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21.
提高我国战略性粮食产品流通控制力,要完善战略性粮食产品的流通支持政策,加强对战略性粮食产品的质量监控和品牌培育,加大对各地区粮油龙头企业的支持力度;完善战略性粮食产品流通市场准入政策,进一步明确粮食收购、粮食和植物油等产品的批发、零售、配送等限制类产业的具体实施细节;加强对战略性粮食产品中薄弱品种和薄弱环节的监管;大力培育有国际竞争力的粮食流通企业,支持国有粮食流通企业"走出去",在全球市场配置资源,实现国内、国际市场互动。 相似文献
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Presence of excess zero in ordinal data is pervasive in areas like medical and social sciences. Unfortunately, analysis of such kind of data has so far hardly been looked into, perhaps for the reason that the underlying model that fits such data, is not a generalized linear model. Obviously some methodological developments and intensive computations are required. The current investigation is concerned with the selection of variables in such models. In many occasions where the number of predictors is quite large and some of them are not useful, the maximum likelihood approach is not the automatic choice. As, apart from the messy calculations involved, this approach fails to provide efficient estimates of the underlying parameters. The proposed penalized approach includes ?1 penalty (LASSO) and the mixture of ?1 and ?2 penalties (elastic net). We propose a coordinate descent algorithm to fit a wide class of ordinal regression models and select useful variables appearing in both the ordinal regression and the logistic regression based mixing component. A rigorous discussion on the selection of predictors has been made through a simulation study. The proposed method is illustrated by analyzing the severity of driver injury from Michigan upper peninsula road accidents. 相似文献
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Xiaodong Yan Hongni Wang Wei Wang Jinhan Xie Yanyan Ren Xinjun Wang 《International Journal of Forecasting》2021,37(3):1147-1155
This article considers ultrahigh-dimensional forecasting problems with survival response variables. We propose a two-step model averaging procedure for improving the forecasting accuracy of the true conditional mean of a survival response variable. The first step is to construct a class of candidate models, each with low-dimensional covariates. For this, a feature screening procedure is developed to separate the active and inactive predictors through a marginal Buckley–James index, and to group covariates with a similar index size together to form regression models with survival response variables. The proposed screening method can select active predictors under covariate-dependent censoring, and enjoys sure screening consistency under mild regularity conditions. The second step is to find the optimal model weights for averaging by adapting a delete-one cross-validation criterion, without the standard constraint that the weights sum to one. The theoretical results show that the delete-one cross-validation criterion achieves the lowest possible forecasting loss asymptotically. Numerical studies demonstrate the superior performance of the proposed variable screening and model averaging procedures over existing methods. 相似文献
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《Statistica Neerlandica》2018,72(2):90-108
Variable selection and error structure determination of a partially linear model with time series errors are important issues. In this paper, we investigate the regression coefficient and autoregressive order shrinkage and selection via the smoothly clipped absolute deviation penalty for a partially linear model with a divergent number of covariates and finite order autoregressive time series errors. Both consistency and asymptotic normality of the proposed penalized estimators are derived. The oracle property of the resultant estimators is proved. Simulation studies are carried out to assess the finite‐sample performance of the proposed procedure. A real data analysis is made to illustrate the usefulness of the proposed procedure as well. 相似文献
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Lévy driven term structure models have become an important subject in the mathematical finance literature. This paper provides
a comprehensive analysis of the Lévy driven Heath–Jarrow–Morton type term structure equation. This includes a full proof of
existence and uniqueness in particular, which seems to have been lacking in the finance literature so far.
相似文献
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This paper considers measurement error from a new perspective. In surveys, response errors are often caused by the fact that respondents recall past events and quantities imperfectly. We explore the consequences of limited recall for the identification of marginal effects. Our identification approach is entirely nonparametric, using Matzkin-type nonseparable models that nest a large class of potential structural models. We show that measurement error due to limited recall will generally exhibit nonstandard behavior, in particular be nonclassical and differential, even for left-hand side variables in linear models. We establish that information reduction by individuals is the critical issue for the severity of recall measurement error. In order to detect information reduction, we propose a nonparametric test statistic. Finally, we propose bounds to address identification problems resulting from recall errors. We illustrate our theoretical findings using real-world data on food consumption. 相似文献
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生产方式和生活方式的变迁使得非物质文化遗产在民间的自发保护传承难以为继,而市场化道路也导致了这种保护传承面临危机。党和政府是民族优秀传统文化的忠实传承者和弘扬者,因而在民族优秀传统文化或非遗保护传承工作上,必须将自己定位于主角,做领导者和组织者。要从非遗对象的静态、动态和意态几个层面,从实物保存、技艺传习和精神内涵阐发等角度实施全方位的保护,走立体保护传承路径。 相似文献
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设计了系统的基本思路,在Visual Studio 2008数据库的基础上,利用OpenGL对矿山巷道,硐室设计等进行三维可视化虚拟,并通过数学模型,对矿井设计进行分析与纠错处理,用C#实现系统的功能。 相似文献