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61.
Christian A. Braudrick Gordon E. Grant Yoshiharu Ishikawa Hiroshi Ikeda 《地球表面变化过程与地形》1997,22(7):669-683
The influence of woody debris on channel morphology and aquatic habitat has been recognized for many years. Unlike sediment, however, little is known about how wood moves through river systems. We examined some dynamics of wood transport in streams through a series of flume experiments and observed three distinct wood transport regimes: uncongested, congested and semi-congested. During uncongested transport, logs move without piece-to-piece interactions and generally occupy less than 10 per cent of the channel area. In congested transport, the logs move together as a single mass and occupy more than 33 per cent of the channel area. Semi-congested transport is intermediate between these two transport regimes. The type of transport regime was most sensitive to changes in a dimensionless input rate, defined as the ratio of log volume delivered to the channel per second (Qlog) to discharge (QW); this ratio varied between 0·015 for uncongested transport and 0·20 for congested transport. Depositional fabrics within stable log jams varied by transport type, with deposits derived from uncongested and semi-congested transport regimes having a higher proportion of pieces orientated normal to flow than those from congested transport. Because wood input rates are higher and channel dimensions decrease relative to piece size in low-order channels, we expect congested transport will be more common in low-order streams while uncongested transport will dominate higher-order streams. Single flotation models can be used to model the stability of individual pieces, especially in higher-order channels, but are insufficient for modelling the more complex intractions that occur in lower-order streams. © 1997 John Wiley & Sons, Ltd. 相似文献
62.
Takeshi Ikeda 《Contributions to Mineralogy and Petrology》1998,132(4):321-335
The garnet-cordierite zone, the highest-grade zone of the Ryoke metamorphic rocks in the Yanai district, SW Japan, is defined
by the coexistence of garnet and cordierite in pelitic rocks. Three assemblages in this zone are studied in detail, i.e. spinel
+ cordierite + biotite, garnet + cordierite + biotite and garnet + biotite, all of which contain quartz, K-feldspar and plagioclase.
The Mg/(Fe + Mg) in the coexisting minerals decreases in the following order: cordierite, biotite, garnet and spinel. Two
facts described below are inconsistent with the paragenetic relation in the K2OFeOMgOAl2O3SiO2H2O (KFMASH) system in terms of an isophysical variation. First, garnet and biotite in the last assemblage have Mg/(Fe + Mg)
higher than those in the second. Second, the first two assemblages are described by the reaction,
while they occur in a single outcrop. The addition of MnO, ZnO and TiO2 to the system can resolve the inconsistencies as follows. The assemblage garnet + biotite can consist of garnet and biotite
higher in Mg/(Fe + Mg) than those in garnet + cordierite + biotite as long as they are enriched in spessartine and depleted
in Al, respectively. The assemblage garnet + cordierite + biotite becomes stable relative to spinel + cordierite + biotite
with increasing spessartine content or decreasing gahnite content and the Ti content of biotite. The constituent minerals
of the assemblages, spinel + cordierite + biotite and garnet + cordierite + biotite, preserve several reaction microstructures
indicative of prograde reactions,
and
together with retrograde reactions,
and
This suggests that the pressure-temperature path of the rocks includes an isobaric heating and an isobaric or decompressional
cooling. The high-grade areas consisting of the K-feldspar-cordierite zone, sillimanite-K-feldspar zone and garnet-cordierite
zone have prograde paths involving isobaric heating and show a southwards increase in pressure with a thermal maximum in the
middle. These high-grade zones are closely associated with the gneissose granitic rocks, suggesting that the Ryoke metamorphism,
one of the typical low-pressure type, is caused by the heat supply from the syn-tectonic granitic rocks that emplaced at the
middle level of the crust.
Received: 22 August 1997 / Accepted: 11 May 1998 相似文献
63.
Gleb Panteleev Dmitri Nechaev Vladimir Luchin Phyllis Stabeno Nikolai Maximenko Motoyoshi Ikeda 《极地研究(英文版)》2008,19(2):123-134
The Bering Sea circulation is derived as a variational inverse of hydrographic profiles( temperature and salinity) , atmospheric climatologies and historical observation of ocean curents. The important result of this study is estimate of the mean climatological sea surface height (SSH) that can be used as a reference for satellite altimetry sea level anomaly data in the Bering Sea region. Numerical experiments reveal that, when combined with satellite altimetry, the obtained reference SSH effectively constrains a realistic reconstruction of the Amukta Pass circulation. 相似文献
64.
Satoru Kojima Tamotsu Nozaki Hidehisa Nagata Ryota Tanahashi Ryoich Kondo Noriaki Okamura Kazuhiro Suzuki Akiko Ikeda Toshio Nakamura Tomoyuki Ohtani 《Environmental Earth Sciences》2014,71(6):2753-2763
Large-scale landslides along the Kubusu and Besso rivers in Toyama Prefecture are developed in the Miocene Iwaine Formation, which is composed of andesitic lava, tuff, and tuff breccia. In the middle member of this formation, the tuff is easily altered to montmorillonite-bearing rock, and subsequently plays an important role in the development of landslides events, which tend to be large-scale events, as the massive lava of the upper member forms a cap rock over the tuff. The Kiritani and Koinami basins, which are flat intermontane basins located along the Kubusu and Besso rivers, respectively, are interpreted as landslide-dammed lakes, later filled with sediment. Accelerator mass spectrometry 14C ages show that the landslides forming each dam occurred simultaneously, at approximately 2500 BP. These ages were measured from wood fragments embedded in the landslide material of Kiritani, and from an in situ stump drowned during the impoundment of Koinami. If the trigger of these landslides was an earthquake, it is most likely to have been the penultimate event along the Atotsugawa fault zone. 相似文献
65.
66.
Measurement of debris mass changes and assessment of the dam-break flood potential of earthquake-triggered Hattian landslide dam 总被引:1,自引:1,他引:0
Ahsan Sattar Kazuo Konagai Takashi Kiyota Takaaki Ikeda Jorgen Johansson 《Landslides》2011,8(2):171-182
The Hattian landslide, which was triggered by the 2005 Kashmir earthquake, formed one of largest landslide dams in the world and it has posed a serious threat of flooding to people living in the lower reach of the Jhelum River. In order to understand deformation occurring in the body of the dam, physical measurements using a Differential Global Positioning System (DGPS) were conducted. Gradual deformation and slowly developing backward erosion initially were observed, leading eventually to a sudden creation of a deep hollow on the downstream slope of the landslide dam. The dimensions of this eroded gully were determined by laser scanning, and the results showed a significant loss of soil volume and a large change in the body of the dam. A breach formation model was used to predict the outflow hydrograph generated by constant downcutting of dam during a breaching event. A run-off analysis of the outflow hydrograph was conducted to evaluate inundation levels of flood waves in case the dam is breached. Hazardous downstream locations were identified near the junction of the Karli and Jhelum Rivers, suggesting a need for early warning system in order to avoid loss of lives. 相似文献
67.
Tsutomu Ikeda 《Journal of Oceanography》2011,67(6):785-790
This study demonstrates reduced electron transfer system (ETS) activity of mixed copepods collected from 5,000 to 7,000 m
depths [3.21 ± 1.25 μl O2 (mg protein)−1 h−1 at 10°C] as compared with mixed copepods from 0 to 200 m depths [5.93 ± 1.66 μl O2 (mg protein)−1 h−1 at 10°C] of the western subarctic Pacific. At the in situ temperature of 1.5°C, the 5,000–7,000 m ETS data, in terms of wet
mass (WM)-specific respiration rates (R), is equivalent to [0.052 ± 0.021 μl O2 (mg WM)−1 h−1] which is similar to or greater than those reported for selected copepods or mixed mesozooplankton from <5,000 m depth by
previous workers. 相似文献
68.
We describe an orthopyroxene–cordierite mafic gneiss from the Nomamisaki metamorphic rocks in the Noma Peninsula, southern Kyushu, Japan. The mineral assemblage of the gneiss is orthopyroxene, cordierite, biotite, plagioclase, and ilmenite. Thermometry based on the Fe–Mg exchange reaction between orthopyroxene and biotite yields a peak metamorphic temperature of 680°C. The stability of cordierite relative to garnet, quartz, and sillimanite defines the upper limit of the peak metamorphic pressure as 4.4 kbar. These features indicate that the Nomamisaki metamorphic rocks underwent low‐pressure high‐temperature type metamorphism. Although a chronological problem still remains, the Nomamisaki metamorphic rocks can be regarded as a western continuation of the Higo Belt. The Usuki–Yatsushiro Tectonic Line, which delineates the southern border of the Higo Belt, is therefore located on the east of the Nomamisaki metamorphic rocks in southern Kyushu. 相似文献
69.
Verification of system identification utilizing shaking table tests of a full‐scale 4‐story steel building 下载免费PDF全文
Yoshiki Ikeda 《地震工程与结构动力学》2016,45(4):543-562
This paper verifies the feasibility of the proposed system identification methods by utilizing shaking table tests of a full‐scale four‐story steel building at E‐Defense in Japan. The natural frequencies, damping ratios and modal shapes are evaluated by single‐input‐four‐output ARX models. These modal parameters are prepared to identify the mass, damping and stiffness matrices when the objective structure is modelled as a four degrees of freedom (4DOF) linear shear building in each horizontal direction. The nonlinearity in stiffness is expressed as a Bouc–Wen hysteretic system when it is modelled as a 4DOF nonlinear shear building. The identified hysteretic curves of all stories are compared to the corresponding experimental results. The simple damage detection is implemented using single‐input‐single‐output ARX models, which require only two measurements in each horizontal direction. The modal parameters are equivalent‐linearly evaluated by the recursive Least Squares Method with a forgetting factor. When the structure is damaged, its natural frequencies decrease, and the corresponding damping ratios increase. The fluctuation of the identified modal properties is the indirect information for damage detection of the structure. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
70.
Contributions of slab fluid and sediment melt components to magmatism in the Mariana Arc–Trough system: Evidence from geochemical compositions and Sr,Nd, and noble gas isotope systematics 下载免费PDF全文
Yasuo Ikeda Keisuke Nagao Teruaki Ishii Daisuke Matsumoto Robert J. Stern Hiroo Kagami Makoto Arima Sherman H. Bloomer 《Island Arc》2016,25(4):253-273
This study presents new major and trace element, mineral, and Sr, Nd, and noble gas isotope geochemical analyses of basalts, gabbro, and clinopyroxenite from the Mariana Arc (Central Islands and Southern Seamount provinces) including the forearc, and the Mariana Trough (Central Graben and Spreading Ridge). Mantle source compositions beneath the Mariana Arc and the Mariana Trough indicate a mantle source that is depleted in high field strength elements relative to MORB (mid‐oceanic ridge basalt). Samples from the Mariana Arc, characterized by high ratios of Ba/Th, U/Th, 84Kr/4He and 132Xe/4He, are explained by addition of fluid from the subducted slab to the mantle wedge. Correlations of noble gas data, as well as large ion lithophile elements, indicate that heavy noble gases (Ar, Kr, and Xe) provide evidence for fluid fluxing into the mantle wedge. On the other hand, major elements and Sr, Nd, He, and Ne isotopic data of basalts from the Mariana Trough are geochemically indistinguishable from MORB. Correlations of 3He/4He and 40Ar/36Ar in the Mariana Trough samples are explained by mixing between MORB and atmosphere. One sample from the Central Graben indicates extreme enrichment in 20Ne/22Ne and 21Ne/22Ne, suggesting incorporation of solar‐type Ne in the magma source. Excess 129Xe is also observed in this sample suggesting primordial noble gases in the mantle source. The Mariana Trough basalts indicate that both fluid and sediment components contributed to the basalts, with slab‐derived fluids dominating beneath the Spreading Ridge, and that sediment melts, characterized by high La/Sm and relatively low U/Th and Zr/Nb, dominate in the source region of basalts from the Central Graben. 相似文献