such genetic testing results. Thirty-four of the 36 women classified on family environment type of the Family Environment Scale (FES) were from Personal Growth-Oriented families. Comparisons of women with and without personal cancer histories resulted in a trend for women with personal cancer histories to be classified as from Independence-Oriented families. Reported distress appears to vary for different family emphases based on family and personal cancer history. A moral-religious family emphasis consistently appeared to be associated with decreased psychological distress. Preliminary analyses comparing these community women (who were not part of a hereditary registry but were self- or physician-referred) seeking genetic testing with normal and distressed family means found that increased cohesion and expressiveness may be related to decreased conflict, indicative of potentially supportive family environments for these women. When compared with normative data, a subset consisting of the Ashkenazi Jewish women showed a trend of less cohesion than normal families, but similar cohesion levels as distressed families.  相似文献   
79.
The potential role of environmental factors in autism spectrum disorders (ASD) is an area of emerging interest within the public and scientific communities. The high degree of heritability of ASD suggests that environmental influences are likely to operate through their interaction with genetic susceptibility during vulnerable periods of development. Evaluation of the plausibility of specific neurotoxicants as etiological agents in ASD should be guided by toxicological principles, including dose-effect dependency and pharmacokinetic parameters. Clinical and epidemiological investigations require the use of sufficiently powered study designs with appropriate control groups and unbiased case ascertainment and exposure assessment. Although much of the existing data that have been used to implicate environmental agents in ASD are limited by methodological shortcomings, a number of efforts are underway that will allow more rigorous evaluation of the role of environmental exposures in the etiology and/or phenotypic expression of the disorder. Surveillance systems are now in place that will provide reliable prevalence estimates going forward in time. Anticipated discoveries in genetics, brain pathology, and the molecular/cellular basis of functional impairment in ASD are likely to provide new opportunities to explore environmental aspects of this disorder.  相似文献   
80.
This study tested a conceptual model of active coping among a predominantly middle-class sample (N = 92) of Black lesbians (ages 18 to 68) attending a Black lesbian retreat. F. B. Tyler's (1978) active coping dimension of psychosocial competence and L. P. Anderson, C. L. Eaddy, and E. A. Williams's (1990) psychosocial competence model for Black Americans emphasizing the role of individual and environmental factors provided the theoretical framework for the study. A theoretical model was developed to examine whether internal (self-esteem, race and lesbian identification) and external (social support, perceived available lesbian, gay, bisexual, and transgendered resources) factors predicted active coping. Results confirmed that the model of internal and external factors was a statistically significant predictor of active coping.  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