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排序方式: 共有268条查询结果,搜索用时 31 毫秒
81.
Eighteen taxa of Middle Devonian (Givetian) gastropods, including two new genera and five new species, are présent in the Tungkangling and Yingtang Formations, Wuxuan and Xiangxhou counties, Guangxi Province, China. Pingtianispira tuberculata gen. et sp. nov., Wuxuanella nodusa gen. et sp. nov. and Wuxuanella luifengshanensis sp. nov., Crenulazone wuxuanensis sp. nov. and Murchisonia luifengshanensis sp. nov. are erected from this distinct fauna. The fauna is dominated by nodose and unusual murchisonioids and has strong European and other Old World realm affinities.  相似文献   
82.
Spatial interaction models commonly use discrete zones to represent locations. The computational requirements of the models normally arise with the square of the number of zones or worse. For computationally intensive models, such as land use–transport interaction models and activity‐based models for city regions, this dependency of zone size is a long‐standing problem that has not disappeared even with increasing computation speed in PCs—it still forces modelers to compromise on the spatial resolution and extent of model coverage as well as on the rigor and depth of model‐based analysis. This article introduces a new type of discrete zone system, with the objective of reducing the time for estimating and applying spatial interaction models while maintaining their accuracy. The premise of the new system is that the appropriate size of destination zones depends on the distance to their origin zone: at short distances, spatial accuracy is important and destination zones must be small; at longer distances, knowing the precise location becomes less important and zones can be larger. The new method defines a specific zone map for every origin zone; each origin zone becomes the focus of its own map, surrounded by small zones nearby and large zones farther away. We present the theoretical formulation of the new method and test it with a model of commuting in England. The results of the new method are equivalent to those of the conventional model, despite reducing the number of zone pairs by 96% and the computation time by 70%. Los modelos de interacción espacial suelen utilizar zonas discretas para representar áreas o puntos de interés. Los requisitos computacionales de estos modelos normalmente aumentan a razón del número de zonas elevadas al cuadrado o más. Para modelos computacionalmente intensivos como los modelos de interacción entre uso de suelo y transporte y los modelos basados en actividades para ciudades‐región, el impacto del tamaño de la zona es un problema persistente no superado aun. Esta limitación persiste a pesar de los grandes avances en la velocidad de procesamiento en computadoras, pues obliga a los modeladores a hacer concesiones entre la resolución espacial y la extensión que abarca el modelo, así como en el rigor y profundidad del análisis. En este artículo se presenta un nuevo tipo de sistema de zonas discretas que: a) tienen como objetivo reducir el tiempo de estimación de la aplicación de modelos de interacción espacial; y b) al mismo tiempo mantienen su nivel de precisión. La premisa que gobierna este nuevo sistema es que el tamaño apropiado de las zonas de destino depende de la distancia a su zona de origen: a distancias cortas, la precisión espacial es importante y las zonas de destino deben ser pequeño; a distancias mas largas, conocer la ubicación precisa es progresivamente menos importante y las zonas pueden ser mayores. El nuevo método define un mapa específico de zonas para cada zona de origen; cada zona de origen se convierte en el foco de su propio mapa, rodeada de zonas cercanas pequeñas y zonas grandes a mayor distancia. El estudio presenta la formulación teórica del nuevo método y su demostración vía un modelo de desplazamientos residencia‐trabajo en Inglaterra. Los resultados del nuevo método son equivalentes a las del modelo convencional, a pesar de reducir del número de pares de zonas en un 96% y el tiempo de cálculo en un 70%. 空间相互作用模型通常采用离散区域代表区位。模型的计算量往往与区域数量呈平方甚至更高阶增长。对于可计算的精细模型,如土地利用‐交通相互作用模型和基于行为的城市区域模型,区域尺度的依赖性是长期存在的问题,即使计算机的计算速度增加,该问题仍无法消除。因此,建模者需在模型空间分辨率和覆盖范围以及模型分析的严谨性和深度上做出权衡。本文介绍了一种新型的离散分区系统,目的在于减少空间相互作用模型估算和计算时间,同时维持其精度。新系统的前提是目标区域的适当尺度取决于与初始区域的距离:在短距离范围内,空间精确性是重要的,且目标区域必须是小的;在更远距离上,位置精度的重要性降低,目标区域可以变大。该方法为每个初始区域制定了具体的尺度地图。每个初始区域成为其自身地图的中心,被近邻的小区域和更远距离的大区域所包围。本文给出了新方法的理论公式,并以英格兰地区的通勤模型进行检验。结果显示,尽管区域对的数量减少了96%,计算时间缩短了70%,但新方法的计算结果等效于常规模型。  相似文献   
83.
Marine spatial planning is emerging as an integrated, resource management-led approach to governing the use of the seas. Recent initiatives include those of some north European countries, including Germany, which has now completed a plan for its federal offshore territory. In this article, an analysis is presented of this pioneering plan and the consultation process behind its production, with a particular emphasis on the treatment of different sectoral interests around which the plan was structured. This revealed the attempts to coordinate not only the different demands at sea by means of allocation of areas and cross-sectoral considerations, but also the uneven representation of activities with certain interests gaining strongly and others effectively marginalized. This study provides early empirical evidence of the tensions involved in the attempt to adopt a spatial approach to marine governance. This new domain for planning is situated in the overlapping, but distinct domains of marine management and spatial planning. The conceptual backgrounds of both are drawn upon in assessing the strengths and weaknesses of the plan and in suggesting how marine plans might gain by giving close attention to the broader principles of marine and strategic planning.  相似文献   
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Abstract

This paper describes some of the changes that affected the coastlines of South Uist and Benbecula following the ‘Great Storm’ of 11 January 2005. The paper considers historical changes in patterns of winter storminess and addresses the issue of whether or not there has been a recent increase in regional storminess, manifested partly by this particular storm. The paper concludes on the basis of available Greenland ice core chemistry data and historical climate data, together with recent meteorological data, that no such increase has taken place. This surprising conclusion is further discussed in relation to current thinking on the nature of recent climate change.  相似文献   
88.
Landscapes of the Ghost Dance: A Cartography of Numic Ritual   总被引:1,自引:0,他引:1  
Recent historical and ethnographic research indicates that the study of ritual behavior could be greatly enhanced by combining parameters of place and landscape use with interpretation of material culture. This strategy is especially useful for identifying the archaeological record of ritual among societies that incorporated topographic features and natural resources into their liturgical order. In this article we apply a behavioral framework to the study of Numic ritual technologies. By intergrating ethnographic and historic data on the geography, practice, and material culture of the nineteenth-century Nevada Ghost Dance, we demonstrate how this framework helps to determine the configuration of a ritual place and its position relative to other ritual and nonritual places.  相似文献   
89.
Alex 《世界》2009,(1):176-176
这个国家位于不列颠群岛最大一个岛上,这是是欧洲大陆伸向大西洋的最西处,是古代北美通往欧洲的咽喉要冲。  相似文献   
90.
Alex 《世界》2009,(2):176-176
地理位置:太平洋南部、介于南极和赤道之间 气候特征:海洋型温带气候 关键词:指环王、南阿尔卑斯山、地球上纬度最靠南的首都 大约8000万到1亿年前,这片土地飘移到了南太平洋,这个孤悬于地球角落里的地方由此保存了地球上最为奇特的物种:不会飞的鸟,体重最大的昆虫和恐龙……这里仿佛与世界其他地方远隔了一道8000万年的时光墙。  相似文献   
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