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21.
22.
Based on previous research results, present-day crustal deformation and gravity fields in the Chinese mainland are analyzed using the GPS data, leveling, gravity and cross-fault deformations. We analyzed strain accumulation of the major faults, and identified locked or high strain accumulation segments. Combining the effects of large earthquakes in the study area, the long-term (decade) probability of large earthquakes in the Chinese mainland is estimated. 相似文献
23.
Yoichiro Fujii 《Pure and Applied Geophysics》1995,144(1):19-37
In order to study characteristics of horizontal crustal strains, we divide the Japanese Islands into 14 tectonic provinces
consistent with the suggestion given byMatsuda (1990). We calculate frequency distribution of strain rates using the results of the Precise Control Survey initiated by
the Geographical Survey Institute in 1973. This survey is a revision of old first- and second-order triangulation networks
by trilateration. The principal axes and principal strains inside all the geodetic triangles are deduced from the comparison
of the old triangulation and the new trilateration networks. The maximum shear strain rates are calculated by dividing the
accumulated strains with the time intervals. The frequency distribution of strain rates is counted for each tectonic province
and for the entire Japanese Islands.
It is proved that the maximum shear strain rate with highest frequency ranges from 0.10–0.15 microstrain/a for 4409 data in
the Japanese Islands. The mean value of the strain rates throughout the Japanese Islands is deduced to be 0.18 microstrain/a.
We also calculated a mean value of strain rates for each tectonic province. Comparison is made between mean geodetic strain
rates in the provinces and Quaternary strain rates estimated by geomorphic data. It is found that 0.3–0.4 microstrain/a of
the highest order strain rate is now prevailing in the Izu province, the south Fossa-Magna collision zone, and some special
provinces along the eastern part of the Japan Sea coast. 相似文献
24.
引入完全规格化的缔合勒让德函数,阐述国际上两类不同规格化的引潮位展开,使引潮位函数表达更加简明,大地系数定义更加规范. 由此得到由Doodson规格化与Hartmann & Wenzel规格化之间的转换系数. 相似文献
25.
A structural model for the seismicity of the Arudy (1980) epicentral area (Western Pyrenees, France)
Noalwenn Dubos-Sallée Bertrand Nivière Pierre Lacan Yves Hervouët 《Geophysical Journal International》2007,171(1):259-270
The Western Pyrenees presents a diffuse and moderate ( M ≤ 5.7) instrumental seismicity. It nevertheless historically suffered from strong earthquakes (I = IX MSK). The seismic sources of these events are not yet clearly identified. We focus on the Arudy (1980) epicentral area ( M = 5.1) and propose here the reactivation of early Cretaceous normal faults of the Iberian margin as a potential source. The late Cretaceous inversion of this basin, first in a left-lateral strike-slip mode and then in a more frontal convergence, resulted in a pop-up geometry. This flower structure attests of the presence of a deep crustal discontinuity.
The present-day geodynamic arrangement suggests that this accident is reactivated in a right lateral mode. This reactivation leads to a strain partitioning between the deep discontinuity that accommodates the lateral component of the motion and shallow thrusts, rooted on this discontinuity. These thrusts accommodate the shortening component of the strain. The distribution of the instrumental seismicity fits well the structural model of the Arudy basin. Whatever the compressive regional context, the structural behaviour of the system explains too the extensive stress tensor determined for the Arudy crisis if we interpret it in terms of strain ellipsoid. Indeed numerical modelling has shown that this concomitant activity of strike-slip and thrust faulting results in an extensive component that can rise 50 per cent of the finite strain.
We identify too a 25–30 km long potential seismic source for the Arudy area. The size of the structure and its potential reactivation in a strike-slip mode suggest that a maximum earthquake magnitude of ∼6.5 could be expected. The extrapolation of this model at the scale of the Western Pyrenees allows to propose other potential sources for major regional historical earthquakes. 相似文献
The present-day geodynamic arrangement suggests that this accident is reactivated in a right lateral mode. This reactivation leads to a strain partitioning between the deep discontinuity that accommodates the lateral component of the motion and shallow thrusts, rooted on this discontinuity. These thrusts accommodate the shortening component of the strain. The distribution of the instrumental seismicity fits well the structural model of the Arudy basin. Whatever the compressive regional context, the structural behaviour of the system explains too the extensive stress tensor determined for the Arudy crisis if we interpret it in terms of strain ellipsoid. Indeed numerical modelling has shown that this concomitant activity of strike-slip and thrust faulting results in an extensive component that can rise 50 per cent of the finite strain.
We identify too a 25–30 km long potential seismic source for the Arudy area. The size of the structure and its potential reactivation in a strike-slip mode suggest that a maximum earthquake magnitude of ∼6.5 could be expected. The extrapolation of this model at the scale of the Western Pyrenees allows to propose other potential sources for major regional historical earthquakes. 相似文献
26.
R. Lehmann 《Journal of Geodesy》1997,71(9):533-540
Geodetic surface integrals play an important role in the numerical solution of geodetic boundary-value problems. In many
cases they can be evaluated using fast methods in the frequency domain (FFT). However, this is not possible in general, because
the domain of integration may be non-trivial (as is the surface of the Earth), the kernel function may not be of convolution
type, or the data distribution may be heterogeneous. Therefore, fast evaluation strategies are also required in the space
domain. They are more difficult to design because only one property is left where a more or less fast evaluation strategy
can be built upon: the potential type of the kernel function. Consequently, the idea is not to replace well-established frequency
domain techniques, but to supplement them. Our approach to this problem goes in two directions: (1) we use advanced cubature
methods where the integration nodes automatically densify in the vicinity of the evaluation points; (2) we use powerful computer
hardware, namely MIMD computers with distributed memory. This enables us to evaluate geodetic surface integrals of any practical
complexity in reasonable time and accuracy. This is shown in a numerical example.
Received: 7 May 1996 / Accepted:17 March 1997 相似文献
27.
28.
Christopher Kotsakis 《Journal of Geodesy》2008,82(4-5):261-260
Transforming height information that refers to an ellipsoidal Earth reference model, such as the geometric heights determined
from GPS measurements or the geoid undulations obtained by a gravimetric geoid solution, from one geodetic reference frame
(GRF) to another is an important task whose proper implementation is crucial for many geodetic, surveying and mapping applications.
This paper presents the required methodology to deal with the above problem when we are given the Helmert transformation parameters
that link the underlying Cartesian coordinate systems to which an Earth reference ellipsoid is attached. The main emphasis
is on the effect of GRF spatial scale differences in coordinate transformations involving reference ellipsoids, for the particular
case of heights. Since every three-dimensional Cartesian coordinate system ‘gauges’ an attached ellipsoid according to its
own accessible scale, there will exist a supplementary contribution from the scale variation between the involved GRFs on
the relative size of their attached reference ellipsoids. Neglecting such a scale-induced indirect effect corrupts the values
for the curvilinear geodetic coordinates obtained from a similarity transformation model, and meter-level apparent offsets
can be introduced in the transformed heights. The paper explains the above issues in detail and presents the necessary mathematical
framework for their treatment.
An erratum to this article can be found at 相似文献
29.
R. Lehmann 《Journal of Geodesy》2000,74(3-4):327-334
The definition and connection of vertical datums in geodetic height networks is a fundamental problem in geodesy. Today,
the standard approach to solve it is based on the joint processing of terrestrial and satellite geodetic data. It is generalized
to cases where the coverage with terrestrial data may change from region to region, typically across coastlines. The principal
difficulty is that such problems, so-called altimetry–gravimetry boundary-value problems (AGPs), do not admit analytical solutions
such as Stokes' integral. A numerical solution strategy for the free-datum problem is presented. Analysis of AGPs in spherical
and constant radius approximation shows that two of them are mathematically well-posed problems, while the classical AGP-I
may be ill posed in special situations.
Received: 2 December 1998 / Accepted: 30 November 1999 相似文献
30.
Tunnel excavation produces stress changes to the ground and strain to the support lining, leading to the closure (convergence) or instability of the excavated area. Convergence recorded after section excavation is assigned to: (i) strain resulting from the progressive tunnel front advance (face advance effect) and (ii) the time-dependent properties of the soil material (ground creep effect). In the present study, based on the geodetic monitoring records of two recent road tunnels in Greece, a simple methodology to estimate the contribution of each of the two effects is presented. Our analysis reveals that at least half of the total deformation of the examined tunnel sections is due to ground creep, indicating that the major portion of tunnel deformation is due to the time-dependent properties of the ground; a result supported by previous studies from other tunnels as well. 相似文献