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This paper presents an answer-perturbation model for the protection of statistical databases. Compared to previous approaches, this model saves both space and time since neither a copy of the original database nor an extra processing of the query set is needed. The modularity of our protection mechanism (perturbation is applied after the query processing, not during it or upon data entry, as in the other approaches) facilitates the implementation. The method presented is user-oriented and since the usability (accuracy) of the statistically altered answers can be fine-tuned, the balance between usability and protection (security) is under the control of the database administrator. 相似文献
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905.
Charbonneau Étienne Bromberg Daniel Henderson Alexander C. 《Public Organization Review》2020,20(1):63-78
Public Organization Review - Since the founding of the field of public administration, scholars have struggled with questions related to the “publicness” of public organizations... 相似文献
906.
Daniel E. Bromberg 《Public Organization Review》2016,16(4):549-560
Though much attention has been given to the relationship between contractor and vendor in regard to governmental accountability, little attention has been paid to the internal struggles that surface in regard to accountability in the procurement process. These informal horizontal relationships often circumvent vertical accountability controls most often thought to ensure equitable vendor selection. Similarly, though much attention has been paid to political influence in contracting, hierarchal organizational structures, and measures of performance, the contract officer-program manager relation has not been explored. Specifically, the informal tension that often forms between the program manager and contract officer has not been examined in regard to such accountability. This paper examines the relationship between the program officer and the contract officer in order to describe how hybrid public administration can affect the contracting process. 相似文献
907.
Dongbing Lai Huiping Xu Daniel Koller Tatiana Foroud 《Journal of applied statistics》2016,43(14):2503-2523
Dementia patients exhibit considerable heterogeneity in individual trajectories of cognitive decline, with some patients showing rapid decline following diagnoses while others exhibiting slower decline or remaining stable for several years. Dementia studies often collect longitudinal measures of multiple neuropsychological tests aimed to measure patients’ decline across a number of cognitive domains. We propose a multivariate finite mixture latent trajectory model to identify distinct longitudinal patterns of cognitive decline simultaneously in multiple cognitive domains, each of which is measured by multiple neuropsychological tests. EM algorithm is used for parameter estimation and posterior probabilities are used to predict latent class membership. We present results of a simulation study demonstrating adequate performance of our proposed approach and apply our model to the Uniform Data Set from the National Alzheimer's Coordinating Center to identify cognitive decline patterns among dementia patients. 相似文献
908.
This article proposes to use a standardized version of the normal-Laplace mixture distribution for the modeling of tail-fatness in an asset return distribution and for the fitting of volatility smiles implied by option prices. Despite the fact that only two free parameters are used, the proposed distribution allows arbitrarily high kurtosis and uses one shape parameter to adjust the density function within three standard deviations for any specified kurtosis. For an asset price model based on this distribution, the closed-form formulas for European option prices are derived, and subsequently the volatility smiles can be easily obtained. A regression analysis is conducted to show that the kurtosis, which is commonly used as an index of tail-fatness, is unable to explain the smiles satisfactorily under the proposed model, because the additional shape parameter also significantly accounts for the deviations revealed in smiles. The effectiveness of the proposed parsimonious model is demonstrated in the practical examples where the model is fitted to the volatility smiles implied by the NASDAQ market traded foreign exchange options. 相似文献
909.
Daniel Gerhard 《统计学通讯:模拟与计算》2016,45(8):2678-2690
A method is proposed to construct simultaneous confidence intervals for multiple linear combinations of generalized linear model parameters, that uses a multivariate normal- or t-distribution together with the signed likelihood root statistic. In an application to a case study simultaneous confidence bands for logistic regression are calculated. A simulation study based on the example evaluation suggests superior performance compared to the common Wald-type approaches. The proposed methods are readily implemented in the R extension package mcprofile. 相似文献
910.
Jianing Di Daniel Wang H. Robert Brashear Vladimir Dragalin Michael Krams 《Pharmaceutical statistics》2016,15(2):109-122
In clinical trials, continuous monitoring of event incidence rate plays a critical role in making timely decisions affecting trial outcome. For example, continuous monitoring of adverse events protects the safety of trial participants, while continuous monitoring of efficacy events helps identify early signals of efficacy or futility. Because the endpoint of interest is often the event incidence associated with a given length of treatment duration (e.g., incidence proportion of an adverse event with 2 years of dosing), assessing the event proportion before reaching the intended treatment duration becomes challenging, especially when the event onset profile evolves over time with accumulated exposure. In particular, in the earlier part of the study, ignoring censored subjects may result in significant bias in estimating the cumulative event incidence rate. Such a problem is addressed using a predictive approach in the Bayesian framework. In the proposed approach, experts' prior knowledge about both the frequency and timing of the event occurrence is combined with observed data. More specifically, during any interim look, each event‐free subject will be counted with a probability that is derived using prior knowledge. The proposed approach is particularly useful in early stage studies for signal detection based on limited information. But it can also be used as a tool for safety monitoring (e.g., data monitoring committee) during later stage trials. Application of the approach is illustrated using a case study where the incidence rate of an adverse event is continuously monitored during an Alzheimer's disease clinical trial. The performance of the proposed approach is also assessed and compared with other Bayesian and frequentist methods via simulation. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献