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871.
V. Kumar G. Venkataramana K.A. Høgda 《International Journal of Applied Earth Observation and Geoinformation》2011
In this study ascending and descending passes interferometric synthetic aperture radar (InSAR) techniques are used for glacier surface velocity estimation in the Himalaya. Single-track interferometric measurements are sensitive to only a single component of the three dimensional (3-D) velocity vectors. European Remote Sensing satellites (ERS-1/2) tandem mission data in ascending and descending tracks provide an opportunity to resolve the three velocity components under the assumption that glacier flow is parallel to its surface. Using the surface slope as an essential input in this technique the velocity pattern of Siachen glacier in Himalaya has been modelled. Glaciers in the Himalayan region maintain excellent coherence of SAR return signals in one-day temporal difference. As a result we could obtain spatially continuous surface velocity field with a precision of fraction of radar wavelength. The results covering the main course of glacier are analysed in terms of spatial and temporal variations. A maximum velocity of 43 cm/day has been observed in the upper middle portion of the glacier. This technique has been found accurate for monitoring the flow rates in this region, suggesting that routine monitoring of diurnal movement Himalayan glaciers would be immensely useful in the present day context of climate change. 相似文献
872.
873.
Earth orientation parameters (EOPs) provide a link between the International Celestial Reference Frame (ICRF) and the International Terrestrial Reference Frame (ITRF). Natural geodynamic processes, such as earthquakes, can cause the motion of stations to become discontinuous and/or non-linear, thereby corrupting the EOP estimates if the sites are assumed to move linearly. The VLBI antenna at the Gilcreek Geophysical Observatory has undergone non-linear, post-seismic motion as a result of the Mw=7.9 Denali earthquake in November 2002, yet some VLBI analysts have adopted co-seismic offsets and a linear velocity model to represent the motion of the site after the earthquake. Ignoring the effects of the Denali earthquake leads to error on the order of 300–600 μas for the EOP, while modelling the post-seismic motion of Gilcreek with a linear velocity generates errors of 20–50 μas. Only by modelling the site motion with a non-linear function is the same level of accuracy of EOP estimates maintained. The effect of post-seismic motion on EOP estimates derived from the International VLBI Service IVS-R1 and IVS-R4 networks are not the same, although changes in network geometries and equipment improvements have probably affected the estimates more significantly than the earthquake-induced deformation at Gilcreek. 相似文献
874.
875.
干涉合成孔径雷达是一项能够对地表变形进行测量的遥感技术,在一个巨大区域内,它的变形测量精度可达亚厘米级,而其空间分辨率则在数十米以内。本文回顾了InSAR技术的基本理论,阐明了它的工作原理,并对应用InSAR技术进行地表变形测量的相关问题进行了讨论。 相似文献
876.
升降轨道ASAR雷达干涉揭示的巴姆地震(Mw6.5)3D同震形变场 总被引:5,自引:0,他引:5
通过对覆盖同一地区的升降轨道ASAR雷达数据进行两路差分干涉(D-INSAR)处理,得到了2003年12月26日伊朗巴姆(Bam)地震(Mw6.5)在两种成像几何状态下的视线向(LOS)同震形变场。利用Okada弹性形变模型对形变场进行正演计算,得到地震断层的几何参数及形变的南北向分量。对得到的干涉条纹图进行相位解绕处理,综合分析两种不同的雷达成像几何关系,并利用模型估计得到的南北向分量,计算了该地震造成的3D同震形变场,结果显示了典型的单断层右旋走滑活动特征。研究表明,合并升降轨道雷达数据,能够为形变模型提供有效约束,用一条简化的断层模型就可以解释升降两条轨能的干涉形变场,更为复杂的双断层模型是不必要的。 相似文献
877.
阐述了基于SAR影像的洪水淹没范围快速提取的融合方法,并为此设计了一个模型。融合的过程通过HIS变换、比值运算法、主成分分析法3种方法来实现。就目前的效果而言,达到了快速提取的目的,但有些问题还有待解决。 相似文献
878.
针对比率边缘检测算子提出了一种自动确定阈值的方法,该方法引入最佳熵的理论到SAR边缘检测中,把基于比率的边缘检测均值比率影像分割成边缘和非边缘两类。此方法执行起来简单、快速,无需人工干预,能避免人为因素的影响。 相似文献
879.
880.
Urban geological hazards involving ground instability can be costly, dangerous, and affect many people, yet there is little information about the extent or distribution of geohazards within Europe’s urban areas. A reason for this is the impracticality of measuring ground instability associated with the many geohazard processes that are often hidden beneath buildings and are imperceptible to conventional geological survey detection techniques. Satellite radar interferometry, or InSAR, offers a remote sensing technique to map mm-scale ground deformation over wide areas given an archive of suitable multi-temporal data. The EC FP7 Space project named PanGeo (2011–2014), used InSAR to map areas of unstable ground in 52 of Europe’s cities, representing ∼15% of the EU population. In partnership with Europe’s national geological surveys, the PanGeo project developed a standardised geohazard-mapping methodology and recorded 1286 instances of 19 types of geohazard covering 18,000 km2. Presented here is an analysis of the results of the PanGeo-project output data, which provides insights into the distribution of European urban geohazards, their frequency and probability of occurrence. Merging PanGeo data with Eurostat’s GeoStat data provides a systematic estimate of population exposures. Satellite radar interferometry is shown to be as a valuable tool for the systematic detection and mapping of urban geohazard phenomena. 相似文献