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排序方式: 共有380条查询结果,搜索用时 451 毫秒
331.
Semiparametric maximum likelihood estimators have recently been proposed for a class of two‐phase, outcome‐dependent sampling models. All of them were “restricted” maximum likelihood estimators, in the sense that the maximization is carried out only over distributions concentrated on the observed values of the covariate vectors. In this paper, the authors give conditions for consistency of these restricted maximum likelihood estimators. They also consider the corresponding unrestricted maximization problems, in which the “absolute” maximum likelihood estimators may then have support on additional points in the covariate space. Their main consistency result also covers these unrestricted maximum likelihood estimators, when they exist for all sample sizes. 相似文献
332.
Carrie Crystal Queenan Mark Ferguson Jon Higbie Rohit Kapoor 《Production and Operations Management》2007,16(6):729-746
Asuccessful revenue management system requires accurate demand forecasts for each customer segment. The forecasts are used to set booking limits for lower value customers to ensure an adequate supply for higher value customers. The very use of booking limits, however, constrains the historical demand data needed for an accurate forecast. Ignoring this interaction leads to substantial penalties in a firm's potential revenues. We review existing unconstraining methods and propose a new method that includes some attractive properties not found in the existing methods. We evaluate several of the common unconstraining methods against our proposed method by testing them on intentionally constrained simulated data. Results indicate our proposed method outperforms other methods in two of three data sets. We also test the revenue impact of our proposed method, expectation maximization (EM), and “no unconstraining” on actual booking data from a hotel/casino. We show that performance varies with the initial starting protection limits and a lack of unconstraining leads to significant revenue losses. 相似文献
333.
Wellner JA 《Lifetime data analysis》2007,13(4):481-496
We review limit theory and inequalities for the Kaplan–Meier Kaplan and Meier (J Am Stat Assoc 53:457–481, 1958) product limit
estimator of a survival function on the whole line . Along the way we provide bounds for the constant in an interesting inequality due to Biotouzé et al. (Ann Inst H Poincaré
Probab Stat 35:735–763, 1999), and provide some numerical evidence in support of one of their conjectures.
Supported in part by NSF grant DMS-0503822 and by NI-AID grant 2R01 AI291968-04. 相似文献
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Multilevel Models in the Study of Dynamic Household Structures 总被引:1,自引:0,他引:1
Harvey Goldstein Jon Rasbash William Browne Geoffrey Woodhouse Michel Poulain 《Revue europeenne de demographie》2000,16(4):373-387
A modelling procedure is proposed for complex, dynamic household data structures where households change composition over time. Multilevel multiple membership models are presented for such data and their application is discussed with an example. 相似文献
336.
Lisa Reyes Mason Kelsey N. Ellis Jon M. Hathaway 《Journal of Community Practice》2019,27(3-4):334-350
ABSTRACT“Backyard” green infrastructure programs are an innovative way to manage urban stormwater, with many social and ecologic benefits. In many programs, however, residents with lower incomes are not reached, though they could benefit from participation, and though their participation could benefit the socioecological system. We examined awareness of and interest in backyard green infrastructure among lower- and moderate-income residents (N = 234). Awareness among our study population is low to moderate, but interest is moderate to high, with variability by some demographic and other characteristics. A spouse/partner, city agency, and/or neighbor may have influential roles in increasing participation in backyard green infrastructure. 相似文献
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The ensemble Kalman filter (EnKF) provides an approximate, sequential Monte Carlo solution to the recursive data assimilation algorithm for hidden Markov chains. The challenging conditioning step is approximated by a linear updating, and the updating weights, termed Kalman weights, are inferred from the ensemble members. The EnKF scheme is known to provide unstable predictions and to underestimate the prediction intervals, and even sometimes to diverge. The underlying cause for these shortcomings is poorly understood. We find that the ensemble members couple in the conditioning procedure and that the coupling increase multiplicatively in the recursive conditioning steps. Under reasonable Gauss‐independence assumptions, exact expressions for this correlation are developed. Moreover, expressions for the precision of the predictions and the downward bias in the empirical variance introduced in one conditioning step are found. These results are confirmed by a Gauss‐linear simulation study. Furthermore, we quantitatively evaluate an alternative, improved EnKF scheme on the basis of transformations of ensemble members under the same Gauss‐independent assumptions. The scheme is compared with the frequently used ensemble inflation scheme. 相似文献