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51.
Volume Contents
Contents Volume 82 相似文献52.
The egion fault, earthquake-related and long-term deformation, Gulf of Corinth, Greece 总被引:1,自引:0,他引:1
On 15 July 1995, the Egion earthquake (Ms = 6.2) occurred in the vicinity of Egion, west-central Greece. Macroseismic observations along the 12 km long E-W trending Egion fault represent short-term or earthquake-related deformation characterized by fairly straight E-W trending surface ruptures with small displacements that mimic the Egion fault geologic offsets and segmentation. Hanging wall converging slip vectors along the Egion fault are clearly related to fault motions at depth. Furthermore, peak accelerations of the built-up area of Egion amount to 0.54 g, that is double the estimated peak acceleration of the Egion coastal area, showing thus close relation between fault trace and attenuation of the ground motion.The Egion fault, with a total geological throw of 200 m and dips to the north at about 55 °, accommodating active tectonic deformation of the Egion area. Its morphotectonic expression reflects long-term deformation in competition with the 1995 earthquake related deformation. The Egion fault is controlling the geomorphic evolution of the Egion area as follows: 1) The fault is defining the evolution of fan-deltas (offshore) and the Meganitas river alluvial plain (onshore). 2) The hanging-wall's greatest subsidence is observed, at the Egion bay, at the central portion of the fault. The Egion bay is located at the central part of the fault showing a strong relationship between the long term slip-rate ratio and the recent coastal morphology. The subsidence gradient or the tectonic activity along the fault is defined by the valley-floor width to valley height index (Vf) of small rivers draining the fault scarp. The Meganitas river course is tilted, when crosses the Egion fault trace, towards the area with the highest subsidence along the fault. 3) Stream incision is more important than slope recession at areas close to the fault trace.All these observations suggest that the Egion fault, which probably hosted the last earthquake, are geomorphically controlling the evolution of a 15 km-long by 5 km-wide zone, fairly similar in dimensions to the surface length of the fault. 相似文献
53.
A complete data set of globally distributed shallow (h , 60 Km) earthquakes have been used for first time to test the possible existence of periodicities in the seismic energy release. Only main shocks of magnitude,M 7.0 were considered, which occurred in the whole Earth during 1898–1985. These magnitudes are converted in seismic energy, which is released during the occurrence of earthquakes, through Bath's formula. The detection of such kind of periodicities is important in seismology, because these patterns may lead to the prediction of large earthquakes. Statistical techniques, such as Maximum Entropy (ME), and two Fourier approaches, the Fast Fourier Transform (FFT) and Power Spectrum (PS) of truncated subrecords of the whole time series have been applied to examine the possible existence of such periodicities in seismic energy release. Furthermore, the even-spacing technique is used to validate our results and a type-curve has been constructed for the data set.The results exhibit a network of periodicities with predominant periods at 3(±0.5), 4.5, 6.5, 8–9, 14–20, and 31–34 years. Some periods were occasionally interrupted. The latter implies that our time-series is not stationary, in that, the spectral peaks drift when the data are viewed through different time windows. The fact that the signal is weak and embedded in less accurate older data could contribute to this effect. The question of stability/validity of the apparently cyclic behaviour of the annual global seismic energy release, is one which requires further investigation. 相似文献
54.
The quick response of civil authorities after a major disaster event in an urban area is essential for the reduction of damages
and impacts to human lives. One of the first critical problems to be solved at the very early stages of response is the optimum
management of emergency vehicles and real time knowledge of the accessibility of the road network. In this article the concept
of using a number of emergency vehicles as sensors for monitoring the traffic conditions in an urban area after a major disaster
event is described. The fleet management system used for this taks is working with ral time DGPS. The system makes use of
existing vehicle fleets in the urban area, rapidly collecting data and covering the whole road network. It records travel
times with the help of the GPS system for every road segment driven through by each vehicle sensor, thus providing a digital
time database from which traffic parameters can be also computed. It can be used for real time monitoring of traffic conditions
under disaster or emergency situations where all the previously available data become invalid or unreliable. ? 2002 Wiley
Periodicals, Inc. 相似文献
55.
Louisiana barrier islands, such as the chain surrounding the southeast region of the state, are experiencing rapid loss of
land area, shoreline erosion, and landward migration due to transgression and in-place drowning, and the landfall of several
major hurricanes in the last decade. Observations of migration rates and overall impacts to these barrier islands are poorly
understood since they do not respond in a traditional way, such as barrier rollover. This paper aims to verify how wave energy
and potential longshore sediment transport trends have influenced the recent evolution of the Chandeleur Islands, by direct
comparison with recent observations of migration and erosion trends. The Chandeleur Islands are characterized by a bidirectional
transport system, with material moving from the central arc to the flanks. The longshore sediment transport along the barrier
islands was calculated after propagation and transformation of waves to breaking (generated using observed winds), and through
the use of a common longshore sediment transport formula. Seasonal variations in wind climate produced changes in the transport
trends and gradients that agree with migration and rotation patterns observed for this barrier island system. Results suggest
that wind dominance produces seasonal oscillations that cause an imbalance in the resulting transport gradients that over
time are responsible for higher rates of transport in the northward direction. These results and data from other works verify
the evolutionary model previously suggested, and qualitatively confirm the recent observations in asymmetric shoreline erosion. 相似文献
56.
This work investigates the efficiency of mixed base isolation, combining passive isolation bearings with semi-active (SAC)
devices, to reduce the floor spectral acceleration in the vicinity of the non-isolated modes’ frequencies. Both analytical
and experimental studies have been carried out. Analytical results of the behaviour of a multiple degree of freedom base isolated
structure demonstrate the efficacy of the method. Though the considered controller is based on a reduced order model with
only two degrees of freedom (2 DOF) without spillover compensation, the results show that, for the type of structures studied
here, spillover effects are not considerable. An experimental study of a 2 DOF model of a base isolated structure equipped
with a semi-active magneto-rheological (MR) damper has been carried out. Due to limitations of the experimental set-up, it
has not been possible to obtain direct experimental evidence of the efficacy of SAC control to improve floor spectra. Nevertheless,
based on the good agreement between analytical and experimental results which validate the considered MR model and control
algorithm, numerical analyses of more relevant configurations illustrated the benefit of the utilization of such devices. 相似文献
57.
Results of large-scale finite element computations are presented for the problem of borehole failure due to the high stresses at great depths. Rock is modelled by an extension of the Mohr–Coulomb flow theory of plasticity for material with Cosserat micro-structure. The introduction of internal length (grain size) improves the computational stability and allows for robust post-localization computations. The presented results show clearly a progressive failure mechanism and the computed failure modes are in a good qualitative agreement with laboratory and field observations. 相似文献
58.
59.
This paper attempts to present and discuss the geomorphological and spatial analyses of Hygassos in the middle Mediterranean (a demos in ancient Bozburun Peninsula) through the application of GIS and photogrammetry, where necessary. The contextual data is composed of the settlement features and humanly constructed terrace relics. In search of the spatial and social territoria, the research questions greatly lean on the present geographical attributes and, the results of a recent survey concerning the ruins situated along a narrow valley in modern Selimiye-K?z?lköy and the Acropolis rising beside. The physical scope encompasses the khora of the Acropolis whose spatial coverage applies to ca. 27.26 km2. As the results show, the socio-economic transformation of Hygassos, under the observance of a major stronghold (Kaletepe), must have been quite dependent on the interplay of the topographical and natural factors, as well as the likely shifts from or to the Acropolis over time. However, ambiguities remain for the resilient western half territory (near immediate Losta Bay) which perhaps encroaches on the frontiers of neighbouring Tymnos. Unfavourable but cultivable areas were preferably used for household construction and terracing whereas the land exposed to maximum erosion was refrained for settling purposes. 相似文献
60.
Ioannis K. Georgiadis Antonios Koroneos Lamprini Papadopoulou Nikolaos Kantiranis Alexios E. Tamparopoulos Ananias Tsirambides 《Mineralogy and Petrology》2014,108(2):187-206
Garnet single crystals of several millimeters in diameter were collected from the uppermost horizon of a soil profile developing immediately on the gneissic rocks of the Vertiskos Unit of the Serbomacedonian Massif in northern Greece. The garnets were analyzed for major elements by EDS analyzer mounted on a scanning electron microscope, and the obtained data were utilized to determine their source rocks. Bivariate diagrams, spider diagrams as well as statistical analysis were used in order to correlate and compare the garnet composition of the basement rocks of the Vertiskos Unit with the existing reference data. This case study demonstrates the difficulty in assigning a source rock to sediment, using only the chemical compositional of detrital garnet. Direct linking of the detrital garnets and the outcropping rocks is not always possible despite well documented outcrop lithologies. This is largely due to a complex metamorphic evolution that leads to overlapping compositions between garnets originating from different lithologies that have undergone similar metamorphic processes and alteration effects. 相似文献