全文获取类型
收费全文 | 916篇 |
免费 | 35篇 |
国内免费 | 8篇 |
专业分类
测绘学 | 39篇 |
大气科学 | 72篇 |
地球物理 | 236篇 |
地质学 | 398篇 |
海洋学 | 36篇 |
天文学 | 126篇 |
自然地理 | 52篇 |
出版年
2021年 | 9篇 |
2020年 | 14篇 |
2019年 | 9篇 |
2018年 | 31篇 |
2017年 | 16篇 |
2016年 | 24篇 |
2015年 | 29篇 |
2014年 | 40篇 |
2013年 | 56篇 |
2012年 | 45篇 |
2011年 | 49篇 |
2010年 | 48篇 |
2009年 | 58篇 |
2008年 | 33篇 |
2007年 | 26篇 |
2006年 | 25篇 |
2005年 | 26篇 |
2004年 | 32篇 |
2003年 | 15篇 |
2002年 | 13篇 |
2001年 | 18篇 |
2000年 | 17篇 |
1998年 | 14篇 |
1997年 | 15篇 |
1996年 | 17篇 |
1995年 | 16篇 |
1994年 | 9篇 |
1993年 | 9篇 |
1992年 | 9篇 |
1991年 | 10篇 |
1990年 | 9篇 |
1989年 | 7篇 |
1988年 | 8篇 |
1987年 | 11篇 |
1986年 | 7篇 |
1985年 | 8篇 |
1983年 | 10篇 |
1982年 | 8篇 |
1981年 | 8篇 |
1980年 | 10篇 |
1979年 | 10篇 |
1978年 | 10篇 |
1977年 | 6篇 |
1976年 | 5篇 |
1975年 | 6篇 |
1974年 | 5篇 |
1973年 | 10篇 |
1971年 | 5篇 |
1914年 | 7篇 |
1910年 | 5篇 |
排序方式: 共有959条查询结果,搜索用时 0 毫秒
31.
32.
Solubility of Pt in sulphide mattes: Implications for the genesis of PGE-rich horizons in layered intrusions 总被引:1,自引:0,他引:1
Raúl O.C. Fonseca Ian H. Campbell Hugh St. C. ONeill Charlotte M. Allen 《Geochimica et cosmochimica acta》2009,73(19):5764-5777
The partitioning of Pt in sulphide melt (matte) has been studied as a function of fS2 and fO2 at 1200 and 1300 °C. The results show that the solubility of Pt in mattes increases strongly with increasing fS2 and decreases weakly with increasing fO2. The increase in Pt solubility with increasing fS2 is attributed to Pt dissolving in the melt as a sulphide species and the weak inverse dependence of Pt solubility on fO2 to the diluting effect of increasing O in the melt at high fO2. These results, coupled with measurements of Pt solubility in silicate melts taken from the literature, allow the calculation of Pt matte/silicate-melt partition coefficients () for a range of conditions pertinent to the formation of Pt-rich horizons in layered intrusions. The calculated values range between 107 and 1011, depending on fO2 and fS2, several orders of magnitude higher than previously published values. Our preferred value for for conditions appropriate to the Merensky Reef is 107 and for the Stillwater Pt-rich horizon 108. The new results are consistent with the magmatic hypothesis for Pt-rich horizons in layered intrusions. 相似文献
33.
Paolo?A.?SossiEmail author Julie?Prytulak Hugh?St.?C.?O’Neill 《Contributions to Mineralogy and Petrology》2018,173(4):27
Vanadium has multiple oxidation states in silicate melts and minerals, a property that also promotes fractionation of its isotopes. As a result, vanadium isotopes vary during magmatic differentiation, and can be powerful indicators of redox processes at high temperatures if their partitioning behaviour can be determined. To quantify the partitioning and isotope fractionation factor of V between magnetite and melt, piston cylinder experiments were performed in which magnetite and a hydrous, haplogranitic melt were equilibrated at 800 °C and 0.5 GPa over a range of oxygen fugacities (\({f_{{{\text{O}}_{\text{2}}}}}\)), bracketing those of terrestrial magmas. Magnetite is isotopically light with respect to the coexisting melt, a tendency ascribed to the VI-fold V3+ and V4+ in magnetite, and a mixture of IV- and VI-fold V5+ and V4+ in the melt. The magnitude of the fractionation factor systematically increases with increasing log\({f_{{{\text{O}}_{\text{2}}}}}\) relative to the Fayalite–Magnetite–Quartz buffer (FMQ), from ?51Vmag-gl = ? 0.63?±?0.09‰ at FMQ ? 1 to ? 0.92?±?0.11‰ (SD) at ≈?FMQ?+?5, reflecting constant V3+/V4+ in magnetite but increasing V5+/V4+ in the melt with increasing log\({f_{{{\text{O}}_{\text{2}}}}}\). These first mineral-melt measurements of V isotope fractionation factors underline the importance of both oxidation state and co-ordination environment in controlling isotopic fractionation. The fractionation factors determined experimentally are in excellent agreement with those needed to explain natural isotope variations in magmatic suites. Furthermore, these experiments provide a useful framework in which to interpret vanadium isotope variations in natural rocks and magnetites, and may be used as a potential fingerprint the redox state of the magma from which they crystallise. 相似文献
34.
Hugh St. C. O'Neill Mark I. Pownceby Victor J. Wall 《Contributions to Mineralogy and Petrology》1989,103(2):216-222
The activity of FeTiO3 in the binary ilmenitepyrophanite (FeTiO3-MnTiO3) solid solution has been determined for the temperature range 1050–1300 K by displacement of the reaction: 2 FeTiO3=2 Fe+2 TiO2+O2 in T-O2 space, using an electrochemical technique with calcia- and yttria-stabilized zirconia solid electrolytes. The activities show small positive deviations from ideality, which, although the data are unusually precise, may be perfectly described by the simple regular solution model, with an interaction parameter, W
Fe-Mn
ilm
, of 2.2±0.3 kJ g-atom–1, which is independent of temperature. This value, together with the experimental data on the partitioning of Fe and Mn between ilmenite and garnet (Pownceby et al. 1987), gives W
Fe-Mn
gt
=1.2±0.5 kJ g-atom–1 for the almandine-spessartine (Fe3Al2Si3O12-Mn3Al2Si3O12) solid solution. 相似文献
35.
Potential of High-Resolution Satellite Data in the Context of Vulnerability of Buildings 总被引:1,自引:2,他引:1
High-resolution space-borne remote sensing data are investigated for their potential to extract relevant parameters for a
vulnerability analysis of buildings in European countries. For an evaluation of large earthquake scenarios, the number of
parameters in models for vulnerability is reduced to a minimum of relevant information such as the type of building (age,
material, number of storeys) and the geological and spatial context. Building-related parameters can be derived from remote
sensing data either directly (e.g. height) or indirectly based on the recognition of the urban structure type in which the
buildings are located. With the potential of a fully- or semi-automatic inventory of the buildings and their parameters, high-resolution
satellite data and techniques for their processing are a useful supporting tool for the assessment of vulnerability. 相似文献
36.
37.
Summary The paper presents a method of evaluating oscillations with a time-variable frequency using a computer. The given function is first interpolated at points which are not distributed equidistantly in time, but the digitizing step varies with time according to a known optional regularity. The spectrum of the obtained function is computed for various of these interpolations and tests are run to determine when the interpolation best compensates the time variation of the frequency. The initial and terminal frequency in the given sample is then determined. The usability of this method with respect to various types of oscillations with a variable frequency and its accuracy in comparison to sonagrams are discussed. 相似文献
38.
Volker Stähle 《Earth and Planetary Science Letters》1975,25(1):71-81
An extensive study of a big number of gneiss specimens with various shock features from the suevite allowed unravelling of the shock behavior of almandite garnets.Almandites in shocked metamorphic rocks show with increasing dynamic pressures strong irregular fracturing. differently oriented sets of planar fractures or elements, brown turbidity and nucleation of minute crystals of an unknown phase in solid garnets. At higher peak pressures garnet was found to break down to (1) orthopyroxene + spinel + glass, and to (2) spinel + glass due to fast shock-melting.Extensive quantitative electron microprobe studies of almandite garnets and their breakdown products were carried out. The breakdown products within the original grain boundaries of the garnets consist of an alumina-rich orthopyroxene (with up to 10 wt. % Al2O3), hercynite to pleonaste spinels and a silica and calcium-rich glass matrix. The chemical zonation of magnesium and manganese of the former garnets is inherited in the composition of the newly formed orthopyroxenes.Petrographic evidence and chemical composition suggest a fast breakdown of the almandite garnets after passing of shock waves at rapidly falling pressures and very high post-shock temperatures within the ejected gneissic rock material. 相似文献
39.
Karel Prikner Jaroslav Střeštík Karel Dobeš Reviewer M. Hvoždara 《Studia Geophysica et Geodaetica》1972,16(3):262-270
Summary The spectral analysis of samples of beating-type pc3 pulsations, recorded at the Budkov Observatory during the summer months of 1968 and 1969 was carried out in the frequency interval10 mHz100 mHz. The average limits of the pulsation frequency range are roughly20 mHz60 mHz. The centre of the occurrence frequency graphs for both components is at the frequency fg 41 mHz. The analysis of three separated daily intervals showed a very slight tendency to a systematic decrease in the frequency of the centre from the morning to the afternoon. The study of the sense of rotation of the pulsation disturbance vector in the (X, Y)-plane showed an overall predominancy of L over R-types during daytime, particularly during the morning. 相似文献
40.
The 2724–2722 Ma Stoughton-Roquemaure Group (SRG) of the Abitibi greenstone belt (the Archean Superior Province, Canada) is a ≤ 2 km thick komatiite–basalt succession intermittently exposed for about 50 km along strike. The ultramafic and mafic rocks occur mainly as pillowed, brecciated, and massive flows with well preserved spinifex textures in the komatiites. Volcanological, comparative stratigraphic and geochemical studies of the group along a volcanic marker horizon at the base of the succession allow the assessment of magma emplacement processes and mantle source rocks. Major feeder channels, secondary distributary tubes surrounded by pillowed flows with minor breccias and hyaloclastites display facies architecture of small volume flow fields (1–2 km3). Within the SRG, Al-depleted (ADK; Barberton-type) and Al-undepleted (AUK; Munro-type) komatiitic lavas are intercalated with tholeiitic basalt flows at a m- to 10s of m scale. Basalts and komatiites are inferred to be mantle plume-related; both rock types form two groups with characteristics of ADK and AUK including Al2O3/TiO2 ~ 9–12 for ADK versus 17–22 for AUK, as well as (Gd/Yb)n with > 1.3 versus ~ 1, respectively. The interdigitation of compositionally different flow units, limited extent of SRG volcanic rocks and facies architecture with the prevalence of small volume flows argue for a relatively small, heterogeneous mantle plume during the incipient stage of the evolution of the Archean Abitibi belt. Assuming that the scale of heterogeneities is comparable to the field expression of compositional changes and stratigraphy, it can be suggested that geochemical plume ‘layering’ is on 10s to 100s of m-scale. The evolution of this Archean mantle plume from inception to demise compares favorably with the Yellowstone hotspot which is assumed to have developed over 17 m.y. and had a diameter of about 300 km. 相似文献