全文获取类型
收费全文 | 9468篇 |
免费 | 37篇 |
国内免费 | 1篇 |
专业分类
管理学 | 1527篇 |
民族学 | 38篇 |
人口学 | 854篇 |
丛书文集 | 36篇 |
理论方法论 | 657篇 |
综合类 | 176篇 |
社会学 | 3889篇 |
统计学 | 2329篇 |
出版年
2024年 | 60篇 |
2023年 | 60篇 |
2020年 | 157篇 |
2019年 | 203篇 |
2018年 | 286篇 |
2017年 | 350篇 |
2016年 | 276篇 |
2015年 | 177篇 |
2014年 | 244篇 |
2013年 | 1479篇 |
2012年 | 340篇 |
2011年 | 300篇 |
2010年 | 219篇 |
2009年 | 218篇 |
2008年 | 192篇 |
2007年 | 238篇 |
2006年 | 208篇 |
2005年 | 208篇 |
2004年 | 194篇 |
2003年 | 171篇 |
2002年 | 185篇 |
2001年 | 225篇 |
2000年 | 209篇 |
1999年 | 179篇 |
1998年 | 134篇 |
1997年 | 132篇 |
1996年 | 132篇 |
1995年 | 113篇 |
1994年 | 110篇 |
1993年 | 101篇 |
1992年 | 148篇 |
1991年 | 128篇 |
1990年 | 121篇 |
1989年 | 114篇 |
1988年 | 97篇 |
1987年 | 95篇 |
1986年 | 100篇 |
1985年 | 112篇 |
1984年 | 115篇 |
1983年 | 127篇 |
1982年 | 101篇 |
1981年 | 89篇 |
1980年 | 86篇 |
1979年 | 95篇 |
1978年 | 92篇 |
1977年 | 81篇 |
1976年 | 70篇 |
1975年 | 70篇 |
1974年 | 59篇 |
1973年 | 63篇 |
排序方式: 共有9506条查询结果,搜索用时 15 毫秒
211.
As no single classification method outperforms other classification methods under all circumstances, decision-makers may solve a classification problem using several classification methods and examine their performance for classification purposes in the learning set. Based on this performance, better classification methods might be adopted and poor methods might be avoided. However, which single classification method is the best to predict the classification of new observations is still not clear, especially when some methods offer similar classification performance in the learning set. In this article we present various regression and classical methods, which combine several classification methods to predict the classification of new observations. The quality of the combined classifiers is examined on some real data. Nonparametric regression is the best method of combining classifiers. 相似文献
212.
A late‐stage clinical development program typically contains multiple trials. Conventionally, the program's success or failure may not be known until the completion of all trials. Nowadays, interim analyses are often used to allow evaluation for early success and/or futility for each individual study by calculating conditional power, predictive power and other indexes. It presents a good opportunity for us to estimate the probability of program success (POPS) for the entire clinical development earlier. The sponsor may abandon the program early if the estimated POPS is very low and therefore permit resource savings and reallocation to other products. We provide a method to calculate probability of success (POS) at an individual study level and also POPS for clinical programs with multiple trials in binary outcomes. Methods for calculating variation and confidence measures of POS and POPS and timing for interim analysis will be discussed and evaluated through simulations. We also illustrate our approaches on historical data retrospectively from a completed clinical program for depression. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
213.
Torben G. Andersen Tim Bollerslev Nour Meddahi 《Econometrica : journal of the Econometric Society》2005,73(1):279-296
We develop general model‐free adjustment procedures for the calculation of unbiased volatility loss functions based on practically feasible realized volatility benchmarks. The procedures, which exploit recent nonparametric asymptotic distributional results, are both easy‐to‐implement and highly accurate in empirically realistic situations. We also illustrate that properly accounting for the measurement errors in the volatility forecast evaluations reported in the existing literature can result in markedly higher estimates for the true degree of return volatility predictability. 相似文献
214.
Steven G. Rivkin Eric A. Hanushek John F. Kain 《Econometrica : journal of the Econometric Society》2005,73(2):417-458
This paper disentangles the impact of schools and teachers in influencing achievement with special attention given to the potential problems of omitted or mismeasured variables and of student and school selection. Unique matched panel data from the UTD Texas Schools Project permit the identification of teacher quality based on student performance along with the impact of specific, measured components of teachers and schools. Semiparametric lower bound estimates of the variance in teacher quality based entirely on within‐school heterogeneity indicate that teachers have powerful effects on reading and mathematics achievement, though little of the variation in teacher quality is explained by observable characteristics such as education or experience. The results suggest that the effects of a costly ten student reduction in class size are smaller than the benefit of moving one standard deviation up the teacher quality distribution, highlighting the importance of teacher effectiveness in the determination of school quality. 相似文献
215.
This research presents the development of behavioral scoring models to predict future customer purchases in an online ordering application. Internet retailing lowers many barriers for customers switching between retailers for repeat purchases; thus, retaining existing customers is a key challenge for achieving profitability. Survey data were collected from 1,089 online customers of two companies. The subjective survey data were then used to predict purchases over the ensuing 12 months based on data from the company databases. The analysis illustrates the general applicability of predictive models of future customer purchases while also demonstrating the need to develop specific models tailored for an individual company's operating and marketing environment. The models provide insight on how companies can target marketing dollars more effectively and allocate investment across multiple operational areas for maximum return. The research answers a call for rigorous research in the area of predictive marketing, an area in which many companies are excelling but where there is a scarcity of detailed knowledge regarding application of such models. 相似文献
216.
217.
Sergio G. Koreisha 《决策科学》1984,15(2):177-196
This article presents an efficient way of dealing with adaptive expectations models—a way that makes use of all the information available in the data. The procedure is based on multiple-input transfer functions (MITFs): by calculating lead and lag cross correlations between innovations associated with the variables in the model, it is possible to determine which periods have the greatest effects on the dependent variable. If information about k periods ahead is required, fitted values for the expectation variables are used to generate k-period-ahead forecasts. These in turn can be used in the estimation of the transfer function equation, which not only contains the usual lagged variables but also allows for incorporation of lead-fitted values for the expectation variables. The MITF identification and estimation procedures used are based on the corner method. The method is contrasted with the Almon distributed-lag approach using a model relating stock market prices to interest rates and expected corporate profits. 相似文献
218.
This paper is concerned with planning work-center capacity levels in manufacturing firms that employ a material requirements planning (MRP) system. It presents four procedures for developing work-center capacity plans designed to insure the production of components and assemblies as specified by the MRP plan and the master production schedule (MPS). These procedures (capacity planning using overall factors, capacity bills, resource profiles, and capacity requirements planning) are compared using simulation analysis. The results indicate that the performance of a procedure when measured against the MPS depends on the operating conditions of the manufacturing system. The results also indicate that the choice of a particular procedure often represents a compromise among the benefits of improved MPS performance, the costs of preparing and processing data, and the premium expenses required for more frequent adjustments in work-center capacity levels. 相似文献
219.
Nancy Rolock Alfred G. Pérez Kevin R. White Rowena Fong 《Child and Adolescent Social Work Journal》2018,35(1):11-20
For nearly four decades, child welfare policy and practice have focused on the achievement of legal permanence for children in foster care. Although federal child welfare policy has resulted in the movement of children from state custody to legally permanent adoptive or guardianship families, little is known about the quality and enduring nature of these placements. A significant challenge of the twenty-first century child welfare system is how to ensure the well-being of children currently living with adoptive parents or guardians. This paper discusses child welfare policy and trends related to post-permanency well-being, including the decrease in Title IV-E foster care caseloads nationwide and the simultaneous increase in Title IV-E adoptive and guardianship caseloads. We highlight the needs of a twenty-first century child welfare system, including increased federal efforts to ensure child permanence and well-being after legal adoption or guardianship has been achieved, as well as more rigorous longitudinal and interdisciplinary research focused on the post-permanency adjustment of children and their families. 相似文献
220.
David G. Phillips 《Clinical Social Work Journal》2009,37(1):1-6
As clinical social work developed in America it was highly influenced by the concepts and techniques of psychoanalysis and
many of its practitioners became interested in seeking psychoanalytic training. More and more psychoanalysts are now coming
from a background in clinical social work due to the development of a network of interdisciplinary training institutes and
the opening of the Institutes of the American Psychoanalytic Association to non-medical candidates. This special issue considers
how psychoanalysis may be affected as more of its practitioners and contributors come from a background in clinical social
work. This introduction reviews the history of the development of clinical social work and outlines the issues related to
“lay analysis” in this country.
相似文献
David G. PhillipsEmail: |