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141.
142.
Broadband strong motion simulation in layered half-space using stochastic Green’s function technique
Y. Hisada 《Journal of Seismology》2008,12(2):265-279
The stochastic Green’s function method, which simulates one component of the far-field S-waves from an extended fault plane
at high frequencies (Kamae et al., J Struct Constr Eng Trans AIJ, 430:1–9, 1991), is extended to simulate the three components of the full waveform in layered half-spaces for broadband frequency
range. The method firstly computes ground motions from small earthquakes, which correspond to the ruptures of sub-faults on
a fault plane of a large earthquake, and secondly constructs the strong motions of the large earthquake by superposing the
small ground motions using the empirical Green’s function technique (e.g., Irikura, Proc 7th Japan Earthq Eng Symp, 151–156, 1986). The broadband stochastic omega-square model is proposed as the moment rate functions of the small earthquakes,
in which random and zero phases are used at higher and lower frequencies, respectively. The zero phases are introduced to
simulate a smooth ramp function of the moment function with the duration of 1/fc s (fc: the corner frequency) and to reproduce
coherent strong motions at low frequencies (i.e., the directivity pulse). As for the radiation coefficients, the theoretical
values of double couple sources for lower frequencies and the theoretical isotropic values for the P-, SV-, and SH-waves (Onishi
and Horike, J Struct Constr Eng Trans AIJ, 586:37–44, 2004) for high frequencies are used. The proposed method uses the theoretical Green’s functions of layered half-spaces
instead of the far-field S-waves, which reproduce the complete waves including the direct and reflected P- and S-waves and
surface waves at broadband frequencies. Finally, the proposed method is applied to the 1994 Northridge earthquake, and results
show excellent agreement with the observation records at broadband frequencies. At the same time, the method still needs improvements
especially because it underestimates the high-frequency vertical components in the near fault range. Nonetheless, the method
will be useful for modeling high frequency contributions in the hybrid methods, which use stochastic and deterministic methods
for high and low frequencies, respectively (e.g., the stochastic Green’s function method + finite difference methods; Kamae
et al., Bull Seism Soc Am, 88:357–367, 1998; Pitarka et al., Bull Seism Soc Am 90:566–586, 2000), because it reproduces the full waveforms in layered media including not only random characteristics at
higher frequencies but also theoretical and deterministic coherencies at lower frequencies. 相似文献
143.
Jan Wiszniowski Marian Hościłowicz Andrzej Skrzyński Jerzy Suchcicki Krzysztof P. Teisseyre 《Acta Geophysica》2008,56(2):391-407
A method of correcting the seismometers’ responses discrepancy for differential measurements of strains and rotations in the
seismic far field is proposed. The method concerns differential calibration of the whole seismometers’ array by electric current.
A model of corrective filtering of the obtained differential signals in the Z domain is given. Two methods of the filter parameters’
estimation are introduced; they are based on the seismometers response to the calibration.
A practical test of the methods — an analysis of a recorded seismic event — is added. Significant reduction of differences
between simultaneous seismic recordings was obtained, which is interpreted as cleaning of differential signal from spurious
elements. 相似文献
144.
On August 7th, 2010, Sanyanyu and Luojiayu debris flows triggered by a heavy rain have lashed Zhouqu City around midnight, leading to catastrophic destruction which killed 1 765 people and resulted in enormous economic loss. The ZHQ Seismic Station is located approximately 170 m west of the outlet of the Sanyanyu Gully. The seismometer deployed at the seismic station started recording seismic signals of ever-enlarging amplitude around 10 minutes before the debris flow rushed out of the Sanyanyu Gully, showing ever approaching seismic source, i.e. the debris flow. In this study, we analyze this seismic event and propose an inversion algorithm to estimate the velocity of the debris flow by searching the best-fitting pairs of envelopes in the synthetic seismograms and the corresponding field seismic records in a least-square sense. Inversion results reveal that, before rushing out of the outlet, the average velocity of the debris flow gradually increased from 6.2 m/s to 7.1 m/s and finally reached 15 m/s at approximately 0.5 km above the outlet and kept this value since then. Obviously, the ever-increasing velocity of the debris flow is the key factor for the following disasters. Compared with other studies, our approach can provide the velocity distribution for the debris flow before its outbreak; Besides, it has the potential to provide technological support for a better understanding of the disaster process of a debris flow. 相似文献
145.
146.
数字化地震仪系统的标定 总被引:2,自引:2,他引:0
介绍了数字地震仪系统传递函数的特征和测定方法,给出了地震仪标定软件的使用方法和计算步骤。结合实际波形数据处理过程,着重对标定计算中参数的设置,以及需要注意的问题进行了讨论和分析。这对于正确快速地获取地震仪的传递函数具有重要的现实意义,有利于国家数字地震台站和区域地震台站地震观测系统的定期标定工作,同时也将促进数字化地震观测资料的应用研究。 相似文献
147.
2011年日本东北部太平洋海域发生MW9.0特大地震,国际上很多著名地震科研机构和学者发布了不同的震源机制解,很多学者也对这些震源机制解进行了评价。选取其中较优的GCMT震源机制解计算模拟日本大地震激发的自由振荡信号,并与湖北地震台网的15个地震仪观测结果进行对比,进而评价各个地震仪在低频段的观测情况以及分析地震仪在不同频段的观测能力。结果表明,总体来说,在1.5~4.5 mHz频段,地震仪观测到的自由振荡信号与理论模拟值符合度较高;在小于1.5 mHz频段,地震仪整体的观测能力不佳;而在大于4.5 mHz频段,观测值振幅明显要低于模拟信号的振幅,表明在该频段信号的实际衰减要比PREM地球模型中衰减快。另外,基于1.5~4.5 mHz频段的球型简正模评估15个地震仪的观测状况,结果表明,大部分的地震仪观测情况较好,有10个台站的观测值与模拟值的符合度在90%以上;而YC、NZH、DJI等台站的符合度较差,其中DJI符合度最差,为0.358。 相似文献
148.
进入21世纪以来,广西地震观测系统得到了迅速的发展.回顾了广西数字地震台网建设的发展历史,重点介绍了“十五”期间广西各级地震台网的建设情况,阐述了广西区域数字测震台网实现与邻省、地方和企业不同属性和类别的台网联网和数据共享后,地震监测能力获得了极大的提高过程. 相似文献
149.
利用一个长750 km的宽频地震台阵所采集到的数据和接收函数方法,获得了横穿塔里木盆地的和田—拜城剖面的壳幔图像。和田凹陷、麦盖提斜坡、巴楚隆起、阿瓦提凹陷、塔北隆起、库车凹陷等地块及其边界断裂有清楚显示,各断裂均切穿岩石圈。地壳分为新近系—第四系沉积层、震旦系—古近系沉积层、上地壳结晶基底、中地壳低密度层、下地壳高密度层、下地壳低密度层等6个层。一般而言,各层的密度随深度增加而增加,但有两个层反常。中地壳的密度低于上地壳结晶基底,下地壳下部的密度低于下地壳上部。中地壳低密度层是一不连续的薄层,厚度3~8 km,深度约25 km。下地壳低密度层是一个连续的薄层,厚度5~10 km,深度约45 km。Moho面的深度在盆地北部为40~50 km,巴楚地块为35~55 km,盆地南部为55~60 km。岩石圈底面的深度为70~80 km。塔里木陆块的岩石圈地幔俯冲到西昆仑之下,但地壳并没有俯冲,地壳与地幔发生解耦。吐木休克断裂北侧的北塔里木地块变形微弱,麻札塔格断裂南侧的南塔里木地块变形强烈,两断裂之间的巴楚地块的变形以地壳的弯曲为特征。和田—麦盖提地块是一个整体但变形强烈。在其中识别出5个大的滑脱-推覆断裂面,造成下地壳地层叠覆和缩短,下地壳低密度层以隧道流的方式挤入中地壳。相比之下,沉积盖层几乎没有变形,说明南塔里木的强烈变形发生在震旦纪之前。 相似文献
150.
对多种图像格式进行了分析对比,并选定CGM图像格式作为"独立记录型折/反射兼容地震仪器系统"数据采集预处理软件的图形输出格式,完成了CGM图像输出通用绘图库的研发,在通用绘图库中采用了动态链接库技术,解决不同软件的应用问题,并给出了人工地震宽角反射/折射探测数据和反射地震剖面的绘图结果. 相似文献