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41.
Dean S. Oliver 《Mathematical Geology》1998,30(7):911-933
In reservoir characterization, the covariance is often used to describe the spatial correlation and variation in rock properties or the uncertainty in rock properties. The inverse of the covariance, on the other hand, is seldom discussed in geostatistics. In this paper, I show that the inverse is required for simulation and estimation of Gaussian random fields, and that it can be identified with the differential operator in regularized inverse theory. Unfortunately, because the covariance matrix for parameters in reservoir models can be extremely large, calculation of the inverse can be a problem. In this paper, I discuss four methods of calculating the inverse of the covariance, two of which are analytical, and two of which are purely numerical. By taking advantage of the assumed stationarity of the covariance, none of the methods require inversion of the full covariance matrix. 相似文献
42.
Robust estimates of magnetotelluric and geomagnetic response functions are determined using the coherency and expected uniformity of the magnetic source field as quality criteria. The method is applied on data sets of three simultaneously recording sites. For the data acquisition we used a new generation of geophysical equipment (S.P.A.M. MkIII), which comprises novel concepts of parallel computing and networked, digital data transmission. The data-processing results show that the amount of noise on the horizontal components of the magnetic field varies considerably in time, between sites and over the frequency range. The removal of such contaminated data beforehand is essential for most data-processing schemes, as the magnetic channels are usually assumed to be free of noise. The standard remote reference method is aimed at reducing bias in response function estimates. However, this does not necessarily improve their precision as our results clearly show. With our method, on the other hand, we can filter out source field irregularities, thereby providing suitable working conditions for the robust algorithm, and eventually obtain considerably improved results. Contrary to previous concepts, we suggest rejecting as much data as feasible in order to concentrate on the remaining parts of high-quality observations. 相似文献
43.
Scott B. Smithson Jon A. Brewer S. Kaufman J.E. Oliver R.L. Zawislak 《Earth and Planetary Science Letters》1980,46(2):295-305
A COCORP deep crustal reflection profile across the Wind River uplift crosses exposed Archean rocks and resolves an unusual complex deep crustal structure at a depth of 24–31 km in an area where depth relations in Precambrian rocks can be inferred. The different levels of exposure across the beveled plunge of the Wind River uplift reveal supracrustal rocks at shallower levels with migmatites and pyroxene granulites at deeper levels. For the first time, deep crustal structure from reflection profiling may be interpreted in terms of exposed basement geology. A folded, multilayered deep structure shown by relfection data resembles multiply folded pyroxene granulite interlayered with granitic gneiss exposed in the central Wind River uplift; isoclinal folding is suggested in the folded layered seismic structure. Earlier seismic reflection studies suggested a simpler lower crust. These data indicate that lower crustal structure may have a complexity similar to deeply eroded Precambrian granulite-facies rocks. If this seismic feature represents folded metamorphic rocks, it seems unlikely that this Archean crust could have been thickened by underplating after 2.7 b.y. B.P. and the crust would have to be at least 30 km thich when this structure was formed. 相似文献
44.
45.
Paul Van Gastel Gregory N. Ivey Michael J. Meuleners Jason P. Antenucci Oliver Fringer 《Continental Shelf Research》2009,29(11-12):1373-1383
Observations are presented of large-amplitude internal waves (LAIWs) generated by the steepening of the internal tide on the Australian North West Shelf (NWS) over a 4-month period extending from strongly stratified summer conditions to weakly stratified winter conditions. The observations are from a site in water depth of 124 m where current and temperature measurements were made from a fixed vertical mooring and a benthic L-shaped spatial array. The observations show the LAIWs at this site to be characterized by strong seasonal variability, with energetic LAIWs of depression being dominant during summer and weaker LAIWs of elevation being dominant during the winter months as the stratification weakens, the upper mixed layer deepens, and the thermocline is close to the bottom. Waves were also seen to propagate from a range of directions towards the observation site. Modeling using the Regional Ocean Modeling System (ROMS v2.1) revealed that internal tide generation in the area occurred at water depths of between 400 and 600 m along an arc of approximately 120 km in length, some 70 km to the northwest of our experimental site. The results demonstrate both the 3D nature as well as the seasonal variation of the LAIW field. 相似文献
46.
With modern imaging and spectral instruments observing in the visible, EUV, X-ray, and radio wavelengths, the detection of
oscillations in the solar outer atmosphere has become a routine event. These oscillations are considered to be the signatures
of a wave phenomenon and are generally interpreted in terms of magnetohydrodynamic (MHD) waves. With multiwavelength observations
from ground- and space-based instruments, it has been possible to detect waves in a number of different wavelengths simultaneously
and, consequently, to study their propagation properties. Observed MHD waves propagating from the lower solar atmosphere into
the higher regions of the magnetized corona have the potential to provide excellent insight into the physical processes at
work at the coupling point between these different regions of the Sun. High-resolution wave observations combined with forward
MHD modeling can give an unprecedented insight into the connectivity of the magnetized solar atmosphere, which further provides
us with a realistic chance to reconstruct the structure of the magnetic field in the solar atmosphere. This type of solar
exploration has been termed atmospheric magnetoseismology. In this review we will summarize some new trends in the observational
study of waves and oscillations, discussing their origin and their propagation through the atmosphere. In particular, we will
focus on waves and oscillations in open magnetic structures (e.g., solar plumes) and closed magnetic structures (e.g., loops and prominences), where there have been a number of observational highlights in the past few years. Furthermore, we
will address observations of waves in filament fibrils allied with a better characterization of their propagating and damping
properties, the detection of prominence oscillations in UV lines, and the renewed interest in large-amplitude, quickly attenuated,
prominence oscillations, caused by flare or explosive phenomena. 相似文献
47.
The theory of magnetohydrodynamic (MHD) waves in solar coronal slabs in a zero-β configuration and for parallel propagation of waves does not allow the existence of surface waves. When oblique propagation
of perturbations is considered, both surface and body waves are able to propagate. When the perpendicular wavenumber is larger
than a certain value, the body kink mode becomes a surface wave. In addition, a sausage surface mode is found below the internal
cutoff frequency. When nonuniformity in the equilibrium is included, surface and body modes are damped by resonant absorption.
In this paper, first, a normal-mode analysis is performed and the period, the damping rate, and the spatial structure of the
eigenfunctions are obtained. Then, the time-dependent problem is solved, and the conditions under which one or the other type
of mode is excited are investigated. 相似文献
48.
K.N. AbazajianE. Calabrese A. CoorayF. De Bernardis S. Dodelson A. FriedlandG.M. Fuller S. HannestadB.G. Keating E.V. Linder C. LunardiniA. Melchiorri R. Miquel E. PierpaoliJ. Pritchard P. SerraM. Takada Y.Y.Y. Wong 《Astroparticle Physics》2011,35(4):177-184
Cosmological and astrophysical measurements provide powerful constraints on neutrino masses complementary to those from accelerators and reactors. Here we provide a guide to these different probes, for each explaining its physical basis, underlying assumptions, current and future reach. 相似文献
49.
Ferraro G Bernardini A David M Meyer-Roux S Muellenhoff O Perkovic M Tarchi D Topouzelis K 《Marine pollution bulletin》2007,54(4):403-422
Studies of operational pollution carried out by European commission - Joint Research Centre in the Mediterranean Sea for the years 1999-2004 are briefly introduced. The specific analysis of the Adriatic Sea for the same period demonstrates that this area has been characterized by a relevant number of illegal discharges from ships. After setting the historical background of the project AESOP (aerial and satellite surveillance of operational pollution in the Adriatic Sea), the content, partners and aim of the project are presented. Finally, the results of the first phase of the AESOP project are presented. The results seem very encouraging. For the first time in the Adriatic, real time detection of oil spills in satellite images and an immediate verification by the Coast Guard has been undertaken. An exploratory activity has also been carried out in collaboration with the University of Ljubljana to use automatic information system (AIS) to identify the ships detected in the satellite images. 相似文献
50.
Ocean/ice interaction at the base of deep-drafted Antarctic ice shelves modifies the physical properties of inflowing shelf
waters to become Ice Shelf Water (ISW). In contrast to the conditions at the atmosphere/ocean interface, the increased hydrostatic
pressure at the glacial base causes gases embedded in the ice to dissolve completely after being released by melting. Helium
and neon, with an extremely low solubility, are saturated in glacial meltwater by more than 1000%. At the continental slope
in front of the large Antarctic caverns, ISW mixes with ambient waters to form different precursors of Antarctic Bottom Water.
A regional ocean circulation model, which uses an explicit formulation of the ocean/ice shelf interaction to describe for
the first time the input of noble gases to the Southern Ocean, is presented. The results reveal a long-term variability of
the basal mass loss solely controlled by the interaction between waters of the continental shelf and the ice shelf cavern.
Modeled helium and neon supersaturations from the Filchner–Ronne Ice Shelf front show a “low-pass” filtering of the inflowing
signal due to cavern processes. On circumpolar scales, the simulated helium and neon distributions allow us to quantify the
ISW contribution to bottom water, which spreads with the coastal current connecting the major formation sites in Ross and
Weddell Seas.
相似文献
Christian B. RodehackeEmail: |