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11.
O. V. Andreeva 《Geology of Ore Deposits》2012,54(1):41-59
Mineral transformation of host rocks and localization of orebodies at the unconformity-type uranium deposits are considered
for the Karku deposit in the northern Ladoga region. It is shown that the great depth of uranium mineral formation and the
peculiar composition of host rocks, along with temperature and chemistry of fluids, played a critical role in variation of
lithostatic and fluid pressure, porosity, and permeability. The compaction of quartz sandstone and gravelstone, which are
typical host rocks at unconformity-type deposits, the development of microstylolithic sutures, conformal structures, pressure
solution and deposition of quartz in free pores gave rise to the closure or constraint of pore space and to increase in pore
pressure of fluids in the deep part of the Riphean troughs with approaching lithostatic loading. A transitional zone between
hydrostatic and lithostatic pressure controlled localization of orebodies and was decisive for uranium mineral formation.
This zone coincided with the Riphean-Paleoproterozoic unconformity and sank somewhat into the crystalline basement. Below
this transitional zone, the intergranular fluid was under a pressure that was close to the pressure on solid phases, i.e.,
P
tot ≈ P
fl. The reliability of this phenomenon is confirmed by cessation of pressure solution-redeposition of quartz and distinct deceleration
of dehydration of hydrous minerals. As is shown for the Karku deposit, the highly hydrated clay minerals of the illite-smectite
series are widespread in its subore portion and lacking at the supraore levels along with termination of quartz regeneration.
It is suggested that a zone of superhigh fluid pressure in deep parts of sedimentary basins constrains localization of uranium
orebodies by structural and stratigraphic unconformity between Riphean and Paleoproterozoic rocks. It is stated that altered
wall rocks at the unconformity-type uranium deposits cannot be identified with products of hydrothermal phyllic and argillic
alteration of host rocks at the medium- and low-temperature endogenic deposits. The main distinctions consist in lack of wall-rock
metasomatic reaction zoning and acid-alkaline evolution of solutions. All transformations of host rocks should be classified
as diverse manifestations of deep catagenesis of sedimentary sequences and buried regolith. The carbon and oxygen isotopic
compositions of calcite from host rocks at the Karku deposit are far from those of magmatic and hydrothermal carbonates. They
are characterized by a high δ18O = +17 to +25‰ and a high dispersion of δ13C = −1.5 to almost −15‰. No granitoid magmatism is known in the regions, where the unconformity-type uranium deposits occur.
Therefore, the rocks of the crystalline basement are the most probable source of uranium, which precipitated on the reductive
barrier as a product of interaction with bitumen contained in the Riphean basal beds. 相似文献
12.
13.
14.
N. A. Andreeva Yu. L. Zyskin O. R. Kalekin Yu. I. Neshpor A. A. Stepanyan V. P. Fomin N. N. Chalenko V. G. Shitov 《Astronomy Letters》2000,26(4):199-203
We present two-year-long observations of the flux of very-high-energy (~1012 eV) gamma rays from the active galactic nucleus Mk 501 performed with a Cherenkov detector at the Crimean Astrophysical Observatory. A gamma-ray flux from the object was shown to exist at confidence levels of 11 and 7 standard deviations for 1997 and 1998, respectively. The flux varied over a wide range. The mean flux at energies >1012 eV, as inferred from the 1997 and 1998 data, is (5.0±0.6)×10?11 and (3.7±0.6)×10?11 cm?2 s?1, respectively. The errors are the sum of statistical observational and modeling errors. The mean power released in the form of gamma rays is ~2×1043 erg s?1 sr?1. 相似文献
15.
L.A. Andreeva I.S. Ivchenko G.P. Milinevsky V.A. Rozhansky Yu.Ya. Ruzhin V.S. Skomarovskyi L.D. Tsendin 《Planetary and Space Science》1984,32(8):1045-1052
Data on the evolution of the density profiles of the neutral and ionized components of barium clouds obtained in “Spolokh” experiments are presented. The ion density in the cigar-like structure exceeds by more than an order of magnitude that of the background plasma, while the density in the plasma tail out flowing from the cigar-like structure is of the same order as that of the background plasma. The Ba+ outflow rate is determined. The results agree with observed cloud motion and with the estimates following from Dzubenko et al. (1983). 相似文献
16.
Integrated geological and geophysical investigation of bottom sediments in the Medvezhii Island region, southwestern margin of the Barents Sea, has made it possible to characterize sediments of diverse types related to the action of hydrocarbon fluids, hemipelagic sedimentation, slope phenomena, and combined influence of all these factors. Relatively homogeneous (in terms of mechanical composition) sediments are subdivided into several lithogenetic types based on the grain size distribution. Relationships of clay minerals, as well as their morphological and structural peculiarities, are described for each type. It is demonstrated that sediments formed under the substantial influence of hydrocarbon fluid fluxes are characterized by a high (relative to hemipelagic sediments) content of smectites and mixed-layer clay minerals of the illite–smectite series. It is assumed that these minerals are authigenic formations in mud volcanic rocks and diapir material. Based on the comparison of clay minerals contents primary source of the material for redeposited sediments has been reconstructed. 相似文献
17.
The space and time dynamics of organic matter concentration in groundwater in the Tungusskoe deposit during the historical 2013 flood in the Amur River is discussed. For comparison analysis, several methods for determining the quantitative characteristics of organic matter (spectrophotometry, gas-chromatographic mass spectrometry, and high-performance liquid chromatography) were applied to different layers of an aquifer at different distances from the shore line. The genesis of many organic substances is due to the inflow of river filtrate and surface water from the inundated floodplain. In the post-flood 2014, groundwater showed a decrease in the total amount of organic components and the presence of low-molecular hydrocarbons, diphenylamine, cosanes, phenanthrene, naphthalene, and derivatives of stearic and palmitic acids. Toxic methyl benzene was identified in most wells. 相似文献
18.
19.
N. K. Andreeva N. A. Kagramanyan T. N. Kheraskova 《Lithology and Mineral Resources》2000,35(4):373-389
New data on the stratigraphy and composition of the Devonian rocks of the Moscow Syneclise were used. Facies-paleogeographic
schemes were compiled for the Lochkovian, Eifelian, Givetian, early-middle Frasnian, late Frasnian, and early-late Famennian
evolutionary stages of the Moscow Syneclise. Seven sedimentation cycles were developed due to sealevel fluctuations and structural
rearrangements in the paleooceanic basins surrounding the East European Platform at that time. The inference was made on the
structural heterogeneity of the platform basement and on differentiated movements as well as on the strike-slip fault nature
of some fragments of the basement relative to each other in the Devonian. 相似文献
20.
On the basis of catalogs spanning more than 100 years, the focal mechanisms and seismicity in the continental and oceanic sides of deep trenches are analyzed. 相似文献