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1.
In situ strength measurements on natural upper-mantle minerals 总被引:1,自引:0,他引:1
Junji Yamamoto Jun-ichi Ando Hiroyuki Kagi Toru Inoue Akihiro Yamada Daisuke Yamazaki Tetsuo Irifune 《Physics and Chemistry of Minerals》2008,35(5):249-257
Using in situ strength measurements at pressures up to 10 GPa and at room temperature, 400, 600, and 700°C, we examined rheological
properties of olivine, orthopyroxene, and chromian-spinel contained in a mantle-derived xenolith. Mineral strengths were estimated
using widths of X-ray diffraction peaks as a function of pressure, temperature, and time. Differential stresses of all minerals
increase with increasing pressure, but they decrease with increasing temperature because of elastic strain on compression
and stress relaxation during heating. During compression at room temperature, all minerals deform plastically at differential
stress of 4–6 GPa. During subsequent heating, thermally induced yielding is observed in olivine at 600°C. Neither orthopyroxene
nor spinel shows complete stress relaxation, but both retain some stress even at 700°C. The strength of the minerals decreases
in the order of chromian-spinel ≈ orthopyroxene > olivine for these conditions. This order of strength is consistent with
the residual pressure of fluid inclusions in mantle xenoliths. 相似文献
2.
3.
Abstract— The lake Lappajärvi impact crater lies in Paleoproterozoic Svecofennian metasedimentary rocks, on the western side of the Central Finland granitoid complex (~1.9 Ga). Two conflicting ages have been reported for the meteorite impact: an age of 77.3 ± 0.4 Ma on the basis of Ar‐Ar whole‐rock data from impact melt samples and a paleomagnetic age of 195 Ma. During studies on impact crater indicator minerals at Lappajärvi, zircons with an atypical appearance were found in suevite boulders. These zircons seemed to have been affected by impact shock metamorphism and it was considered that they would be good candidates for ion microprobe U‐Pb dating, allowing a new and independent age estimate for the impact event at Lappajärvi. Four spot analyses on two black‐coated zircons plotted close to the upper intercept end of the concordia curve giving an approximate age of 1.8 Ga for the source rock. Seventeen analyses were done on three dull zircon grains showing patchy impact‐related partial recrystallization. Most of these data fell fairly well on a single discordia line with intercept ages of 73.3 ± 5.3 Ma and 1854 ± 51 Ma. However, five of the data spots near the lower intercept end fell on the younger side of the line. This was interpreted to indicate post‐impact loss of lead. Importantly, the new ion microprobe U‐Pb age of 73.3 ± 5.3 Ma is in a very good agreement with the previously reported Ar‐Ar age. 相似文献
4.
The Optimal Design of TMD for Offshore Structures 总被引:15,自引:0,他引:15
This paper presents the optimal design procedure of Tuned Mass Damper(TMD)for re-ducing vibration of an actual steel jacket offshore platform excited by random wave loading.In this study,a frequency domain is taken.The force on the structure is determined by use of the linearized Morisonequation for an input Power Spectral Density(PSD)of wave elevation.The sensitivity of optimum valuesof TMD to characteristic parameters of random wave spectrum is analyzed.An optimized TMD designfor the modeled platform is given based on design conditions and the findings of the study. 相似文献
5.
We conducted powder neutron diffraction for δ-AlOOH samples with and without Mg and Si ions under ambient conditions in order
to investigate the long-standing problem of the symmetry of this phase. The observed reflection conditions clearly show that
the space group of pure δ-AlOOH is P21
nm with ordered hydrogen bonds, whereas that of δ-(Al0.86Mg0.07Si0.07)OOH is Pnnm or Pnn2 with disordered hydrogen bonds. It is more likely that the space group of δ-(Al0.86Mg0.07Si0.07)OOH is Pnnm, because cation or hydrogen ordering that breaks the mirror plane perpendicular to c axis in the Pnnm structure would not occur. The previously reported inconsistency for the space group of this phase was caused by the substitution
of Mg and Si ions to Al site, i.e., the disordered cations with different valences may fluctuate hydrogen positions, and the
disordered hydrogen causes the symmetry change. 相似文献
6.
Hidemi Ishibashi Hiroyuki Kagi Shoko Odake Hiroyuki Ohfuji Hiroshi Kitawaki 《Geochemistry International》2016,54(10):882-889
Field Emission SEM (FESEM) textural observations, crystal size distribution (CSD) analyses, UV-excited luminescence imaging, and photoluminescence (PL) microspectroscopy excited by 488 nm laser were conducted on two texturally contrasting samples of carbonado, a kind of natural polycrystalline diamond from the Central African Republic (CAR). The investigated carbonado samples A and B show extremely different textures: sample A is made up of faceted crystals accompanied by abundant, small rectangular pores, whereas sample B has a granular texture with coarser crystals and scarce, large pores. Diamond crystals smaller than 2–3 µm are enriched in sample A but depleted in sample B. These textural features indicate that sample B diamonds were annealed under thermodynamically stable P–T conditions. The pore characteristics indicate that fluid permeability was higher for sample A than sample B. Photoluminescence (PL) spectra indicate that samples A and B correspond to Group A and B carbonados in the classification of Kagi et al. (1994), respectively, so that sample A reveals emissions from the H3 center without any N–V0 derived emission at 575 nm, whereas sample B shows emissions from the 3H center and the N–V0 defect. In addition, UV-excited luminescence images and photoluminescence spectra for sample B indicate that the rims of diamond crystals within several microns of a pore show luminescence features similar to those of Group AB carbonados (Kagi et al., 1994), indicating that this Group AB material was formed from Group B by irradiation from pore-filling, radioactive-element-bearing materials at a low temperature. The extent of the low-temperature irradiation is considered to depend on fluid permeability, and the Group A material was strongly irradiated due to its permeable texture whereas the Group B material was not significantly irradiated due to its less permeable granular texture. These results indicate that Group B carbonados have retained their original PL spectral features produced under high pressures and temperatures at mantle depths. 相似文献
7.
Hiroyuki Kagi Dmitry A. Zedgenizov Hiroaki Ohfuji Hidemi Ishibashi 《Geochemistry International》2016,54(10):834-838
We report cloudy micro- and nano-inclusions in a superdeep diamond from São-Luiz, Brazil which contains inclusions of ferropericlase (Mg, Fe)O and former bridgmanite (Mg, Fe)SiO3 and ringwoodite (Mg, Fe)2SiO4. Field emission-SEM and TEM observations showed that the cloudy inclusions were composed of euhedral micro-inclusions with grain sizes ranging from tens nanometers to submicrometers. Infrared absorption spectra of the cloudy inclusions showed that water, carbonate, and silicates were not major components of these micro- and nano-inclusions and suggested that the main constituent of the inclusions was infrared-inactive. Some inclusions were suggested to contain material with lower atomic numbers than that of carbon. Mineral phase of nano- and micro-inclusions is unclear at present. Microbeam X-ray fluorescence analysis clarified that the micro-inclusions contained transition metals (Cr, Mn, Fe, Co, Ni, Cu, Zn) possibly as metallic or sulfide phases. The cloudy inclusions provide an important information on the growth environment of superdeep diamonds in the transition zone or the lower mantle. 相似文献
8.
D. A. Zedgenizov A. L. Ragozin V. V. Kalinina H. Kagi 《Geochemistry International》2016,54(10):890-900
This paper discusses mineralogy of Ca-rich inclusions in ultra-deep (sublithospheric) diamonds. It was shown that most of the Ca-rich majoritic garnets are of metabasic (eclogitic) affinity. The observed variation in major and trace element composition is consistent with variations in the composition of the protolith and the degree of enrichment or depletion during interaction with melts. Major and trace element compositions of the inclusions of Ca minerals in ultra-deep diamonds indicate that they crystallized from Ca-carbonatite melts that were derived from partial melting of eclogite bodies in deeply subducted oceanic crust in the transition zone or even the lower mantle. The occurrence of merwinite or CAS inclusions in ultra-deep diamonds can serve as mineralogical indicators of the interaction of metaperidotitic and metabasic mantle lithologies with alkaline carbonatite melts. The discovery of the inclusions of carbonates in association with ultra-deep Ca minerals can not only provide additional support for their role in the diamond formation process but also help to define additional mantle reservoirs involved in global carbon cycle. 相似文献
9.
Kwangjin JU Moyngsuk KIL Sanghyok RI Tongchol KIM Lining ZHANG Maocang YAN Guangxu LIU 《海洋湖沼学报(英文)》2022,(1):336-346
Although the immunomodulatory activity of bamboo vinegar and charcoal powder (BVC) has been increasingly documented in domestic animals, the use of BVC as immun... 相似文献
10.
John K. Volkman Robert Alexander Robert Ian Kagi Garry Wayne Woodhouse 《Geochimica et cosmochimica acta》1983,47(4):785-794
Analyses of some Australian crude oils show that many contain varying concentrations of A/ B-ring demethylated hopanes. These range from C26 to C34 and have been identified from their retention times and mass spectral data as 17α(H)-25-norhopanes. Comparison of hopane and demethylated hopane concentrations and distributions in source-related, biodegraded oils suggests that demethylated hopanes are biotransformation products of the hopanes. Further, it appears that the process occurs at a late stage of biodegradation, after partial degradation of steranes has occurred. Demethylated hopanes are proposed as biomarkers for this stage of severe biodegradation. The presence of these compounds in apparently undegraded crude oils is thought to be due to the presence of biodegraded crude oil residues which have been dissolved by the undegraded crude oil during accumulation in the reservoir sands. The timing of hopane demethylation, relative to the degradation of other compounds, has been assessed and the progressive changes in crude oil composition with increasing extent of biodegradation have been identified. The use of demethylated hopanes as maturity parameters for severely biodegraded crude oils, and the applicability of established biomarker maturity parameters to such oils, are also discussed. 相似文献