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991.
桩-土滑动摩擦的试验研究 总被引:25,自引:5,他引:25
静力压入桩贯入地基时,桩侧表面与土之间产生滑动摩擦。通过在改进的仪器上进行的室内试验,研究了桩-土滑动摩擦及其时效性,为静压桩沉桩过程的数值模拟和承载力分析打下了基础。 相似文献
992.
993.
某化验楼因不均匀沉降,造成墙体和地面开裂,根据该楼地基松散填土具有高压缩性、性质差异大、欠固结等地质特性,采取静压灌浆法加固该地基,使其地基土承载力标准值提高了2~3倍,静压灌浆后建筑物停止沉降,效果显著。 相似文献
994.
995.
基于唐海—商都宽频带地震台阵2006—2009年连续三年的波形记录,利用环境噪声相位自相关函数对台阵下方的莫霍面反射P波进行分析。通过对同一个台站多个时间段的自相关结果进行分组、采用两步叠加处理增加信号强度:① 在组内进行线性叠加,对组间的叠加结果进行相位加权叠加;② 基于华北地区的背景速度结构信息,在地壳平均速度5%不确定性的时窗内,根据自相关函数包络线的二阶导数最大值确定P波的莫霍面反射时间,经时间−深度转化,获得台阵下方的莫霍面深度。结果显示,莫霍面从东南向西北总体由浅变深,中间有小幅度的起伏。噪声自相关方法确定的莫霍面平均深度相较于参考的接收函数结果的偏差为0.8 km,相应的双程走时偏差约为0.3 s。以月份叠加的自相关函数结果显示,PmP信号的噪声源具有显著的季节性变化。自相关函数的波形特征显示华北地区的地壳−地幔转换带的速度梯度模式不同。
相似文献996.
According to the fracture mechanics rupture model of earthquakes put forward by us, several equations to compute tectonic
ambient shear stress value τ0 have been derived [equations (1), (2), (3), (5)]. τ0 values for intermediate and small earthquakes occurred in Chinese mainland and Southern California have been calculated by
use of these equations. The results demonstrate that the level and distribution of τ0 are closely related to the location where large earthquakes will occur, i.e. the region with higher level of τ0 will be prone to occur large earthquakes and the region with lower level will usually occur small earthquakes. According
to the spatial distribution of τ0, the seismic hazard regions or the potential earthquake source regions can in some degree be determined. According to the
variation of τ0 with time, the large earthquake occurrence time can be roughly estimated. According to the distribution of τ0 in Southern California and variation with time, three high stress level regions are determined, one (Goldfield area) of them
is the present seismic hazard region.
Contribution No. 98A02023, Institute of Geophysics, State Seismological Bureau, China 相似文献
997.
Jing Liu Youcai Tang Kai Tao Chunquan Yu Jie Chen Jieyuan Ning Yongshun John Chen Yongge Feng 《地震科学(英文版)》2010,23(6):627-636
We have developed a new stacking technique in ambient noise tomography to obtain high-quality dispersion curves of Rayleigh waves.This technique is used to stack the vertical components of the Estimated Green Functions(EGFs) obtained respectively from cross correlation of the ambient noise data recorded by a remote seismic station and one of the short distance seismic stations of a seismic array.It is based on a phase-matched filter and is implemented by a four-step iterative process:signal compression,stacking,signal extraction and signal decompression.The iterative process ends and gives the dispersion curve of Rayleigh wave when the predicted one and the processing result converge.We have tested the method using the vertical components of synthetic Rayleigh wave records.Results show that this new stacking method is stable and it can improve the quality of dispersion curves.In addition,we have applied this method to real data.We see that the results given by our new technique are obviously better than the ones employing the traditional method which is a three-step process:signal compression,signal extraction and signal decompression.In conclusion,the new method proposed in this paper can improve the signal to noise ratio of EGFs,and can therefore potentially improve the resolution of ambient noise tomography. 相似文献
998.
The resonance frequencies of the 250‐m‐high arch dam of Mauvoisin are obtained by way of ambient vibration tests. It is observed that the resonance frequencies initially increase with rising water level and then decrease with a further rise. This is linked to the two competing features of increasing entrained mass of water (reduction of the resonance frequencies) and of dam stiffening due to closing of the vertical construction joints (augmentation of the resonance frequencies). The ambient vibration test results are complemented by those obtained during earthquakes at an array of 12 accelerographs. Copyright © 2000 John Wiley & Sons, Ltd. 相似文献
999.
将软土地层中地铁车站结构与周围土体地震时产生的水平加速度,以静态的水平加速度代替,使两者作用下结构内力最大值相等、出现部位相同,实现将动力问题转化为静力问题。结果表明,该方法能反映软土地层中两层三跨地铁车站的在地震时的动力响应,是适用于工程设计的简单、实用的数值方法。 相似文献
1000.
Recent results of in situ measurements and their interest for a seismic assessment of existing buildings are presented and analysed. The present paper (Part I) is devoted to the experimental programme. The response to ambient vibrations, harmonic excitation and shock loading is recorded on intact buildings but also after their structure or their vicinity was modified. These tests aim to identify the dynamic behaviour of ordinary intact buildings built in a conventional practise. Moreover, taking advantage of their demolition, it was possible (through these tests) to determine the actual influence of the light work elements, full precast facade panels, bearing masonry walls, and the presence of neighbouring joined buildings. These experiments realized on real buildings show that information gathered from ambient measurements provide reliable and efficient data of real interest for a clear understanding of the actual building behaviour. The advantage of integrating these data in the vulnerability assessment is presented and discussed in the next paper (Part II). Copyright © 2005 John Wiley & Sons, Ltd. 相似文献