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101.
岩体结构效应的综合反演分析 总被引:1,自引:0,他引:1
本文根据多点位移计现场测量的位移值,结合洞室开挖时一般性的变形规律和基本地质知识,探讨了反演推断洞室周围岩体结构的理论和方法,并且利用某一实际工程进行了验证。 相似文献
102.
Data compiled from monitoring the displacement resulting from the Xintan landslide in China was analyzed. The stability of
the demonstrated colluvial slope has a close correlation with two parameters, the velocity of the displacement and the angle
of the surface vector. The stability trend can be described and evaluated by both the velocity of the displacement and the
vector angles. The displacement vector angle, for which there is no substitute, serves as an explicit criterion for the stability
of the slope, hence it is significant in the prediction of the catastrophic movement of landslides. A systematic analysis
of the features of the vector angles of the surface displacement space and time was performed. The evolving mechanism of space-time
and the characteristics of the displacement vector angles were deduced. On the basis of these deductions and by using principles
of statistics, the double-parameter threshold for forecasting the stability of the colluvial slopes was established. According
to the double-parameter threshold, a calculation and evaluation of stability was completed in terms of the monitoring data
of the F-series of points on the Xintan slope. The forecast results coincided with the destabilized timetable, thus demonstrating
that the double-parameter criterion has, to a certain extent, precision and practical application for forecasting of landslides. 相似文献
103.
We identify two likely normal faults on Europa, of lengths ≈30 and 11 km. A simple flexural model of fault-related topography gives effective elastic thicknesses of 1.2 and 0.15 km, respectively, and the resulting inferred fault strength is of order 1 MPa. The maximum fault displacement: length ratio for each fault is ≈0.02, comparable with values on silicate planets. We combine this observation with a modified linear elastic fracture mechanics model to conclude that the shear modulus of the Europan surface must be significantly less than that for unfractured ice. The low value of the modulus is probably due to near-surface fracturing or porosity, which will affect the material's radar properties and seismic velocities. For a likely reduction in shear modulus of an order of magnitude, the driving stresses inferred are about 6–8 MPa, much higher than present-day diurnal tidal stresses. However, stresses approaching these values can be generated by non-synchronous rotation or polar wander, while stresses exceeding these values arise during ice shell freezing. If the entire larger fault breaks, it will generate an event of seismic magnitude Ms≈5.3. 相似文献
104.
105.
106.
Climate-induced population displacement and resettlement is an ongoing problem around the world, and one that is being exacerbated by climate change. To date, most attempts to address this problem have taken a top-down approach in which international justice, legal and humanitarian frameworks are extended ‘downwards’ by policymakers and governments to local populations. However, there has been limited systematic work that emphasizes the abilities of affected peoples themselves to develop and formulate their own justice-based solutions. This paper presents an analytical framework for thinking about ‘bottom-up’ claims-making that emphasizes naming, blaming, claiming and framing. The framework enables claims-making to be distinguished from other forms of community-based agency, such as adaptation. The paper also suggests a normative framework to support policymakers and practitioners in helping communities facing displacement to make claims. The normative framework focuses on the barriers to, and opportunities for, claims-making ‘from below’. 相似文献
107.
This study details the observed effects ofatmospheric stability on characteristics of thesurface layer in a low wind speed (U = 1.5 m s-1)regime of tropical West Africa. Theaerodynamic roughness length, z0, anddisplacement height, d, obtained from profilewind-speed data at our bush land site (height 2 m)have values of 0.24 ± 0.10 m and 1.54 ± 0.04 mrespectively. In the unstable range (-2.5 < Ri < -0.1; Riis gradient Richardson number), thestandard deviation in wind speed fluctuations, u, increased from 0.57 ± 0.19 m s-1 toa maximum of 0.7 ± 0.2 m s-1 in near-neutralconditions, and in the stable range, the parameterdecreased rapidly to 0.41 ± 0.15 m s-1 at Ri 0.2.In the same stability range, the horizontal winddispersion, , decreased withincreasing stability from 19 ± 8 deg. to 13 ± 5 deg.The surface-layer integral quantity, u/u*, when plottedas a function of stability, is in agreement with theempirical results. The ratio ofsensible heat flux (estimated) to the net radiationranged between 0.1 and 0.2 at nighttime,increasing to about 0.5 during the daytime, and showeda strong dependency on season. 相似文献
108.
Rocks are naturally filled with cracks and pores that are saturated with one or more fluid phases. Many problems in rock mechanics, petroleum engineering, geophysics, etc. deal with cracks and discontinuities in rock formations. These problems should consider effects of a porous medium. Displacement discontinuity method (DDM) as an indirect boundary element method is particularly ideal for problems involving fractures and discontinuities. However, the DDM in its original form is limited to elastic problems. The paper uses a fundamental solution of a point displacement discontinuity in poroelastic medium to obtain the solution for a poroelastic DDM. Then it introduces a numerical formulation and implementation for the poroelastic DDM in a code named CEP-DDM (Constant Element Poroelastic DDM). The accuracy and validity of the proposed solution and the newly developed code are verified by two analytical solutions, another numerical solution, and some field measurements. These results showed good agreement between CEP-DDM and other methods’ results. The verifications prove the accuracy and applicability of the proposed numerical model in a wide range of real-world problems. 相似文献
109.
青藏高原拉萨地块早白垩纪火山岩古地磁结果及其构造意义 总被引:1,自引:1,他引:0
对青藏高原拉萨地块早白垩纪火山岩15个采点的古地磁测定,揭示了一组高温特征剩磁分量.实验结果表明采样剖面获得的早白垩统卧荣沟组的古地磁结果全部为正极性,显示与早白垩纪正极性超静带的极性特征相似.对岩石的显微镜观察表明岩石未受后期热液化学交代作用和风化作用,这表明所获得的高温分量很可能代表岩石形成时的原生剩磁.其特征剩磁方向为:偏角D=18.4°,倾角I=26.5°,α95=8.6°;相应的极位置为:经度ψp=220.3°E,纬度λp=66.4°N,dp=9.3°,dm=6.9°,古纬度plat=14.0°.通过对比拉萨地块以北诸地块早白垩纪古地磁结果,认为拉萨地块在早白垩纪已与芜塘地块碰撞拼合在一起,而自早白垩纪以来相对欧亚大陆发生了1500±600km的构造缩短.结合拉萨地块已有的晚白垩纪和古新纪古地磁数据,认为欧亚大陆的最南缘(拉萨地块)在印度/欧亚大陆发生碰撞前自早白垩纪一始新纪一直处于北纬12.8°~14°N低纬度位置,并未发生明显的纬向运动. 相似文献
110.
滑坡位移预测预报是滑坡防灾减灾的重要组成部分,提高滑坡位移预测的准确性与精确度是该项研究的重点与难点。本文在滑坡位移预测中考虑了监测样本的离群值,通过忽略、指定与修正离群值3种方式,研究滑坡位移预测样本离群值的最优处理方式。以三峡库区朱家店滑坡为例,基于ARIMA(p,d,q)模型,分别对累积位移与位移速率时间序列开展了预测研究。研究结果表明:修正离群值的预测结果介于忽略和指定离群值两者之间,更适用于存在监测离群值的滑坡位移预测;对于ARIMA模型,更适合采用位移速率进行预测预报;使用位移速率时间序列ARIMA(1,0,1)并修正离群值的预测结果为:2016年和2017年6月份滑坡前缘GP3"阶跃"位移分别为79. 0 mm和70. 2 mm,截止2017年8月,GP3累积位移将达1647. 7 mm。 相似文献