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   8172篇
  免费   126篇
  国内免费   1篇
管理学   1104篇
民族学   29篇
人口学   710篇
丛书文集   31篇
理论方法论   696篇
综合类   134篇
社会学   3672篇
统计学   1923篇
  2020年   115篇
  2019年   172篇
  2018年   167篇
  2017年   258篇
  2016年   175篇
  2015年   155篇
  2014年   181篇
  2013年   1515篇
  2012年   245篇
  2011年   201篇
  2010年   185篇
  2009年   159篇
  2008年   225篇
  2007年   223篇
  2006年   183篇
  2005年   158篇
  2004年   137篇
  2003年   128篇
  2002年   144篇
  2001年   184篇
  2000年   163篇
  1999年   147篇
  1998年   128篇
  1997年   128篇
  1996年   125篇
  1995年   110篇
  1994年   83篇
  1993年   126篇
  1992年   137篇
  1991年   119篇
  1990年   130篇
  1989年   108篇
  1988年   106篇
  1987年   111篇
  1986年   99篇
  1985年   84篇
  1984年   115篇
  1983年   98篇
  1982年   94篇
  1981年   63篇
  1980年   93篇
  1979年   105篇
  1978年   72篇
  1977年   82篇
  1976年   70篇
  1975年   85篇
  1974年   68篇
  1973年   54篇
  1972年   61篇
  1971年   52篇
排序方式: 共有8299条查询结果,搜索用时 15 毫秒
221.

Background

Previous physical activity (PA) tracking studies have examined the stability of overall PA and/or PA types, but few have investigated how specific types of sport/exercise track over the life course. The aim of this study was to determine how specific sports/exercises in midlife track and predict future sport/exercise and PA in men transitioning to old age.

Methods

Seven thousand seven hundred thirty-five men (aged 40–59?years) recruited in 1978–80 were followed up after 12, 16 and 20?years. At each wave men self-reported participation in sport/exercise. Frequent sport/exercise participants (>?1/month) reported the types of sport/exercise they engaged in. Men also reported total PA, health status, lifestyle behaviours and socio-demographic characteristics. Stability of each sport/exercise was assessed using kappa statistics and intraclass correlation coefficients. Logistic regression estimated the odds of participating in sport/exercise and being active at 20-year follow up according to specific types of sport/exercise in midlife.

Results

Three thousand three hundred eighty-four men with complete data at all waves were included in analyses. Tracking of specific sports/exercises ranged from fair to substantial, with golf being the most common and most stable. Bowls was the most frequently adopted. Odds of participating in sport/exercise and being active in old age varied according to sport/exercise types in midlife. Golf and bowls in midlife were the strongest predictors of sport/exercise participation in old age. Golf, cricket and running/jogging in midlife were among the strongest predictors of being active in old age. Compared to participating in just one sport/exercise in midlife, sampling multiple sports/exercises was more strongly associated with sport/exercise participation and being active in old age.

Conclusion

The stability of sport/exercise participation from midlife to old age varies by type. Specific sports/exercises in midlife may be more likely to predict future PA than others. However, participating in a range of sports/exercises may be optimal for preserving PA into old age.
  相似文献   
222.
This article analyses international policy discussions on migration and development (M&D) and contrasts these with the actual M&D policies and practices of 11 European countries who were among the main proponents of this international discourse. Desk research of public documents and accompanying information sought from these 11 governments as well as in the European Commission (EC) provide the basis for a comparative analysis of their overall M&D policies and strategies, and institutional settings for formulating and implementing these. The comparison shows that M&D policy and practice remains in a tentative and experimental phase, and that countries experience difficulties reflecting their international positions in their own policies, as well as in learning from their own efforts and those of others. While stressing the developmental potential of migration in international discussions, most of the countries’ policies still reflect an understanding of migration as a problem and a preoccupation with short‐term domestic interests.  相似文献   
223.
Using longitudinal data across eight years, this study examined how parents' familism values in early adolescence predicted youths' depressive symptoms in young adulthood via youths' familism values and family time. We examined these processes among 246 Mexican‐origin families using interview and phone‐diary data. Findings revealed that fathers' familism values predicted male and female youths' familism values in middle adolescence. For female youth only, fathers' familism values also predicted youths' family time in late adolescence. The link between family time and young adults' depressive symptoms depended on parental acceptance and adolescent gender: Among female and male youth, family time predicted fewer depressive symptoms, but only when paternal acceptance was high. For female adolescents only, family time predicted fewer depressive symptoms when maternal acceptance was high but more depressive symptoms when maternal acceptance was low. Findings highlight family dynamics as the mechanisms through which familism values have implications for youths' adjustment.  相似文献   
224.
Urbanization has been identified as a threat to biodiversity due to landscape modifications. Studies of parasite ecology in urbanized areas lagged behind those made on macro organisms. Here we studied infection prevalence of haemosporidian parasites in an avian community of an urban forest from Germany, and its relationship with bird abundance and body mass. We used PCR to amplify a fragment of the mtDNA cyt b gene to determine the infection status of birds, and bird point counts to determine bird relative abundances. The avifauna was dominated by two small sized insectivore passerines (Parus major, Cyanistes caeruleus), representing ~40 % of the total bird records. The highest haemosporidian prevalence was recorded for Turdus philomelos (100 %) and for Fringilla coelebs (75 %). Bird abundance and body mass were positively associated with infection status for two haemosporidian genera: Plasmodium and Leucocytozoon. Infection rate was lower in juveniles compared to adult birds. We recorded a total of 7 Plasmodium, 26 Haemoproteus, and 10 Leucocytozoon lineages. Avian malaria (P. relictum) was detected infecting 5 individuals of P. major, the most abundant species in the community. These results, together with those of previous studies at the same site, suggest that potentially any of the genetic haemosporidian lineages detected in this urban forest can be transmitted across native and pet bird species, and to species of conservation concern housed at aviaries.  相似文献   
225.
Tropical forested ecosystems provide multiple ecosystem services to rural and urban landscapes, with carbon storage gaining particular attention. Deforestation due to rural-urban transitions may lead to a reduction in carbon storage ability. Coastal mangrove forests are particularly at risk from deforestation due to their location in the rapidly urbanizing coastal zone, and the city state of Singapore is an extreme example, losing as much as 90 % of its original mangrove cover due to land reclamation and reservoir construction. Knowledge of mangrove ecosystem services may allow better conservation, restoration and incorporation of remaining mangrove patches into the urban landscape. Focusing on the regulating ecosystem service of carbon storage, mangrove carbon stocks have been estimated for Singapore using a combination of field and remote sensing techniques. Biomass carbon showed substantial spatial variation, with old, contiguous mangrove patches containing a higher density of biomass carbon than fragmented, river-fringing or restored mangroves. In total, national biomass carbon equated to 116,117.1 megagrams of carbon (Mg C), and a coarse estimate of the total carbon stock (including soil carbon) suggests that Singapore’s mangroves may store 450,571.7 Mg C. While lower than other regional estimates focused on natural, oceanic mangroves, this is a significant carbon stock for a disturbed, urban mangrove system, and may be equivalent to the average annual carbon emissions of 621,000 residents. This analysis, alongside a review of other urban forest studies, highlights the importance of forested ecosystems such as mangroves in providing a carbon storage ecosystem service to urban areas.  相似文献   
226.
The geographies of the current generation of young people are markedly distinct from previous generations by virtue of their access to a virtual playground. The vast majority of young people now engage in video gaming as a leisure activity. Drawing on findings from the 2009/2010 WHO Health Behaviour in School-aged Children study this paper set out to investigate the factors that might be associated with higher levels of video gaming. Information was collected from 4404 school students aged 11, 13 and 15 years, using anonymised self-completed questionnaires. Higher usage was defined as game play exceeding two hours a day. Separate analyses were conducted for boys and girls. For both genders higher levels of game playing was associated with early adolescence, opposite sex friends and minimal parental mediation. Bullying and going to bed hungry were associated with higher usage for boys only, while life satisfaction and family activities were linked to girls’ game playing only. Parents were identified as effective mediators of young people’s video game usage. The study identified gendered motivations for higher levels of game play, suggesting different interventions for boys and girls may be required in order for young people to create a balanced approach to video gaming.  相似文献   
227.
This paper explores how online actions such as the practice of digital self-writing shape our offline identity. We start with an examination of the concept of hupomnemata – a practice of self-writing in which notes are kept as a ‘material record of things read, heard, or thought’ in the intent of shaping the self [Foucault (1997). Self writing. In P. Rabinow (Ed.), Ethics, subjectivity and truth. The essential works of Foucault, 1954–1984. Volume 1 (pp. 207–222). New York, NY: The New Press p. 209] – before arguing that the practice of digital content curation can be understood as a modern-day variant of the Greco-Roman hupomnemata. Although the work of the digital curator is conducted online, this paper positions contemporary curatorial practices as acts of self-exploration, self-cultivation, and self-care, which nourish offline identity and which ultimately work to shape the offline, corporeal self.  相似文献   
228.
This study examines three-year post-baseline outcomes for a randomized controlled trial of Swedish antisocial youths who received either multidimensional treatment foster care (MTFC) or treatment as usual (TAU). Several studies in our literature review indicated that MTFC intervention is preferred to the alternative (TAU) in the USA during follow-up. Two studies (one conducted in the UK and one in Sweden) have shown indications of a washout effect between the intervention alternatives during follow-up. However, this study showed few but positive significant outcomes at follow-up for the MTFC programme in comparison to TAU. Juveniles who participated in MTFC spent fewer days in locked settings and had committed fewer violent crimes, according to the social case records. Two key features of the MTFC programme certainly merit use in general social service—namely, reducing exposure to deviant peers and increasing school participation.  相似文献   
229.
Emotional relationships in infant–mother dyads in families where mothers provided full‐time childcare were compared with those of families where mothers used in‐home childcare providers and family childcare providers (= 245). Infant relationships with childcare providers were also studied. Emotional relationships were adequate in all three childcare arrangements, but infant–mother dyads in in‐home childcare arrangements displayed healthier emotional relationships than infant–mother dyads in mother care arrangements; no differences in the health of emotional relationships with infants emerged among the three types of childcare providers (mother care, in‐home childcare, family childcare). Infant–mother dyads in in‐home childcare arrangements also displayed healthier emotional relationships than infant–in‐home childcare caregiver dyads, but infant–mother and infant–caregiver dyads were comparable in family childcare families. Emotional relationships in infant–mother and infant–caregiver dyads were not correlated, regardless of the type of childcare.  相似文献   
230.
The 2014 release of a new set of purchasing power parity (PPP) conversion factors (PPPs) for 2011 has prompted a revision of the World Bank’s international poverty line. In revising the line, we have sought to minimize changes to the real purchasing power of the earlier $1.25 line (in 2005 PPPs), so as to preserve the integrity of the goalposts for international targets such as the Sustainable Development Goals (SDGs) and the World Bank’s twin goals – which were set with respect to that line. In particular, the new line was obtained by inflating the same fifteen national poverty lines – originally used by Ravallion et al. (World Bank Econ. Rev. 23(2): 163–184 2009) to construct the $1.25 line – to 2011 prices in local currency units, and then converting them to US dollars using 2011 PPP conversion factors. With a small approximation, this procedure yields a new international poverty line of $1.90 per person per day. In combination with other changes described in the paper, this revision leads to relatively small changes in global poverty incidence for 2011: from 14.5 % using the old method to 14.1 % using the new method. In 2012, the new reference year for the global count, we find 12.7 % of the world’s population, or 897 million people, are living in extreme poverty. There are changes in the regional composition of poverty, but they are also relatively small. This paper documents methodological decisions taken in the process of updating both the poverty line and the consumption and income distributions at the country level, including issues of inter-temporal and spatial price adjustments. It also describes various caveats and limitations of the approach taken.  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