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51.
Nobuyuki Oda 《Solar physics》1984,93(2):243-255
Time-sequential high quality photographs of the photospheric granule on a quiet region of the disc center obtained at the Pic-du-Midi Observatory by Kawaguchi are analyzed. The size variation of individual granules in the area of 54×52 on the photosphere are traced over a period of 4 min. The granules are classified according to their morphological features as follows. (1) Active granules, they repeat the expansion and the fragmentation. (2) Quiet granules, they do not alter the size noticeably during the observed time span. (3) Declining granules, they disappear without further fragmentation or merging.The distribution of active granules on the photosphere reveals a presence of a cellular pattern. The relationships between the cellular pattern and the brightness on the quiet photosphere are investigated. The results show that there is a good spatial correlation between them. The autocorrelation analysis shows a kind of periodicity on the photospheric intensity and its mean wavelengths are 11.3. The size of the cellular pattern is comparable, in magnitude, to that of mesogranulation found by Novemberet al. (1981) on the velocitygram obtained at the Sacramento Peak Observatory. Then the cellular pattern revealed by the chain of granules in the present study may be bentatively identified as the mesogranulation. The possible physical connection between the mesogranulation and the clumpy assemblage of active granules is briefly discussed. 相似文献
52.
A 27-kyr record of environmental change in central Asia inferred from the sediment record of Lake Hovsgol,northwest Mongolia 总被引:1,自引:0,他引:1
Takuma Murakami Nagayoshi Katsuta Koshi Yamamoto Nobuki Takamatsu Masao Takano Takefumi Oda Genki I. Matsumoto Kazuho Horiuchi Takayoshi Kawai 《Journal of Paleolimnology》2010,43(2):369-383
Geochemistry of a sediment core from Lake Hovsgol, northwest Mongolia provides a continuous, 27-kyr history of the response of the lake and the surrounding catchment to climate change. Principle component (PC) analysis of 19 major and trace elements, total inorganic carbon (TIC), and total organic carbon (TOC) in the bulk sediment samples revealed that the 21 chemical components can be grouped into four assemblages—group-1: Na, Mg, Ca, Sr, and TIC, hosted in carbonate minerals (calcite, dolomite, and magnesian calcite); group-2: Ni, Cu, and Zn, recognized as biophilic trace metals, and TOC; group-3: Al, K, Ti, V, Fe, Rb, Cs, Ba, and Pb, composed of rock-forming minerals; and group-4: Cr, Mn, and As, sensitive to the redox condition of the sediment. The four element assemblages originated from three relevant processes. Group-1 and group-2 components are authigenic products and comprise the end member on the PC-1 score, whose variation reflects changes in the water volume, i.e. the balance between precipitation and evaporation (P/E). Group-3 components from detrital materials of the catchment contribute to the PC-2 score, whose variability indicates erosion/weathering intensity in the drainage basin, which might be controlled by the amount of vegetation cover associated with moisture change. The group-4 components of redox-sensitive elements contribute to the PC-3 score and are not an end member because of their small amount. The first two PC scores suggest a sequential record of paleo-moisture evolution in central Asia. The P/E balance in the Lake Hovsgol region, inferred from the PC-1 score, gradually increased during the glacial/interglacial transition. This resembles climate change of the North Atlantic region on the glacial–interglacial scale, but does not reflect the abrupt climate shifts such as the warm Bølling-Allerød and the cold Younger Dryas of the North Atlantic on the millennial scale. A periodic variation of ~8.7 kyr was observed in the PC-2 score profile of detrital input to Lake Hovsgol over the last glacial and Holocene. The decrease in detrital input coincided with the copious supply of moisture from the Asian monsoon regime and the North Atlantic westerly winds to the Baikal drainage basin, which includes Lake Hovsgol. Our geochemical records from Lake Hovsgol demonstrate that the climate system of interior continental Asia was strongly influenced by change on both Milankovitch and sub-Milankovitch scales. 相似文献
53.
GeoJournal - Examining the spatial variation of surface temperature is an important criterion to create livable urban environment. To examine the cause of heat island variation in the study area... 相似文献
54.
Evaluation of Excess Pore Water Pressure Characteristics in Sand Mat Used for Recycling Dredged Soil
The design of sand mats should be reviewed on the basis of excess pore pressure behavior, which can be obtained by combining the characteristics of soft ground with the permeability of the mats. In this study, a banking model test was performed using dredged sand as the mat material to investigate the hydraulic gradient distribution of sand mats. The results were compared with numerical analysis results utilizing Terzaghi's one-dimensional consolidation equation. The results showed that the pore pressure was influenced by an increase in the amount of settlement at the central part of the sand mat as the height of the embankment increased. The measured decrease of the pressure head due to the residing water pressure in the sand mat was delayed compared to the numerical analysis results. Accordingly, sand mats should be laid to reduce the increased hydraulic gradient at the central part of the embankment. 相似文献
55.
ABSTRACTWhen dredged soil containing coarse soil is used for the construction of reclaimed ground that is in contact with the surface of seawater, there is a high possibility of the generation of nonuniformly reclaimed ground due to the segregation of fine-grained soil from coarse-grained soil. It is difficult to assume uniform properties of reclaimed ground because the properties are defined and formed by the spontaneously segregating sedimentation. Estimation of the soil’s volume change lacks accuracy if the properties of the reclaimed ground are assumed to be always uniform. Therefore, for pump-dredged reclamation, a predictive study and various experiments are required to estimate the physics and properties of the dredged soil sedimentation. Accordingly, this study demonstrates a modeling test to understand the characteristics of the sedimentary ground using the changing ratio of fraction of the sample passing through a 75-µm sieve. The effect of particle arrangement on hindered settling properties, sedimentation properties, the distribution of water content of sedimentary ground, and physical properties can be determined by the modeling test. The study also suggests the calculation method for the travel distance of the outlet and the volume of input soil based on the experimental results. 相似文献
56.
Minoru Oda 《Astrophysics and Space Science》1986,118(1-2):67-70
Japan's two X-ray astronomy satellites, HAKUCHO and TENMA, have been actively in operation leading to deeper understandings of the neutron star physics. Other satellite and balloon projects have been performed under international collaborators.Paper presented at the IAU Third Asian-Pacific Regional Meeting, held in Kyoto, Japan, between 30 September–6 October, 1984. 相似文献
57.
Y. Fukada S. Hayakawa I. Kasahara F. Makino Y. Tanaka H. Akiyama M. Matsuoka J. Nishimura M. Oda M. Nakagawa H. Sakurai V. S. Iyenger P. K. Kunte R. K. Manchanda B. V. Sreekantan 《Astrophysics and Space Science》1976,42(1):245-248
The size of the hard X-ray source in the Crab Nebula was observed with scintillation counters on board two balloons at a lunar occulatation on 24 January, 1975. The Gaussian width of the source is 34 (+17, –14) and the center thereof is offset from the pulsar by 6±4 at position angle 102°. The observed time profile can also be fitted to an alternative model of two line sources whose intensities are 48% at 11 and 25.5% at 7 on both sides of the pulsar.Paper presented at the COSPAR Symposium on Fast Transients in X- and Gamma-Rays, held at Varna, Bulgaria, 29–31 May, 1975. 相似文献
58.
Isao Motoyama Nobuaki Niitsuma Toshiaki Maruyama Hiroki Hayashi Shin-ichi Kamikuri Masamichi Shiono Toshiya Kanamatsu Kaori Aoki Chikako Morishita Kyoko Hagino Hiroshi Nishi Motoyoshi Oda 《Island Arc》2004,13(1):289-305
Abstract Shipboard and shore‐based investigation on siliceous and calcareous microfossil biostratigraphy, magneto‐stratigraphy and tephrostratigraphy identified numerous datum events from the sedimentary sequences of Sites 1150 and 1151 drilled on the forearc basin of northern Japan by the Ocean Drilling Program Leg 186. Some 83 datum events were selected to construct new age–depth models for the sites. Based on the reliable magneto‐stratigraphy from the Pleistocene to the Upper Miocene, which were correlated to the standard geomagnetic polarity timescale, and on excellent records of diatom and radiolarian biostratigraphy throughout the sequences, the shipboard age model was revised. Major revisions referred to stratigraphic position of the Miocene–Pliocene boundary that has been shifted more than 200 m downward in each sequence. The age–depth relations of the forearc sites represent drastic changes in the sedimentation rate—extremely high (40 cm/k.y. on average) in the Early Pliocene and low (less than 2 cm/k.y. on average) in the Middle Miocene—and several hiatuses exist throughout the sequence. The drastic changes can be related mostly to changes in diatom sedimentation and the tectonics of the Japanese Island Arc. Local ages for some foraminiferal, calcareous nannofossil and radiolarian bioevents are estimated from the age–depth models at each site. These newly calibrated bioevents and biozones as well as established diatom biostratigraphy are incorporated into the updated magneto‐biochronologic timescale, which will contribute to an improvement in biochronologic accuracy of Neogene sediments in northern Japan and adjacent areas. 相似文献
59.
We estimate a rate of inner-core differential rotation from time variations of splitting functions of seven core modes of the Earth’s free oscillations excited by eight large earthquakes in a period of 1994–2003. The splitting functions and moment tensor elements are simultaneously determined for each core mode by a spectral fitting technique. The estimated moment tensor well agrees with Harvard CMT solution. The splitting functions are corrected for the effect of mantle heterogeneity using a 3D mantle velocity model. Inner-core rotation angle about the Earth’s spin axis is determined for each core mode as a function of event year by comparison of the corrected and reference splitting functions. Mean rotation rate of six core modes is estimated at 0.03±0.18° per year westward, and this value is insignificantly different from zero. Therefore, the inner core is not rotating at a significant rate relatively to the crust and mantle. 相似文献
60.