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141.
Fausto Grassa Giorgio Capasso Rocco Favara Salvatore Inguaggiato 《Pure and Applied Geophysics》2006,163(4):781-807
Hydrochemical (major and some minor constituents), stable isotope ( and , δ13CTDIC total dissolved inorganic carbon) and dissolved gas composition have been determined on 33 thermal discharges located throughout
Sicily (Italy) and its adjacent islands. On the basis of major ion contents, four main water types have been distinguished:
(1) a Na-Cl type; (2) a Ca-Mg > Na-SO4-Cl type; (3) a Ca-Mg-HCO3 type and (4) a Na-HCO3 type water. Most waters are meteoric in origin or resulting from mixing between meteoric water and heavy-isotope end members.
In some samples, δ18O values reflect the effects of equilibrium processes between thermal waters and rocks (positive 18O-shift) or thermal waters and CO2 (negative 18O-shift). Dissolved gas composition indicates the occurrence of gas/water interaction processes in thermal aquifers. N2/O2 ratios higher than air-saturated water (ASW), suggest the presence of geochemical processes responsible for dissolved oxygen
consumption. High CO2 contents (more than 3000 cc/litre STP) dissolved in the thermal waters indicate the presence of an external source of carbon
dioxide-rich gas. TDIC content and δ13CTDIC show very large ranges from 4.6 to 145.3 mmol/Kg and from –10.0‰ and 2.8‰, respectively. Calculated values indicate the significant
contribution from a deep source of carbon dioxide inorganic in origin. Interaction with Mediterranean magmatic CO2 characterized by heavier carbon isotope ratios ( value from -3 to 0‰ vs V-PDB (CAPASSO et al., 1997, GIAMMANCO et al., 1998; INGUAGGIATO et al., 2000) with respect to MORB value and/or input of CO2-derived from thermal decomposition of marine carbonates have been inferred. 相似文献
142.
The Gran Paradiso nappe of the northwestern Alps mostly consists of augen gneisses derived from the Alpine deformation of
Permian granitoids. The regional foliation of the augen gneisses developed at lower amphibolite facies conditions and is associated
with a top-to-west sense of shear. The granitoid protolith is preserved in the kilometre-scale low-strain domain of the Piantonetto
Valley and mainly consists of a porphyritic metagranite including joints, leucocratic dykes and biotite-rich schlieren. In
this low-strain domain, the Alpine deformation is mainly localized in discrete ductile shear zones within weakly foliated
metagranite. The shear zones mostly dip towards S–SE in a shallow (shear zones
1) to steep inclination (shear zones
2). The shear zones show typical features that can be explained by reactivation of pre-existing joints and planar compositional
heterogeneities. Palaeostress and strain analysis indicate that shear zones and the metagranite foliation both formed in the
presence of a strong component of flattening. The kinematics of individual shear zones depends on the orientation of the original
heterogeneities (acting as nucleation planes) and by partitioning of strain components at the kilometre-scale with concentration
of the flattening component to the Piantonetto low-strain domain. The strain geometry and the kinematics of individual shear
zones within Piantonetto are not directly connected to the top-to-west sense of tectonic transport observed elsewhere in the
Gran Paradiso nappe. However, the bulk stress ellipsoid reconstructed for the incipient shear zone network within very weakly
deformed granites is oriented consistently with the bulk direction of tectonic transport within the Gran Paradiso massif.
We conclude that the shear zone network of the Piantonetto Valley is representative of the incipient stages of ductile deformation
of a granite nappe. Even if its architecture is determined by the arrangement of pre-existing structural and compositional
heterogeneities, aspects of the large-scale bulk strain can be derived from this local shear zone pattern. 相似文献
143.
We present the calculation of the probability production of an electron–positron pair in the presence of a strong magnetic field with time-varying strength. The calculation takes into account the presence of a strong, constant and uniform gravitational field in the same direction of the magnetic field. The results show that the presence of the gravitational field in general enhances very much the production of pairs. In particular, high-energy pairs are more likely produced in the presence of the gravitational field than in Minkowski spacetime. 相似文献
144.
145.
Philip C. Farese Giorgio DallOglio Josh Gundersen Brian Keating Slade Klawikowski Lloyd Knox Alan Levy Chris ODell Alan Peel Lucio Piccirillo John Ruhl Peter Timbie 《New Astronomy Reviews》2003,47(11-12):1033
COMPASS is an on-axis 2.6-m telescope coupled to a correlation polarimeter. The entire instrument was built specifically for CMB polarization studies. Careful attention was given to receiver and optics design, stability of the pointing platform, avoidance of systematic offsets, and development of data analysis techniques. Here we describe the experiment, its strengths and weaknesses, and the various things we have learned that may benefit future efforts to measure the polarization of the CMB. 相似文献
146.
Elisa Rojo-Nieto Carmen Garrido-Pérez Giorgio Anfuso-Melfi Francisco Lopez-Aguayo Diego Sales-Marquez Jose Antonio Perales-Vargas-Machuca 《Estuaries and Coasts》2011,34(6):1129-1139
This paper reports a study of the occurrence and levels of polycyclic aromatic hydrocarbons (PAHs) in a bay characterised
by a chronic persistent impact. A total of 55 sediment samples were taken at different depths up to 111 m in two sampling
campaigns. Chemical analyses were carried out by gas chromatography-mass spectroscopy. The results indicate that: (1) significant
spatial variations exist, (2) levels of PAHs are related more strongly to the spatial distribution of sediments than to mineralogy/granulometry,
(3) the sediments are slightly-to-moderately contaminated by PAHs, and (4) these PAHs derive from pyrolytic and petrogenic
sources. Through use of an innovative data classification system (proposed according to depth and spatial location of sampling
points), and using factorial and cluster techniques, five zones have been differentiated depending on the contamination level
and source. 相似文献
147.
Stefano Bianchi Giorgio Matt Fabrizio Nicastro Delphine Porquet Jacques Dubau 《Monthly notices of the Royal Astronomical Society》2005,357(2):599-607
We have calculated the equivalent widths of the absorption lines produced by Fe xxv and Fe xxvi in a Compton-thin, low-velocity photoionized material illuminated by the nuclear continuum in active galactic nuclei. The results, plotted against the ionization parameter and the column density of the gas, are a complement to those presented by Bianchi & Matt for the emission lines from the same ionic species. As an extension to the work by Bianchi & Matt, we also present a qualitative discussion on the different contributions to the He-like iron emission line complex in the regimes where recombination or resonant scattering dominates, providing a useful diagnostic tool to measure the column density of the gas. Future high-resolution missions (e.g. Astro-E2 ) will allow us to fully take advantage of these plasma diagnostics. In the meantime, we compare our results with an up-to-date list of Compton-thick and unobscured (at least at the iron line energy) Seyfert galaxies with emission and/or absorption lines from H- and He-like iron observed with Chandra and XMM–Newton . 相似文献
148.
Projection, or conjugate gradient like, methods are becoming increasingly popular for the efficient solution of large sparse sets of unsymmetric indefinite equations arising from the numerical integration of (initial) boundary value problems. One such problem is soil consolidation coupling a flow and a structural model, typically solved by finite elements (FE) in space and a marching scheme in time (e.g. the Crank–Nicolson scheme). The attraction of a projection method stems from a number of factors, including the ease of implementation, the requirement of limited core memory and the low computational cost if a cheap and effective matrix preconditioner is available. In the present paper, biconjugate gradient stabilized (Bi‐ CGSTAB) is used to solve FE consolidation equations in 2‐D and 3‐D settings with variable time integration steps. Three different nodal orderings are selected along with the preconditioner ILUT based on incomplete triangular factorization and variable fill‐in. The overall cost of the solver is made up of the preconditioning cost plus the cost to converge which is in turn related to the number of iterations and the elementary operations required by each iteration. The results show that nodal ordering affects the perfor mance of Bi‐CGSTAB. For normally conditioned consolidation problems Bi‐CGSTAB with the best ILUT preconditioner may converge in a number of iterations up to two order of magnitude smaller than the size of the FE model and proves an accurate, cost‐effective and robust alternative to direct methods. Copyright © 2001 John Wiley & Sons, Ltd. 相似文献
149.
150.
Massimiliano Favalli Fabrizio Innocenti Maria Teresa Pareschi Giorgio Pasquarè Stefano Branca 《Geodinamica Acta》2013,26(5):279-290
AbstractA Digital Elevation Model (DEM) of Mt. Etna is presented; it has altimetric and planimetric resolution of 1 m and 5 m, respectively, and covers an area of about 120 km . This 3-D view of Mt. Etna allowed both recognition and location of the main morphostructural and volcano-tectonic features of the volcano. A slope map has been generated from the DEM; on the basis of slope distributions and surface textures, five acclivity domains have been recognized. The largest domain, south of the summit craters, reflects the occurrence of old plateau lavas, distinct from central volcanoes which built the present Etnean volcanic system. Interaction between the central volcanoes, with their summit calderas and failed slopes, produced the other recognised domains. Furthermore, newly identified relevant morphostructural lines are discussed. © Elsevier, Paris 相似文献