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   9392篇
  免费   124篇
  国内免费   4篇
教育   6570篇
科学研究   1063篇
各国文化   89篇
体育   724篇
综合类   2篇
文化理论   99篇
信息传播   973篇
  2022年   76篇
  2021年   125篇
  2020年   174篇
  2019年   311篇
  2018年   376篇
  2017年   340篇
  2016年   302篇
  2015年   199篇
  2014年   207篇
  2013年   1791篇
  2012年   200篇
  2011年   197篇
  2010年   168篇
  2009年   143篇
  2008年   151篇
  2007年   136篇
  2006年   144篇
  2005年   120篇
  2004年   136篇
  2003年   110篇
  2002年   103篇
  2001年   135篇
  2000年   131篇
  1999年   117篇
  1998年   78篇
  1997年   78篇
  1996年   91篇
  1995年   70篇
  1994年   62篇
  1993年   95篇
  1992年   114篇
  1991年   120篇
  1990年   122篇
  1989年   98篇
  1988年   88篇
  1987年   109篇
  1986年   101篇
  1985年   110篇
  1984年   92篇
  1983年   96篇
  1982年   97篇
  1981年   79篇
  1980年   78篇
  1979年   104篇
  1978年   97篇
  1977年   89篇
  1976年   78篇
  1974年   70篇
  1973年   68篇
  1971年   58篇
排序方式: 共有9520条查询结果,搜索用时 15 毫秒
181.
The rate of citation duplication was examined in three databases: MEDLINE, BIOSIS, and LIFE SCIENCES COLLECTION. Duplicate citations were found to be more pertinent than unique citations. The duplicate citations came from a highly compact literature, while those from a single database were very widely scattered. The pertinent duplicated citations were more likely to be retrieved in searches that had more terms overall, had a higher percentage of thesaurus terms, and had terms which appeared in both title and abstract. These results suggest that the rate of duplication of citations in multidatabase searches may be used to rank output according to probable pertinence.  相似文献   
182.
Acute coronary syndrome (ACS) is a term for a range of clinical signs and symptoms suggestive of myocardial ischemia. It results in functional and structural changes and ultimately releasing protein from injured cardiomyocytes. These cardiac markers play a major role in diagnosis and prognosis of ACS. This study aims to assess the efficacy of heart type fatty acid binding protein (h-FABP) as a marker for ACS along with the routinely used hs-TropT. In our observational study, plasma h-FABP (cut-off 6.32 ng/ml) and routinely done hs-Trop T (cutoff 0.1 and 0.014 ng/ml) were estimated by immunometric laboratory assays in 88 patients with acute chest pain. Based on the clinical and laboratory test findings the patients were grouped into ACS (n = 41) and non-ACS (n = 47). The diagnostic sensitivity, specificity, NPV, PPV and ROC curve at 95 % CI were determined. Sensitivity of hs-TropT (0.1 ng/ml), hs-TropT (0.014 ng/ml) and h-FABP were 53, 86 and 78 % respectively and specificity for the same were 98, 73 and 70 % respectively. Sensitivity, specificity and NPV calculated for a cut-off combination of hs-TropT 0.014 ng/ml and h-FABP was 100, 51 and 100 % respectively. These results were substantiated by ROC analysis. Measurement of plasma h-FABP and hs-TropT together on admission appears to be more precise predictor of ACS rather than either hs-Trop T or h-FABP.  相似文献   
183.
184.
We present a practical way of adapting and using four research-based assessments for different purposes in an electricity and magnetism course for K-8 science teachers. The course is designed to accomplish conceptual change toward accepted scientific conceptions as well as introducing teachers to materials and activities appropriate for their classrooms. Our data support that using the research-based tests to identify alternative conceptions and discuss test results with teachers is a promising way to use the knowledge of alternative conceptions in professional development. We also identify some mismatches between the research of conceptual change and its use in programs of professional development.
Ji ShenEmail:
  相似文献   
185.
Factors that influence the incidence of utilization deficiencies and other recall/strategy-use patterns on a strategic memory task were evaluated in two hundred and fourteen 7- and 9-year-old children. Both utilization deficiencies and the incidence of children showing increases in both recall and strategy use over phases were more likely to be observed on phase transitions involving prompting or when different lists of items were included on consecutive trials; in contrast, increases in recall in the absence of increases in strategy use were more likely to be found between trials consisting of the same stimulus items. This research clearly indicates that patterns of recall/strategy-use relations, including utilization deficiencies, vary meaningfully with the age of the child and a variety of contextual factors.  相似文献   
186.
For this study, information on Who Bullies Who was collected from 54 school classes with 918 children (M age = 11) and 13,606 dyadic relations. Bullying and victimization were viewed separately from the point of view of the bully and the victim. The two perspectives were highly complementary. The probability of a bully-victim relationship was higher if the bully was more dominant than the victim, and if the victim was more vulnerable than the bully and more rejected by the class. In a bully-victim dyad, boys were more often the bullies. There was no finding of sex effect for victimization. Liking reduced and disliking increased the probability of a bully-victim relationship.  相似文献   
187.
Infant joint attention has been observed to be related to social-emotional outcomes in at-risk children. To address whether this relation is also evident in typically developing children, 52 children were tested at 12, 15, 24, and 30 months to examine associations between infant joint attention and social outcomes. Twelve-month initiating and responding to joint attention were related to 30-month social competence and externalizing behavior, even when accounting for 15-month temperament ratings, 24-month cognition and language, and demographic variables. These results suggest that, in addition to associations with language and cognition, infant joint attention reflects robust aspects of development that are related to individual differences in the emergence of social and behavioral competence in childhood.  相似文献   
188.
The aims of this study were (a) to determine whether Spanish children with reading disabilities (RD) show a speech perception deficit and (b) to explore the locus and nature of this perceptive deficit. A group of 29 children with RD, 41 chronological age-matched controls, and 27 reading ability-matched younger controls were tested on tasks of speech perception. The effect of linguistic unit (word vs. syllable) and type of phonetic contrast (voicing, place and manner of articulation) were analyzed in terms of the number of errors and the response time. The results revealed a speech perception deficit in Spanish children with RD that was independent of the type of phonetic contrast and of linguistic unit.  相似文献   
189.
OBJECTIVE: This study examines the relationship between parental self-confidence, warmth, and involvement, and corporal punishment in families of children with attention deficit/hyperactivity disorder (ADHD). METHOD: The diagnosis of ADHD was established through clinical interviews with the parents, children, and teachers, according the criteria in DSM-IV-TR. This diagnosis was also established by having the parents complete the Conners' Parent Rating Scale, and the teachers complete the Conners' Teacher Rating Scale. Two groups of Iranian parents, one group with children who have ADHD (N=130) and a control group (N=120), completed questionnaires measuring parental self-confidence and parenting styles. RESULTS: Parents of children with ADHD were found to have lower self-confidence and less warmth and involvement with their children, and used corporal punishment significantly more than the parents of control children. CONCLUSIONS: The study provides strong evidence that children with ADHD are at considerable risk of abuse by their parents. Rather than focusing only on the child's ADHD, treatment may also need to address the parents' functioning.  相似文献   
190.
OBJECTIVE: Children who are physically maltreated are at risk of a range of adverse outcomes in childhood and adulthood, but some children who are maltreated manage to function well despite their history of adversity. Which individual, family, and neighborhood characteristics distinguish resilient from non-resilient maltreated children? Do children's individual strengths promote resilience even when children are exposed to multiple family and neighborhood stressors (cumulative stressors model)? METHODS: Data were from the Environmental Risk Longitudinal Study which describes a nationally representative sample of 1,116 twin pairs and their families. Families were home-visited when the twins were 5 and 7 years old, and teachers provided information about children's behavior at school. Interviewers rated the likelihood that children had been maltreated based on mothers' reports of harm to the child and child welfare involvement with the family. RESULTS: Resilient children were those who engaged in normative levels of antisocial behavior despite having been maltreated. Boys (but not girls) who had above-average intelligence and whose parents had relatively few symptoms of antisocial personality were more likely to be resilient versus non-resilient to maltreatment. Children whose parents had substance use problems and who lived in relatively high crime neighborhoods that were low on social cohesion and informal social control were less likely to be resilient versus non-resilient to maltreatment. Consistent with a cumulative stressors model of children's adaptation, individual strengths distinguished resilient from non-resilient children under conditions of low, but not high, family and neighborhood stress. CONCLUSION: These findings suggest that for children residing in multi-problem families, personal resources may not be sufficient to promote their adaptive functioning.  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