全文获取类型
收费全文 | 4981篇 |
免费 | 1073篇 |
国内免费 | 1549篇 |
专业分类
测绘学 | 874篇 |
大气科学 | 715篇 |
地球物理 | 909篇 |
地质学 | 3076篇 |
海洋学 | 844篇 |
天文学 | 97篇 |
综合类 | 418篇 |
自然地理 | 670篇 |
出版年
2024年 | 53篇 |
2023年 | 149篇 |
2022年 | 291篇 |
2021年 | 402篇 |
2020年 | 299篇 |
2019年 | 372篇 |
2018年 | 317篇 |
2017年 | 296篇 |
2016年 | 296篇 |
2015年 | 318篇 |
2014年 | 307篇 |
2013年 | 348篇 |
2012年 | 369篇 |
2011年 | 423篇 |
2010年 | 374篇 |
2009年 | 368篇 |
2008年 | 365篇 |
2007年 | 311篇 |
2006年 | 297篇 |
2005年 | 274篇 |
2004年 | 170篇 |
2003年 | 156篇 |
2002年 | 180篇 |
2001年 | 153篇 |
2000年 | 130篇 |
1999年 | 131篇 |
1998年 | 77篇 |
1997年 | 78篇 |
1996年 | 54篇 |
1995年 | 33篇 |
1994年 | 25篇 |
1993年 | 39篇 |
1992年 | 36篇 |
1991年 | 26篇 |
1990年 | 20篇 |
1989年 | 15篇 |
1988年 | 5篇 |
1987年 | 13篇 |
1986年 | 9篇 |
1985年 | 3篇 |
1984年 | 5篇 |
1983年 | 4篇 |
1982年 | 1篇 |
1981年 | 5篇 |
1980年 | 1篇 |
1979年 | 2篇 |
1977年 | 1篇 |
1958年 | 2篇 |
排序方式: 共有7603条查询结果,搜索用时 15 毫秒
911.
通过分析气象数据的特点和RIA(Rich Internet Application)技术的优势,为实现气象影像数据的高效发布,对网络地图发布的关键技术进行了详细的研究。主要包括缓存切片的分层分块规则建立,影像数据瓦片缓存目录构建,动态切片生成技术,Flex客户端地图展示技术。结果表明:与传统基于Web的地图发布技术相比,RIA技术具有界面元素丰富,交互响应快,大数据量显示效率高的优势。此外,还能够在改变地图缩放级别时,实现地图数据的快速加载和无缝拼接,这为后续气象GIS平台的开发以及高效运行奠定了基础。 相似文献
912.
由于地球自转导致的自由核章动(FCN)及内核自由章动(FICN)等地球简正模是地球内部动力学过程的重要表征,也是认识核幔边界和内外核边界的重要手段,其包含的物理信息可为目前地球深部的研究手段比较匮乏的情况下获得地球深内部结构及物理性质和研究核幔及内外核耦合提供非常重要的约束。本文围绕地球自由核章动利用全球地球动力学计划观测网提供的全球超导重力观测资料和国际VLBI服务组织提供的章动观测资料,采用不同方法研究了自由核章动的本征周期和品质因子等 相似文献
913.
914.
915.
Up to now, detailed strategies and algorithms of automatic change detection for road networks based on GIS have not been discussed. This paper discusses two different strategies of automatic change detection for images with low resolution and high resolution using old GIS data, and presents a buffer detection and tracing algorithm for detecting road from low-resolution images and a new profile tracing algorithm for detecting road from high-resolution images. For feature-level change detection (FL-CD), a so-called buffer detection algorithm is proposed to detect changes of features. Some ideas and algorithms of using GIS prior information and some context information such as substructures of road in high-resolution images to assist road detection and extraction are described in detail. 相似文献
916.
GeoStar is the registered trademark of GIS software made by WTUSM in China. By means of the GeoStar, multi-scale images, DEMs, graphics and attributes integrated in very large seamless databases can be created, and the multi-dimensional dynamic visualization and information extraction are also available. This paper describes the fundamental characteristics of such huge integrated databases, for instance, the data models, database structures and the spatial index strategies. At last, the typical applications of GeoStar for a few pilot projects like the Shanghai CyberCity and the Guangdong provincial spatial data infrastructure (SDI) are illustrated and several concluding remarks are stressed. 相似文献
917.
In this paper, two cases of data consistency problems are discussed in Multi-user Geographical Information System. When a user updates some spatial data that have been accessed by other users in database, or executes an UNDO/REDO operation, data consistency will probably be destroyed. To solve the problem caused by the first case, a “Notification-Reread Method” is introduced. As for the second case, there are many problems to be studied. 相似文献
918.
OGC Web Map Service is one kind of OGC Portrayal Services belongs to OGC Web Service model and it provides multi-platform interoperability of spatial data set. This paper presents a method for implementing OGC Web Map Service based on Web Service technique and introduces the detailed process. 相似文献
919.
Data acquisition and modeling are the two important, difficult and costful aspects in a Cybercity project. 2D-GIS is mature and can manage a lot of spatial data. Thus 3D-GIS should make the best of data and technology of 2D-GIS. Construction of a useful synthetic environment requires integration of multiple types of information like DEM, texture images and 3D representation of objects such as buildings. In this paper, the method for 3D city landscape data model and visualization based on integrated databases is presented. Since, the data volume of raster are very huge, special strategies (for example, pyramid gridded method) must be adopted in order to manage raster data efficiently. Three different methods of data acquisition, the proper data structure and a simple modeling method are presented as well. At last, a pilot project of Shanghai Cybercity is illustrated. 相似文献
920.
On the basis of the authors' experiences of setting up an NGDC Web site, this paper attempts to present some significant aspects about the security of NGDC based on ASP. They include data storing, database maintenance, new technical support and so on. Firstly, this paper discusses how to provide the security of data which is saved in the hosts of NGDC. The security model of “Networks-DB Server-DB-DB Object” is also presented. In Windows NT Server, Internet Information Server (i. e., IIS) is in charge of transferring message and the management of Web sites. ASP is also based on IIS. The advantages of virtual directory technique provided by IIS are emphasized. 相似文献