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   1917篇
  免费   103篇
  国内免费   18篇
管理学   83篇
民族学   18篇
人口学   21篇
丛书文集   126篇
理论方法论   65篇
综合类   1112篇
社会学   138篇
统计学   475篇
  2024年   3篇
  2023年   12篇
  2022年   11篇
  2021年   13篇
  2020年   38篇
  2019年   42篇
  2018年   51篇
  2017年   84篇
  2016年   61篇
  2015年   74篇
  2014年   86篇
  2013年   228篇
  2012年   109篇
  2011年   92篇
  2010年   85篇
  2009年   85篇
  2008年   87篇
  2007年   83篇
  2006年   81篇
  2005年   67篇
  2004年   70篇
  2003年   90篇
  2002年   122篇
  2001年   88篇
  2000年   57篇
  1999年   38篇
  1998年   27篇
  1997年   23篇
  1996年   21篇
  1995年   31篇
  1994年   10篇
  1993年   14篇
  1992年   7篇
  1991年   10篇
  1990年   10篇
  1989年   6篇
  1988年   8篇
  1987年   4篇
  1986年   4篇
  1985年   1篇
  1982年   1篇
  1981年   1篇
  1979年   1篇
  1978年   1篇
  1977年   1篇
排序方式: 共有2038条查询结果,搜索用时 78 毫秒
81.
Linear increments (LI) are used to analyse repeated outcome data with missing values. Previously, two LI methods have been proposed, one allowing non‐monotone missingness but not independent measurement error and one allowing independent measurement error but only monotone missingness. In both, it was suggested that the expected increment could depend on current outcome. We show that LI can allow non‐monotone missingness and either independent measurement error of unknown variance or dependence of expected increment on current outcome but not both. A popular alternative to LI is a multivariate normal model ignoring the missingness pattern. This gives consistent estimation when data are normally distributed and missing at random (MAR). We clarify the relation between MAR and the assumptions of LI and show that for continuous outcomes multivariate normal estimators are also consistent under (non‐MAR and non‐normal) assumptions not much stronger than those of LI. Moreover, when missingness is non‐monotone, they are typically more efficient.  相似文献   
82.
A problem of using a non‐convex penalty for sparse regression is that there are multiple local minima of the penalized sum of squared residuals, and it is not known which one is a good estimator. The aim of this paper is to give a guide to design a non‐convex penalty that has the strong oracle property. Here, the strong oracle property means that the oracle estimator is the unique local minimum of the objective function. We summarize three definitions of the oracle property – the global, weak and strong oracle properties. Then, we give sufficient conditions for the weak oracle property, which means that the oracle estimator becomes a local minimum. We give an example of non‐convex penalties that possess the weak oracle property but not the strong oracle property. Finally, we give a necessary condition for the strong oracle property.  相似文献   
83.
The paper proposes a new test for detecting the umbrella pattern under a general non‐parametric scheme. The alternative asserts that the umbrella ordering holds while the hypothesis is its complement. The main focus is put on controlling the power function of the test outside the alternative. As a result, the asymptotic error of the first kind of the constructed solution is smaller than or equal to the fixed significance level α on the whole set where the umbrella ordering does not hold. Also, under finite sample sizes, this error is controlled to a satisfactory extent. A simulation study shows, among other things, that the new test improves upon the solution widely recommended in the literature of the subject. A routine, written in R, is attached as the Supporting Information file.  相似文献   
84.
85.
我国农村经济增长与社会福利存在明显的区域非均衡性,二者均呈现出自东部向西部递减的规律;大部分省、市经济增长和社会福利的耦合度经历了从勉强协调向基本协调过渡的发展过程,二者的协调程度还有进一步提升的空间;经济增长指数与耦合度表现出了一致的波动性,经济子系统对整个系统具有牵引作用.当前,加快发展农村经济,扩大对农村地区的必要性供给,推进农村地区的城镇化进程是实现我国农村地区经济增长与社会福利协同发展的有效途径.  相似文献   
86.
利用国家重点研发计划重点专项2018年调研数据,构建了自然灾害冲击对农村家庭非农就业选择影响的理论框架,采用Probit模型验证了自然灾害冲击对农户家庭成员非农就业选择的影响。研究发现:自然灾害冲击对农户家庭成员非农就业选择有显著正向影响,这一正向影响会随着自然灾害强度的增加而不断提升;人力资本和社会资本的嵌入,会弱化自然灾害对农户家庭成员非农就业选择的影响,信贷约束却会强化这一影响。这意味着现阶段面对自然灾害冲击,农户家庭成员应积极尝试非农就业,不仅能够促进资本存量重构,还可以缓解家庭生计压力,增加农户家庭收入,避免农户家庭因灾致贫。  相似文献   
87.
To incorporate newcomers into membership, a group employs socialization strategies to transform the characteristics of the newcomers, so that it can admit them with the confidence that their behaviour will not endanger group unity. Analyses of socialization emphasize that novices' interiorization of an institutional definition of group behaviour is a necessary condition to ensure successful socialization. The contemporary Religious Society of Friends in Britain, however, is a non-doctrinal religious movement that avoids defining the content of its beliefs and practices. To analyse the socializing interaction between members and newcomers in this movement in Britain, and among co-religionists in the USA, this inquiry applies a model of socialization that does not include assumptions about the role played by cognition in socialization (Long and Hadden 1983). My results show that: (a) the diffuseness in Friends' collective explanations of institutional conduct supports novices' identification with institutional practice, and (b) experimental and affective components in socialization motivate novices to imitate institutional behaviour despite the fact that Friends have no authoritative explanations of such behaviour. The data suggest that socialization and social cohesion are not necessarily as strongly cognitive-oriented phenomena as they were previously thought to be. This finding has important implications for thinking about social cohesion in postmodern society.  相似文献   
88.
Direct applications of remote sensing thermal infrared (TIR) data in landscape ecological research are rare due to limitations in the sensors, calibration, and difficulty in interpretation. Currently there is a general lack of methodology for examining the relationship between land surface temperatures (LST) derived from TIR data and landscape patterns extracted from optical sensors. A separation of landscapes into values directly related to their scale and signature is a key step. In this study, a Landsat ETM+ image of Indianapolis, Unites States, acquired on June 22, 2000, was spectrally unmixed (using spectral mixture analysis, SMA) into fraction endmembers of green vegetation, soil, high albedo, and low albedo. Impervious surface was then computed from the high and low albedo images. A hybrid classification procedure was developed to classify the fraction images into seven land use and land cover (LULC) classes. Using the fractional images, the landscape composition and pattern were examined. Next, pixel-based LST measurements were correlated with the landscape fractional components to investigate LULC based relationships between LST and impervious surface and green vegetation fractions. An examination of the relationship between the LULC and LST maps with landscape metrics was finally conducted to deepen understanding of their interactions. Results indicate that SMA-derived fraction images were effective for quantifying the urban morphology and for providing reliable measurements of biophysical variables. LST was found to be positively correlated with impervious surface fraction but negatively correlated with green vegetation fraction. Each temperature zone was associated with a dominant LULC category. Further research should be directed to the theoretical and applied implications of describing such relationships between LULC patterns and urban thermal conditions.
Dengsheng LuEmail:
  相似文献   
89.
We propose two preprocessing algorithms suitable for climate time series. The first algorithm detects outliers based on an autoregressive cost update mechanism. The second one is based on the wavelet transform, a method from pattern recognition. In order to benchmark the algorithms'' performance we compare them to existing methods based on a synthetic data set. Eventually, for exemplary purposes, the proposed methods are applied to a data set of high-frequent temperature measurements from Novi Sad, Serbia. The results show that both methods together form a powerful tool for signal preprocessing: In case of solitary outliers the autoregressive cost update mechanism prevails, whereas the wavelet-based mechanism is the method of choice in the presence of multiple consecutive outliers.  相似文献   
90.
Significant research has focused on influencing senior leadership, and this study offers new insights into building internal relationships and informal coalitions to provide strategic counsel. These strategies involve internal communications, a neglected area of research and practice. The findings are based on in-depth interviews with 30 executives representing multiple departments in four U.S. companies. A new role justifying public relations’ membership in executive decision teams is internal boundary spanning or gathering intelligence internally across business units, and requires public relations to have a seat at multiple decision tables.  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