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   854篇
  免费   34篇
  国内免费   52篇
测绘学   467篇
大气科学   34篇
地球物理   59篇
地质学   138篇
海洋学   48篇
天文学   8篇
综合类   101篇
自然地理   85篇
  2023年   1篇
  2022年   13篇
  2021年   22篇
  2020年   32篇
  2019年   36篇
  2018年   14篇
  2017年   31篇
  2016年   39篇
  2015年   39篇
  2014年   36篇
  2013年   67篇
  2012年   63篇
  2011年   64篇
  2010年   35篇
  2009年   40篇
  2008年   52篇
  2007年   53篇
  2006年   61篇
  2005年   66篇
  2004年   42篇
  2003年   38篇
  2002年   32篇
  2001年   17篇
  2000年   14篇
  1999年   11篇
  1998年   10篇
  1997年   3篇
  1996年   4篇
  1994年   1篇
  1990年   2篇
  1988年   1篇
  1986年   1篇
排序方式: 共有940条查询结果,搜索用时 15 毫秒
141.
精确时空立体景观虚拟现实的构建与应用方法研究   总被引:5,自引:4,他引:1  
本文提出一种适应人眼双目立体视觉的、可以精确进行三维量测的虚拟现实系统概念 ,阐述了这种系统的社会需求、理论依据和构建技术 ,特别详细讨论了人造立体视觉所应遵循的几何物理条件 ,三维模型数据获取方法、立体模型显示与立体观测方法、以及虚景与实景叠加等技术问题 ,并给出相应的解决方案 ,列出了应用成功的范例  相似文献   
142.
基于虚拟土理念的中国耕地资源价值核算初探   总被引:2,自引:0,他引:2  
在经济高速发展带来土地资源日趋紧张的形势下,深化对耕地资源价值的认识,有助于实现耕地资源空间布局优化和耕地市场化流转.该文在明确虚拟土内涵与类型划分的基础上,从经济、社会和生态价值属性出发,运用收益还原法、替代法等方法,以省级为单位,分别测算了中国产能虚拟土、资源虚拟土和生态虚拟土价值,通过SPSS聚类分析和GIS空间分析,从虚拟土角度分析我国耕地资源价值的空间分布差异.研究结果表明,产能虚拟土得分最高的广东省是得分最低的内蒙古自治区的8.94倍;资源虚拟土得分最高的上海市是得分最低的黑龙江省的96.10倍;生态虚拟土得分最高的上海市是得分最低的贵州省的9.25倍.在空间分布上,产能虚拟土与纬度气候带分布基本一致,资源虚拟土分布受经济影响较大,而生态虚拟土分布则受气候和经济因素共同作用.  相似文献   
143.
ABSTRACT

In recent years there has been a surge in land investments, primarily in the African continent, but also in Asia and Latin America. This increase in land investment was driven by the food pricing crisis of 2007–2008. Land investors can be identified from a variety of sectors, with actors ranging from hedge funds to national companies. Many water-scarce countries in the Middle East and North Africa (MENA) are among these financiers, and primarily invest in Africa. Recognizing the potential for “outsourcing” their food security (and thereby also partly their water security), Middle Eastern countries such as Jordan, Qatar and the United Arab Emirates have invested in land for food production in Africa. The extent to which this is happening is still unclear, as many contracts are not yet official and the extent of the leases is vague. This paper investigates the land investments and acquisitions by Middle Eastern countries. It also seeks to analyse what effect, if any, these investments can have on the potential for conflict reduction and subsequent peacebuilding in the Middle East region as the activity removes pressure from transboundary water resources.

EDITOR D. Koutsoyiannis ASSOCIATE EDITOR K. Aggestam  相似文献   
144.
增强现实及其在导航与位置服务中的应用   总被引:1,自引:0,他引:1  
对增强现实从概念内涵、发展历程、关键技术及应用领域等方面进行了论述;对如何使其为导航与位置服务带来个性化的深度服务,并延伸至泛在测绘等领域进行了探讨;最后就增强现实的发展趋势和待解决的问题阐述了观点。  相似文献   
145.
为了形象地表现层状地质体形态,本文利用VRML在虚拟环境中建立了3维地质体。根据层状地质体的实际情况,本文利用VRML中的几何形体建模节点ElevationGrid和IndexedFaceSet创建了3维地质体的虚拟现实模型。该方法利用钻孔数据获取层面数据,使用Surfer软件进行数据插值,得到网格化数据文件,用网格化文件与ElevationGrid节点相结合,模拟地质体上下表面,用IndexedFaceSet节点建立两层表面边界,从而构成一个视觉上闭合的3维实体。最后用此方法建立了层状地质体的虚拟现实模型实例。  相似文献   
146.
从信息技术应用的角度,通过整合3维GIS,虚拟现实技术和信息集成等信息技术,为电网实现3维可视化提出一个技术机构,它可以从多分辨率、多尺度、多时空等多种角度实现电网的3维可视化。论文阐述了该系统的技术架构以及实现的关键技术,如合成建模、可视化仿真、信息集成、可视化,为电网规划设计、工程建设、运行维护3维可视化提出一种建设思路,相信对从事相关工作的同行能有所裨益。  相似文献   
147.
Abstract

Gaia Journeys is a collaborative multimedia musical and virtual reality art performance conceived by author Williams, with the aid of staff at the Denver Museum of Nature & Science. Inspired by astronauts who spoke of seeing a border-less world from orbit, Gaia Journeys’ chief goal was to deliver this experience to museum audiences via photo-realistic virtual depictions of the Earth (from orbit as well as via spherical photographic panoramas taken from the ground) choreographed to live musical accompaniment. Gaia Journeys took place in the high resolution digital ‘fulldome’ Gates Planetarium, with Williams playing the violin and keyboards, enhancing a previously recorded backing track, while visuals were generated with SCISS AB's Uniview. The eight tracks of audio were three-dimensionally spatialised to the 16.4 sound system of the Gates Planetarium, providing an immersive sound experience to match the visuals. The audience feedback was generally positive, with great interest in repeat or similar future programming. These visitor evaluations suggest the potent power of the new class of digital planetaria for displaying virtual globe datasets to the public, via both multimedia entertainment like Gaia Journeys as well as traditional lectures.  相似文献   
148.
Abstract

Virtual Australia is not a well-defined or agreed concept. This discussion paper conceptualises Virtual Australia as a ‘virtual [digital] model containing and representing all non-trivial objects and their contextual environment – from blue sky to bedrock – in real world Australia’. It describes a scenario for Virtual Australia, one or two decades from now, in which the locations and conditions of non-trivial objects and their environment are updated automatically through a combination of remote sensing and wireless communication technologies in support of a ‘Supranet’. It then examines the concept of the ‘Supranet’ – a pervasive information network based largely on wireless technology linking the physical world to a virtual model in real time – and develops and discusses three principal characteristics of the Supranet: the ability to have or collect specific information (know); the ability to process information (think); and the ability to communicate that information. If, in the near future, any or all non-trivial devices are to some extent able to know, think and communicate, the potential for object autonomy will be realised.  相似文献   
149.
Typhoons are usually accompanied by strong winds, heavy rain, storm surges and other disastrous events, and they are the most severe weather phenomena in the western part of the North Pacific Ocean. Visualisation is a key technology for analysing and presenting climate simulations and observations together with related social and ecological data. Virtual globes are a logical platform for visualising such geospatial data via the Internet. To implement interactive visualisation of typhoon data within virtual globes, this study provides a 3D texture-mapping algorithm to render volume textures on a globe. In addition, a systematic framework is proposed in which a hierarchical octree-based multiresolution data structure is implemented to organise the large volume dataset, and a graphics processing unit-based dynamic interpolation approach is proposed to obtain a smooth effect. Finally, the structure is combined with a level of detail strategy to enable the rendering of dynamic volumetric data at an acceptable interactive frame rate. To demonstrate the capabilities of this framework, data for a simulated typhoon event were rendered in World Wind, an open-source virtual globe. The experimental results demonstrate that the application of the proposed strategies can result in an interactive visualisation performance that renders typhoon data on virtual globes.  相似文献   
150.
One of the problems in virtual globes technologies is the real-time representation of vegetal species. In forest or garden representations, the low detailed plants produce a lack of realism. Efficient techniques are required to achieve accurate interactive visualisation due to the great number of polygons the vegetal species have. This article presents a multi-resolution model based on a geometric representation of vegetal species that allows the application to perform the progressive transmission of the model, that is, the transmission of a simple representation followed by successive refinements of it. It has a hardware-oriented design in order to obtain interactive frame rates. The geometric data of the objects are stored in the graphics processing unit and, moreover, the change from one approximation to another is obtained by performing mathematical calculations in this graphics hardware. The multi-resolution model presented here enables instancing: as many vegetal species as desired can be rendered with different levels of detail, while all of them are accessing the same geometric data. This model has been used to build a real-time representation of a not imaginary scenario.  相似文献   
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