全文获取类型
收费全文 | 456篇 |
免费 | 24篇 |
国内免费 | 48篇 |
专业分类
测绘学 | 190篇 |
大气科学 | 19篇 |
地球物理 | 53篇 |
地质学 | 80篇 |
海洋学 | 94篇 |
天文学 | 5篇 |
综合类 | 67篇 |
自然地理 | 20篇 |
出版年
2022年 | 5篇 |
2021年 | 7篇 |
2020年 | 9篇 |
2019年 | 11篇 |
2018年 | 4篇 |
2017年 | 24篇 |
2016年 | 15篇 |
2015年 | 15篇 |
2014年 | 23篇 |
2013年 | 29篇 |
2012年 | 28篇 |
2011年 | 21篇 |
2010年 | 25篇 |
2009年 | 28篇 |
2008年 | 38篇 |
2007年 | 38篇 |
2006年 | 38篇 |
2005年 | 31篇 |
2004年 | 40篇 |
2003年 | 21篇 |
2002年 | 19篇 |
2001年 | 17篇 |
2000年 | 8篇 |
1999年 | 10篇 |
1998年 | 10篇 |
1997年 | 3篇 |
1996年 | 4篇 |
1995年 | 2篇 |
1994年 | 2篇 |
1993年 | 1篇 |
1991年 | 1篇 |
1989年 | 1篇 |
排序方式: 共有528条查询结果,搜索用时 0 毫秒
81.
Application of synthetic aperture radar (SAR) imagery to volcano mapping in the humid tropics: a case study in East Java, Indonesia 总被引:3,自引:0,他引:3
Simon A. Carn 《Bulletin of Volcanology》1999,61(1-2):92-105
Volcanoes in humid tropical environments are frequently cloud covered, typically densely vegetated and rapidly eroded. These
factors complicate field and laboratory studies and even the basic identification of potentially active volcanoes. Numerous
previous studies have highlighted the potential value of radar remote sensing for volcanology in equatorial regions. Here,
cloud- and vegetation-penetrating LHH-band (λ≈24 cm) synthetic aperture radar (SAR) data from the Japanese Earth Resources Satellite (JERS-1) are used to investigate
persistently active volcanoes and prehistoric calderas in East Java, Indonesia. The LHH-band JERS-1 SAR produces high-spatial-resolution (18 m) imagery with relatively high incidence angle that highlights structures
and topographic variations at or greater than the wavelength scale while minimising geometrical distortions such as layover
and foreshortening. These images, along with Internet browse data derived from the Canadian RADARSAT mission, provide new
evidence relating regional tectonics to volcanism throughout East Java. Volcanic events, such as caldera collapse at the Tengger
caldera, appear to have been partly controlled by northwest-aligned faults related to intra-arc sedimentary basins. Similar
regional controls appear important at historically active Lamongan volcano, which is encircled by numerous flank maars and
cinder cones. A previously undocumented pyroclastic sheet and debris avalanche deposit from the Jambangan caldera complex
is also manifested in the synoptic radar images. At the currently active Semeru volcano these data permit identification of
recent pyroclastic flow and lahar deposits. Radar data therefore offer a valuable tool for mapping and hazard assessment at
late Quaternary volcanoes. The criteria developed in the analysis here could be applied to other regions in the humid tropics.
Received: 25 June 1998 / Accepted: 20 January 1999 相似文献
82.
83.
84.
85.
Spectral library search is emerging as a viable approach for material identification and mapping by reusing spectral knowledge gained from hyperspectral remote sensing across space and time. The potential of retrieving meaningful spectral material identifications in the presence of reflectance of spectra of various material types and with various similarity metrics has been assessed in this study. Test reflectance spectra of various vegetation, minerals, soils and urban material types are identified by searching through the composite reflectance spectral library obtained by combining various institutional reflectance spectral libraries. The accuracy of material identifications under various conditions: (i) in the presence of identical, similar and dissimilar spectra; (ii) in the presence of only identical and dissimilar spectra; and (iii) in the presence of only dissimilar spectra has been assessed with several similarity metrics. Results indicate the possibility of obtaining 100% accurate material identifications by library search if the spectral library contains identical spectra. However, the presence of a large number of similar spectra, despite the presence of identical spectra, is found to increase false positives, thereby reducing the accuracy of retrievals to 82% at best. Further, the accuracy of material identifications in the presence of similar spectra is similarity metric-dependent and varied from about 52% (obtained from Binary Encoding) to 82% (obtained from Normalized Spectral Similarity Score). Overall, results support the possibility of using independent reflectance spectral libraries for material identification while calling for robust spectral similarity metrics. 相似文献
86.
Peng Zhuangzhi Yu Xin School of Remote Sensing Information Engineering Wuhan University Luoyu Road Wuhan China 《测绘科技情报》2007,(1)
目前空间数据的传输效率低下已成为制约WebGIS发展的主要瓶颈之一。多线程技术以及多点连接在提高系统吞吐率、有效利用系统资源、改善用户任务之间的通信效率等方面有着显著作用。本文采用地图分层和图面分割的方法以及Java多线程和多点连接技术实现了WebGIS空间数据的高效传输。 相似文献
87.
88.
Planktonic bacteria are abundant in the Chukchi Borderland region. However, little is known about their diversity and the roles of various bacteria in the ocean. Seawater samples were collected from two stations K2S and K4S where sea ice was melting obviously. The analysis of water samples with fluorescence in situ hybridization (FISH) showed that DMSP-degrading bacteria accounted for 13% of the total bacteria at the station K2S. No aerobic anoxygenic phototrophic (AAP) bacteria were detected in both samples. The bacterial communities were characterized by two 16S rRNA gene clone libraries. Sequences fell into four major lineages of the domain Bacteria, including Proteobacteria (Alpha, Beta and Gamma subclasses), Bacteroidetes, Actinobacteria and Firmicutes. No significant difference was found between the two clone libraries. SAR11 and Rhodobacteraceae clades of Alphaproteobacteria and Pseudoalteromonas of Gammapro-teobacteria constituted three dominant fractions in the clone libraries. A total of 191 heterotrophic bacterial strains were isolated and 76% showed extracellular proteolytic activity. Phylogenetic analysis reveals that the isolates fell into Gammaproteobacteria, Bacteroidetes, Actinobacteria and Firmicutes. The most common genus in both the bacterial isolates and protease-producing bacteria was Pseudoalteromonas. UniFrac data showed suggestive differences in bacterial communities between the Chukchi Borderland and the northern Bering Sea. 相似文献
89.
网络环境下地震科技信息资源建设初探 总被引:1,自引:0,他引:1
本文就网络环境下地震科技信息资源建设中的信息组织及资源共享等问题进行探讨。 相似文献
90.