全文获取类型
收费全文 | 8539篇 |
免费 | 610篇 |
国内免费 | 544篇 |
专业分类
测绘学 | 5103篇 |
大气科学 | 446篇 |
地球物理 | 702篇 |
地质学 | 1121篇 |
海洋学 | 715篇 |
天文学 | 301篇 |
综合类 | 783篇 |
自然地理 | 522篇 |
出版年
2024年 | 14篇 |
2023年 | 53篇 |
2022年 | 265篇 |
2021年 | 325篇 |
2020年 | 329篇 |
2019年 | 291篇 |
2018年 | 210篇 |
2017年 | 505篇 |
2016年 | 477篇 |
2015年 | 448篇 |
2014年 | 491篇 |
2013年 | 565篇 |
2012年 | 617篇 |
2011年 | 522篇 |
2010年 | 399篇 |
2009年 | 375篇 |
2008年 | 468篇 |
2007年 | 498篇 |
2006年 | 463篇 |
2005年 | 400篇 |
2004年 | 331篇 |
2003年 | 255篇 |
2002年 | 201篇 |
2001年 | 216篇 |
2000年 | 170篇 |
1999年 | 121篇 |
1998年 | 138篇 |
1997年 | 106篇 |
1996年 | 97篇 |
1995年 | 71篇 |
1994年 | 44篇 |
1993年 | 56篇 |
1992年 | 45篇 |
1991年 | 25篇 |
1990年 | 26篇 |
1989年 | 25篇 |
1988年 | 14篇 |
1987年 | 15篇 |
1986年 | 15篇 |
1985年 | 1篇 |
1982年 | 4篇 |
1977年 | 2篇 |
排序方式: 共有9693条查询结果,搜索用时 15 毫秒
131.
基于车载序列影像的建筑立面纹理的快速重建 总被引:5,自引:0,他引:5
提出了一种基于车载序列影像的建筑立面纹理快速重建的方法。首先进行影像预处理,包括畸变差改正、树木遮挡去除等,然后对影像进行自动纠正,在此基础上,自动选择拼接点对影像进行拼接。实验证明了本文方法的有效性。 相似文献
132.
Quick Bird遥感影像的几何校正 总被引:1,自引:0,他引:1
以高分辨率的Quick Bird卫星数据为对象,经影像信息融合,使处理后的图像分辨率提高且接近真彩色,具有良好的判识效果;选择若干个GPS地面控制点作为参考点,以遥感图像处理软件ER Mapper6.2为平台,对图像进行二次多项式几何精校正,纠正后的图像点位误差在lm左右,说明纠正后的图像具有较高的几何精度. 相似文献
133.
Landsat7 ETM+影像的融合和自动分类研究 总被引:25,自引:0,他引:25
利用SFIM、MLT、HPF和修改的Brovey(MB)等遥感影像融合算法对Landsat 7 ETM 影像进行融合和自动分类研究,并就融合影像的光谱保真度、高频空间信息融人度和分类精度对这些方法进行评价。结果表明SFIM变换几乎完全保持了原始影像的光谱特点,并具有最高的平均分类精度;MB变换具有最高的高频空间信息融人度;MLT变换也具有较高的分类精度;只有HPF变换的各项指标都不突出。所有4种融合影像的分类精度都较原始影像的分类精度有明显的提高。这表明,源于同一传感器系统的不同分辨率影像的融合可以避免异源传感器融合影像所常见的各种参数、时相和配准误差,所以能够明显地提高影像的自动分类精度。 相似文献
134.
135.
本文主要讨论了利用空间投影一空间斜墨卡托(SOM)投影进行卫星遥感图像精纠正与定位,解决缺少控制点地区卫星遥感图像精纠正与定位问题,并根据正反算公式讨论了卫星遥感图像纠正的空间投影数学基础。 相似文献
136.
The analysis of the time and space distribution of specular (reflecting) points in bistatic altimetry between GPS and CHAMP
satellites or SAC-C (taken as examples) is extended from Wagner and Klokočník (2003 J. Geod 77: 128–138). We demonstrate a
significantly higher number and density of reflecting points in bistatic altimetry in comparison with traditional monostatic
altimetry. After an outline of our older accuracy assessment for the vertical position of the reflecting point, we add a new
independent derivation and compare both approaches. We account for orbit errors of both the transmitters (GPS) and receiver
(CHAMP) satellites, and the measurement (delay) error. We found that the accuracy of the vertical position of the reflecting
point decreases only slowly with increasing off-nadir angle and that the orbit errors must be accounted for if decimeter and
better accuracy is required. In this paper, we do not study errors such as state of the ocean, technical parameters of the
receiving system, and atmospheric corrections. 相似文献
137.
Joanne Poon Clive S. Fraser Zhang Chunsun Zhang Li Armin Gruen 《The Photogrammetric Record》2005,20(110):162-171
The growing applications of digital surface models (DSMs) for object detection, segmentation and representation of terrestrial landscapes have provided impetus for further automation of 3D spatial information extraction processes. While new technologies such as lidar are available for almost instant DSM generation, the use of stereoscopic high-resolution satellite imagery (HRSI), coupled with image matching, affords cost-effective measurement of surface topography over large coverage areas. This investigation explores the potential of IKONOS Geo stereo imagery for producing DSMs using an alternative sensor orientation model, namely bias-corrected rational polynomial coefficients (RPCs), and a hybrid image-matching algorithm. To serve both as a reference surface and a basis for comparison, a lidar DSM was employed in the Hobart testfield, a region of differing terrain types and slope. In order to take topographic variation within the modelled surface into account, the lidar strip was divided into separate sub-areas representing differing land cover types. It is shown that over topographically diverse areas, heighting accuracy to better than 3 pixels can be readily achieved. Results improve markedly in feature-rich open and relatively flat terrain, with sub-pixel accuracy being achieved at check points surveyed using the global positioning system (GPS). This assessment demonstrates that the outlook for DSM generation from HRSI is very promising. 相似文献
138.
A generic network design in close range photogrammetry is one where optimal multi-ray intersection geometry is obtained with as few camera stations as practicable. Hyper redundancy is a concept whereby, once the generic network is in place, many additional images are recorded, with the beneficial impact upon object point precision being equivalent to the presence of multiple exposures at each camera position within the generic network. The effective number of images per station within a hyper redundant network might well be in the range of 10 to 20 or more. As is apparent when it is considered that a hyper redundant network may comprise hundreds of images, the concept is only applicable in practice to fully automatic vision metrology systems, where it proves to be a very effective means of enhancing measurement accuracy at the cost of minimal additional work in the image recording phase. This paper briefly reviews the network design and accuracy aspects of hyper redundancy and illustrates the technique by way of the photogrammetric measurement of surface deformation of a radio telescope of 26 m diameter. This project required an object point measurement accuracy of σ = 0·065 mm, or 1/400 000 of the diameter of the reflector. 相似文献
139.
冬、春季的天气影响系统既有共同点,又有不同之处。通过近20a大-暴雪个例的物理成因及卫星云图等特征的分析,总结出有预报意义的指标。 相似文献
140.
胡翠珍 《沙漠与绿洲气象(新疆气象)》2002,25(3):9-11
通过对2001年9月22-23日南疆西北部山区特大暴雨的环流背景、物理量场、卫星云图分析,揭示了这场特大暴雨的物理机制和各要素场特征。 相似文献