全文获取类型
收费全文 | 591篇 |
免费 | 96篇 |
国内免费 | 73篇 |
专业分类
测绘学 | 72篇 |
大气科学 | 9篇 |
地球物理 | 256篇 |
地质学 | 379篇 |
海洋学 | 13篇 |
天文学 | 3篇 |
综合类 | 24篇 |
自然地理 | 4篇 |
出版年
2023年 | 4篇 |
2022年 | 4篇 |
2021年 | 5篇 |
2020年 | 17篇 |
2019年 | 17篇 |
2018年 | 11篇 |
2017年 | 18篇 |
2016年 | 23篇 |
2015年 | 19篇 |
2014年 | 35篇 |
2013年 | 36篇 |
2012年 | 21篇 |
2011年 | 24篇 |
2010年 | 20篇 |
2009年 | 41篇 |
2008年 | 33篇 |
2007年 | 40篇 |
2006年 | 40篇 |
2005年 | 40篇 |
2004年 | 35篇 |
2003年 | 42篇 |
2002年 | 32篇 |
2001年 | 19篇 |
2000年 | 13篇 |
1999年 | 23篇 |
1998年 | 19篇 |
1997年 | 26篇 |
1996年 | 21篇 |
1995年 | 16篇 |
1994年 | 14篇 |
1993年 | 10篇 |
1992年 | 7篇 |
1991年 | 7篇 |
1990年 | 3篇 |
1989年 | 6篇 |
1988年 | 6篇 |
1987年 | 5篇 |
1986年 | 1篇 |
1985年 | 2篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1978年 | 2篇 |
1977年 | 1篇 |
排序方式: 共有760条查询结果,搜索用时 31 毫秒
1.
形变大地测量学的进展、问题与地震预报 总被引:12,自引:7,他引:5
简要概括了形变大地测量学的革命性进展,研讨了它的科学特色、功能和定义以及对地球科学和防灾减灾的推动。形变大地测量学有助于从根本上击破多年来制约地震预报的“瓶颈”,但也存在不少急待解决的问题。着重研讨了在21世纪前10年,形变大地测量学如何依托多年的学科积累并充分受益于人造卫星和数字化等新技术,开展创新性研究和试验以推进地震预报。为此,对当前的研究工作提出了12条科学技术途径。最后对学科名称提出了建议。 相似文献
2.
辽南早元古代辽河群中片麻状花岗岩的变形温度显示出645—690℃,550—610℃和485℃±三组温度值,表明花岗岩遭受了三幕构造变形。而区域构造解析亦表明辽河群在早元古时期经历了三幕构造变动。花岗岩的温度系列与区域变形序列具有一致性,排除了花岗岩晚期构造侵位的可能性。变形温度以550—610℃居多,意味着该幕构造形迹保存最好。第三幕变形变质作用相对较弱,仅局部出现485℃的温度值。 相似文献
3.
1 IntroductionDiscontinuousDeformationAnalysis(DDA)developedbyShiin 1 980’s[1 ,2 ] maybeusedtocalculatethedeformationanddisplacementsinamulti blocksystemandtoanalyzetherelationbe tweenforcesanddisplacementsinthesystem .Ifthesurveydisplacementofeverypointordirectionisknown,alldisplacementsanddeformationsofblocks,eventheglide ,theclosureandthestretchoftheboundary planeofblocks ,canbecalculated .TheresultisoptimallyfittedaccordingtotheLeastSquarePrinciple.DDAismainlyusedinrockblockssystems… 相似文献
4.
Deep dissolution affects great part of soluble rocks (e.g. gypsum and anhydrite) of the Western Italian Alps. The related superficial phenomena (sinkholes, gravity-induced processes and a local worsening of geomechanical rock properties) are not limited to typical karsts landscape and cause slope instability also affecting populated sites and infrastructures. The paper aims to describe general characteristic of dissolution phenomena, to interpret their conditioning factors and evolutionary stages and to assess possible hazards due to their superficial effects.The search for evidences of deep dissolution leads to the selection of representative sites in the central part of the Western Italian Alps (Piemonte and Valle d'Aosta Region). Detailed geological and geomorphological studies have been used to classify the selected sites by type, size and variable state of activity. Very different evolutionary stages of dissolution phenomena have been interpreted by comparison of case-studies: some are early “embryonic”; others are more evolved, up to typical sinkholes, or even remodelled by other phenomena. Some cases show an extreme complexity in the interactions between corrosion phenomena and other geomorphic processes: slope deformations, from one side, and karst, fluvial and glacial phenomena, to the other. A wide range of movement rates on slope instabilities induced by deep dissolution have been estimated by topographic and geomorphic data. Geochemical data on removed rocks by dissolution indicate 0.4 mm/year values for local subsidence. Historical and technical data indicate low frequency of major dissolution-induced collapses, but highlight widespread damages to tunnels, roads and buildings, especially along slopes. 相似文献
5.
6.
Engineering projects that require deformation monitoring frequently utilize geodetic sensors to measure displacements of target
points located in the deformation zone. In situations where control stations and targets are separated by a kilometer or more,
GPS can offer higher precision position updates at more frequent intervals than can normally be achieved using total station
technology. For large-scale deformation projects requiring the highest precision, it is therefore advisable to use a combination
of the two sensors. In response to the need for high precision, continuous GPS position updates in harsh deformation monitoring
environments, a software has been developed that employs triple-differenced carrier-phase measurements in a delayed-state
Kalman filter. Two data sets were analyzed to test the capabilities of the software. In the first test, a GPS antenna was
displaced using a translation stage to mimic slow deformation. In the second test, data collected at a large open pit mine
were processed. It was shown that the delayed-state Kalman filter developed could detect millimeter-level displacements of
a GPS antenna. The actual precision attained depends upon the amount of process noise infused at each epoch to accommodate
the antenna displacements. Higher process noise values result in quicker detection times, but at the same time increase the
noise in the solutions. A slow, 25 mm displacement was detected within 30 min of the full displacement with sigma values in
E, N and U of ±10 mm or better. The same displacement could also be detected in less than 5 h with sigma values in E, N and U of ±5 mm or better. The software works best for detecting long period deformations (e.g., 20 mm per day or less) for which
sigma values of 1–2 mm are attained in all three solution components. It was also shown that the triple-differenced carrier-phase
observation can be used to significantly reduce the effects of residual tropospheric delay that would normally plague double-differenced
observations in harsh GPS environments.
相似文献
Don KimEmail: |
7.
8.
形变,应变短临前兆标志体系 总被引:1,自引:0,他引:1
建立各手段的前兆异常标志,从而组合各类前兆标志体系是“八五”地震短临预报攻关研究项目的重要目标之一。本文以形变,应变手段的主要研究对象,初步建立了一个形变应变短临前兆标志体系,并总结出了各种异常的判别标志,为利用系统优化理论和专家系统理论进一步研究形变应前兆系统和地震之间的关系,从而为提高中短期地震预报的水平打下了一定的基础。 相似文献
9.
S. Mazzoli 《International Journal of Earth Sciences》1995,84(4):781-793
Analysis of strain in Jurassic argillites forming part of the folded and thrusted sedimentary succession of the Lagonegro basin (southern Italian Apennines) has been carried out using ellipsoid-shaped reduction spots as strain markers. Most of the determined finite strain ellipsoids are of oblate type and show a peculiar distribution of the maximum extension direction (X), with maxima either subparallel or subperpendicular to the local fold axes. Using the strain matrix method, two different deformation histories have been considered to assist the interpretation of the observed finite strain pattern. A first deformation history involved vertical compaction followed by horizontal shortening (occurring by a combination of true tectonic strain and volume loss), whereby all strain is coaxial and there is no change in the intermediate axis of the strain ellipsoid. By this type of deformation sequence, which produces a deformation path where total strain moves from the oblate to the prolate strain field and back to the oblate field, prolate strain ellipsoids can be generated and may be recorded where tectonic deformation has not been large enough to reverse pretectonic compaction. This type of deformation history may be of local importance within the study area (i.e. it may characterize some fold hinge regions) and, more generally, is probably of limited occurrence in deformed pelitic rocks. A second deformation sequence considered the superposition of pre-tectonic compaction and tectonic strain consisting of initial layer-parallel shortening followed by layer-parallel shear (related to flexural folding). Also in this instance, volume change during tectonic deformation and tectonic plane strain have been assumed. For geologically reasonable amounts of volume loss due to compaction and of initial layer-parallel shortening, this type of deformation history is capable of producing a deformation path entirely lying within the oblate strain field, but still characterized by a changeover, during deformation, of the maximum extension axis (X) from a position parallel to the fold axis to one perpendicular to it. This type of deformation sequence may explain the main strain features observed in the study area, where most of the measured finite strain ellipsoids, determined from the limb regions of flexural folds, display an oblate shape, irrespective of the orientation of their maximum extension direction (X) with respect to the local structural trends. More generally, this type of deformation history provides a mechanism to account for the predominance of oblate strains in deformed pelitic rocks. 相似文献
10.
The behaviour of quartz during metamorphism is studied based on two case studies from the Barrovian terrains of Sulitjelma in arctic Scandinavia and Loch Tay in the Central Highlands Dalradian of Scotland. Both terrains preserve evidence for metamorphism in pelites involving nucleation and growth of garnet at different times in the deformation history. Data are presented on the size, shape and crystallographic orientation of quartz preserved as inclusions in garnet and as grains in the surrounding matrix. While quartz-grains remain small and dispersed between mica grains, deformation appears to be dominated by grain-boundary sliding accommodated by dissolution–precipitation. At amphibolite facies, textural coarsening occurs by dissolution of small quartz grains and growth of larger quartz grains, coupled with segregation of quartz from mica. As a result, quartz deforms by dislocation creep, developing crystallographic preferred orientations (CPO) consistent with both coaxial and non-coaxial strain. Quartz CPOs with <0001> axes lying parallel to foliation and stretching direction are commonly developed, and best explained by mechanical rotation of inequant (detrital?) quartz grains. There is no evidence for selective entrapment of quartz inclusions in garnet on the basis of quartz crystallographic orientation. 相似文献