全文获取类型
收费全文 | 74篇 |
免费 | 0篇 |
专业分类
测绘学 | 1篇 |
大气科学 | 1篇 |
地球物理 | 10篇 |
地质学 | 48篇 |
海洋学 | 8篇 |
天文学 | 4篇 |
自然地理 | 2篇 |
出版年
2022年 | 5篇 |
2021年 | 1篇 |
2020年 | 4篇 |
2019年 | 3篇 |
2018年 | 6篇 |
2017年 | 7篇 |
2016年 | 2篇 |
2014年 | 5篇 |
2013年 | 8篇 |
2012年 | 2篇 |
2011年 | 5篇 |
2010年 | 3篇 |
2009年 | 5篇 |
2008年 | 2篇 |
2007年 | 3篇 |
2006年 | 2篇 |
2005年 | 1篇 |
2004年 | 1篇 |
2002年 | 2篇 |
2000年 | 2篇 |
1998年 | 1篇 |
1996年 | 1篇 |
1992年 | 2篇 |
1984年 | 1篇 |
排序方式: 共有74条查询结果,搜索用时 234 毫秒
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.
17.
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
18.
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
19.
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
20.
E. S. Andreeva B. A. Anoshin V. E. Kunitsyn E. A. Leont’eva 《Geomagnetism and Aeronomy》2011,51(6):783-793
The outputs of the IRI-2001 and NeQuick ionospheric models are compared with radio tomographic (RT) images of the ionosphere
near the crest of the equatorial anomaly (EA) between Manila and Shanghai (about 850 cross sections overall). The values of
the slant total electron content measured in an RT experiment as opposed to the corresponding values derived from the IRI-2001
and NeQuick models are analyzed. A comparison of model cross sections and ionosonde measurements revealed discrepancies in
the critical frequencies of the ionospheric F2 layer, which were the strongest in the region of high spatial gradients close to the crest of the EA. The specific features
of the dynamics of the EA are discussed based on the results of the models and radio tomography. Our analysis has shown that
the IRI-2001 and NeQuick models mainly reproduce the “plasma fountain effect” but are incapable of recognizing the stable
structural features of the EA observed on RT reconstructions, for example, the daytime orientation of the mature core of the
EA parallel to geomagnetic field lines. A method to correct the IRI-2001 and NeQuick models in the vicinity of the EA crest
is suggested. 相似文献