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   2711篇
  免费   104篇
  国内免费   20篇
管理学   75篇
民族学   24篇
人口学   24篇
丛书文集   285篇
理论方法论   69篇
综合类   1923篇
社会学   39篇
统计学   396篇
  2023年   12篇
  2022年   7篇
  2021年   24篇
  2020年   29篇
  2019年   31篇
  2018年   24篇
  2017年   41篇
  2016年   42篇
  2015年   54篇
  2014年   75篇
  2013年   208篇
  2012年   150篇
  2011年   151篇
  2010年   125篇
  2009年   138篇
  2008年   161篇
  2007年   184篇
  2006年   220篇
  2005年   208篇
  2004年   183篇
  2003年   170篇
  2002年   122篇
  2001年   109篇
  2000年   75篇
  1999年   45篇
  1998年   48篇
  1997年   25篇
  1996年   37篇
  1995年   32篇
  1994年   18篇
  1993年   16篇
  1992年   17篇
  1991年   10篇
  1990年   7篇
  1989年   11篇
  1988年   12篇
  1987年   4篇
  1986年   1篇
  1985年   3篇
  1981年   1篇
  1979年   1篇
  1978年   1篇
  1977年   2篇
  1975年   1篇
排序方式: 共有2835条查询结果,搜索用时 15 毫秒
1.
This paper presents a simple and robust method for obtaining a comprehensive understanding of the joint period and radius distribution in Kepler exoplanets. The proposed method is based on particle swarm optimization and bivariate Normal Inverse Gaussian distribution. Furthermore, in the construction of the probability density function, this study selects planet-host stars with the GK-type. The injecting approach is also employed to solve the survey completeness of sample. The resulting occurrence rate of Earth analogs is 0.025 with a 95% bootstrap confidence interval between 0.023 and 0.032.  相似文献   
2.
In this paper, we consider a statistical estimation problem known as atomic deconvolution. Introduced in reliability, this model has a direct application when considering biological data produced by flow cytometers. From a statistical point of view, we aim at inferring the percentage of cells expressing the selected molecule and the probability distribution function associated with its fluorescence emission. We propose here an adaptive estimation procedure based on a previous deconvolution procedure introduced by Es, Gugushvili, and Spreij [(2008), ‘Deconvolution for an atomic distribution’, Electronic Journal of Statistics, 2, 265–297] and Gugushvili, Es, and Spreij [(2011), ‘Deconvolution for an atomic distribution: rates of convergence’, Journal of Nonparametric Statistics, 23, 1003–1029]. For both estimating the mixing parameter and the mixing density automatically, we use the Lepskii method based on the optimal choice of a bandwidth using a bias-variance decomposition. We then derive some convergence rates that are shown to be minimax optimal (up to some log terms) in Sobolev classes. Finally, we apply our algorithm on the simulated and real biological data.  相似文献   
3.
The case-cohort design is widely used as a means of reducing the cost in large cohort studies, especially when the disease rate is low and covariate measurements may be expensive, and has been discussed by many authors. In this paper, we discuss regression analysis of case-cohort studies that produce interval-censored failure time with dependent censoring, a situation for which there does not seem to exist an established approach. For inference, a sieve inverse probability weighting estimation procedure is developed with the use of Bernstein polynomials to approximate the unknown baseline cumulative hazard functions. The proposed estimators are shown to be consistent and the asymptotic normality of the resulting regression parameter estimators is established. A simulation study is conducted to assess the finite sample properties of the proposed approach and indicates that it works well in practical situations. The proposed method is applied to an HIV/AIDS case-cohort study that motivated this investigation.  相似文献   
4.
Respect for the elderly and hence the associated rights support a generational contract. Nevertheless, the case of the recent debate on the universal retirement scheme in Hong Kong has raised concerns about its strength. We identify relevant items from the sixth wave of the World Values Survey to explore the orientations of different generations toward others. The analysis shows differences between younger and older generations. Regression analyses show that values are not significant in explaining the differences, but various positions, including sex, marital status, and education, and perceptions of the elderly are relevant. Such differences across generations might weaken the generational contract and potentially engender conflicts as shown in the recent debate about the retirement scheme. We suggest short‐ and long‐term interest calculations, informed by their positions, play a more significant role in policy discussions and decisions, rather than simply appealing to values.  相似文献   
5.
6.
The additive hazards model is one of the most commonly used regression models in the analysis of failure time data and many methods have been developed for its inference in various situations. However, no established estimation procedure exists when there are covariates with missing values and the observed responses are interval-censored; both types of complications arise in various settings including demographic, epidemiological, financial, medical and sociological studies. To address this deficiency, we propose several inverse probability weight-based and reweighting-based estimation procedures for the situation where covariate values are missing at random. The resulting estimators of regression model parameters are shown to be consistent and asymptotically normal. The numerical results that we report from a simulation study suggest that the proposed methods work well in practical situations. An application to a childhood cancer survival study is provided. The Canadian Journal of Statistics 48: 499–517; 2020 © 2020 Statistical Society of Canada  相似文献   
7.
We consider the problem of supplementing survey data with additional information from a population. The framework we use is very general; examples are missing data problems, measurement error models and combining data from multiple surveys. We do not require the survey data to be a simple random sample of the population of interest. The key assumption we make is that there exists a set of common variables between the survey and the supplementary data. Thus, the supplementary data serve the dual role of providing adjustments to the survey data for model consistencies and also enriching the survey data for improved efficiency. We propose a semi‐parametric approach using empirical likelihood to combine data from the two sources. The method possesses favourable large and moderate sample properties. We use the method to investigate wage regression using data from the National Longitudinal Survey of Youth Study.  相似文献   
8.
四川盆地卤水分布广泛,资源丰富, 早为世人所瞩目,中三叠统雷口坡组是四川盆地最早开采天然气和盐卤的层系之一。根据盆地雷口坡组大量钻井资料研究表明,盆地雷口坡组主要成盐期分别为雷三2 期和雷四2 期,在盆地东部和南部由于受到古隆起的影响,盐岩地层已被剥蚀难以保存,现今盐岩主要分布在开江古隆起和泸州古隆起的西部以及天井山古隆起的南部(华蓥山以西—龙门山以东的川西—川中地区)。印支运动对盆地雷口坡组盐岩在平面的迁移起着十分重要的作用,根据不同时期盐岩统计数据看,两期盐盆在平面上具有向西迁移、叠加的特征,其中川中的GS1 井就钻遇了这两期的盐岩。  相似文献   
9.
系统总结了在伸展构造背景下,导致反映构造特征的地层倾角模式复杂化的多种因素。沉积相的不同、岩性变化、井眼状况和测井作业时间等多种因素都可能使地层倾角资料复杂化。进一步指出在拉张盆地中,进行倾角资料的构造解释,必须了解其构造样式的多样性和复杂性,解释存在的多解性。重点解剖了铲式断层在横剖面情况下,对于不同构造位置下的倾角模式。详细分析了一个倾角模式对应多种构造样式的倾角构造解释实例。倾角资料的构造解释应是综合解释,既要综合井筒的相关地质资料,又要综合测井与地质知识,还必须考虑综合地震资料。  相似文献   
10.
社会公益组织作为传播正能量的社会团体,是政府与社会组织的公益性的连结点。政府需要公益组织连接社会成员需求,获得社会认可;公益组织也希望得到政府的鼓励,获得公益影响。政府与公益组织良性互动的原因在于政府权威与社会自由之间的平衡。通过研究河南省J志愿者协会的发展现状,阐释了政府与公益组织良性发展的原因是政府职能边界的模糊性、公益组织的目标与政府具有一致性和公益组织必须适应环境的要求。  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