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   188214篇
  免费   8340篇
  国内免费   155篇
  196709篇
  2020年   2778篇
  2019年   3445篇
  2018年   3661篇
  2017年   4099篇
  2016年   4710篇
  2015年   3932篇
  2014年   4805篇
  2013年   23464篇
  2012年   4976篇
  2011年   4282篇
  2010年   4092篇
  2009年   4858篇
  2008年   4433篇
  2007年   4056篇
  2006年   4492篇
  2005年   4408篇
  2004年   3886篇
  2003年   3476篇
  2002年   3340篇
  2001年   4049篇
  2000年   3907篇
  1999年   3661篇
  1998年   2895篇
  1997年   2728篇
  1996年   2644篇
  1995年   2454篇
  1994年   2412篇
  1993年   2389篇
  1992年   3039篇
  1991年   2845篇
  1990年   2689篇
  1989年   2549篇
  1988年   2535篇
  1987年   2526篇
  1986年   2561篇
  1985年   2757篇
  1984年   2752篇
  1983年   2497篇
  1982年   2449篇
  1981年   2418篇
  1980年   2247篇
  1979年   2529篇
  1978年   2333篇
  1977年   2246篇
  1976年   2050篇
  1975年   2237篇
  1974年   2313篇
  1973年   2246篇
  1972年   1831篇
  1971年   1725篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
961.
Prior research has shown that parenting stress levels can be quite high among families of children with attention deficit hyperactivity disorder (ADHD). This study investigated the degree to which such stress was related not only to the child's ADHD, but also to various other child, parent, and family-environment circumstances. Multimethod assessments were conducted on 104 clinic-referred children with ADHD. Data collected from these subjects were entered into hierarchical multiple-regression analyses, utilizing the Parenting Stress Index as the criterion. The results showed that child and parent characteristics accounted for a substantial portion of the variance in overall parenting stress. The child's oppositional-defiant behavior and maternal psychopathology were especially potent predictors. The severity of the child's ADHD, the child's health status, and maternal health status also emerged as significant predictors. These findings are discussed in terms of their impact upon the clinical management of children with ADHD.The authors are grateful to Mary Maher and Paula Nevins for their assistance in collecting and coding the data. The authors would also like to thank Dr. Kenneth Fletcher for his helpful comments regarding the statistical analyses.  相似文献   
962.
A short-term longitudinal study was conducted to determine whether self-regulation at 4 years could be predicted from child and maternal measures obtained when the children were age 24 months. The subjects were 69 children and their mothers drawn from the general community. Criterion behaviors assessed at 4 years were those suggestive of attention-deficit hyperactivity disorder. Of the 24-month child measures, maternal ratings of the child's impulsivity and attention span, plus an objective measure of delay ability, were the most effective predictors. Maternal negativity, as assessed in mother-child interaction, predicted the criterion behaviors, even after the child's behavior as an elicitor of maternal behavior was controlled. Maternal child-rearing attitudes on the dimensions of warmth and aggravation were also effective predictors, even after controlling for the child's emotionality as a possible determinant of maternal attitudes. It is argued that the results with the maternal attitude measures provide support for the hypothesis that maternal behavior is a contributor to the development of self-regulation.This research was supported by a State of Ohio Academic Challenge Grant to the Bowling Green State University Clinical Psychology Program, and by a Basic Grant awarded to the first author by the Bowling Green State University Faculty Research Committee. The authors are grateful to Eric Dubow, Douglas Ullman, and two anonymous reviewers for their helpful comments and criticisms on previous versions of this article.  相似文献   
963.
964.
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   
965.
Two studies with the same subjects examined dyslexic children's puzzling superiority in forced left ear (LE) dichotic recall with consonant-vowel (CV) combinations. Thirty dysphonemic dyslexics were compared to 30 age-matched and 30 younger reading-matched normal readers. The children were tested in directed attention dichotic listening and in pseudoword decoding, word recognition, reading comprehension, spelling, arithmetic, and general intelligence (IQ). Failure to replicate the LE effect in the first experiment or in free-recall trials suggests its probable origin in aberrant attention/arousal rather than in deviant verbal lateralization. Experiment two replicated the superior LE effect in comparison to both control groups but also found the dyslexics poorer at the right ear (RE). Laterality coefficients confirmed that the dyslexics were more weakly lateralized. Corrections for stimulus dominance revealed that the uncorrected scores (1) concealed the extreme difficulty of the task and (2) obscured floor effects in the LE performance of the normals. Correlations suggest cautiously that CV lateralization may be associated inversely with reading comprehension and word decoding in the dyslexics and normal readers. The results provide mild support for the hypothesis that weak attentional lateralization for CVs in dyslexia may result from the precocious development of posterior right hemisphere attentional systems in compensation for presumed posterior left hemisphere lesions. No support was found for the competing hypothesis that such weak lateralization may be a component of the dyslexics' primary, correlated, or secondary deficit symptomatology.  相似文献   
966.
Twenty-four boys with attention deficit-hyperactivity disorder (ADHD) participating in an intensive summer treatment program each received b.i.d. placebo and two doses of methylphenidate (MPH, 0.3 mg/kg and 0.6 mg/kg) crossed with two classroom settings: a behavior modification classroom including a token economy system, time out and daily home report card, and a regular classroom setting not using these procedures. Dependent variables included classroom observations of on-task and disruptive behavior, academic work completion and accuracy, and daily self-ratings of performance. Both MPH and behavior modification alone significantly improved children's classroom behavior, but only MPH improved children's academic productivity and accuracy. Singly, behavior therapy and 0.3 mg/kg PMH produced roughly equivalent improvements in classroom behavior. Further, the combination of behavior therapy and 0.3 mg/kg MPH resulted in maximal behavioral improvements, which were nearly identical to those obtained with 0.6 mg/kg MPH alone.The authors gratefully acknowledge the assistance of Patricia Donovan, Michelle Berry, Mary Ingram, Patricia Wells, Beth Gnagy, Karen Greenslade, Mary Hamilton, and the entire staff of the Western Psychiatric Institute and Clinic ADHD Summer Treatment Program.  相似文献   
967.
It is known that speed and accuracy in recognizing words are constrained by the frequency of occurrence of these words ("frequency effect"). This study examines the relationship between educational level and the word frequency effect. We postulated that individual exposure to words that are rated lower in frequency tables should be greater among subjects with higher education and therefore hypothesized that the magnitude of the frequency effect should not be as marked within such a population as among subjects with a lesser educational level. A total of 40 neurologically healthy adults, half with an average of 18 years of formal education and the other half with an average of 11 years, participated in a lexical decision experiment. Results confirmed our hypothesis; that is, significant frequency effects on reaction times were obtained in both groups but this effect was of greater magnitude for the less educated as opposed to the more educated subgroup. The significance of this finding is discussed by reference to current models of word recognition.  相似文献   
968.
This study was undertaken to confirm previous findings that Long-Evans rats exhibit age-related changes in the diurnal/nocturnal distribution of water intake and to examine the circadian pattern of these age-related changes. Twenty-one aged and 10 young pathogen-free rats were continuously monitored for water consumption over 12:12 h light/dark cycles. ANOVA, profile analysis, and cosinor analysis each demonstrated that aged rats differed from young rats. The age-related changes in circadian pattern can be described as a blunted rhythm (decreased amplitude) and an altered timing of peak activity (advanced acrophase). These differences, however, were only apparent in a subset of aged rats with the remaining aged rats exhibiting a circadian pattern indistinguishable from that of the young group.  相似文献   
969.
Learning a bimanual coordination task (synchronization to a visually specified phasing relation) was studied as a dynamical process over 5 days of practicing a required phasing pattern. Systematic probes of the attractor layout of the 5 Ss' coordination dynamics (expressed through a collective variable, relative phase) were conducted before, during, and after practice. Depending on the relationship between the initial coordination dynamics (so-called intrinsic dynamics) and the pattern to be learned (termed behavioral information, which acts as an attractor of the coordination dynamics toward the required phasing), qualitative changes in the phase diagram occurred with learning, accompanied by quantitative evidence for loss of stability (phase transitions). Such effects persisted beyond 1 week. The nature of change due to learning (e.g., abrupt vs. gradual) is shown to arise from the cooperative or competitive interplay between behavioral information and the intrinsic dynamics.  相似文献   
970.
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   
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