首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   90篇
  免费   9篇
  2024年   1篇
  2023年   4篇
  2022年   1篇
  2020年   4篇
  2019年   3篇
  2018年   6篇
  2017年   7篇
  2016年   5篇
  2015年   6篇
  2014年   3篇
  2013年   22篇
  2012年   5篇
  2011年   4篇
  2010年   6篇
  2009年   6篇
  2008年   3篇
  2007年   3篇
  2006年   3篇
  2004年   1篇
  2003年   1篇
  2002年   1篇
  1997年   1篇
  1996年   1篇
  1983年   1篇
  1976年   1篇
排序方式: 共有99条查询结果,搜索用时 31 毫秒
51.
This paper examines the evolution of territorial imbalances in per capita income in the Central and Eastern Europe regions between 1990 and 2001. In order to overcome the limitations of conventional convergence analysis, we have combined a non-parametric approach that allows us to study the dynamics of the entire cross-section distribution, with a series of theoretical results and measures taken from the literature on personal income distribution. The results obtained show an overall reduction in regional inequality over the study period. This process has been compatible with the simultaneous presence of between-country convergence and within-country divergence. Likewise, we have observed a reduction in the development gap between the sample regions and Western Europe. In any event, the polarization of the distribution under consideration has decreased, while the registered level of intra-distribution mobility is relatively low. Furthermore, the analysis highlights the important role played in explaining the distribution dynamics by factors such as the national component, spatial location, productive structure, agglomeration economies and the percentage of gross domestic product devoted to investment.  相似文献   
52.
A reliable assessment of historical metallic tie-rods requires both the estimation of actual tensile load and the identification of dominant defects. Despite high defectiveness resulting from traditional metalworking techniques, so far the latter aspect has not been duly addressed in the literature. In this article, several methodologies are discussed aimed at integrating the usual inspection practice. All studies were performed on the tie-rods of Milan Cathedral. Metallurgical analyses allowed to recognize the main features of the material. Mechanical characterization in the perspective of Elasto-Plastic Fracture Mechanics (EPFM) indicated the conditions for crack propagation. Several Non-Destructive Techniques (NDTs) commonly used in Mechanical Engineering (i.e., guided waves, eddy currents, pulsed active thermography) were examined and adapted to this unconventional application. Based on the combination of all the mentioned methods, a multidisciplinary procedure was defined, which allows the evaluation of the crack significance with reference to the estimated working stress.  相似文献   
53.
The Port‐Vendres 4 shipwreck is evidence of coastal export trade between Hispania Citerior and Narbonne in 40/30 BC. The cargo is made up of a particular assemblage of Roman wine amphoras (Pascual 1, Dressel 1B and Lamboglia 2) destined for Gallic markets. Archaeological and archaeometric analyses conducted on a selection of the amphoras allowed the provenance of the cargo to be identified as Hispania Citerior and the central‐southern Tyrrhenian coast of Italy. Iluro and/or Baetulo are proposed as the ports of departure, enabling the reconstruction of the trade route and the historical and economic significance of this shipwreck.  相似文献   
54.
55.
The determination of the chemical composition of different parts of wall paintings (pigments, mortars and binders) provides information about technology of preparation of an artefact. Herein, we present a multi-methodological characterisation of wall paintings from a Roman archaeological site in Cuma, focusing on differences between an indoor (domus) and outdoor fabrication (a temple, Tempio con Portico (TCP)). Both pigments, binders and mortars were studied via a combination of destructive/μ-destructive (mass spectrometry, ionic chromatography, ICP-based techniques) and non-destructive (Raman microscopy, small-angle neutron scattering (SANS) and X-ray diffraction) methodologies. Particularly, the systematic presence of dolomite only in mortars from TCP may suggest an intentional use of such limestone for the outdoor fabrication of public interest. Differences between TCP and domus are also related to the composition of the pigment binder. In particular, the detected binders (studied by LC-MS/MS and GC-MS) were proteinaceous in the case of domus (possibly egg and animal glue) and drying oils in the case of TCP. Ultimately, our multi-methodological study provides an overall picture of the material components of paintings from fabrications with different use, proposing a hypothesis on technological choices according to conservative and destination reasons.  相似文献   
56.
Abstract

Far from being a value shared by the country’s political parties, republican Italy’s constitution has given rise to confrontation depending on the interpretations given to it in the main phases of transition of the country’s political system. Antifascism as a fundamental statute of public life, on the one hand, and the great parliamentary system framework, on the other, established the boundaries of democratic legitimacy. Although this process contributed to strengthening the country’s democratic foundations, particularly with regard to the risk of a possible authoritarian swing in the aftermath of World War II, it also affected a political dialectic strongly conditioned by the delegitimizing element underlying the constitutional charter. Attempts at institutional reform as well as opposition to any understanding between the two parties that benefited the most from a literal interpretation of the constitution, that is, the Christian Democratic Party and the Italian Communist Party, often ran the risk of being demonized. This led to a kind of short-circuit which, in the long run, eroded the democratic fabric itself, feeding the spiral of mutual delegitimation that marked the political life of the country in these republican years.  相似文献   
57.
ABSTRACT The geographical distribution and persistence of regional/local unemployment rates in heterogeneous economies (such as Germany) have been, in recent years, the subject of various theoretical and empirical studies. Several researchers have shown an interest in analyzing the dynamic adjustment processes of unemployment and the average degree of dependence of the current unemployment rates or gross domestic product from the ones observed in the past. In this paper, we present a new econometric approach to the study of regional unemployment persistence, in order to account for spatial heterogeneity and/or spatial autocorrelation in both the levels and the dynamics of unemployment. First, we propose an econometric procedure suggesting the use of spatial filtering techniques as a substitute for fixed effects in a panel estimation framework. The spatial filter computed here is a proxy for spatially distributed region‐specific information (e.g., the endowment of natural resources, or the size of the “home market”) that is usually incorporated in the fixed effects coefficients. The advantages of our proposed procedure are that the spatial filter, by incorporating region‐specific information that generates spatial autocorrelation, frees up degrees of freedom, simultaneously corrects for time‐stable spatial autocorrelation in the residuals, and provides insights about the spatial patterns in regional adjustment processes. We present several experiments in order to investigate the spatial pattern of the heterogeneous autoregressive coefficients estimated for unemployment data for German NUTS‐3 regions. We find widely heterogeneous but generally high persistence in regional unemployment rates.  相似文献   
58.
Metals held important symbolic and political values for the indigenous communities of the Caribbean islands. However, metal objects are not abundant in indigenous archaeological sites, and their study has hitherto been very limited. This paper presents the results of the first analytical programme focused on metal artifacts recovered in a range of Taíno sites in Cuba, chronologically covering the periods before and after contact with Europeans. Our aims were: (a) to identify metallurgical traditions related to a diversity of cultural or learning backgrounds; (b) to investigate the origins of different metal artifacts found in Cuba, as a proxy to reconstruct patterns of exchange and interaction among indigenous communities and between these and Europeans; and (c) to approach the meaning and symbolism of different metals by considering their contexts of appropriation and use. The techniques employed included optical microscopy, SEM–EDS, pXRF and PIXE. The results allow a diachronic picture of the procurement, transformation, use and symbolism of metals in Cuba with broader implications for Caribbean archaeology. We reveal culture-specific Taíno choices in their interaction with materials and value systems from continental America and Europe. We also discuss the selective appropriation, recontextualization and meaning of different metals in the indigenous cultures.  相似文献   
59.
(Spatial) panel data are routinely modeled in discrete time (DT). However, compelling arguments exist for continuous‐time (CT) modeling of (spatial) panel data. Particularly, most social processes evolve in CT, so that statistical analysis in DT is an oversimplification, gives an incomplete representation of reality, and may lead to misinterpretation of estimation results. The most compelling reason for a CT approach is that, in contrast to DT modeling, it allows adequate modeling of dynamic adjustment processes. This article introduces spatial dependence in a CT modeling framework. We propose a nonlinear structural equation model (SEM) with latent variables for estimation of the exact discrete model (EDM), which links CT model parameters to DT observations. The use of a SEM with latent variables enables a specification that accounts for measurement errors in the variables, leading to a reduction of attenuation bias (i.e., disattenuation). The SEM‐CT model with spatial dependence developed here is the first dynamic SEM with spatial dependence. A simple regional labor market model for Germany, comprising changes in unemployment and population as endogenous state variables, and changes in regional average wages and in the structure of the manufacturing sector as exogenous input variables, illustrates this spatial econometric SEM‐CT framework. El modelamiento de datos panel espaciales se realiza habitualmente utilizando una conceptualización del tiempo discreto (TD). Sin embargo, existen argumentos de peso para conceptualizar el tiempo de manera continua (TC). En concreto, la mayoría de procesos sociales se desarrolla en TC, por lo que el análisis estadístico en DT trae como consecuencia una simplificación excesiva de los procesos, da una representación incompleta de la realidad, y puede conducir a una interpretación errónea de los resultados de la estimación. La razón más convincente para el uso de un enfoque CT es que a diferencia de modelos DT, una conceptualización CT permite el modelado adecuado de los procesos de ajuste dinámico (dynamic adjustment). Este artículo incorpora la dependencia espacial en un marco de modelamiento con CT. Los autores proponen un modelo de ecuaciones estructurales no lineal (nonlinear structural equation model ‐SEM) con variables latentes para la estimación del modelo discreto exacto (exact discrete model‐EDM), que vincula los parámetros del modelo CT a las observaciones de DT. El uso de un SEM con variables latentes permite una especificación que da cuenta de los errores de medición en las variables, dando lugar a una reducción del sesgo de atenuación (es decir, “desatenuacion”). El modelo SEM‐CT con dependencia espacial desarrollado en el presente estudio es el primer SEM dinámico con dependencia espacial. Para ilustrar el marco conceptual SEM‐CT los autores presentan un modelo simple del mercado laboral regional de Alemania. El modelo está compuesto por los cambios en el desempleo y la población como variables endógenas de estado, y los cambios en los salarios regionales promedio y en la estructura del sector manufacturero como variables de entrada exógenas. (空间)面板数据通常基于离散时间(DT)进行建模。然而更令人信服的观点是基于连续时间(CT)进行(空间)面板数据建模。特别是多数社会过程均在连续时间中演化,基于离散时间的统计分析可能过度简化,使得对现实状况的表达不完备,并可能导致对估计结果的错误解释。相比于离散时间(DT)建模,连续时间(CT)建模最具说服力的原因在于在建模过程中允许足够多的动态调整。本文介绍了CT模型框架中的空间依赖性。把CT模型参数链接到DT观察值中,我们提出了用于估计精确离散模型(EDM)的包含潜变量的非线性结构方程模型(SEM)。包含潜在变量的SEM提供了变量测量误差的计算方案,使得衰减偏差(如反衰减性)减小。本文了提出的空间相关SEM‐CT模型是第一个动态空间相关的SEM模型,并以德国一个简单的区域劳动力市场模型为例,以失业和人口构成变化为内生状态变量,以区域平均工资和制造业结构部门变化为外生输入变量,阐述了该空间计量SEM‐ CT模型的框架。  相似文献   
60.
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号