全文获取类型
收费全文 | 2339篇 |
免费 | 424篇 |
国内免费 | 504篇 |
专业分类
测绘学 | 212篇 |
大气科学 | 37篇 |
地球物理 | 686篇 |
地质学 | 1719篇 |
海洋学 | 191篇 |
天文学 | 10篇 |
综合类 | 148篇 |
自然地理 | 264篇 |
出版年
2024年 | 6篇 |
2023年 | 25篇 |
2022年 | 69篇 |
2021年 | 67篇 |
2020年 | 74篇 |
2019年 | 114篇 |
2018年 | 81篇 |
2017年 | 124篇 |
2016年 | 122篇 |
2015年 | 113篇 |
2014年 | 152篇 |
2013年 | 276篇 |
2012年 | 146篇 |
2011年 | 137篇 |
2010年 | 117篇 |
2009年 | 136篇 |
2008年 | 156篇 |
2007年 | 160篇 |
2006年 | 144篇 |
2005年 | 128篇 |
2004年 | 127篇 |
2003年 | 121篇 |
2002年 | 77篇 |
2001年 | 73篇 |
2000年 | 110篇 |
1999年 | 58篇 |
1998年 | 54篇 |
1997年 | 43篇 |
1996年 | 30篇 |
1995年 | 33篇 |
1994年 | 27篇 |
1993年 | 22篇 |
1992年 | 26篇 |
1991年 | 17篇 |
1990年 | 18篇 |
1989年 | 11篇 |
1988年 | 21篇 |
1987年 | 7篇 |
1986年 | 5篇 |
1985年 | 12篇 |
1984年 | 6篇 |
1983年 | 4篇 |
1982年 | 7篇 |
1981年 | 4篇 |
1980年 | 1篇 |
1979年 | 6篇 |
排序方式: 共有3267条查询结果,搜索用时 593 毫秒
991.
Rock relationships in the Mogok metamorphic belt, Tatkon to Mandalay, central Myanmar 总被引:5,自引:0,他引:5
A.H.G. Mitchell Myint Thein Htay Kyaw Min Htun Myint Naing Win Thura Oo Tin Hlaing 《Journal of Asian Earth Sciences》2007,29(5-6):891-910
The Mogok metamorphic belt (MMB), over 1450 km long and up to 40 km wide, consists of regionally metamorphosed rocks including kyanite and sillimanite schists and granites lying along the Western margin of the Shan Plateau in central Myanmar and continuing northwards to the eastern Himalayan syntaxis. Exposures in quarries allow correlation of Palaeozoic meta-sedimentary, early Mesozoic meta-igneous and late Mesozoic intrusive rocks within a 230 km long northerly-trending segment of the MMB, from Tatkon to Kyanigan north of Mandalay, and with the Mogok gemstone district 100 km to the northeast. Relationships among the metamorphic and intrusive rocks, with sparse published radiometric age controls, indicate at least two metamorphic events, one before and one after the intrusion of Late Jurassic to early Cretaceous calc-alkaline rocks. These relationships can be explained by either of two possible tectonic histories. One, constrained by correlation of mid-Permian limestones across Myanmar, requires early Permian and early Jurassic regional metamorphic events, prior to an early Tertiary metamorphism, in the western part of but within a Shan-Thai – western Myanmar block. The second, not compatible with a single laterally continuous Permian limestone, requires pre-Upper Jurassic regional metamorphism and orogenic gold mineralization in the Mergui Group and western Myanmar, early Cretaceous collision of an east-facing Mergui-western Myanmar island arc with the Shan Plateau, and early Tertiary metamorphism in the MMB related to reversal in tectonic polarity following the arc-Plateau collision. 相似文献
992.
Structural and geological characteristics of a “seismic gap” in the central part of the Kuril Island Arc 总被引:1,自引:0,他引:1
R. G. Kulinich B. Yu. Karp B. V. Baranov E. P. Lelikov V. N. Karnaukh M. G. Valitov S. M. Nikolaev T. N. Kolpashchnikova I. B. Tsoi 《Russian Journal of Pacific Geology》2007,1(1):3-14
The results of the cruise of R/V Akademik M.A. Lavrentiev conducted by the Pacific Institute of Oceanology, Far East Division of the Russian Academy of Sciences and the Shirshov Institute of Oceanology, Russian Academy of Sciences in August to September 2005 are considered. The aim of the works was to specify the tectonic structure, seismogenic potential, and tsunamigenic hazard of the central segment of the Kuril Island Arc. The complex studies involved single-channel seismic profiling, gravimetry, magnetometry, detailed bathymetry, dredge sampling of sea-floor rocks and sediments, and gas geochemistry. Geophysical and geological data are reported. It was demonstrated that the target area is an active tectonic destruction zone, the zone boundaries were outlined, and the main internal structural and compositional heterogeneities were identified. 相似文献
993.
Effect of brittle fracture on the rheological structure of the lithosphere and its application in the Ordos 总被引:2,自引:0,他引:2
An empirical formula for the fracture strength of the principal rock type in the lithosphere is obtained based on the experimental data from previous studies, in which the effects of the confining pressure, size of the rock sample, temperature, strain rate and the pore pressure are taken into account, the empirical formulae for the effects of them are also presented. By comparing the frictional strength to the fracture strength calculated using the new empirical formula, it is shown that frictional sliding is dominant in the upper crust but brittle fracture is dominant in the lower part of the crust and the lithosphere beneath the crust. Therefore the fracture mechanism must be taken into account in the study of the rheological structure of the lithosphere. The empirical formula for the fracture strength is applied to study the rheological structure of the lithosphere in the Ordos block. Brittle regime in the rheological structure can be divided into two sub-regions, in one of which brittle fracture and in the other frictional sliding are dominant, respectively, unlike previous conventional studies in which frictional sliding is assumed to be the only factor; the magnitude of the rheological strength of the lithosphere calculated by the empirical formula is also lower than that obtained in previous conventional studies. 相似文献
994.
Clive E. Willman 《Mineralium Deposita》2007,42(5):449-463
The Bendigo and Castlemaine goldfields are classic examples of structurally controlled orogenic gold deposits in the Bendigo
Zone of central Victoria, SE Australia. Detailed mapping and biostratigraphic interpretation has led to a better understanding
of the regional structural controls of this type of gold-quartz mineralisation. Mineralised quartz veins are hosted by the
Castlemaine Group, an Early-to-Middle Ordovician turbidite succession at least 3,000 m thick. Gold deposits are controlled
by low-displacement faults that are clustered into several belts (the goldfields) indicating a regional structural control.
The timing of mineralisation overlapped with that of the major period of deformation including folding, cleavage development
and regional faulting. The Bendigo and Castlemaine goldfields are located in an area termed the Whitelaw thrust sheet bounded
by two unmineralised, high-displacement, regional-scale faults. Mapping has revealed an interrelationship between the regional-scale
faults, regional structural style and goldfield location. The goldfields lie immediately west of the boundary between the
upper and lower portions of the thrust sheet and are characterised by symmetric folds with sub-horizontal to synclinal enveloping
surfaces, relatively low co-axial strains and moderate cleavage development. The non-gold-bearing areas immediately east of
each goldfield correspond with the lower part of the Whitelaw thrust sheet and are characterised by higher non-coaxial strains,
stronger cleavage and folds with wide west-dipping limbs giving rise to easterly vergent sections and steeply west-dipping
enveloping surfaces. That mineralisation was an integral part of the thin-skinned style of deformation in the central Bendigo
Zone is indicated by timing relationships and the interrelationship between local-scale mineralised structures and regional-scale
features such as large-displacement unmineralised faults, regional variations in fold style and overall thrust sheet geometry.
The work supports previous models that suggest mineralised fluids were focussed along a linked system of deep-seated faults.
The primary conduits may have been major regional-scale ‘intrazone’ faults, which are inferred to sole into detachments near
the base of the Castlemaine Group. It is proposed that these structures linked with minor intrazone faults and then with networks
of low-displacement mineralised faults that were strongly controlled by folds. The location of minor intrazone faults was
probably controlled by internal thrust sheet geometry. The distribution of gold deposits and of gold production suggests that
maximum fluid flow was concentrated along the eastern margins of networks of low-displacement faults. 相似文献
995.
Elemental and Sm-Nd isotopic geochemistry on detrital sedimentary rocks in the Ganzi-Songpan block and Longmen Mountains 总被引:1,自引:0,他引:1
Chen Yuelong Liu Fei Zhang Hongfei Nie Lanshi Jiang Liting 《Frontiers of Earth Science》2007,1(1):60-68
Systematic results of major and trace element geochemistry and Sm-Nd isotopic geochemistry on detrital sedimentary rocks of
Precambrian to Triassic in the Ganzi-Songpan block and Longmen Mountains are presented. The rocks are classified into greywackes
or feldspar sandstones, grains of which are the mixtures of mafic rocks, felsic rocks, and quartz+calcite. Total rare earth
elements (REE) contents of the rocks increase gradually and negative Eu anomalies become more obvious from Precambrian to
Triassic, which may indicate intensifying crustal anatexis. Tectonic setting was stable during the Late Paleozoic, therefore
there are obvious negative Ce anomalies. Nd model ages are between 1.6 Ga and 2.4 Ga, which are very similar to those of the
Yangtze craton, South Qinling and North Qinling belts and quite different from those of the North China craton. Therefore,
provenance of the sedimentary rocks in the Ganzi-Songpan block and Longmen Mountains was the Yangtze craton and/or the Qinling
orogen, which evolved on the basis of the Yangtze craton. The correlation between provenances and tectonostratigraphic strata
of the western Yangtze craton shows that the source materials should be primarily from Neoproterozoic. Secondary sources were
Archean and Paleoproterozoic strata. Triassic clastic sedimentary rocks contain Late Paleozoic mantle-derived materials, represented
by the Emeishan Permian flood basalts. Spatial distribution of initial Nd isotopic compositions indicates that denudating
areas were in the east and the north and depositing areas of deep water were in the west and the south for the Ganzi-Songpan
basin during Triassic.
Translated from Geology in China, 2006, 33(1): 109–118 [译自: 中国地质] 相似文献
996.
The active role of fluids in the formation of ore-localizing structures expressed in dilatancy and hydraulic fracturing is suggested from the results of detailed comprehensive study of the Tokur gold deposit in the Upper Amur region, Russia, and the surveying of the published data on fluid pressure that characterizes formation of other hydrothermal deposits different in depth, morphology of orebodies, and their localization with respect to rocks of various permeability. Development conditions and possible implications of hydraulic fracturing for ore formation are considered. Indications of involvement of this mechanism in the orebody formation at the Pokrovsky, Berezovsky, and Nezhdaninsky gold deposits in Russia and the Bendigo deposit in Australia are discussed. 相似文献
997.
Preliminary results of an optically stimulated luminescence dating study in the western Murray Basin in semi-arid south-eastern Australia are presented. The ultimate objective of the dating study is a reconstruction of dune formation indicative of palaeoclimatic changes in this region. So far, one site has been dated using the single-aliquot regenerative (SAR) dose protocol for quartz. A high scatter in individual palaeodoses was observed, which is unexpected in supposedly well bleached aeolian deposits. Therefore other sources of variability such as microdosimetry and bioturbation have to be taken into account. Nevertheless, the resulting ages are in chronostratigraphic order and document a long aeolian record from 180 to 9 ka. 相似文献
998.
The Dongjiahe ophiolite complex occurring in the western Bikou terrane that is composed chiefly of serpentinite, listwanitizational peridotite, gabbro, cumulus gabbro, and sub-alkaline meta-basalt, possesses a rock association of typical ophiolite sequence. The metaperidotite is depleted in light rare earth element (LREE), whereas the gabbro and meta-basalt from the studied ophiolite sequence, generated by the same parental magmas those have close affinity to the MORB (Mid-ocean ridge basalt), their REE and immobile elements patterns imply an ocean in the northern margin of the Yangtze plate during the Neoproterozoic period. The zircon LA-ICP-MS U-Pb dating for the gabbro yields a weighted mean age of 839.2±8.2Ma, suggesting that the basin occurred during the Neoproterozoic period. 相似文献
999.
In this paper, we make a comparative analysis and correlation test for the seismic activities in the South Japan and the Ludong-Huanghai block (a secondary tectonic unit in the North China) and approach the relationship between the energy release processes of these two areas by using co-integration analysis and Granger causality test for the time series of random variables. The results show that the seismic activities in these two areas are correlative and synchronous to a certain extent, and their release series of cumulative strain energy are contemporaneously cor-relative. Both energy series are first-order difference stationary processes and there is secular and steady co-integration between them. We make a positive analysis on the first-order difference energy series through Granger causality test based on vector error correction (VEC) model and find there is unilateral Granger causality and prominent co-integration between the two energy release processes. 相似文献
1000.