全文获取类型
收费全文 | 137篇 |
免费 | 24篇 |
国内免费 | 25篇 |
专业分类
测绘学 | 14篇 |
大气科学 | 8篇 |
地球物理 | 48篇 |
地质学 | 56篇 |
海洋学 | 11篇 |
天文学 | 3篇 |
综合类 | 13篇 |
自然地理 | 33篇 |
出版年
2023年 | 2篇 |
2022年 | 4篇 |
2021年 | 4篇 |
2020年 | 2篇 |
2019年 | 8篇 |
2018年 | 3篇 |
2017年 | 8篇 |
2016年 | 3篇 |
2015年 | 4篇 |
2014年 | 4篇 |
2013年 | 5篇 |
2012年 | 6篇 |
2011年 | 5篇 |
2010年 | 3篇 |
2009年 | 6篇 |
2008年 | 21篇 |
2007年 | 7篇 |
2006年 | 6篇 |
2005年 | 10篇 |
2004年 | 4篇 |
2002年 | 3篇 |
2001年 | 8篇 |
2000年 | 5篇 |
1999年 | 7篇 |
1998年 | 7篇 |
1997年 | 7篇 |
1996年 | 5篇 |
1995年 | 6篇 |
1994年 | 3篇 |
1993年 | 2篇 |
1992年 | 2篇 |
1991年 | 3篇 |
1990年 | 2篇 |
1989年 | 1篇 |
1988年 | 3篇 |
1987年 | 1篇 |
1980年 | 6篇 |
排序方式: 共有186条查询结果,搜索用时 218 毫秒
61.
Non-linear elastic response of rocks has been widely observed in laboratory, but very few seismic studies are reported in the literature, even though it is the most natural environment where this feature could be observed. Analytic solutions to the non-linear wave propagation phenomena are not readily available, and there is a need to use approximated techniques. It is clear that when a seismic wave propagates through a homogeneous non-linear elastic media, it will be perturbed by the non-linearity. This perturbation can be treated as a source of scattering, spreading the energy of the primary wave in space and time, contributing to the seismic coda. This is in some sense similar to the effect of heterogeneities. The properties of the coda due to the non-linearity depend on the amount of non-linearity and the seismic moment. Using a perturbation approach we calculate the amplitude of the scattered waves, and show that it can describe reasonably well the main features of real seismic codas. 相似文献
62.
63.
Seismic tomography has been one of the primary tools to image the interior of the earth and other elastic structures. To date the inversions of compressional ( P ) and shear ( S ) wave speeds have been carried out separately under the assumption that P traveltimes are affected only by the P wave speed of the elastic media and S traveltimes by the S wave speed. Using numerical and analytical solutions, we show that for finite-frequency seismic waves, S wave speed perturbations may have significant effects on P waveforms. This suggests that when waveform-derived traveltime and amplitude anomalies are used in tomographic inversions, the P -wave measurements should be related to not only P wave speed perturbations but also S wave speed perturbations. 相似文献
64.
65.
For some strain in the strike slip zone is difficult to be determined accurately in the classification scheme of the 7 elements of the ellipse of the strike slip strain ellipse (PDZ, R, R', P, T, Y and local contraction), the properties of the strain elements in all directions in the strained ellipse were reunderstood by analyzing the causal relationship between the mechanical state and the strain properties in a certain direction. A new model of the Riedel shear system was proposed, which contained 4 pure strain zones (pure right walk slip, pure left walking slip, pure extrusion, pure Stretch Strain Zone) and 4 complex strain zones (both stretching and right walking, both stretching and left walking, both extrusion and left walking, both extrusion and right walking slip strain zone). The closer the crack was to the direction of a single strain band, the stronger the corresponding property. The model included all the elements of the traditional model and made up for its vacancy. It proved the rationality of the left (right) row left (right) order and the double tectonic belt rule. At the same time, three research examples of Bohai Sea were cited to illustrate the application of the model: (1) The synchronous and perpendicular spatial-temporal relationship between compressive and extensional stress fields in strike-slip zones, as well as the unified but not contradictory dialectical relationship between them, were illustrated through the example of the co-controlled cycle formation of northeastern depression in Laizhou Bay Depression; (2) The Bohai Sea walk was enumerated. The research results of the slip transition zone illustrated the strain trend law of the extensional or compressive transition zone in the strike-slip zone; (3) The relationship between the strike of the effective fracture and the extensional strain zone in the present strike-slip stress field was illustrated by giving an example of the effective fracture research results of a buried hill structure in the Bohai Sea. 相似文献
66.
67.
为研究磁尾感应电场对上行离子的加速,对磁层亚暴期间尾向地磁场在向偶极位形弛豫过程中产生的感应电场进行了理论研究。结果表明:在偶极化过程中磁场的BX分量下降,BZ分量上升,并产生随时间变化的单峰结构的感应电场,其峰值可超过20mv/m;当子午面内地心距离由6R,变化到16RE时,感应电场峰值呈逐渐增大趋势;随着z坐标的增大(远离赤道面)或Y坐标的增大(远离子午面),感应电场峰值呈逐渐减小趋势;感应电场峰值随磁场向偶极形弛豫周期的减小而增大.理论计算得到的感应电场随时间变化曲线及峰值与观测结果符合较好,本文还对上行离子在感应磁场中的加速进行了估算. 相似文献
68.
总结了川中地区的油气藏综合化探异常模式类型及与油气藏类型的对应关系,并运用水平分异理论推演了随油气藏储量在不同历史附段其油气化探综合导演模式所发生的相应变化。油气藏综合化探异常模式对油气藏类型及物性具有良好的良好指示作用,可根据油气藏的综合化探异常模式进行地质反演,从而对所在地区的油气远景进行预测。 相似文献
69.
以紫阳县城滑坡为例,采用灰色理论的单序列一阶线性动态模型,在探讨滑坡变形规律的基础上,着重研究了滑坡变形的趋势预测及主要特征点变形的位移反演,为全面研究滑坡各阶段的变形规律提出了一种分析方法 相似文献
70.