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Quaternary tephra of Mt. Osore-zan was dated by electron spin resonance. Quartz grains were separated from the tephra and ESR signals of Al and Ti centres were measured at 77 K. The signals of Al and Ti centres which have a complicated hyperfine structure were simplified by using wider field modulations width (5 gauss) than usually used (0.5–1 gauss). The influence of 5 gauss modulation width on the measurement of the signal intensity of Al and Ti centres was investigated. The intensity of the signal increases linearly with gamma irradiation and total doses obtained were 178 to 273 Gy and ESR ages were 0.19 to 0.32 Ma. These ages agree with the estimated age of about 0.3 Ma from the correlation of volcanic ash and terrace level. 相似文献
74.
Tadashi Shimamura Shohei Yanagita Kazuo Yamakoshi Kenichi Nogami Okio Arai Yuji Tazawa Koichi Kobayashi 《Earth and Planetary Science Letters》1979,42(3):379-382
Isotopic compositions of potassium and calcium in individual magnetic spherules were determined. No significant anomaly was observed for potassium within twice the statistical error (2σ), although for calcium isotopes enrichments of46Ca,44Ca and42Ca were observed in one spherule. The relative excess of46Ca,44Ca and42Ca in the spherule agrees with the relative yield of spallogenic calcium isotopes observed in iron meteorites. This fact indicates that the enrichment in the calcium isotopes was caused by cosmic ray irradiation of the spherule in outer space. 相似文献
75.
When earthquake activity begins, it may be a foreshock sequence to a larger earthquake, a swarm, or a simple main-shock-aftershock sequence. This paper is concerned with the conditional probability that it will be foreshock activity of a later larger earthquake, depending on the occurrence pattern of some early events in the sequence. The earthquake catalogue of the Japan Meteorological Agency (1926-1993, MJ ≥4) is decomposed into a large number of clusters in time and space in order to compare statistical features of foreshocks with those of swarms and aftershocks. Using such a data set, Ogata, Utsu & Katsura (1995) revealed some discriminating features of foreshocks relative to the other types of clusters, for example the events' closer proximity in time and space, and a tendency towards chronologically increasing magnitudes, which encouraged us to construct models which forecast the probability of the earthquakes being foreshocks. Specifically, the probability is a function of the history of magnitude differences, spans between origin times and distances between epicentres within a cluster. For purposes of illustration, the models were fitted to the early part of the data (1926-1975) and the validity of the forecasting procedure was checked on data from the later period (1976-1993). Two procedures for evaluating the performance of the probability forecast are suggested. Furthermore, for the case where only a single event is available (i.e. either it is the first event in a cluster or an isolated event), we also forecast the probability of the event being a foreshock as a function of its geographic location. Then, the validity of the forecast is demonstrated in a similar manner. Finally, making use of the multi-element prediction formula, we show that the forecasting performance is enhanced by the joint use of the information in the location of the first event, and that in the subsequent interevent history in the cluster. 相似文献
76.
Koichi Watanabe Chinatsu Yachi Xiao Jing Song Saori Kakuyama Miyuki Nishibe Serina Michigami 《Journal of Atmospheric Chemistry》2018,75(1):71-84
Measurements of hydroperoxides (H2O2 and MHP) at ground level were made from 2012 to 2015 in Imizu City, Toyama Prefecture in central Japan. H2O2 and MHP concentrations ranged from 0.01 to 3.5 ppb and from below the level of detection (< 0.01 ppb) to 1.4 ppb, respectively. The concentrations of H2O2 and MHP were high in the summer and low in the winter. The H2O2 concentration was at its maximum in July and August, whereas the concentration of O3 in the daytime was highest in May and June. The ratio of [H2O2]/[SO2] presented clear seasonal variations. Many cases showed the condition of [H2O2] < [SO2], called oxidant limitation especially in the cold months. Hydroperoxide concentrations in the rainwater were also high in the summer. The concentrations of MHP were much lower than those of H2O2 in the rain water. High concentrations of H2O2 (> 2.5 ppb) were detected in the summer during the inflow of air pollution. The concentrations of H2O2 were significantly high in July and August of 2013. The H2O2 was well correlated with the O3 in July and August whereas there was no correlation between O3 and H2O2 in May and June. There was a negative correlation between NOX and H2O2. 相似文献
77.
Abstract Ground penetrating radar (GPR) and high‐resolution shallow reflection seismic surveying were carried out to investigate the subsurface geology in and around the Uemachi Fault zone in the Yamato River area, Osaka, Japan. Shallow drilling in the area showed a major displacement event during the middle Pleistocene. The main Uemachi Fault plane could be clearly imaged on the seismic section, except for the most shallow 200 m. Several shallow normal fault planes with less displacement could be detected on both sides of the fault plane. GPR profiles confirmed the presence of several shallow normal faults within the area near the fault zone. These shallow faults could be followed in all of the GPR profiles crossing the fault zone. The integration of seismic section, GPR profiles and drilling data led to a conceptual model that explains the evolution of the Uemachi Fault system. The proposed model suggests the occurrence of several cycles of small vertical displacement along the deep part of the fault plane caused by the regional east–west compressional stress. The ductile nature of the shallow sedimentary cover and the absence of confining pressure in the shallow part allow for a considerable amount of plastic bending before failing in the shallow sedimentary layers. This bending generates stretching force within the shallow sedimentary cover, which in time, along with gravitational force, gives rise to the formation of the swarm of normal faults within the shallow layers near the fault zone. Some of the detected faults extend to a depth of less than 3 m below the ground surface, suggesting that the last tectonic activity along the fault plane may have occurred recently. 相似文献
78.
Correction to: Microtremor array method using spatial autocorrelation analysis of Rayleigh-wave data
Hayashi Koichi Asten Michael W. Stephenson William J. Cornou Cécile Hobiger Manuel Pilz Marco Yamanaka Hiroaki 《Journal of Seismology》2022,26(4):629-629
Journal of Seismology - 相似文献
79.
Hayashi Koichi Asten Michael W. Stephenson William J. Cornou Cécile Hobiger Manuel Pilz Marco Yamanaka Hiroaki 《Journal of Seismology》2022,26(4):601-627
Journal of Seismology - Microtremor array measurements, and passive surface wave methods in general, have been increasingly used to non-invasively estimate shear-wave velocity structures for... 相似文献
80.
Koichi Unami Felix Kofi Abagale Macarius Yangyuoru Abul Hasan M. Badiul Alam Gordana Kranjac-Berisavljevic 《Stochastic Environmental Research and Risk Assessment (SERRA)》2010,24(5):725-733
Droughts and floods are two opposite but related hydrological events. They both lie at the extremes of rainfall intensity
when the period of that intensity is measured over long intervals. This paper presents a new concept based on stochastic calculus
to assess the risk of both droughts and floods. An extended definition of rainfall intensity is applied to point rainfall
to simultaneously deal with high intensity storms and dry spells. The mean-reverting Ornstein–Uhlenbeck process, which is
a stochastic differential equation model, simulates the behavior of point rainfall evolving not over time, but instead with
cumulative rainfall depth. Coefficients of the polynomial functions that approximate the model parameters are identified from
observed raingauge data using the least squares method. The probability that neither drought nor flood occurs until the cumulative
rainfall depth reaches a given value requires solving a Dirichlet problem for the backward Kolmogorov equation associated
with the stochastic differential equation. A numerical model is developed to compute that probability, using the finite element
method with an effective upwind discretization scheme. Applicability of the model is demonstrated at three raingauge sites
located in Ghana, where rainfed subsistence farming is the dominant practice in a variety of tropical climates. 相似文献