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91.
从豹皮菌中的新鲜子实体的乙醇提取物中分离得到一种NMDA受体格抗剂,经理化常数和波谱数据的测定鉴定为2-Amino-3-(1,2-dicarboxyethylthio)propanoicacid非对映异构体的混合物,该化合物是首次从豹皮菌中得到,经进一步分离,得到两种非对映体异构体。 相似文献
92.
Depositional features and transportation mechanism of valley-filling Iwasegawa and Kaida debris avalanches, Japan 总被引:1,自引:1,他引:0
The depositional features of two valley-filling debris avalanche deposits were studied to reveal their transportation and
depositional mechanisms. The valley-filling Iwasegawa debris avalanche deposit (ca. 0.1 km3) is distributed along the valleys at the southeastern foot of Tashirodake Volcano, northern Honshu, Japan. Debris-avalanche
blocks range in size from <35 m proximally to <10 m in the distal zone and consist dominantly of fragile materials. Debris-avalanche
matrix percentages increase from 35–60% in the proximal zone to 95% in the distal zone. The debris-avalanche matrix is greater
in volume (80–90%) at the bottom and margins of the deposit. Normal grading of large clasts and reverse grading of wood logs
and branches occur within the debris-avalanche matrix. Preferred orientation of 311 wood logs and branches within the deposit
coincide with the interpreted local flow direction. The basal part of the deposit is characterized by (1) erosional features
and incorporated clasts of underlying material; (2) a higher proportion (30–50%) of incorporated clasts than the upper part;
and (3) reverse grading of clasts.
The valley-filling Kaida debris avalanche deposit (50 000 y B.P., >0.3 km3) is distributed along the valleys at the eastern-southeastern foot of Ontake Volcano, central Japan. Debris-avalanche blocks
range in size from <25 m proximally to <7 m in the medial zone. Debris-avalanche matrix percentages increase from 50–70% in
the proximal zone to 80% in the distal zone. The debris-avalanche matrix is more abundant (80–90%) at the bottom part of the
deposit. Deformation structures observed in the debris-avalanche blocks include elongation, folding, conjugate reverse faults,
and numerous minor faults in unconsolidated materials. Lithic components within the debris-avalanche matrix tend to have a
higher percentage of plucked clasts from the adjacent underlying formations.
A Bingham "plug flow" model is consistent with the transportation and depositional mechanisms of the valley-filling debris
avalanches. In the plug of the debris avalanche, fragile blocks were transported without major rupturing due to relatively
small shear stresses in regions of small strain rate. The debris-avalanche matrix was mainly produced by shearing at the bottom
and margins of the avalanche. Valley-filling debris avalanches tend to have smaller debris-avalanche blocks and larger amounts
of debris-avalanche matrix than do unconfined debris avalanches. These differences may be due to disaggregation of debris-avalanche
blocks by shearing against valley walls and interaction between debris-avalanche blocks and valley walls. Oriented wood logs
and branches, reverse grading of clasts at the base, and a higher proportion of incorporated clasts at the base are interpreted
to result from shearing along the bottom and valley walls.
Received: 25 March 1998 / Accepted: 10 October 1998 相似文献
93.
The cation distribution of natural and heated ferromagnesian olivine with chemical composition, Fo67Fa33, from metagabbro was examined by X-ray diffraction. Heating and quenching experiments were made by a newly devised apparatus which enables us to obtain very fast quenching speed in comparison with the usual technique. The distribution constants, K D=(Fe+2/Mg) M1/(Fe+2/Mg) M2, of the natural samples were less than 1.07, and those of heat-treated samples were more than 1.15, indicating that cation ordering takes place with temperature. The distribution of Fe+2 and Mg is nearly random at low temperatures, whereas Fe+2 shows a slight but significant preference for a smaller M1 site at high temperatures. The change of the distribution constant was observed on specimens which were heated for a short period of time (6–1,060 s) and quenched within 10 ms. Thus the rate of the cation reordering reaction is a very fast process. The lattice parameters b and c decrease whereas a increases with the increase of distribution constant. The overall effect on unit cell volume is a decrease with the increasing distribution constant, suggesting the presence of significant pressure dependence of the cation distribution towards the ordering of Fe at M1 site in ferromagnesian olivine. 相似文献
94.
Masao Kitamura Masayasu Tokonami Nobuo Morimoto 《Contributions to Mineralogy and Petrology》1975,51(3):167-172
The distribution of Ti atoms in oxy-kaersutite has been studied by the neutron diffraction method. The cation distribution over the three octahedral sites determined by the x-ray method (Kitamura and Tokonami, 1971) is as follows; M1∶0.40MG+0.60 FE, M2∶0.75 MG+0.25 FE, M3∶0.50 MG+0.50 FE, where MG and FE represent (Mg+Al) and (Fe+Ti), respectively. The neutron diffraction study indicates that Ti atoms are enriched in the M1 site more than M2 and M3 sites as follows; M1∶0.40 MG+0.33 Fe+0.27 Ti, M2∶ 0.75 MG+0.23 Fe+0.02 Ti, M3∶0.50 MG+0.46 Fe+0.04 Ti. This distribution agrees with the result based on the Madelung energy of oxy-kaersutite by Whittaker (1972). 相似文献
95.
We present a numerical simulation of the fast magnetosonic shock wave formation during a two-current-loop collision by using
a magnetohydrodynamical model. It is shown that the rarefaction waves are generated in the initial stage when the two current
loops start to collide. After the rarefaction waves propagate away from the excited region, the fast magnetosonic waves with
density enhancement can be produced for the simulation when the current strength of the loop is weak. As the current becomes
strong enough, the magnetosonic shock waves can be generated in the direction perpendicular to that of the two-loop collision. 相似文献
96.
It has been thought that granitic crust,having been formed on the surface,must have survived through the Earth’s evolution because of its buoyancy.At subduction zones continental crust is predominantly created by arc magmatism and is returned to the mantle via sediment subduction,subduction erosion, and continental subduction.Granitic rocks,the major constituent of the continental crust,are lighter than the mantle at depths shallower than 270 km,but we show here,based on first principles calculations, that beneath 270 km they have negative buoyancy compared to the surrounding material in the upper mantle and transition zone,and thus can be subducted in the depth range of 270-660 km.This suggests that there can be two reservoirs of granitic material in the Earth,one on the surface and the other at the base of the mantle transition zone(MTZ).The accumulated volume of subducted granitic material at the base of the MTZ might amount to about six times the present volume of the continental crust.Our calculations also show that the seismic velocities of granitic material in the depth range from 270 to 660 km are faster than those of the surrounding mantle.This could explain the anomalous seismic-wave velocities observed around 660 km depth.The observed seismic scatterers and reported splitting of the 660 km discontinuity could be due to jadeite dissociation,chemical discontinuities between granitic material and the surrounding mantle,or a combination thereof. 相似文献
97.
Panon Latcharote Khaled Al-Salem Anawat Suppasri Tanuspong Pokavanich Shinji Toda Yogeesha Jayaramu Abdullah Al-Enezi Alanoud Al-Ragum Fumihiko Imamura 《Natural Hazards》2018,92(1):127-143
This paper explores the ways that Mongolian pastoral-nomadic herders and supporting aid organizations anticipate, interpret, and respond to dzud, a form of winter storm that prevents livestock grazing and often results in large-scale herd deaths. Analysis is drawn from organizational reports, government speeches, and mass media that have been collected to give a complex, multi-faceted understanding of the collection, distribution, and interpretation of data pertaining to the social and scientific construction of this natural hazard. Using critical discourse analysis, this study asks how herder perspectives and needs have been incorporated into reports and action plans of international development organizations. The collected documents provide insight into the ways that knowledge is constructed, disseminated and valued among policy makers, development planners and herders. Additionally, the findings indicate disagreement between stakeholders as to when to declare a national emergency, and how to best help herders respond to the increasing frequency of dzud. While some organizations rely on traditional recovery mechanisms, others have turned to technological solutions, all aiming to assist herders in adequately responding to and recovering from one dzud before another occurs. From the analysis of policy proposals, this study aims to understand and inform the ways that international development programs, government officials, and herders work to preserve pasturelands and herding lifestyles threatened by dzud. 相似文献
98.
The 11 March 2011 East Japan Earthquake and Tsunami caused unprecedented damage to well-engineered buildings and coastal structures. This report presents some notable field observations of structural damage based on our surveys conducted along the Sanriku coast in April and June 2011. Engineered reinforced concrete buildings failed by rotation due to the high-velocity and deep tsunami inundation: entrapped air in the buildings and soil liquefaction by ground shaking could have contributed to the failure. The spatial distribution pattern of destroyed and survived buildings indicates that the strength of tsunami was affected significantly by the locations of well-engineered sturdy buildings: weaker buildings in the shadow zone tended to survive while jet and wake formations behind the sturdy buildings enhanced the tsunami forces. We also found that buildings with breakaway walls or breakaway windows/doors remained standing even if the surrounding buildings were washed away or destroyed. Several failure patterns of coastal structures (seawalls) were observed. Flow-induced suction pressure near the seawall crown could have caused the failure of concrete panels that covered the infill. Remarkable destruction of upright solid-concrete type seawalls was closely related with the tsunami induced scour and soil instability. The rapid decrease in inundation depth during the return-flow phase caused soil fluidization down to a substantial depth. This mechanism explains severely undermined roads and foundations observed in the area of low flow velocities. 相似文献
99.
Youta?SugaiEmail author Kenji?Tsuchiya Victor?S.?Kuwahara Shinji?Shimode Kazuhiro?Komatsu Akio?Imai Tatsuki?Toda 《Journal of Oceanography》2016,72(4):577-587
This study aimed to clarify the vertical differences in bacterial growth and grazing pressure on bacteria by heterotrophic nanoflagellates (HNF) and to identify the controlling factors of bacterial growth in temperate coastal waters of Sagami Bay, Japan. In addition to environmental factors, the annual monthly variations in bacterial growth rate (BGR) and the relative abundance of bacteria to HNF (BA/HNFA) were investigated in the euphotic and disphotic layers between May 2012 and May 2013. Significant vertical differences in BGR and BA/HNFA were evident between the two layers during the thermal stratification times of May to October 2012 and April to May 2013. BGR indicated significantly stronger limitation of bacterial growth in the euphotic layer compared to the disphotic layer. In contrast, significantly lower BA/HNFA was observed in the euphotic layer, suggesting significantly higher grazing pressure on bacteria by HNF. However, significant differences in BGR and BA/HNFA were not observed between the two layers from November 2012 to Match 2013, when the water column was well-mixed vertically due to the cooling and wind-induced mixing of surface water. This study indicates that bacteria in the euphotic layer grow less actively and are more vulnerable to predatory grazing by HNF relative to the disphotic layer during the stratification period. Further, multiple regression analyses indicate that bacterial growth was most controlled by the concentrations of chlorophyll a and dissolved organic carbon in the euphotic and disphotic layers, respectively. 相似文献
100.
Jianguo Du Kazuhiro Amita Shinji Ohsawa Youlian Zhang Chunli Kang Makoto Yamada 《Applied Geochemistry》2010
The formation of imminent hydrochemical precursors of earthquakes is investigated by the simulation for water–rock reaction in a brittle aquifer. Sixty-one soaking experiments were carried out with granodiorite and trachyandesite grains of different sizes and three chemically-distinct waters for 6 to 168 h. The experimental data demonstrate that water–rock reaction can result in both measurable increases and decreases of ion concentrations in short times and that the extents of hydrochemical variations are controlled by the grain size, dissolution and secondary mineral precipitation, as well as the chemistry of the rock and groundwater. The results indicate that water–rock reactions in brittle aquifers and aquitards may be an important genetic mechanism of hydrochemical seismic precursors when the aquifers and aquitards are fractured in response to tectonic stress. 相似文献