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1.
Segregation of incompatible elements at grain interfaces may have considerable influence on the physical and chemical properties of mantle rocks. Using a recently developed predictive model to estimate the interface enrichment of elements based on their mineral/melt partitioning (Hiraga and Kohlstedt, companion paper), we consider interface enrichment for a simplified model peridotite consisting of olivine, orthopyroxene, and clinopyroxene. Our calculated results reveal the following: (1) Significant amounts of heavy alkali elements and rare gases likely reside at grain-grain interfaces, whereas interface concentrations of less incompatible are less pronounced. (2) The contribution of the chemical components stored at interfaces to whole-rock chemistry strongly depends on mineral mode and, most importantly, on grain size. (3) Grain size reduction resulting from dynamic recrystallization can increase the total storage of highly incompatible elements on grain interfaces and thereby will diminish their concentration in mineral grains. (4) Analysis of Cs concentrations in mantle clinopyroxenes potentially provides estimates of the grain size of mantle rocks. (5) Transport through peridotite will be dominated by diffusion along interfaces rather than through grain interiors for elements less compatible than Lu. 相似文献
2.
3.
Tadashi Kondo Hiroshi Sawamoto Akira Yoneda Manabu Kato Akihito Matsumuro Takehiko Yagi Takumi Kikegawa 《Pure and Applied Geophysics》1993,141(2-4):601-611
A new multi-anvil type high-presure apparatus has been developed using sintered diamond anvils to generate pressures over 30 GPa and temperatures up to about 2000°C. A maximum sample volume of about 1 mm3 is available in this system. The pressure was confirmed by dissociation of forsterite into Mg-perovskite and periclase. The basic techniques and problems in utilizing sintered diamond in the MA8 type high-pressure apparatus are discussed with an emphasis on the future prospect of incorporating simultancous X-ray diffraction observation. 相似文献
4.
Sanae Koizumi Takehiko Hiraga Chihiro Tachibana Miki Tasaka Tomonori Miyazaki Tamio Kobayashi Asako Takamasa Naoki Ohashi Satoru Sano 《Physics and Chemistry of Minerals》2010,37(8):505-518
Synthesized mineral powders with particle size of <100 nm are vacuum sintered to obtain highly dense and fine-grained polycrystalline
mantle composites: single phase aggregates of forsterite (iron-free), olivine (iron containing), enstatite and diopside; two-phase
composites of forsterite + spinel and forsterite + periclase; and, three-phase composites of forsterite + enstatite + diopside.
Nano-sized powders of colloidal SiO2 and highly dispersed Mg(OH)2 with particle size of ≤50 nm are used as chemical sources for MgO and SiO2, which are common components for all of the aggregates. These powders are mixed with powders of CaCO3, MgAl2O4, and Fe(CO2CH3)2 to introduce mineral phases of diopside, spinel, and olivine to the aggregates, respectively. To synthesize highly dense
composites through pressureless sintering, we find that calcined powders should be composed of particles that have: (1) fully
or partially reacted to the desired minerals, (2) a size of <100 nm and (3) less propensity to coalesce. Such calcined powders
are cold isostatically pressed and then vacuum sintered. The temperature and duration of the sintering process are tuned to
achieve a balance between high density and fine grain size. Highly dense (i.e., porosity ≤1 vol%) polycrystalline mantle mineral
composites with grain size of 0.3–1.1 μm are successfully synthesized with this method. 相似文献
5.
Takehiko Yagi Yoshiaki Ida Yosiko Sato Syun-Iti Akimoto 《Physics of the Earth and Planetary Interiors》1975,10(4):348-354
The pressure dependence of the three lattice parameters and unit cell volume of fayalite (Fe2SiO4 olivine) was determined by X-ray diffraction under hydrostatic pressures up to 70 kbar. In order to eliminate stress inhomogeneity within a composite material consisting of a specimen mixed with an internal-pressure standard, a liquid (1 : 1 mixture of ethanol and methanol) was used as a pressure-transmitting medium. The isothermal bulk modulus calculated on the basis of the second-order Birch-Murnaghan equation of state gives the values K0 = 1.19 ± 0.10 Mbar and K0′ = 7 ± 4, and if we assume K0′ = 5: K0 = 1.24 ± 0.02 Mbar. Three axes of fayalite were found to be compressible in the following order, b >c >a. Comparisons with the results obtained under non-hydrostatic compression are made. 相似文献
6.
Ken?NiwaEmail author Takehiko?Yagi Kenya?Ohgushi 《Physics and Chemistry of Minerals》2011,38(1):21-31
Compression behaviors of CaIrO3 with perovskite (Pv) and post-perovskite (pPv) structures have been investigated up to 31.0(1.0) and 35.3(1) GPa at room
temperature, respectively, in a diamond-anvil cell with hydrostatic pressure media. CaIrO3 Pv and pPv phases were compressed with the axial compressibility of β
a > β
c > β
b and β
b > β
a > β
c, respectively and no phase transition was observed in both phases up to the highest pressure in the present study. The order
of axial compressibility for pPv phase is consistent with the crystallographic consideration for layer structured materials
and previous experimental results. On the other hand, Pv phase shows anomalous compression behavior in b axis, which exhibit constant or slightly expanded above 13 GPa, although the applied pressure remained hydrostatic. Volume
difference between Pv and pPv phases was gradually decreased with increasing pressure and this is consistent with the results
of theoretical study based on the ab initio calculation. Present results, combined with theoretical study, suggest that these
complicate compression behaviors in CaIrO3 under high pressure might be caused by the partially filled electron of Ir4+. Special attention must be paid in case of using CaIrO3 as analog materials to MgSiO3, although CaIrO3 exhibits interesting physical properties under high pressure. 相似文献
7.
Taku Okada Takehiko Yagi Daisuke Nishio-Hamane 《Physics and Chemistry of Minerals》2011,38(4):251-258
The phase relations and compression behavior of MnTiO3 perovskite were examined using a laser-heated diamond-anvil cell, X-ray diffraction, and analytical transmission electron
microscopy. The results show that MnTiO3 perovskite becomes unstable and decomposes into MnO and orthorhombic MnTi2O5 phases at above 38 GPa and high temperature. This is the first example of ABO3 perovskite decomposing into AO + AB2O5 phases at high pressure. The compression behavior of volume, axes, and the tilting angle of TiO6 octahedron of MnTiO3 perovskite are consistent with those of other A2+B4+O3 perovskites, although no such decomposition was observed in other perovskites. FeTiO3 is also known to decompose into two phases, instead of transforming into the CaIrO3-type post-perovskite phase and we argue that one of the reasons for the peculiar behavior of titanate is the weak covalency
of the Ti–O chemical bonds. 相似文献
8.
After syntheses of partially molten diopside-forsterite polycrystalline aggregates doped with various solutes, we analyzed the equilibrium segregation of Ni, Mn, Sr, Al, Yb, Y, Nd, La, and Ti at interfaces between diopside/diopside, diopside/forsterite and, forsterite/forsterite grains based on STEM/EDX (scanning transmission electron microscopy/energy dispersive X-ray spectrometry) to examine the effects of ionic size, valence state, co-segregation, and interface type on interface chemistry. We derive relationships between two quantities describing interface segregation and X-ray intensities acquired both from areas that include an interface and from areas that do not. These segregation quantities are (i) interface excess density and (ii) interface enrichment factor, which rely on Gibbsian thermodynamics and the Langmuir-McLean segregation model, respectively. Interface excess densities, which vary from −0.5 to 10 atoms/nm2, indicate that the level of interface excess density depends on solutes and sample assemblage. Interface enrichment factors, which range from almost 1 to 130, reveal that the ionic size of the solutes affects their segregation via production of misfit lattice strain due to the difference between the size of a solute ion and that of the ideal strain-free lattice site. The ionic sizes of Yb and Y are almost identical to the size of the strain-free site; however, their segregation is significant indicating that a difference in valence state between the host elements (i.e., Ca and Mg) and the solutes also drives segregation. In contrast to other solutes, segregation characteristics of Al differ from these simple segregation rules. Segregation quantities do not change with interface type, indicating that the number of sites available for segregants and the driving force for segregation are similar among type of interfaces. We compare the element partitioning between diopside-melt and diopside-interfaces within the same sample assemblages. These two partition coefficients coincide if we approximate the number of segregation sites at interfaces as equivalent to 2 mono-atomic layers. Examination of the energetics in crystal-melt partitioning reveals that the interface segregation energy is essentially equal to the solute solution energy in a crystal. 相似文献
9.
Akira Yamaguchi Takehiko Setoyanagi Mitsuru Ebihara 《Meteoritics & planetary science》2006,41(6):863-874
Abstract— We studied the texture, mineralogy, and bulk chemical composition of Dhofar 007, a basaltic achondrite. Dhofar 007 is a polymict breccia that is mostly composed of coarse‐grained granular (CG) clasts with a minor amount of xenolithic components, such as a fragment of Mg‐rich pyroxene. The coarse‐grained, relict gabbroic texture, mineral chemistry, and bulk chemical data of the coarse‐grained clast indicate that the CG clasts were originally a cumulate rock crystallized in a crust of the parent body. However, in contrast to monomict eucrites, the siderophile elements are highly enriched and could have been introduced by impact events. Dhofar 007 appears to have experienced a two‐stage postcrystallization thermal history: rapid cooling at high temperatures and slow cooling at lower temperatures. The presence of pigeonite with closely spaced, fine augite lamellae suggests that this rock was cooled rapidly from higher temperatures (>0.5 °C/yr at ˜1000 °C) than typical cumulate eucrites. However, the presence of the cloudy zone in taenite and the Ni profile across the kamacite‐taenite boundaries indicates that the cooling rate was very slow at lower temperatures (˜1–10 °C/Myr at <600–700 °C). The slow cooling rate is comparable to those in mesosiderites and pallasites. The two‐stage thermal history and the relative abundance of siderophile elements similar to those for metallic portions in mesosiderites suggest that Dhofar 007 is a large inclusion of mesosiderite. However, we cannot rule out a possibility that Dhofar 007 is an anomalous eucrite. 相似文献
10.
Asami Sano-Furukawa Takehiko Yagi Taku Okada Hirotada Gotou Takumi Kikegawa 《Physics and Chemistry of Minerals》2012,39(5):375-383
X-ray diffraction measurements of distorted rutile-type oxyhydroxides β-GaOOH, InOOH, β-CrOOH, and β-CrOOD were taken at a
maximum pressure of up to 35 GPa under quasi-hydrostatic conditions, at ambient temperature. Anomalies in the evolution of
the relative lattice constants and the axial ratios of β-GaOOH, InOOH, and β-CrOOD suggest anisotropic stiffening along the
a- and/or b-axes where the hydrogen bond is formed. The changes were observed at 15 GPa in β-GaOOH and InOOH and at 4 GPa in β-CrOOD.
The pressures were higher in oxyhydroxides that have longer O…O distances of the hydrogen bond at ambient pressure. In contrast,
such stiffening behavior was not observed in CrOOH, which has a significant short O…O distance and strong hydrogen bond. The
stiffening behaviors observed in the present study can be attributed to the symmetrization of the hydrogen bonds in oxyhydroxides,
as was previously found in δ-AlOOH(D). 相似文献