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:      
  示例: 沙坡头地区,人工植被区,变化  检索词用空格隔开表示必须包含全部检索词,用“,”隔开表示只需满足任一检索词即可!
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   2579篇
  免费   30篇
管理学   255篇
民族学   35篇
人口学   281篇
丛书文集   5篇
理论方法论   213篇
综合类   57篇
社会学   1258篇
统计学   505篇
  2024年   40篇
  2023年   44篇
  2022年   32篇
  2021年   43篇
  2020年   117篇
  2019年   100篇
  2018年   206篇
  2017年   231篇
  2016年   182篇
  2015年   102篇
  2014年   127篇
  2013年   440篇
  2012年   211篇
  2011年   99篇
  2010年   85篇
  2009年   74篇
  2008年   73篇
  2007年   55篇
  2006年   48篇
  2005年   41篇
  2004年   31篇
  2003年   38篇
  2002年   28篇
  2001年   24篇
  2000年   15篇
  1999年   11篇
  1998年   6篇
  1997年   9篇
  1996年   7篇
  1995年   7篇
  1994年   9篇
  1993年   4篇
  1992年   7篇
  1991年   7篇
  1990年   7篇
  1989年   8篇
  1988年   7篇
  1987年   4篇
  1986年   5篇
  1985年   4篇
  1984年   2篇
  1979年   2篇
  1978年   2篇
  1977年   2篇
  1975年   2篇
  1974年   1篇
  1973年   3篇
  1972年   1篇
  1971年   2篇
  1967年   1篇
排序方式: 共有2609条查询结果,搜索用时 15 毫秒
71.
Until the end of the 1990s, mortality patterns and trends in Estonia, Latvia and Lithuania were remarkably similar. However, from the year 2000 onwards, life expectancy trends in the three countries started to diverge. In particular, sustainable progress in Estonia over the period 2000–2007 contrasts with stagnation in Latvia, and even worsening trends in Lithuania. These contradictory changes seem to be mainly explained by contrasting dynamics in mortality from cardiovascular diseases, external causes of death and digestive system diseases. Whereas cardiovascular and external-cause mortality declined in Estonia and Latvia, worsening or stagnation of mortality from these causes of death was observed in Lithuania. The negative mortality changes in Lithuania were also reinforced by a striking increase in mortality from alcohol-related digestive system diseases. The findings suggest that the divergence in health trends between the three countries may be attributable to their varying degrees of success in implementing structural health care reforms and specific health policy measures. By contrast, the very recent improvement (since 2008) is parallel in the three countries and is largely because of the introduction of rather similar anti-alcohol measures.  相似文献   
72.
A prevalence of heavy-tailed, peaked and skewed uncertainty phenomena have been cited in literature dealing with economic, physics, and engineering data. This fact has invigorated the search for continuous distributions of this nature. In this paper we shall generalize the two-sided framework presented in Kotz and van Dorp (Beyond beta: other continuous families of distributions with bounded support and applications. World Scientific Press, Singapore, 2004) for the construction of families of distributions with bounded support via a mixture technique utilizing two generating densities instead of one. The family of Elevated Two-Sided Power (ETSP) distributions is studied as an instance of this generalized framework. Through a moment ratio diagram comparison, we demonstrate that the ETSP family allows for a remarkable flexibility when modeling heavy-tailed and peaked, but skewed, uncertainty phenomena. We shall demonstrate its applicability via an illustrative example utilizing 2008 US income data.  相似文献   
73.
In empirical Bayes inference one is typically interested in sampling from the posterior distribution of a parameter with a hyper-parameter set to its maximum likelihood estimate. This is often problematic particularly when the likelihood function of the hyper-parameter is not available in closed form and the posterior distribution is intractable. Previous works have dealt with this problem using a multi-step approach based on the EM algorithm and Markov Chain Monte Carlo (MCMC). We propose a framework based on recent developments in adaptive MCMC, where this problem is addressed more efficiently using a single Monte Carlo run. We discuss the convergence of the algorithm and its connection with the EM algorithm. We apply our algorithm to the Bayesian Lasso of Park and Casella (J. Am. Stat. Assoc. 103:681–686, 2008) and on the empirical Bayes variable selection of George and Foster (J. Am. Stat. Assoc. 87:731–747, 2000).  相似文献   
74.
In this paper we introduce a new extension for the Birnbaum–Saunder distribution based on the family of the epsilon-skew-symmetric distributions studied in Arellano-Valle et al. (J Stat Plan Inference 128(2):427–443, 2005). The extension allows generating Birnbaun–Saunders type distributions able to deal with extreme or outlying observations (Dupuis and Mills, IEEE Trans Reliab 47:88–95, 1998). Basic properties such as moments and Fisher information matrix are also studied. Results of a real data application are reported illustrating good fitting properties of the proposed model.  相似文献   
75.
Local or infinitesimal Bayesian robustness is a powerful tool to study the sensitivity of posterior magnitudes, which cannot be expressed in a simple manner. For these expressions, the global Bayesian robustness methodology does not seem adequate since the practitioner cannot avoid using inappropriate classes of prior distributions in order to make the model mathematically tractable. This situation occurs, for example, when we compute some types of premiums in actuarial statistics in order to fix the premium to be charged to an insurance policy. In this paper, analytical and simple expressions that allow us to study the sensitivity of premiums, which are usually used in automobile insurance are provided by using the local Bayesian robustness methodology. Some examples are examined by using real automobile claim insurance data.  相似文献   
76.
Censuses do not usually collect information on the departure of children and the consequent contraction of the family; however, they sometimes do include useful information on these phenomena and their evolution. On these questions this article presents a new use of the 1971 and 1981 Canadian censuses. From the analysis, it is estimated that the timing of children's departure from their family of origin was almost the same in 1981 as in 1971; median age at departure was identical: 20.5 for women and 22.3 for men. Broken families, more numerous than in the past, become contracted earlier than unbroken families; among unbroken families, the contraction phase started earlier in 1981 than in 1971 among large or medium-sized families while it began later among small families. The method developed here succeeds with the Canadian data in palliating the lack of surveys; it would be interesting to test it on data from other Western societies.  相似文献   
77.
Starting with longitudinal data on two cohorts of women living in the Alpes-Maritimes in 1982 (a sample of 1,500 women in total) we try to establish the role of the spatial distribution of opportunities at a number of key stages in the life cycle: marriage, birth of first child, making professional use of qualifications, confrontation of a situation of professional risk and professional mobility during the years immediately following the completion of studies. The underlying hypothesis is that control of social location often depends on the control of spatial location.  相似文献   
78.
    
To date, imogolite nanotubes (INTs) have been primarily used for environmental applications such as dye and pollutant degradation. However, imogolite's well-defined porous structure and distinctive electro-optical properties have prompted interest in the system's potential for energy-relevant chemical reactions. The imogolite structure leads to a permanent intrawall polarization arising from the presence of bifunctional surfaces at the inner and outer tube walls. Density functional theory simulations suggest such bifunctionality to encompass also spatially separated band edges. Altogether, these elements make INTs appealing candidates for facilitating chemical conversion reactions. Despite their potential, the exploitation of imogolite's features for photocatalysis is at its infancy, thence relatively unexplored. This perspective overviews the basic physical-chemical and optoelectronical properties of imogolite nanotubes, emphasizing their role as wide bandgap insulator. Imogolite nanotubes have multifaceted properties that could lead to beneficial outcomes in energy-related applications. This work illustrates two case studies demonstrating a step-forward on photocatalytic hydrogen production achieved through atomic doping or metal co-catalyst. INTs exhibit potential in energy conversion and storage, due to their ability to accommodate functions such as enhancing charge separation and influencing the chemical potentials of interacting species. Yet, tapping into potential for energy-relevant application needs further experimental research, computational, and theoretical analysis.  相似文献   
79.
80.
Statistics and Computing - Two algorithms are proposed to simulate space-time Gaussian random fields with a covariance function belonging to an extended Gneiting class, the definition of which...  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