全文获取类型
收费全文 | 773篇 |
免费 | 16篇 |
国内免费 | 29篇 |
专业分类
测绘学 | 491篇 |
大气科学 | 18篇 |
地球物理 | 29篇 |
地质学 | 41篇 |
海洋学 | 48篇 |
天文学 | 149篇 |
综合类 | 30篇 |
自然地理 | 12篇 |
出版年
2023年 | 2篇 |
2022年 | 4篇 |
2021年 | 17篇 |
2020年 | 10篇 |
2019年 | 15篇 |
2018年 | 7篇 |
2017年 | 35篇 |
2016年 | 33篇 |
2015年 | 35篇 |
2014年 | 38篇 |
2013年 | 39篇 |
2012年 | 44篇 |
2011年 | 45篇 |
2010年 | 32篇 |
2009年 | 39篇 |
2008年 | 43篇 |
2007年 | 45篇 |
2006年 | 61篇 |
2005年 | 34篇 |
2004年 | 29篇 |
2003年 | 35篇 |
2002年 | 36篇 |
2001年 | 15篇 |
2000年 | 18篇 |
1999年 | 15篇 |
1998年 | 17篇 |
1997年 | 16篇 |
1996年 | 13篇 |
1995年 | 7篇 |
1994年 | 13篇 |
1993年 | 6篇 |
1992年 | 9篇 |
1991年 | 5篇 |
1990年 | 1篇 |
1989年 | 2篇 |
1988年 | 1篇 |
1987年 | 1篇 |
1986年 | 1篇 |
排序方式: 共有818条查询结果,搜索用时 0 毫秒
141.
142.
为建立适用于遥感相机定标的实验室,需要有几何标定的算法和软件对摄影图像进行计算.使用近景摄影测量中基于3维控制场的定标方法,对单CCD四波段遥感相机进行了几何定标,研究并自主编程实现了直接线性变换DLT(Direct Linear Transformation)算法,与基于空间后方交会算法的定标结果进行了精度对比.结论... 相似文献
143.
LD2000 System with 3S and Multi—sensor 总被引:2,自引:0,他引:2
This paper introduces a car-borne road information collecting and updating system (LD2000) developed by Wuhan Technical University of Surveying and Mapping.This system is capable of collecting road network information and creating digital road network effectively by means of GPS,GIS and multi-sensor integration.The design and development of LD 2000 system are also presented in this paper. 相似文献
144.
145.
146.
147.
148.
James W. Beletic Sean Adkins Barry Burke Robert Reich Bernie Kosicki Vyshnavi Suntharalingham Charlie Bleau Ray DuVarney Richard Stover Jerry Nelson Francois Rigaut 《Experimental Astronomy》2005,19(1-3):103-109
All of the extremely large telescopes (ELTs) will utilize sodium laser guide star (LGS) adaptive optics (AO) systems. Most of these telescopes plan to use the Shack-Hartmann approach for wavefront sensing. In these AO systems, the laser spots in subapertures at the edge of the pupil will suffer from spot elongation due to the 10 km extent of the sodium layer and the large separation from the projection laser. This spot elongation will severely degrade the performance of standard geometry wavefront sensing systems. In this paper, we present a CCD with custom pixel morphology that aligns the pixels of each subaperture with the radial extension of the LGS spot. This CCD design will give better performance than a standard geometry CCDs for continuous wave lasers. In addition, this CCD design is optimal for a pulsed sodium laser. The pixel geometry enables each subaperture to follow a laser pulse traversing the sodium layer, providing optimal sampling of a limited number of detected photons. In addition to novel pixel layout, this CCD will also incorporate experimental JFET sense amplifiers and use CMOS design approaches to simplify the routing of biases, clocks and video output. This CCD will attain photon-noise limited performance at high frame rates, and is being incorporated in the plans for the Thirty Meter Telescope (TMT). 相似文献
149.
S. P. Willner 《Experimental Astronomy》1994,3(1-4):147-148
A camera design with only four lens elements gives good imaging performance at a working focal ratio of f/4.4. 相似文献
150.
This study introduces the new results of a novel low-cost digital zenith camera system operated in Turkey that uses astronomical and geodetic instrumentation. Currently, it is possible to determine deflections of the vertical (DoV) components by using a vast amount of information gathered from geo-referenced star images, tilt measurements, and Global Navigation Satellite System technology. This new design of an astro-geodetic camera system is used for calculating DoV components with 12 independent solutions on a test station in Istanbul, and additional observations were performed to investigate the external accuracy of the system on a test network. A specific leveling method is developed to align system toward the zenithal direction. The final results of the observations on a test station located in Istanbul indicate that the accuracy of the system is about ±0.19 arc-seconds in latitude and ±0.28 arc-seconds in longitude determination. The system has been further tested on a network with 4 control points that have averagely 20?km baselines. At the test network, the root mean square of the average value of the vertical deflections is calculated as ±0.36 arc-seconds. Furthermore, DoV components are compared with the values that are calculated using global geopotential models. 相似文献