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Cross-checks between the Washington and Miami Geosecs radiocarbon laboratories verify that results on identical samples measured at the two laboratories agree with the stated accuracy of each laboratory which is±4‰inΔ14C.  相似文献   
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土壤中稀土元素地球化学研究进展   总被引:12,自引:1,他引:12  
综述了土壤中稀土元素含量、稀土赋存形态、稀土生物有效性、稀土在土壤环境中的分布规律、迁移方式及其影响因子。讨论了稀土微肥应用中应注意的问题以及由此带来的环境效应,并探讨了建立具有普遍适用性的稀土生物有效性方法学的途径等。  相似文献   
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3D indoor navigation in multi‐story buildings and under changing environments is still difficult to perform. 3D models of buildings are commonly not available or outdated. 3D point clouds turned out to be a very practical way to capture 3D interior spaces and provide a notion of an empty space. Therefore, pathfinding in point clouds is rapidly emerging. However, processing of raw point clouds can be very expensive, as these are semantically poor and unstructured data. In this article we present an innovative octree‐based approach for processing of 3D indoor point clouds for the purpose of multi‐story pathfinding. We semantically identify the construction elements, which are of importance for the indoor navigation of humans (i.e., floors, walls, stairs, and obstacles), and use these to delineate the available navigable space. To illustrate the usability of this approach, we applied it to real‐world data sets and computed paths considering user constraints. The structuring of the point cloud into an octree approximation improves the point cloud processing and provides a structure for the empty space of the point cloud. It is also helpful to compute paths sufficiently accurate in their consideration of the spatial complexity. The entire process is automatic and able to deal with a large number of multi‐story indoor environments.  相似文献   
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Amber-signs in the Latvian nation-state’s semiotics, constructed during the interwar period, are only bits and pieces of a complex system such as the State. However, the resonance that amber semiotics effectuated, despite its actual rarity, was and still is remarkably influential. Amber was extensively deployed as a signifier to the territory and its people, places and things; it signified patria, belonging and the homeland. Such State semiotics, according to Deleuze–Guattarian concepts, is distinguished as a signifying regime of signs characterized by its universal deception and regulated by State-controlled interpretations, facialized centres, and a high degree of deterritorializations. We examine the thresholds of territoriality-deterritorialization relations and expressions of amber signs during the Latvian nation-state’s and the Soviet Union’s semiotic regimes, conceptualized as indexes, symbols and icons. By tracing and mapping of these territorialisation movements we enrich our understanding of how effective the created semiotics are, and in what variety of forms and territorialities, including linguistic, craftsmanship, and varied place makings, they are expressed in a particular regime. Such territorial perspective thus shifts the focus from what and why these signs mean (e.g., national identity, homeland) to where, when and how (e.g., dynamics of various State’s territorialities) they become operational. Among other national products that emit signs, amber proved to be most effective in the functioning of State’s signifying semiotics in Latvia, representing thoroughly the strangleholds and the continuity of such deceptive semiotics.  相似文献   
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The aim of the study was to determine the effects of climate variability, agricultural land drainage and afforestation of agricultural land on river discharge. The study was conducted in the Vienziemīte stream basin (6 km2), where discharge was monitored on a daily basis during the time period of 1946–2010. In the stream basin, natural afforestation of agricultural land began in the 1950s, and in the mid-1970s artificial drainage systems were installed in all agricultural land (70% of the total basin area). Climate variability and artificial drainage were the main factors observed to be affecting stream discharge. The changes were most evident in annual and seasonal mean, minimum and maximum streamflow. There was no effect of afforestation of agriculture land on stream discharge.  相似文献   
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以W Arcview/GIS为工具 ,结合传统的火焰蔓延数学模型 ,发展了复杂系统条件下城市地震次生火灾蔓延的计算机仿真模型 ,并结合福州市主要建筑物结构类型的具体情况 ,提出了根据建筑物类型来区分不同可燃物类型的划分方案。结合火源、风向风力、可燃物分布等因素 ,该模型在地震时可用以判定某一时段内可能的延烧区域 ,估计地震次生火灾的灾害程度及其直接经济损失  相似文献   
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I.InternationalRiversandtheLancangMekongRiverInternationalriversaredefinedastheriverswhichflowacrostwoortwomorecountries.Upt...  相似文献   
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