首页 | 官方网站   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   90322篇
  免费   2937篇
  国内免费   3篇
社会科学   93262篇
  2023年   511篇
  2021年   538篇
  2020年   1525篇
  2019年   2217篇
  2018年   2143篇
  2017年   3225篇
  2016年   2454篇
  2015年   2061篇
  2014年   2655篇
  2013年   18893篇
  2012年   2520篇
  2011年   2336篇
  2010年   2029篇
  2009年   2202篇
  2008年   2121篇
  2007年   1928篇
  2006年   2156篇
  2005年   2311篇
  2004年   2195篇
  2003年   1926篇
  2002年   2013篇
  2001年   2071篇
  2000年   1832篇
  1999年   1733篇
  1998年   1454篇
  1997年   1309篇
  1996年   1282篇
  1995年   1311篇
  1994年   1252篇
  1993年   1227篇
  1992年   1216篇
  1991年   1173篇
  1990年   1175篇
  1989年   995篇
  1988年   1089篇
  1987年   962篇
  1986年   882篇
  1985年   1072篇
  1984年   1117篇
  1983年   982篇
  1982年   895篇
  1981年   811篇
  1980年   790篇
  1979年   843篇
  1978年   726篇
  1977年   661篇
  1976年   596篇
  1975年   568篇
  1974年   469篇
  1973年   396篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
61.
The current study examined the role of hypothalamic‐pituitary‐adrenal reactivity (a physiological indicator of stress) in early infancy as a mediator of the relationship between maternal postpartum depression and toddler behavior problems. Participants were 137 at‐risk mothers and their children participating in a longitudinal study of intergenerational transmission of risk. Mothers’ depression was measured five times during the infants’ first 18 months. Infant cortisol was collected during a social stressor (the still‐face paradigm) when infants were 6 months old, and mothers reported on toddlers’ internalizing and externalizing symptoms at 18 months. Among this sample of high‐risk mother–infant dyads, early postpartum depression predicted atypical infant cortisol reactivity at 6 months, which mediated the effect of maternal depression on increased toddler behavior problems. Clinical implications are discussed.  相似文献   
62.
This article analyzes the development prospects and problems for the Eurasian Economic Union (EAEU). It examines issues of integration within the EAEU, as well as interactions with other countries, both CIS (Commonwealth of Independent States) and non-CIS. The main problem of integration within the EAEU is the dominance of redistributive motives over productive ones. This article assesses the extent of Russian oil and gas transfers to EAEU partners and the impact of tax maneuvers on their size. It shows that the creation of mechanisms for redistributing profits within the EAEU will allow a positive economic effect to materialize from free trade agreements with non-CIS countries. The article assesses the risks for the EAEU related to Russia’s introduction of a unilateral ban on food imports from countries on the sanctions list and to the possible establishment of tariffs on trade with Ukraine.  相似文献   
63.
In 2015, the United Nations (UN) issued probabilistic population projections for all countries up to 2100, by simulating future levels of total fertility and life expectancy and combining the results using a standard cohort component projection method. For the 40 countries with generalized HIV/AIDS epidemics, the mortality projections used the Spectrum/Estimation and Projection Package (EPP) model, a complex, multistate model designed for short-term projections of policy-relevant quantities for the epidemic. We propose a simpler approach that is more compatible with existing UN projection methods for other countries. Changes in life expectancy are projected probabilistically using a simple time series regression and then converted to age- and sex-specific mortality rates using model life tables designed for countries with HIV/AIDS epidemics. These are then input to the cohort component method, as for other countries. The method performed well in an out-of-sample cross-validation experiment. It gives similar short-run projections to Spectrum/EPP, while being simpler and avoiding multistate modelling.  相似文献   
64.
Coopetition (collaboration between competitors) can facilitate product innovation, but there is still debate about how it is suited to radical or incremental innovation. This paper argues that the early and later phases of coopetitive new product development (NPD) pose different benefits and risks for the innovation types. Building on the tensions approach to value creation and appropriation, we develop a series of hypotheses on the role of coopetition in NPD alliances and focal firm's innovation output. The hypotheses are tested on a quantitative data set of 1049 NPD alliances in the German medical and machinery sectors. The results show that, while coopetition is advantageous for incremental innovation in both pre‐launch and launch phases, radical innovation benefits from coopetition in the launch phase only.  相似文献   
65.
The article proposes a Gender Politics of Aging approach to the study of aging societies. The approach recognizes the feminization of old age, ageism’s roots in sexist discourse, and the need to recognize the role of politics in driving demographic debates. Drawing together arguments from feminist gerontology and political demography, the article argues that the intersection of politics and gender must be considered if appropriate responses to an older, feminized demography are to be produced. I conclude that the work of aging feminists provides a rich vein of research and praxis from which a gender politics of aging approach can draw.  相似文献   
66.
This study examines how the relationship between entrepreneurial orientation and firm growth is shaped by learning orientation in technologically sophisticated environments. We draw upon an information processing perspective that emphasizes alignment between information processing demands and support mechanisms. Using data from 116 small to medium‐sized enterprises in the Netherlands, we observe that the ability of entrepreneurial orientation to drive firm growth greatly depends on the joint consideration of technological sophistication and learning orientation. Our findings contribute to a better understanding of how configurations of strategic orientations and environmental considerations work in concert to influence the efficacy of organizational entrepreneurial efforts dramatically.  相似文献   
67.
68.
2018 marks the 50th anniversary of Enoch Powell’s infamous ‘Rivers of Blood’ speech, an intervention that is still viewed as one of the most incendiary statements of the perceived decay and violence likely to follow legislation intended to assure minoritised British citizens of equal rights regardless of their ethnic origin. In this essay, Sally Tomlinson (one of Britain’s foremost multicultural theorists) reflects on Powell’s legacy and the contemporary scene where in the US, UK and across Europe, White resentment and fear is increasingly shaping ‘mainstream’ debates about nationhood, migration and education.  相似文献   
69.
Mary K. Fagan 《Infancy》2019,24(3):338-355
Infant development has rarely been informed by the behavior of infants with sensory differences despite increasing recognition that infant behavior itself creates sensory learning opportunities. The purpose of this study of object exploration was to compare the behavior of hearing and deaf infants, with and without cochlear implants, in order to identify the effects of profound sensorineural hearing loss on infant exploration before cochlear implantation, the behavioral effects of access to auditory feedback after cochlear implantation, and the sensory motivation for exploration behaviors performed by hearing infants as well. The results showed that 9‐month‐old deaf infants explored objects as often as hearing infants but they used systematically different approaches and less variation before compared to after cochlear implantation. Potential associations between these early experiences and later learning are discussed in the context of embodied developmental theory, comparative studies, and research with adults. The data call for increased recognition of the active sensorimotor nature of infant learning and future research that investigates differences in sensorimotor experience as potential mechanisms in later learning and sequential memory development.  相似文献   
70.
In this article, we introduce tempered Mittag-Leffler Lévy processes (TMLLP). TMLLP is represented as tempered stable subordinator delayed by a gamma process. Its probability density function and Lévy density are obtained in terms of infinite series and Mittag-Leffler function, respectively. Asymptotic forms of the tails and moments are given. A step-by-step procedure of the parameters estimation and simulation of sample paths is given. We also provide main results available for Mittag-Leffler Lévy processes (MLLP) and some extensions which are not available in a collective way in a single article. Our results generalize and complement the results available on Mittag-Leffler distribution and MLLP in several directions. Further, the asymptotic forms of the moments of the first-exit times of the TMLLP are also discussed.  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-23

京公网安备 11010802026262号