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991.
Martin B. Kalinowski Anders Axelsson Marc Bean Xavier Blanchard Theodore W. Bowyer Guy Brachet Simon Hebel Justin I. McIntyre Jana Peters Christoph Pistner Maria Raith Anders Ringbom Paul R. J. Saey Clemens Schlosser Trevor J. Stocki Thomas Taffary R. Kurt Ungar 《Pure and Applied Geophysics》2010,167(4-5):517-539
A global monitoring system for atmospheric xenon radioactivity is being established as part of the International Monitoring System that will verify compliance with the Comprehensive Nuclear-Test-Ban Treaty (CTBT) once the treaty has entered into force. This paper studies isotopic activity ratios to support the interpretation of observed atmospheric concentrations of 135Xe, 133mXe, 133Xe and 131mXe. The goal is to distinguish nuclear explosion sources from civilian releases. Simulations of nuclear explosions and reactors, empirical data for both test and reactor releases as well as observations by measurement stations of the International Noble Gas Experiment (INGE) are used to provide a proof of concept for the isotopic ratio based method for source discrimination. 相似文献
992.
Chi Hsin Lin Vincent W. Lee Maria I. Todorovska Mihailo D. Trifunac 《Soil Dynamics and Earthquake Engineering》2010
The zero-stress boundary conditions at the surface of the half-space in the presence of surface and sub-surface cavities for in-plane, incident cylindrical P- and SV-waves have always posed challenging problems. The outgoing cylindrical P- and SV-waves can be represented by Hankel functions of radial distance coupled with the sine and cosine functions of angle. Together, at the half-space surface the P- and SV-wave functions are not orthogonal over the semi-infinite radial distance from 0 to infinity. Thus, to simultaneously satisfy the zero in-plane, normal, and shear stresses, an approximation of the geometry is often made. This paper presents an analytical formulation of the boundary-valued problem, where the Hankel wave functions are expressed in integral form, changing the representation from cylindrical to rectangular coordinates, so that the zero-stress boundary conditions at the half-space surface can be applied in a more straightforward way. 相似文献
993.
Mafic enclaves in the rhyolitic products of Lipari historical eruptions; relationships with the coeval Vulcano magmas (Aeolian Islands, Italy) 总被引:1,自引:0,他引:1
The recent finding of mafic enclaves in the Rocche Rosse (RR) lava flow, the last magmatic product on Lipari (Aeolian Islands,
Italy) (AD 1230 ± 40), opens the possibility to investigate in detail the most recent magmatic system of the island, an important
issue for the volcanic hazard assessment of the area. The RR lava flow is an aphyric rhyolitic coulée consisting of grey and
black pumice and black and grey obsidian. Enclaves have ellipsoidal to spheroidal shape and vary from mm-sized in the central
portion of the flow, to cm-sized, at the top and in the flow front, where they are also more abundant. Enclaves are shoshonitic-latitic
(group A) and trachytic (group B) in composition. The mineralogy of group A consists of dominant clinopyroxene crystals with
minor abundance of feldspar (plagioclase > K-feldspar), olivine and biotite, while group B is composed of feldspar (K-feldspar > plagioclase)
with minor clinopyroxene, olivine and biotite. Geochemical modeling suggests that the host rhyolitic rocks could be the product
of AFC (Assimilation plus Fractional Crystallization) of a magma compositionally similar to the associated shoshonitic-latitic
enclaves, which, in turn, could be obtained, through an AFC process, from the primitive melts erupted as olivine hosted melt
inclusions during the last 15 ka at Vulcano. The already-known last 42 ka relationship between Lipari and Vulcano Islands
is here reinforced until historical time, especially for the last 1 ka. The geochemical and petrological overlap between Lipari
and Vulcano is interpreted to reflect the existence of a similar magmatic system underneath the two islands. The nearly aphyric
RR rhyolites are interpreted to be the products of a superheated (temperature far above the liquidus) and initially water-undersaturated
magma that underwent degassing close to the surface inhibiting microlite crystallization. 相似文献
994.
A. Attolico M. R. Gallipoli P. Harabaglia V. Lapenna M. Mucciarelli A. B. Rosa 《Bulletin of Earthquake Engineering》2010,8(5):1131-1140
The Basilicata region (Italy) is affected by the intense seismic activity of the Apenninic Chain. Since 1998 the University
of Basilicata and the Institute of Methodologies for Environmental Analysis (IMAA-CNR) started a multi-parametric geophysical
monitoring including seismometers and accelerometers. The 1996 marked the initial deployment of the Civil Protection of Province
of Potenza accelerometric network with permanent real-time link since 2006. In 2003, the Basilicata regional government started
a microzonation project that allowed the University and IMAA-CNR to manage a mobile accelerometric network and to redesign
the permanent seismic and accelerometric network. This paper reviews the main results achieved so far, the data that will
be contributed to ITACA (the Italian Accelerometric network) and the future developments of the two networks. 相似文献
995.
996.
Lidia Romero-Viana Brendan J. Keely Antonio Camacho Eduardo Vicente M. Rosa Miracle 《Journal of Paleolimnology》2010,43(4):771-786
We analysed photosynthetic pigments in annually laminated sediment of meromictic Lake La Cruz, Spain, to cope with the timing
and characterisation of primary productivity changes over the last four centuries. The photosynthetic pigments identified
included chlorophyll a and b (and its derivatives) and specific carotenoids of different algal groups, such as zeaxanthin, lutein, alloxanthin, diadinoxanthin
and diatoxanthin among others. Marker pigments of phototrophic sulfur bacteria were also observed, including bacteriochlorophyll
a derivatives, homologue series of bacteriophaeophytins d and bacterial carotenoids okenone and chlorobactene. We investigated the diagenetic processes of pigment alteration in anoxic
sediments and the possible implications for paleoproductivity reconstruction and interpretation. The lack of systematic down-core
changes in diagenetic indicators suggests that variability of sedimentary pigment concentrations is the result of changes
in lake productivity. The lower concentration of algal photosynthetic pigments in the bottom of sediment sequence corresponds
to the onset of meromictic conditions. Before that, sediment was not continuously anoxic and the preservation of pigments
was reduced. Regarding photosynthetic bacteria, green sulfur bacteria derivatives indicate that population growth was limited
until the settled organic matter was sufficient to provide enough sulphide. Moreover, the presence of bacterioviridine, an
oxidised derivative of bacteriochlorophyll a, suggest the competitive relation among photosynthetic bacteria. The high relative abundance of zeaxanthin indicates the
dominance of picocyanobacteria in the primary productivity over the last centuries. Fluctuations of the pigment signal observed
in the sediment sequence during the meromictic period were well correlated with fluctuations of solar activity. 相似文献
997.
998.
New Methods for Modeling Laterolog Resistivity Corrections 总被引:1,自引:1,他引:0
Jadwiga Anna Jarzyna Adam Cichy Dezső Drahos Attila Galsa Maria Joanna Bała Andrzej Ossowski 《Acta Geophysica》2016,64(2):417-442
The paper presents methods for laterolog response modeling. In Coulomb’s charges method, Laplace’s equation is solved for the electric field distribution in rock medium with internal boundaries between different resistivity layers. There, the boundary problem is reduced to Fred-holm integral equation of the second kind. The second method uses a finite element array to model apparent resistivity from laterolog. The task is treated as DC problem and the Laplace equation is solved numerically. The presented methods were applied to borehole data covering a typical stratigraphie section of the Fore-Sudetic Monocline in southwestern Poland. Apparent resistivity was calculated using the Coulomb’s charges method and alternatively modeled using a finite element method which gave similar results. Then, a series of linear corrections for borehole, shoulder bed, and filtration effects for apparent resistivity obtained by the Coulomb’s charges method demonstrated the feasibility of calculating true resistivity of virgin and invaded zones. The proposed methods provide a flexible solution in modeling which can be adapted to other logs. 相似文献
999.
1000.