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991.
In the present article, we propose the generalized ratio-type and generalized ratio-exponential-type estimators for population mean in adaptive cluster sampling (ACS) under modified Horvitz-Thompson estimator. The proposed estimators utilize the auxiliary information in combination of conventional measures (coefficient of skewness, coefficient of variation, correlation coefficient, covariance, coefficient of kurtosis) and robust measures (tri-mean, Hodges-Lehmann, mid-range) to increase the efficiency of the estimators. Properties of the proposed estimators are discussed using the first order of approximation. The simulation study is conducted to evaluate the performances of the estimators. The results reveal that the proposed estimators are more efficient than competing estimators for population mean in ACS under both modified Hansen-Hurwitz and Horvitz-Thompson estimators. 相似文献
992.
Copulas are powerful explanatory tools for studying dependence patterns in multivariate data. While the primary use of copula models is in multivariate dependence modelling, they also offer predictive value for regression analysis. This article investigates the utility of copula models for model‐based predictions from two angles. We assess whether, where, and by how much various copula models differ in their predictions of a conditional mean and conditional quantiles. From a model selection perspective, we then evaluate the predictive discrepancy between copula models using in‐sample and out‐of‐sample predictions both in bivariate and higher‐dimensional settings. Our findings suggest that some copula models are more difficult to distinguish in terms of their overall predictive power than others, and depending on the quantity of interest, the differences in predictions can be detected only in some targeted regions. The situations where copula‐based regression approaches would be advantageous over traditional ones are discussed using simulated and real data. The Canadian Journal of Statistics 47: 8–26; 2019 © 2018 Statistical Society of Canada 相似文献
993.
994.
Paul Meyvisch Ariel Alonso Wim Van der Elst Geert Molenberghs 《Pharmaceutical statistics》2019,18(3):304-315
The individual causal association (ICA) has recently been introduced as a metric of surrogacy in a causal‐inference framework. The ICA is defined on the unit interval and quantifies the association between the individual causal effect on the surrogate (ΔS) and true (ΔT) endpoint. In addition, the ICA offers a general assessment of the surrogate predictive value, taking value 1 when there is a deterministic relationship between ΔT and ΔS, and value 0 when both causal effects are independent. However, when one moves away from the previous two extreme scenarios, the interpretation of the ICA becomes challenging. In the present work, a new metric of surrogacy, the minimum probability of a prediction error (PPE), is introduced when both endpoints are binary, ie, the probability of erroneously predicting the value of ΔT using ΔS. Although the PPE has a more straightforward interpretation than the ICA, its magnitude is bounded above by a quantity that depends on the true endpoint. For this reason, the reduction in prediction error (RPE) attributed to the surrogate is defined. The RPE always lies in the unit interval, taking value 1 if prediction is perfect and 0 if ΔS conveys no information on ΔT. The methodology is illustrated using data from two clinical trials and a user‐friendly R package Surrogate is provided to carry out the validation exercise. 相似文献
995.
在社会转型的背景下,我国群体性事件的数量不断攀升,极大地影响了社会的和谐稳定。本文应用\"情景-次级情景-对象-要素\"模型对各类群体性事件案例进行分解,提取相关的影响因素,构建多维情景空间模型,并提出了用于群体性事件预测的卷积神经网络模型,阐述了其基本原理,然后结合实例说明了其应用。通过根据多维情景空间模型对群体性事件案例进行编码形成的数据样本集,来训练该预测模型,并用AUC值评估其有效性。最后分析了不同影响因素在群体性事件预测中的作用以及应急管理主体的应对方向。 相似文献
996.
Konstantina Chalkou;Tasnim Hamza;Pascal Benkert;Jens Kuhle;Chiara Zecca;Gabrielle Simoneau;Fabio Pellegrini;Andrea Manca;Matthias Egger;Georgia Salanti; 《Research Synthesis Methods》2024,15(4):641-656
Some patients benefit from a treatment while others may do so less or do not benefit at all. We have previously developed a two-stage network meta-regression prediction model that synthesized randomized trials and evaluates how treatment effects vary across patient characteristics. In this article, we extended this model to combine different sources of types in different formats: aggregate data (AD) and individual participant data (IPD) from randomized and non-randomized evidence. In the first stage, a prognostic model is developed to predict the baseline risk of the outcome using a large cohort study. In the second stage, we recalibrated this prognostic model to improve our predictions for patients enrolled in randomized trials. In the third stage, we used the baseline risk as effect modifier in a network meta-regression model combining AD, IPD randomized clinical trial to estimate heterogeneous treatment effects. We illustrated the approach in the re-analysis of a network of studies comparing three drugs for relapsing–remitting multiple sclerosis. Several patient characteristics influence the baseline risk of relapse, which in turn modifies the effect of the drugs. The proposed model makes personalized predictions for health outcomes under several treatment options and encompasses all relevant randomized and non-randomized evidence. 相似文献
997.
《Risk analysis》2018,38(9):1795-1801
Flexibility and adaptability are key capabilities for coping with persistent and pervasive uncertainties. The systematic organization of these capabilities is often called “adaptive management”; it is key to effective hazard management and important in risk governance. Vigilance is a requirement for effective adaptation. However, two distinct types of vigilance are necessary. Type 1 vigilance directly supports adaptive management. It is vigilance when you know what you are looking for: warning signals, filling gaps in knowledge, making sure that systems are working, etc. Vigilance of another sort, type 2 vigilance, is needed to address the surprises and institutional failures that are not part of orderly adaptive planning. Type 2 vigilance is vigilance when you don't know what to look for: observing and reflecting on confusing signals, anomalies, unacknowledged responsibilities, and surprises. The two types of vigilance require different institutional capabilities, and hence may work against each other in practice. Type 1 vigilance requires focus and a strong, knowledge‐based organizing framework. Type 2 vigilance, in contrast, requires defocusing and a questioning approach to both observations and concepts. This dilemma, coupled with demands for flexibility, is a severe challenge for organizations. There are a variety of actions and arrangements at various levels of societal organization that could maintain and enhance vigilance in managing hazards. Necessary, however, is the societal and institutional recognition that vigilance of more than one type is an essential part of hazard management and the commitment to follow through. Maintaining vigilance requires effort and must be an ongoing process. 相似文献
998.
当前就业难、用工荒并存的重要原因是劳动力市场不健全导致匹配效率低。本文基于面板数据,利用自适应Lasso方法对我国劳动力市场匹配效率的影响因素进行实证研究。研究发现,技工学校等职业培训机构、人才市场等职业市场机构的发展对劳动力市场匹配效率有显著影响,相对于需求方而言,提高匹配效率应更多从供给侧入手,这是根本之策。应整合优化职业教育资源,提高劳动力质量和适用性,更好地满足加快建设创新型国家、全面建设现代化经济体系的需要。 相似文献
999.
《Stat》2018,7(1)
A method is introduced for variable selection and prediction in linear regression problems where the number of predictors can be much larger than the number of observations. The methodology involves minimizing a penalized Euclidean distance, where the penalty is the geometric mean of the ℓ1 and ℓ2 norms of regression coefficients. This particular formulation exhibits a grouping effect, which is useful for model selection in high‐dimensional problems. Also, an important result is a model consistency theorem, which does not require an estimate of the noise standard deviation. An algorithm for estimation is described, which involves thresholding to obtain a sparse solution. Practical performances of variable selection and prediction are evaluated through simulation studies and the analysis of real datasets. © 2018 The Authors. Stat Published by John Wiley & Sons Ltd. 相似文献
1000.
Hiba Nassar 《统计学通讯:理论与方法》2018,47(12):3029-3042
In this article, we consider a version of the functional Hodrick–Prescott filter for functional time series. We show that the associated optimal smoothing operator preserves the “noise-to-signal ratio” structure. Moreover, as the main result, we propose a consistent estimator of this optimal smoothing operator. 相似文献