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91.
We simulated quartz-type GeO2 and investigated its high-pressure transformation using the molecular dynamics (MD) simulation method with a model potential. The calculated results under hydrostatic compression indicated that a pressure-induced amorphization of quartz-type GeO2 originated from the mechanical instability of the quartz lattice as, in previous theoretical studies of SiO2. Furthermore, quartz-type GeO2 directly transformed to a rutile-like structure with only subtle displacements of ions under σ
x
y
imposed shear stressed decompression. This is the first reproduction of the quartz-to-rutile transformation. A possible pathway
of this transition is proposed in this study.
Received: 14 April 1999 / Revised, accepted: 11 August 1999 相似文献
92.
93.
Stability constants were determined for60Co (II)-amino acid complexes in sodium perchlorate media at an ionic strength=0.67, using cation exchange resins. Stability constants were, for Co(II)-phenylalanine, log
1=4.4, log
2=8.2, log
3=11.7, for Co(II)-histidine, log
1=7.4. for Co(II)-valine, log
1=4.3, log
2=8.5, for Co(II)-proline, log
1=4.1, and for Co(II)-tyrosine, log
1=7.2, respectively. The abundance of Co(II)-amino acid complexes in seawater was calculated from these stability constants on the basis of chemical equilibrium, assuming the concentration of individual amino acid to be 10–7 to 10–8 mol l–1. It was inferred that the Co(II)-amino acid complexes are probably not formed abundantly in seawater while inorganic species of60Co(II) may still be dominant for a short period of time after discharge into seawater as liquid waste. 相似文献
94.
Shigeru Aoki Kazuo Shibuya Akihiro Masuyama Taku Ozawa Koichiro Doi 《Journal of Oceanography》2002,58(3):519-523
Global Positioning System (GPS) measurements of the vertical displacement of fast ice near Syowa Station, Antarctica, were
conducted between April and December 1998 to evaluate measurements of sea level variation derived with a conventional bottom
pressure gauge (BPG). The BPG-derived sea level revealed a seasonal variation of about 0.13 m, with a high in April–June and
a low in November–December. The GPS-derived sea level, combined with observed sea ice thickness, supported the BPG result,
with an RMS error of 0.007 m. Our result also demonstrates that GPS is a powerful technique for monitoring sea level variations.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
95.
A framework for economic loss estimation due to seismic transportation network disruption: a spatial computable general equilibrium approach 总被引:4,自引:4,他引:0
This paper presents a framework for assessing the economic impact of disruption in transportation that can relate the physical
damage to transportation networks to economic losses. A spatial computable general equilibrium (SCGE) model is formulated
and then integrated with a transportation model that can estimate the traffic volumes of freight and passengers. Economic
equilibrium under a disruption in the transportation network is computed subject to the condition that the adjustment of labor
and capital inputs is restricted; the model reflects slow adjustment of these linked to the state of recovery. As a case study,
the model reviews the large Niigata-Chuetsu earthquake of 2004. Considering the damage to the transportation infrastructure,
the model indicates the extent of the economic losses arising from the earthquake distributed over regions as a consequence
of the intra- and interregional trade in a regional economy. The results show that 20% of the indirect losses occur in the
Niigata region directly affected by the earthquake, whereas 40% of the total losses are experienced in the Kanto region and
non-negligible losses reach rather remote zones of the country such as Okinawa. 相似文献
96.
Ichiro Takeuchi Kaoruko Mizukawa Tokutaka Ikemoto Kotaro Tsuchiya 《Marine pollution bulletin》2009,58(5):663-9029
Biomagnification profiles of polycyclic aromatic hydrocarbons (PAHs), alkylphenols, and polychlorinated biphenyls (PCBs) from the innermost part of Tokyo Bay, Japan were analyzed using stable carbon (δ13C) and nitrogen (δ15N) isotope ratios as guides to trophic web structure. δ15N analysis indicated that all species of mollusks tested were primary consumers, while decapods and fish were secondary consumers. Higher concentrations of PCBs occurred in decapods and fish than in mollusks. In contrast, concentrations of PAHs and alkylphenols were lower in decapods and fish than in mollusks. Unlike PCBs, whose concentrations largely increased with increasing δ15N (i.e. increasing trophic level), all PAHs and alkylphenols analyzed followed a reverse trend. Molecular weights of PAHs are lower than those of PCBs, therefore low membrane permeability caused by large molecular size is an unlikely factor in the “biodilution” of PAHs. Organisms at higher trophic levels may rapidly metabolize PAHs or they may assimilate less of them. 相似文献
97.
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
98.
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
99.
Contribution of shallow groundwater rapid fluctuation to soil salinization under arid and semiarid climate 总被引:4,自引:0,他引:4
Mohamed Khaled Ibrahimi Tsuyoshi Miyazaki Taku Nishimura Hiromi Imoto 《Arabian Journal of Geosciences》2014,7(9):3901-3911
Rising saline shallow groundwater and associated soil salinization problems are widespread especially in arid and semiarid areas. There have been numerous studies on groundwater-associated salinity, but more information is required on the effects of groundwater frequent and high fluctuations on soil salinization. In the present study, laboratory experiments and numerical simulations using HYDRUS-1D model were carried out for this purpose. The experimental and modeling results showed that groundwater fluctuation caused not only the accumulation of more salt in the soil profile compared to stable groundwater, but also an enhancement of the mechanism. Water table fluctuation induced a much greater spreading of the bromide (Br) tracer within the column than the constant water table. The Br content was on average five orders of magnitude greater under a fluctuating water table than under a constant one. Further, the numerical simulations showed that an increase in the groundwater fluctuation frequency brought about an increase in soil surface salinization under the same evaporation boundary conditions. Additional simulations with HYDRUS-1D were used to study the effects of various management strategies on soil salinization induced by shallow groundwater. Hence, by reducing the evaporation rate through the application of surface mulching, a significant reduction of salt concentration at the soil surface was observed. Moreover, frequent irrigations with small quantities were effective to reduce soil surface salt accumulation induced by saline shallow groundwater. 相似文献
100.
Taku Yoshimura Kenji Morinaga Seiji Oshimo Yoshinobu Konishi Tsuneo Goto 《新西兰海洋与淡水研究杂志》2013,47(2):591-604
The annual distribution and dispersal of early‐stage phyllosoma of the Japanese spiny lobster Panulirus japonicus were examined in the East China Sea and the Sea of Japan off western Japan. Early‐stage larvae were sampled mainly in summer and relatively near the coast off western Kyusyu Island. Few larvae were found in the other three seasons in the East China Sea and the Sea of Japan. This finding suggests that P. japonicus larvae are retained in coastal areas for a few months after hatching until stage V and are transported offshore until autumn, before they grow to stage VI. Examination of archival drifter data off western Kyusyu Island during the spawning season of P. japonicus supported the relatively rapid dispersal of the larvae from the East China Sea near Japan to the Pacific Ocean or the Sea of Japan. Larval transport from the East China Sea to the Pacific Ocean, which is considered to be a main distribution area of middle‐ and late‐stage larvae, would occur in the south at approximately 32–33°N in the East China Sea near western Kyusyu Island. 相似文献