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   30010篇
  免费   1368篇
各国政治   1318篇
工人农民   1848篇
世界政治   1877篇
外交国际关系   1136篇
法律   18484篇
中国共产党   2篇
中国政治   135篇
政治理论   6415篇
综合类   163篇
  2023年   100篇
  2021年   105篇
  2020年   491篇
  2019年   532篇
  2018年   1839篇
  2017年   1801篇
  2016年   1720篇
  2015年   648篇
  2014年   667篇
  2013年   2671篇
  2012年   770篇
  2011年   1493篇
  2010年   1566篇
  2009年   1202篇
  2008年   1338篇
  2007年   1351篇
  2006年   688篇
  2005年   639篇
  2004年   771篇
  2003年   648篇
  2002年   588篇
  2001年   768篇
  2000年   712篇
  1999年   565篇
  1998年   362篇
  1997年   271篇
  1996年   309篇
  1995年   283篇
  1994年   258篇
  1993年   255篇
  1992年   371篇
  1991年   394篇
  1990年   369篇
  1989年   337篇
  1988年   370篇
  1987年   338篇
  1986年   396篇
  1985年   360篇
  1984年   316篇
  1983年   294篇
  1982年   243篇
  1981年   199篇
  1980年   184篇
  1979年   266篇
  1978年   165篇
  1977年   140篇
  1975年   118篇
  1974年   145篇
  1973年   110篇
  1972年   99篇
排序方式: 共有10000条查询结果,搜索用时 109 毫秒
991.
Getting along with peers becomes increasingly important to health and well-being during early adolescence (10–14 years). Young adolescents may succeed with peers when they are well-liked by and popular among the larger peer group (or at the group-level of social complexity). They might also fare well with peers when they are able to form numerous mutual and high quality friendships (at the dyadic-level of social complexity). Theory emphasizes the interrelatedness of different types of peer experiences, but few longitudinal studies have examined the interplay among and between group- and dyadic-level peer experiences in the same study. As a result, it is not known whether group-level peer experiences are predictors of dyadic-level peer experiences, and/or vice versa. To address this limitation, this study examined the prospective and reciprocal relations between four indices of peer experiences, preference (or being highly liked and not disliked by peers), popularity (or having a reputation as popular), friendship quantity (or having many mutual friends), and friendship or relationship quality, during early adolescence. Participants were 271 adolescents (49% girls; Mage?=?11.52 years) who completed peer nominations of preference and popularity, a self-report measure of friendship quality, and nominated friends at two waves (Wave 1: November, Grade 6; Wave 2: October, Grade 7). Structural equation modeling indicated that friendship quantity predicted increases in preference and popularity and that friendship quality predicted increases in friendship quantity. Initial popularity was associated with decreases in preference. The importance of these findings for future research is discussed along with study limitations.  相似文献   
992.
Residential mobility is one documented stressor contributing to higher delinquency and worse educational outcomes. Sensitive period life course models suggest that certain developmental stages make individuals more susceptible to the effects of an exposure, like residential mobility, on outcomes. However, most prior research is observational, and has not examined heterogeneity across age or gender that may inform sensitive periods, even though it may have important implications for the etiology of adolescent development. Moreover, there are important translational implications for identifying the groups most vulnerable to residential mobility to inform how to buffer adverse effects of moving. In this study, low-income families were randomized to residential mobility out of public housing into lower poverty neighborhoods using a rental subsidy voucher (“experimental voucher condition”), and were compared to control families remaining in public housing. The sample was comprised of 2829 youth (51% female; 62% Non-Hispanic Black, 31% Hispanic, 7% other race). At baseline, youth ranged from 5 to 16 years old. This study hypothesized that random assignment to the housing voucher condition would generate harmful effects on delinquency and educational problems, compared to the control group, among boys who were older at baseline. The results confirmed this hypothesis: random assignment to the experimental voucher condition generating residential mobility caused higher delinquency among boys who were 13–16 years old at baseline, compared to same-age, in-place public housing controls. However, residential mobility did not affect delinquency among girls regardless of age, or among boys who were 5–12 years old at baseline. The pattern of results for educational problems was similar but weaker. Families with teenage boys are particularly vulnerable to residential transitions. Incorporating additional supports into housing programs may help low-income, urban families to successfully transition to lower poverty neighborhoods.  相似文献   
993.
Organized youth programs provide a context where adolescents experience strong emotions and may develop new ways of thinking about and dealing with emotions. The current study examined youth’s reports of positive and negative emotions arising during the course of their work in different types of project-based programs; learning about emotions from different sources (e.g., from observing peers, interacting with adult staff, or engaging in self-reflection); and longitudinal associations between emotional experiences and learning. Quantitative data were collected at two time points from 319 youth (57% female; M age?=?15.8 years; 33% Latino, 29% Black, 32% White, 6% other) participating in 14 Midwestern programs focused on Leadership, Arts and Performance (Arts), and Science, Technology, Engineering, and Math (STEM). Overall, positive emotions occurred more frequently than negative emotions, but emotional experiences differed based on the focus of the program. There were few significant differences in emotional learning from various sources (self, peers, staff) across the three types of programs. Multiple regression models controlling for prior learning indicated that, consistent with theory, positive emotions predicted subsequent learning about emotions from all sources. In contrast, negative emotions predicted increased learning from peers but decreased learning from self, suggesting that experiencing negative (vs. positive) emotions may lead youth to attend to different sources of information. The study’s findings have implications for theory, research, and practice.  相似文献   
994.
Adverse childhood experiences (ACEs) have been identified as a key risk factor associated with a wide range of negative life outcomes, including juvenile delinquency. Much less work has explored whether certain combinations of ACEs, or typologies of trauma, exist, and whether or not these subgroups are differentially associated with certain youth-level and/or community-level characteristics. The current study uses latent class analysis to examine ACE typologies among a sample of over 92,000 juvenile offenders between the ages of 10 and 18 in the state of Florida (52% male, 37.3% White, 46.8% Black, 15.9% Hispanic). Multilevel multinomial logistic regression is used to assess the relationship between both individual- and community-level factors and class membership. The findings suggest that a total of five distinct ACE typologies exist among the sample of juvenile offenders, and age, race, and sex were significantly associated with class membership. Additionally, controlling for individual-level characteristics, community-level measures of immigrant concentration, residential instability, and two separate measures of concentrated disadvantage and affluence were significantly related to class membership. This study contributes to the understanding of adverse childhood experiences, and adds to existing knowledge regarding the relationship between contextual factors and childhood abuse, maltreatment, and trauma. The identification of ACE subgroups with distinct characteristics may help guide prevention strategies and tailor treatment provided by the juvenile justice system.  相似文献   
995.
Psychological empowerment encompasses several key aspects of youth civic and sociopolitical development. Most research has focused on psychological empowerment’s emotional component, which entails learned hopefulness about one’s own ability to participate in and lead community change efforts. Fewer studies have assessed critical awareness of how social power operates—psychological empowerment’s cognitive component. The confluence of these two components has been termed critical hopefulness. A complex relationship exists between these two components, and previous research has found relatively small proportions of participants reporting both high levels of critical awareness and simultaneously high levels of hopefulness about their ability to exert influence in the sociopolitical domain. The current study of urban high school students in the Northeastern U.S. (n?=?389; 53.5% female) investigates heterogeneity according to these two components of psychological empowerment. Latent class cluster analyses were conducted and seven distinct groups of participants emerged. Students identifying as Hispanic/Latinx were more likely to be classified into a profile group exhibiting critical hopefulness. Differences were observed between psychological empowerment profile groups on self-reported levels of psychological sense of community, civic engagement, and social justice orientation. Furthermore, a larger proportion of this overall sample was classified into groups that exhibited critical hopefulness than in a previous study of adults. These findings provide useful insights for efforts to engage young people in civic life and to promote sociopolitical development.  相似文献   
996.
Developmental imbalance models attribute the rise in risk-taking during adolescence to a universal imbalance between rising reward sensitivity and lagging cognitive control. This study tested predictions of an alternate Lifespan Wisdom Model that distinguishes between exploratory/adaptive (e.g., sensation seeking) and maladaptive (e.g., acting-without-thinking, delay discounting) risk-taking propensities and attributes the latter to a sub-set of youth with weak cognitive control. Latent trajectory modeling of six waves of data from 387 adolescents (52% females; spanning average ages of 11–18 years) revealed distinct sub-groups with heterogeneous trajectory patterns for acting-without-thinking and delay-discounting. Only those trajectory groups with weak cognitive control, characterized as “high-increasing” acting-without thinking and “high-stable” delay discounting were predictive of a maladaptive risk-taking outcome, namely substance use disorder. Sensation seeking demonstrated a universal peak, but high levels of sensation seeking were not associated with weakness in cognitive control and were unrelated to substance use disorder, controlling for impulsivity. The findings suggest that maladaptive risk-taking characterized by weak cognitive control over reward-driven impulses is a phenomenon limited to only a sub-set of youth.  相似文献   
997.
Despite the large contingent of students living in rural areas, existing research on the processes that precede the college enrollment of rural adolescents is limited. With a particular focus on gender, this study investigated rural adolescents’ perceptions of family and place and how these perceptions related to their educational aspirations and subsequent college enrollment using a nationwide sample of rural adolescents (N?=?3456; 52.5% female). Female adolescents reported higher academic achievement, educational aspirations, parental expectations, and family responsibility and enrolled in two-year and four-year institutions at greater rates compared to male adolescents, who reported significantly higher rural identity and perceptions of job opportunities in the rural community. Utilizing a multiple group moderated mediation approach, the results provided evidence that adolescents’ increased perceptions of their parents’ educational expectations were associated with increased educational aspirations and college enrollment and that adolescents’ increased perceptions of job opportunities in their rural community were associated with decreased educational aspirations. In addition, the results showed that gender moderated the relation between perceptions of job opportunities in the rural community and postsecondary enrollment. These findings highlight how the developmental resources of family and place relate to adolescents’ educational aspirations and subsequent postsecondary enrollment.  相似文献   
998.
Friends provide important social contexts for student development. Research has shown that adolescent friends are similar to each other in their interest and values for different school subjects. Yet our current understanding does not extend to knowing whether selection, deselection, or socialization processes are responsible for this phenomena. Without this knowledge, it is very difficult for parents, teachers, and schools to know how and when to intervene. This study investigated selection, deselection, and socialization effects on adolescent students’ task values for academic (languages, math and science, and social sciences) and non-academic subject areas (the arts and physical education). A social network approach was used to examine two waves of annual data collected from school-based networks of adolescents in the first and second years of high school education in Finland (N?=?1419; female?=?48.6%; mean age at first measurement point?=?16). The results revealed that adolescents tended to select friends with similar levels of task values (friend selection) for the arts and physical education, but friends did not become more similar in these areas over time (friend socialization). In contrast, there was evidence of friend socialization, but not friend selection, for the academic school subjects. Across all subjects, differences in task values did not predict friendship dissolution (friend deselection). These findings suggest that to a significant extent, students make agentic choices in developing friendship with schoolmates based on their task values in non-academic subjects. The resultant friend contexts that individuals created, in turn, affected their task values in academic subject areas. These results shed light on the complexity of friend effect mechanisms on task values at the subject domain-specific level.  相似文献   
999.
The isolation of spermatozoa from sexual assault swabs using proteinase K   总被引:1,自引:0,他引:1  
The most common examination in sexual offences is the identification of spermatozoa in aqueous extracts from swabs. Using Proteinase K with sodium dodecyl sulphate, it is possible to digest all the cellular material apart from the spermatozoa, resulting in a quick and effective method of their isolation. Spermatozoa were detected in 18 extracts using this treatment when the normal method had failed to reveal all but one of them.  相似文献   
1000.
A simple but rigorous approach is offered for evaluating the evidential value of single locus DNA autoradiographs. This approach does not use a binning technique and it does not treat alleles as discrete variables. Instead, the allele distribution is considered to be continuous. The variation between two comparable bands is assessed using previously determined experimental parameters. The Bayesian treatment leads to an expression of the "quality of a match".  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