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161.
渔塘铅锌矿田,面积100km~2以上,1986年以前间断勘查三十多年,只探明铅锌金属量20000t。1986年后开展科学研究,发现富矿体有两种类型,产于原地藻灰岩中者集中而稳定,属Ⅰ—Ⅱ勘探类型;产于礁间沉积物中者分散且稳定性差,属Ⅱ—Ⅳ勘探类型。以此认识布置钻探工作,取得了在贫矿中寻找富矿的重大进展,探明铅锌金属量500000t的富矿体。 相似文献
162.
根据中、美两国合作开展的西藏深反射地震结果,提出雅鲁藏布江缝合带(YZS)的"双陆内俯冲"构造模式和缝合带南、北分别存在着不同特征的、规模不一的部分熔融层;提出YZS处断裂向深部延深有限,认为YZS处地壳增厚有4种机制:①地壳规模的大的俯冲增厚;②上部地壳内的俯冲和背冲增厚;③下地壳内的底部垫托增厚和挤压增厚;④深部熔融体的向上挤入而引起的地壳增厚.提出可能存在两条大的伸展性断裂,造成江孜南、北地块间出现了大升降. 相似文献
163.
164.
Perturbation of fluvial sediment fluxes following the 2008 Wenchuan earthquake 总被引:1,自引:0,他引:1 下载免费PDF全文
Wei Wang Vincent Godard Jing Liu‐Zeng Dirk Scherler Chong Xu Jinyu Zhang Kejia Xie Olivier Bellier Claire Ansberque Julia de Sigoyer ASTER Team 《地球表面变化过程与地形》2017,42(15):2611-2622
Quantifying the removal of co‐seismic landslide material after a large‐magnitude earthquake is central to our understanding of geomorphic recovery from seismic events and the topographic evolution of tectonically active mountain ranges. In order to gain more insight into the fluvial erosion response to co‐seismic landslides, we focus on the sediment fluxes of rivers flowing through the rupture zone of the 2008 Mw 7.9 Wenchuan earthquake in the Longmen Shan of the eastern Tibetan Plateau. Over the post‐seismic period of 2008–2013, we annually collected river sediment samples (0.25–1 mm) at 19 locations and measured the concentration of cosmogenic 10Be in quartz. When compared with published pre‐earthquake data, the 10Be concentrations declined dramatically after the earthquake at all sampling sites, but with significant spatial differences in the amplitude of this decrease, and were starting to increase toward pre‐earthquake level in several basins over the 5‐year survey. Our analysis shows that the amplitude of 10Be decrease is controlled by the amount of landslides directly connected to the river network. Calculations based on 10Be mixing budgets indicate that the sediment flux of the 0.25–1 mm size fraction increased up to sixfold following the Wenchuan earthquake. Our results also suggest that fluvial erosion became supply limited shortly after the earthquake, and predict that it could take a few years to several decades for fluvial sediment fluxes to go back to pre‐earthquake characteristics, depending on catchment properties. We also estimate that it will take at least decades and possibly up to thousands of years to remove the co‐seismic landslide materials from the catchments in the Longmen Shan. Copyright © 2017 John Wiley & Sons, Ltd. 相似文献
165.
166.
印度板块俯冲到藏南之下的深反射证据 总被引:11,自引:1,他引:11
喜马拉雅和相邻的西藏高原,构成了地球上最大的高原和异常厚地壳的地区,是作为印度板块和亚洲板块新生代碰撞的结果,并被认作是典型的陆-陆碰撞[1.2.3.]地带。在此,我们报道了用深地震反射剖面方法进行本区地壳成像的第一个结果,试验的100km长剖面,布置在特提斯喜马拉雅(TethyanHimalaya)最南端,且跨过了喜马拉雅山脊,接近高喜马拉雅(HighHimalaya)地带,剖面显示了在地壳中部有一强反射带。它可能代表了一个活动的道冲断裂,印度板块是沿此断裂俯冲到藏南之下;上地壳反射使人们联想到上地壳存在着大规模的叠瓦状结构;莫霍反射来自本区双倍正常地壳厚度的巨厚地壳的底部。这些结果对西藏南端地壳增厚,是由于印度大陆地壳整体俯冲到包括特提斯喜马拉雅地区地壳之下的观点,给予了实质性的支持。 相似文献
167.
WANG Qian LI Guangjie WANG Liancheng ZHENG Baigong LI Ming. College of Construction Engineering Jilin University Changchun China. College of Geoexploration Science & Technology China. Jilin Team of Geological Survey of China Building Materials Industry Changchun China 《东北亚地学研究》2009,(4):221-225
Helong City is located in the northeastern Changbai Mountain with a poor geological environment, there often occur debris flows, collapses and landslides; especially debris flows restrict the local economic development. Based on fractal theory and the surveying data of 34 debris flows, the authors studied fractal feature of debris flow gully and its various situations of fractal dimensions in different observation scales. The nonlinear relation reveals the development of non-uniformity and self similarity of debris flow gully 相似文献
168.
The GOES C7.5 flare on 20 February 2002 at 11:07 UT is one of the first solar flares observed by RHESSI at X-ray wavelengths. It was simultaneously observed at metric/decimetric wavelengths by the Nançay radioheliograph (NRH) which provided images of the flare between 450 and 150 MHz. We present a first comparison of the hard X-ray images observed with RHESSI and of the radio emission sites observed by the NRH. This first analysis shows that: (1) there is a close occurrence between the production of the HXR-radiating most energetic electrons and the injection of radio-emitting non-thermal electrons at all heights in the corona, (2) modifications with time in the pattern of the HXR sources above 25 keV and of the decimetric radio sources at 410 MHz are observed occurring on similar time periods, (3) in the late phase of the most energetic HXR peak, a weak radio source is observed at high frequencies, overlying the EUV magnetic loops seen in the vicinity of the X-ray flaring sites above 12 keV. These preliminary results illustrate the potential of combining RHESSI and NRH images for the study of electron acceleration and transport in flares. 相似文献
169.
G. Bellucci E. D'Aversa D. Cruikshank R.N. Clark D. Matson T.B. McCord P.D. Nicholson the Cassini VIMS Team 《Icarus》2004,172(1):141-148
During the Cassini-Jupiter flyby, VIMS observed Io at different phase angles, both in full sunlight and in eclipse. By using the sunlight measurements, we were able to produce phase curves in the visual through all the near infrared wavelengths covered by the VIMS instrument (0.85-5.1 μm). The phase angle spanned from ∼2° to ∼120°. The measurements, done just after Io emerged from Jupiter's shadow, show an increase of about 15% in Io's reflectance with respect to what would be predicted by the phase curve. This behavior is observed at wavelengths >1.2 μm. Moreover, just after emergence from eclipse an increase of about 25% is observed in the depth of SO2 frost bands at 4.07 and 4.35 μm. At 0.879<λ<1.04 μm the brightening is 10-24%. Below λ=0.879 μm the brightening, if present, should be less than the precision of our measurements (∼5%). Apparently, these observations are not explained neither by a diverse spatial distribution of SO2 on the Io' surface nor by atmospheric SO2 condensation on the surface during the eclipse. 相似文献
170.
The three-dimensional distribution of change in phase travel time of an active region below the solar surface can be constructed
with the technique of acoustic imaging. The interpretation of the distribution of measured phase travel time perturbation
suffers from the finite spatial resolution of the acoustic lenses. In the ray approximation, the phase travel time perturbation
measured in acoustic imaging can be expressed as an integral of the product of the relative sound-speed perturbation and a
kernel. Forward computations show that the vertical resolution of phase travel time perturbation is poor even in the ray approximation.
In this study, we discuss the inversion of phase travel time perturbations to estimate the relative sound-speed perturbation
with a regularized least-squares inversion method. The tests with model perturbations of sound speed show that the inversion
reasonably recovers the distribution of the model perturbation. We also apply the inversion method to the measured phase travel
time perturbation of active region NOAA 7981. 相似文献