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61.
Konstantin D. Litasov Eiji Ohtani Akio Suzuki Kenichi Funakoshi 《Physics and Chemistry of Minerals》2007,34(3):159-167
High-pressure in situ X-ray diffraction experiment of Fe- and Al-bearing phase D (Mg0.89Fe0.14Al0.25Si1.56H2.93O6) has been carried out to 30.5 GPa at room temperature using multianvil apparatus. Fitting a third-order Birch–Murnaghan equation of state to the P–V data yields values of V 0 = 86.10 ± 0.05 Å3; K 0 = 136.5 ± 3.3 GPa and K′ = 6.32 ± 0.30. If K′ is fixed at 4.0 K 0 = 157.0 ± 0.7 GPa, which is 6% smaller than Fe–Al free phase D reported previously. Analysis of axial compressibilities reveals that the c-axis is almost twice as compressible (K c = 93.6 ± 1.1 GPa) as the a-axis (K a = 173.8 ± 2.2 GPa). Above 25 GPa the c/a ratio becomes pressure independent. No compressibility anomalies related to the structural transitions of H-atoms were observed in the pressure range to 30 GPa. The density reduction of hydrated subducting slab would be significant if the modal amount of phase D exceeds 10%. 相似文献
62.
Igor?S.?SharyginEmail authorView authors OrcID profile Anton?Shatskiy Konstantin?D.?Litasov Alexander?V.?Golovin Eiji?Ohtani Nikolay?P.?Pokhilenko 《Contributions to Mineralogy and Petrology》2018,173(3):22
We performed an experimental study, designed to reproduce the formation of an unusual merwinite?+?olivine-bearing mantle assemblage recently described as a part of a Ca-rich suite of inclusions in sublithospheric diamonds, through the interaction of peridotite with an alkali-rich Ca-carbonatite melt, derived from deeply subducted oceanic crust. In the first set of experiments, we studied the reaction between powdered Mg-silicates, olivine and orthopyroxene, and a model Ca-carbonate melt (molar Na:K:Ca?=?1:1:2), in a homogeneous mixture, at 3.1 and 6.5 GPa. In these equilibration experiments, we observed the formation of a merwinite?+?olivine-bearing assemblage at 3.1 GPa and 1200 °C and at 6.5 GPa and 1300–1400 °C. The melts coexisting with this assemblage have a low Si and high Ca content (Ca#?=?molar 100?×?Ca/(Ca?+?Mg)?>?0.57). In the second set of experiments, we investigated reaction rims produced by interaction of the same Ca-carbonate melt (molar Na:K:Ca?=?1:1:2) with Mg-silicate, olivine and orthopyroxene, single crystals at 3.1 GPa and 1300 °C and at 6.5 GPa and 1400 °C. The interaction of the Ca-carbonate melt with olivine leads to merwinite formation through the expected reaction: 2Mg2SiO4 (olivine)?+?6CaCO3 (liquid)?=?Ca3MgSi2O8 (merwinite)?+?3CaMg(CO3)2 (liquid). Thus, our experiments confirm the idea that merwinite in the upper mantle may originate via interaction of peridotite with Ca-rich carbonatite melt, and that diamonds hosting merwinite may have a metasomatic origin. It is remarkable that the interaction of the Ca-carbonate melt with orthopyroxene crystals does not produce merwinite both at 3.1 and 6.5 GPa. This indicates that olivine grain boundaries are preferable for merwinite formation in the upper mantle. 相似文献
63.
A. D. Chanyshev K. D. Litasov A. F. Shatskiy E. Ohtani 《Doklady Earth Sciences》2014,458(2):1277-1280
This work is one of the stages of study of the deep C-O-H fluid and investigates the behavior of polycyclic aromatic hydrocarbons (PAHs) under conditions of the Earth’s mantle. The composition of the C-O-H fluid in the upper mantle is estimated as a mixture of H2O and CH4 with a minor amount of H2 and heavier hydrocarbons. Some theoretical calculations show that the stability of heavy hydrocarbons (alkanes, alkenes, and PAHs) increases with an increase in temperature. This paper presents the results of an XRD study of PAHs stability in multianvil presses on a Spring-8 accelerator (Japan). The primary compositions were chosen according to the abundance of PAHs in nature. In situ diffraction spectrums were recorded to determine the PAHs stability field. It was established that the PAHs become unstable at a pressure of 6–9 GPa and a temperature of 873–1073 K. 相似文献
64.
Sujoy?GhoshEmail author Konstantin?Litasov Eiji?Ohtani 《Contributions to Mineralogy and Petrology》2014,167(2):964
We determined the melting phase relations, melt compositions, and melting reactions of carbonated peridotite on two carbonate-bearing peridotite compositions (ACP: alkali-rich peridotite + 5.0 wt % CO2 and PERC: fertile peridotite + 2.5 wt % CO2) at 10–20 GPa and 1,500–2,100 °C and constrain isopleths of the CO2 contents in the silicate melts in the deep mantle. At 10–20 GPa, near-solidus (ACP: 1,400–1,630 °C) carbonatitic melts with < 10 wt % SiO2 and > 40 wt % CO2 gradually change to carbonated silicate melts with > 25 wt % SiO2 and < 25 wt % CO2 between 1,480 and 1,670 °C in the presence of residual majorite garnet, olivine/wadsleyite, and clinoenstatite/clinopyroxene. With increasing degrees of melting, the melt composition changes to an alkali- and CO2-rich silicate melt (Mg# = 83.7–91.6; ~ 26–36 wt % MgO; ~ 24–43 wt % SiO2; ~ 4–13 wt % CaO; ~ 0.6–3.1 wt % Na2O; and ~ 0.5–3.2 wt % K2O; ~ 6.4–38.4 wt % CO2). The temperature of the first appearance of CO2-rich silicate melt at 10–20 GPa is ~ 440–470 °C lower than the solidus of volatile-free peridotite. Garnet + wadsleyite + clinoenstatite + carbonatitic melt controls initial carbonated silicate melting at a pressure < 15 GPa, whereas garnet + wadsleyite/ringwoodite + carbonatitic melt dominates at pressure > 15 GPa. Similar to hydrous peridotite, majorite garnet is a liquidus phase in carbonated peridotites (ACP and PERC) at 10–20 GPa. The liquidus is likely to be at ~ 2,050 °C or higher at pressures of the present study, which gives a melting interval of more than 670 °C in carbonated peridotite systems. Alkali-rich carbonated silicate melts may thus be produced through partial melting of carbonated peridotite to 20 GPa at near mantle adiabat or even at plume temperature. These alkali- and CO2-rich silicate melts can percolate upward and may react with volatile-rich materials accumulate at the top of transition zone near 410-km depth. If these refertilized domains migrate upward and convect out of the zone of metal saturation, CO2 and H2O flux melting can take place and kimberlite parental magmas can be generated. These mechanisms might be important for mantle dynamics and are potentially effective metasomatic processes in the deep mantle. 相似文献
65.
Eiji Sasao 《Island Arc》2013,22(2):170-184
A petrographic study of sandstones from the Miocene Mizunami Group in Central Japan has been performed on core samples from a single borehole, in order to evaluate the provenance of the sedimentary rock. Evaluation of the provenance is based on bulk mineral, heavy mineral and plagioclase contents and on whole rock chemical compositions. The sandstones studied are divisible into three types; the first type is characterized by the occurrence of biotite and plagioclase ranging from albite to oligoclase, the second type is characterized by the dominance of amphibole and labradorite with pyroxene (clinopyroxene > orthopyroxene), and the third type is characterized by the dominance of pyroxene (orthopyroxene > clinopyroxene) and andesine with lesser labradorite, bytownite and anorthite. The first type is interpreted to be derived from the basement granite, whereas the others were derived mostly from volcanic ash, judging from their mineral compositions. The volcanic activity that supplied the volcanic ash to the Mizunami Basin occurred in two phases, distinguishable by variations in their mineralogical and geochemical compositions, an indication of change in character of the volcanic activity. This petrographic study of the sandstones in the Mizunami Group suggests that unrecognized volcanic activity occurred around the Mizunami Basin, even though potential provenance of the volcanic ash has not yet been identified. 相似文献
66.
Eiji Watanabe Michio J. Kishi Akio Ishida Maki Noguchi Aita 《Journal of Oceanography》2012,68(5):703-718
The response of phytoplankton to the Beaufort shelf-break eddies in the western Arctic Ocean is examined using the eddy-resolving coupled sea ice–ocean model including a lower-trophic marine ecosystem formulation. The regional model driven by the reanalysis 2003 atmospheric forcing from March to November captures the major spatial and temporal features of phytoplankton bloom following summertime sea ice retreat in the shallow Chukchi shelf and Barrow Canyon. The shelf-break warm eddies spawned north of the Barrow Canyon initially transport the Chukchi shelf water with high primary productivity toward the Canada Basin interior. In the eddy-developing period, the anti-cyclonic rotational flow along the outer edge of each eddy moving offshore occasionally traps the shelf water. The primary production inside the warm eddies is maintained by internal dynamics in the eddy-maturity period. In particular, the surface central area of an anti-cyclonic eddy acquires adequate light, nutrient, and warm environment for photosynthetic activity partly attributed to turbulent mixing with underlying nutrient-rich water. The simulated biogeochemical properties with the dominance of small-size phytoplankton inside the warm eddies are consistent with the observational findings in the western Arctic Ocean. It is also suggested that the light limitation before autumn sea ice freezing shuts down the primary production in the shelf-break eddies in spite of nutrient recovery. These results indicate that the time lag between the phytoplankton bloom in the shelf region following the summertime sea ice retreat and the eddy generation along the Beaufort shelf break is an important index to determine biological regimes in the Canada Basin. 相似文献
67.
Yuki Shibazaki Eiji Ohtani Hiroshi Fukui Takeshi Sakai Seiji Kamada Daisuke Ishikawa Satoshi Tsutsui Alfred Q.R. Baron Naoya Nishitani Naohisa Hirao Kenichi Takemura 《Earth and Planetary Science Letters》2012
We have determined the density evolution of the sound velocity of dhcp-FeHx (x ≈ 1) up to 70 GPa at room temperature, by inelastic X-ray scattering and by X-ray diffraction. We find that the variation of VP with density is different for the ferromagnetic and nonmagnetic dhcp-FeHx, and that only nonmagnetic dhcp-FeHx follows Birch's law. Combining our results with Birch's law for iron and assuming an ideal two-component mixing model, we obtain an upper bound of the hydrogen content in the Earth's inner core, 0.23(6) wt.% H, corresponding to FeH0.13(3). The iron alloy with 0.23(6) wt.% H can satisfy the density, and compressional and shear sound velocities of the PREM inner core, assuming that there are no other light elements in the inner core. 相似文献
68.
LQR control with frequency‐dependent scheduled gain for a semi‐active floor isolation system
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Yundong Shi Tracy C. Becker Sachi Furukawa Eiji Sato Masayoshi Nakashima 《地震工程与结构动力学》2014,43(9):1265-1284
Floor isolation is an alternative to base isolation for protecting a specific group of equipment installed on a single floor or room in a fixed‐base structure. The acceleration of the isolated floor should be mitigated to protect the equipment, and the displacement needs to be suppressed, especially under long‐period motions, to save more space for the floor to place equipment. To design floor isolation systems that reduce acceleration and displacement for both short‐period and long‐period motions, semi‐active control with a newly proposed method using the linear quadratic regulator (LQR) control with frequency‐dependent scheduled gain (LQRSG) is adopted. The LQRSG method is developed to account for the frequency characteristics of the input motion. It updates the control gain calculated by the LQR control based on the relationship between the control gain and dominant frequency of the input motion. The dominant frequency is detected in real time using a window method. To verify the effectiveness of the LQRSG method, a series of shake table tests is performed for a semi‐active floor isolation system with rolling pendulum isolators and a magnetic‐rheological damper. The test results show that the LQRSG method is significantly more effective than the LQR control over a range of short‐period and long‐period motions. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
69.
Mineral physics data related to the deep dehydration of stagnant slabs are summarized. The hydrogen diffusion in minerals of the mantle transition zone is not fast enough to homogenize the transition zone on the geological time scale, and hydrogen is expected to be unevenly distributed there. The hydrous fluid formed in the transition zone tends to percolate into shallower depths to form gravitationally stable hydrous magmas at the base of the upper mantle. We need further studies on the relation of intraplate volcanism above the stagnant slab and deep dehydration, because we expect the geochemical fingerprints of deep dehydration to be quite different from those of shallow dehydration from the subducting slabs. 相似文献
70.
Single crystalline San Carlos olivine (1 mm cube) was transformed to (Mg,Fe)2SiO4β-phase at 13.5–15 GPa, 1030–1330 °C for 0–600 min using a multi-anvil high pressure apparatus. The α-β transformation occurred
by incoherent surface nucleation and interface-controlled growth and recovered partially transformed samples showed sharply
defined reaction rim. The growth rate of the β-phase rim significantly decreased with time and the growth eventually ceased.
TEM observations revealed that many dislocations were created in both the relict olivine just near the α-β interface and the
β-phase in the rim, which show evidence for deformation caused by interfacial stresses associated with the misfit elastic
strain of the transformation. The observed tangled dislocation texture in β-phase suggested that the β-phase rim was hardened
and relaxation of the interfacial stress was retarded. This probably caused a localized pressure drop in the relict olivine
and decreased the growth rate. Time-dependent growth rates of β-phase is possibly controlled by the rheology of β-phase, which
must be considered for the prediction of the olivine metastability in the subducting slabs.
Received: 24 January 1997 / Revised, accepted: 24 July 1998 相似文献