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161.
The effect of regional ocean loading on predicted rates of crustal uplift and gravitational change due to glacial isostatic adjustment (GIA) is determined for Antarctica. The effect is found to be significant for the ICE-3G and ICE-5G loading histories (up to ?8 mm/year and ?3 mm/year change in uplift rate and ?3 cm/year and ?1 cm/year equivalent water height change (EWHC) of surface mass, respectively). The effect is smaller (+1 mm/year; +0.25 cm/year) for the IJ05 loading history. The impact of ocean loading on the rate of change of the long-wavelength zonal harmonics of the Earth’s gravitational field is also significantly smaller for IJ05 than ICE-3G. A simple analytical formula is derived that is accurate to about 3% in a root-mean-square sense that relates predicted or observed gravitational change at the surface of the Earth (r = a) to the EWHC. A fundamental difference in the definition of the load histories accounts for the differing sensitivities to ocean loading. IJ05 defines its surface load history relative to the present-day surface load, rather than specifying an absolute loading history, and thus implicitly approximates the temporal and spatial mass exchange between grounded ice and open ocean. In contrast, ICE-3G and ICE-5G specify an absolute load history and explicit regional ocean loading substantially perturbs predicted GIA rates. Conclusions of previous studies that used IJ05 predictions without ocean loading are relatively robust. 相似文献
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163.
In this contribution, the regularized Earth’s surface is considered as a graded 2D surface, namely a curved surface, embedded
in a Euclidean space . Thus, the deformation of the surface could be completely specified by the change of the metric and curvature tensors, namely
strain tensor and tensor of change of curvature (TCC). The curvature tensor, however, is responsible for the detection of
vertical displacements on the surface. Dealing with eigenspace components, e.g., principal components and principal directions
of 2D symmetric random tensors of second order is of central importance in this study. Namely, we introduce an eigenspace
analysis or a principal component analysis of strain tensor and TCC. However, due to the intricate relations between elements
of tensors on one side and eigenspace components on other side, we will convert these relations to simple equations, by simultaneous
diagonalization. This will provide simple synthesis equations of eigenspace components (e.g., applicable in stochastic aspects).
The last part of this research is devoted to stochastic aspects of deformation analysis. In the presence of errors in measuring
a random displacement field (under the normal distribution assumption of displacement field), the stochastic behaviors of
eigenspace components of strain tensor and TCC are discussed. It is applied by a numerical example with the crustal deformation
field, through the Pacific Northwest Geodetic Array permanent solutions in period January 1999 to January 2004, in Cascadia
Subduction Zone. Due to the earthquake which occurred on 28 February 2001 in Puget Sound (M
w > 6.8), we performed computations in two steps: the coseismic effect and the postseismic effect of this event. A comparison
of patterns of eigenspace components of deformation tensors (corresponding the seismic events) reflects that: among the estimated
eigenspace components, near the earthquake region, the eigenvalues have significant variations, but eigendirections have insignificant
variations. 相似文献
164.
165.
Francis Albarède Erik E. Scherer Minik Rosing Martin Bizzarro 《Geochimica et cosmochimica acta》2006,70(5):1261-1270
When recent geological calibrations of the 176Lu decay constant are used, the 176Lu-176Hf ages of chondrites are consistently 4% too old (∼4.75 Ga). Here, we suggest that this discrepancy reflects the photoexcitation of the long-lived 176Lu ground state to the short-lived isomeric state (T1/2 = 3.7 h) by γ-rays irradiating early condensates. Irradiation may have been of solar origin and taking place at the inner edge of the nebular disk. Alternatively, the source of γ-rays could have been one or more supernova(e) exploding in the vicinity of the solar nebula. Such photoexcitation has been experimentally observed, but requires γ-ray photons that have energies in excess of 838 keV. At this stage, we cannot assess whether the Hf isotope composition of the Bulk Silicate Earth differs from that of chondrites, eucrites, and the 4.56 Ga old Martian meteorite ALH84001, and therefore, whether the precursor material for these different planetary bodies received comparable fluences of γ-rays. 相似文献
166.
167.
Nils Aall Barricelli Tormod Clemetsen Kjell Aashamar Erik Bølviken 《Earth, Moon, and Planets》1979,21(4):419-437
In this paper we describe a CDC-Cyber 74 program for computer simulation of the evolution of a system consisting of a large number of objects in orbit around a central body or primary. Some preliminary tests done with the program will also be described. 相似文献
168.
We have measured the habit planes of plate rhabdites [(Fe, Ni)3P] with respect to the parent kamacite phase (α, Fe-Ni) in eight hexahedrites. This was accomplished using x-ray diffraction plus two-surface trace analysis. Results show that plate rhabdites form on either {001} or {122} planes in the parent kamacite. The meteorite Uwet exhibits a {112} habit plane which is possibly an anomaly due to the occurrence of a large shock event during rhabdite nucleation (~ 550–650 °C). 相似文献
169.
170.