全文获取类型
收费全文 | 5078篇 |
免费 | 1094篇 |
国内免费 | 1254篇 |
专业分类
测绘学 | 441篇 |
大气科学 | 864篇 |
地球物理 | 1349篇 |
地质学 | 2812篇 |
海洋学 | 658篇 |
天文学 | 295篇 |
综合类 | 413篇 |
自然地理 | 594篇 |
出版年
2024年 | 27篇 |
2023年 | 97篇 |
2022年 | 229篇 |
2021年 | 280篇 |
2020年 | 220篇 |
2019年 | 273篇 |
2018年 | 303篇 |
2017年 | 284篇 |
2016年 | 282篇 |
2015年 | 263篇 |
2014年 | 305篇 |
2013年 | 324篇 |
2012年 | 333篇 |
2011年 | 351篇 |
2010年 | 334篇 |
2009年 | 306篇 |
2008年 | 284篇 |
2007年 | 247篇 |
2006年 | 221篇 |
2005年 | 221篇 |
2004年 | 188篇 |
2003年 | 188篇 |
2002年 | 224篇 |
2001年 | 211篇 |
2000年 | 185篇 |
1999年 | 192篇 |
1998年 | 169篇 |
1997年 | 150篇 |
1996年 | 125篇 |
1995年 | 86篇 |
1994年 | 95篇 |
1993年 | 92篇 |
1992年 | 68篇 |
1991年 | 54篇 |
1990年 | 44篇 |
1989年 | 30篇 |
1988年 | 30篇 |
1987年 | 22篇 |
1986年 | 20篇 |
1985年 | 17篇 |
1984年 | 14篇 |
1983年 | 8篇 |
1982年 | 6篇 |
1981年 | 6篇 |
1980年 | 4篇 |
1966年 | 1篇 |
1965年 | 1篇 |
1963年 | 1篇 |
1958年 | 1篇 |
1954年 | 3篇 |
排序方式: 共有7426条查询结果,搜索用时 15 毫秒
101.
Many regions around the world require improved gravimetric data bases to support very accurate geoid modeling for the modernization
of height systems using GPS. We present a simple yet effective method to assess gravity data requirements, particularly the
necessary resolution, for a desired precision in geoid computation. The approach is based on simulating high-resolution gravimetry
using a topography-correlated model that is adjusted to be consistent with an existing network of gravity data. Analysis of
these adjusted, simulated data through Stokes’s integral indicates where existing gravity data must be supplemented by new
surveys in order to achieve an acceptable level of omission error in the geoid undulation. The simulated model can equally
be used to analyze commission error, as well as model error and data inconsistencies to a limited extent. The proposed method
is applied to South Korea and shows clearly where existing gravity data are too scarce for precise geoid computation. 相似文献
102.
田晋 《武汉大学学报(信息科学版)》2009,34(1):113-116
给出了局部大地水准面精化系统的总体结构以及各分系统的详细设计与实现方法,开发了旨在对相关重力测量数据实现自动化处理的局部大地水准面精化系统工具软件,并应用于某区域实际大地水准面的精确计算。实践证明,该系统能有效提高相关数据的处理效率,有助于局部大地水准面精化过程的规范化。 相似文献
103.
现代测绘学在构建数字地球中的作用 总被引:3,自引:0,他引:3
叙述了数字地球的由来、概念和作用。从现代测绘学的发展,阐述了它在构建数字地球中的作用和地位。 相似文献
104.
针对目前我国GIS应用现状,在应用需求调查和分析的基础上,介绍了哈尔滨市城市建设基础信息系统建设过程的经验,提出了特大城市建立城市基础信息系统的方案。 相似文献
105.
根据1957与1982年两个时期的地形冈并结合1995与2008年的遥感卫星影像提取城镇建设用地专题信息。利用ArcGIS建立广佛都市区城镇建设用地数据库.采用分形维度的计锋方法,对广佛都市区城市蔓延的情况进行测度和分析。结果表明广佛都市区三个发展阶段城镇建设用地面积增长速度并不均匀,具有加速发展的特点。四个测度年份的分形维数分别为1.6454,1.6285,1.5586和1.5270,均在1-2之间.分形维数呈递降趋势,总体下降了0.1184,城市发展模式由紧凑型逐渐向松散型演变,存在城市蔓延情况,而且城市发展模式以年均0.14%的速度从紧凑型向松散型演变。广佛都市区城市蔓延的地域分异较为明硅,具有较强的空间集聚性和中心向心件,广州和佛山毗邻地区以及中心城区是城市蔓延的活跃区和集中区,1982—1995年问研究区内蔓延速度比1995.2008年间要快。通过深入分析发现,经济快速发展、城市人口的持续增长、交通道路网络的建设是广佛都市区快速扩张和城市蔓延的基本动力因素之一,开发区土地扩张,进一步加剧了无序扩张和城市蔓延。 相似文献
106.
107.
卫星测高问题的球谐级数解法 总被引:3,自引:0,他引:3
研究了球界面下卫星测高问题的解法,利用有限逼近方法得到了下列结论:若陆地部分是球冠,则卫星测高问题的解可以转换成关于球谐级数位系统的线性方程组。同时证明了常用的Stokes问题、Dirichlet问题、Neumann问题可以看成卫星测高问题的特殊情况。 相似文献
108.
Multiresolution Terrian Model in GIS 总被引:1,自引:0,他引:1
DEM, which becomes a major component of geographic information processing in earth and engineering sciences, has been studied in the GIS literature for a long time. We use DEM to represent the terrain in GIS. The more data are available, the better representations of a terrain can be built. But not all tasks in the framework of a given application necessarily require the same accuracy, and even a single task may need different levels of accuracy in different areas of the domain. Multiresolution models, such as LOD, offer the possibility of representing and analyzing a terrain at a range of different levels of detail. In this paper, some key issues in multiresolution DEM model are studied. Three main models are focused on Hierarchical TIN(HTIN), multiresolution terrain model based Delaunay and Hierarchical Dynamic Simplification. The advantages and disadvantages of these methods are analyzed. The technology of tile to tile edge match is studied to maintain the consistency between adjacent edges and tile edges in HTIN model. And the Hypergraph based Objected oriented Model(HOOM) is presented to divide and code spatial area and describe the terrain feature in adding and deleting points based on Delaunay rule retriangulating. The conclusions have been drawn in the end. 相似文献
109.
When SINS (strap-down inertial navigation system) is combined with GPS, the observability of the course angle is weak. Although the course angle error is improved to some extent through Kalman filtering, the course angle still assumes a divergent trend. This trend is aggravated further when using low-cost and low-accuracy SINS. In order to restrain this trend, a method that uses AHRS to substitute for SINS course angle information is put forward aimed at the hardware component characteristic of the low-cost and low-accuracy SINS including AHRS (attitude and heading reference system) and IMU (inertial measurement unit). Real static and dynamic experiments show that the method can restrain the divergent trend of the navigation system angle effectively, and the positioning accuracy is high. 相似文献
110.
Xiaodong Zhang Ho Jin Kim Clinton Streeter David A. Claypool Ramesh Sivanpillai Santhosh Seelan 《国际地球制图》2013,28(7):537-551
Precision agriculture often relies on high-resolution imagery to delineate the variability within a field. Airborne Environmental Research Observational Camera (AEROCam) was designed to meet the needs of agriculture producers, ranchers, and researchers, who require high-resolution imagery in a near real-time environment for rapid decision support. AEROCam was developed and operated through a unique collaboration between several departments at the University of North Dakota, including the Upper Midwest Aerospace Consortium (UMAC), the School of Engineering and Mines, and flight operations at the John D. Odegard School of Aerospace Sciences. AEROCam consists of a Redlake MS4100 area-scan multi-spectral digital camera that features a 1920 × 1080 CCD array (7.4-μm detector) with 8-bit quantization. When operated at ~2 km above ground level, multispectral images with four bands in the visible and near infrared have a ground sample distance of 1 m with a horizontal extent of just over 1.6 km. Depending on the applications, flying at different altitudes can adjust the spatial resolution from 0.25 to 2 m. Rigorous spectral and radiometric calibrations allow AEROCam to be used in a variety of applications, qualitative and quantitative. Equipped with an inertial measurement unit (IMU) system, the images acquired can be geo-referenced automatically and delivered to end users near real time through our Digital Northern Great Plains system (DNGP). The images are also available to zone mapping application for precision farming (ZoneMAP), an online decision support tool for creating management zones from remote sensing imagery and data from other sources. Operational since 2004, AEROCam has flown over 250 sorties and delivered over 150,000 images to the users in the Northern Great Plains region, resulting in numerous applications in precision agriculture and resource management. 相似文献