全文获取类型
收费全文 | 20554篇 |
免费 | 2936篇 |
国内免费 | 4431篇 |
专业分类
测绘学 | 1491篇 |
大气科学 | 3064篇 |
地球物理 | 4255篇 |
地质学 | 10953篇 |
海洋学 | 2928篇 |
天文学 | 1910篇 |
综合类 | 1270篇 |
自然地理 | 2050篇 |
出版年
2024年 | 159篇 |
2023年 | 446篇 |
2022年 | 946篇 |
2021年 | 1211篇 |
2020年 | 1083篇 |
2019年 | 1131篇 |
2018年 | 1313篇 |
2017年 | 1254篇 |
2016年 | 1255篇 |
2015年 | 1035篇 |
2014年 | 1252篇 |
2013年 | 1296篇 |
2012年 | 1341篇 |
2011年 | 1427篇 |
2010年 | 1314篇 |
2009年 | 1251篇 |
2008年 | 1167篇 |
2007年 | 1238篇 |
2006年 | 1116篇 |
2005年 | 669篇 |
2004年 | 560篇 |
2003年 | 559篇 |
2002年 | 658篇 |
2001年 | 576篇 |
2000年 | 436篇 |
1999年 | 421篇 |
1998年 | 310篇 |
1997年 | 323篇 |
1996年 | 265篇 |
1995年 | 267篇 |
1994年 | 247篇 |
1993年 | 190篇 |
1992年 | 175篇 |
1991年 | 114篇 |
1990年 | 104篇 |
1989年 | 119篇 |
1988年 | 85篇 |
1987年 | 66篇 |
1986年 | 63篇 |
1985年 | 56篇 |
1984年 | 47篇 |
1983年 | 47篇 |
1982年 | 43篇 |
1981年 | 30篇 |
1980年 | 28篇 |
1979年 | 38篇 |
1977年 | 17篇 |
1976年 | 18篇 |
1975年 | 24篇 |
1973年 | 17篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
131.
132.
A possible mechanism of the ascent of material within the Earth’s crust and mantle is the mechanism of hydroextrusion, i.e.,
the effect of squeezing of material under excess pressure. The major factors that predetermine the high plasticity of the
material and its ability to produce hydroextrusions are high lithostatic pressures and temperatures. The phenomenon of hydroextrusion
can be most clearly illustrated by the example of the origin of salt diapirs. The driving force of hydroextrusions of material
in the crust and mantle is excess pressure, which can result from lateral differences between the densities of rocks (as is
the case during the development of salt diapirs) and phase transitions associated with a volume increase. When the material
of the upper mantle undergoes partial melting with the derivation of basaltic melts at depths of 60–100 km, excess pressures
reach 80 MPa, whereas the plasticity limit of 20% melted rocks is no higher than 5 MPa. As a result, the partially molten
material is forced from the melting region toward zones with lower lithostatic pressures. A local temperature increase in
the transitional zones in the Earth’s mantle at positive dP/dT values of the phase transitions also gives rise to excess pressures, whose values can range from 100 to 800 MPa at a 0.5–3.0%
volume change and which can be the driving force during the origin of mantle plumes.
Original Russian Text ? V.N. Anfilogov, Yu.V. Khachai, 2006, published in Geokhimiya, 2006, No. 8, pp. 873–878. 相似文献
133.
134.
135.
A. V. Maslov M. V. Isherskaya Yu. L. Ronkin M. T. Krupenin N. P. Gorbunova T. Ya. Gulyaeva O. P. Lepikhina O. Yu. Popova G. M. Yatluk 《Lithology and Mineral Resources》2006,41(3):250-270
Variation of geochemical modules and indices in mudstones from the Upper Vendian Kairovo and Shkapovo groups of the Shkapovo-Shikhan Basin provides the comprehensive information on changes in maturity of the fine aluminosiliciclastic material delivered in the basin, characterizes the redox environment in bottom water, and makes it possible to reconstruct the rock composition in provenance and its evolution through time. The generally moderate maturity of the fine terrigenous clastic material suggests that a nearly semiarid-semihumid climate dominated in paleodrainage area throughout the Late Vendian. It has been established that reducing environment did not exist in bottom water of the central Shkapovo-Shikhan Basin throughout the Late Vendian. Intermediate rocks prevailed in the paleodrainage area. More silicic rocks could occur only in the early Staropetrovo and late Salikhovo times. Data points of mudstones from the Kairovo and Shkapovo Groups plotted on the Cr-Ni, Co-V, Co/Hf-Ce/Cr, La-Th, and La/Sm-Sc/Th diagrams indicate that both Archean and more mature Paleoproterozoic crustal blocks existed in different proportions in the Late Vendian within source areas. 相似文献
136.
137.
138.
A. V. Maslov V. N. Podkovyrov Yu. L. Ronkin M. T. Krupenin E. Z. Gareev V. M. Gorozhanin 《Stratigraphy and Geological Correlation》2006,14(2):126-149
In the mid-1980s, it was concluded based on geochemical study that Th, Sc, La concentrations and ratios Th/Sc, La/Sc and Eu/Eu* did not wary significantly in the post-Archean time. It was impossible to judge about compositional variations of upper crust during the Riphean and Vendian, because data of that time characterized a limited number of samples from the post-Archean basins of Australia, New Zealand, and Antarctic. Considered in this work are variations of Eu/Eu*, LREE/HREE, Th/Sc, and La/Sc ratios in Upper Precambrian fine-grained siliciclastic rock of the Southern Urals western flank (Bashkirian meganticlinorium) and Uchur-Maya region (Uchur-Maya plate and Yudoma-Maya belt). As is established, only the Eu anomaly in the studied siliciclastic rocks is practically identical to this parameter of the average post-Archean shale. Three other parameters plot on the Riphean-Vendian variation curves with positive and negative excursions of diverse magnitude, which do not coincide always in time. It is assumed that these excursions likely mark stages of local geodynamic activity, destruction of pre-Riphean cratons, and progressing recycling of sedimentary material during the Riphean. 相似文献
139.
140.
The excitation of the ballooning instability by the eigenoscillations of coronal loops is analyzed using the energy method. The second variation of the potential energy for the case of a plasma—plasma boundary is obtained via the linearized ideal MHD equations. It is shown that the eigenmodes of a magnetic tube and of a toroidal coronal loop coincide in a first approximation. The bending oscillations of the loops are able to excite the ballooning instability when β ? 1. The effects of the instability in solar coronal loops are discussed. 相似文献