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81.
Statistical estimation of maximum peak ground acceleration at a given point of a seismic region 总被引:2,自引:1,他引:1
A straightforward procedure is suggested for statistical estimation of maximum peak ground acceleration, Amax (T), that will occur at a given point of a seismic region in future time period T. This procedure is based on the Bayesian approach and includes estimation of three unknown parameters;b, the slope of acceleration-frequency law; , the maximum regression acceleration; , the rate of significant accelerations at the point under question. Uncertainty characteristics of Amax (T)-estimates as well as of all estimated parameters are given. The suggested approach is illustrated for two sites in Southern California. 相似文献
82.
83.
Two 14C accelerator mass spectrometry (AMS) wiggle‐match dated peat sequences from Denmark and northern England record changes in mire surface wetness reconstructed using plant macrofossil and testate amoebae analyses. A number of significant mid–late Holocene climatic deteriorations (wet shifts) associated with declines in solar activity were recorded (at ca. 2150 cal. yr BC, 740 cal. yr BC, cal. yr AD 930, cal. yr AD 1020, cal. yr AD 1280–1300, cal. yr AD 1640 and cal. yr AD 1790–1830). The wet shifts identified from ca. cal. yr AD 930 are concurrent with or lag decreases in solar activity by 10–50 years. These changes are replicated by previous records from these and other sites in the region and the new records provide improved precision for the ages of these changes. The rapidly accumulating (up to 2–3 yr cm?1, ~1310 yr old, 34 14C dates) Danish profile offers an unprecedented high‐resolution record of climate change from a peat bog, and has effectively recorded a number of significant but short‐lived climate change events since ca. cal. yr AD 690. The longer time intervals between samples and the greater length of time resolved by each sample in the British site due to slower peat accumulation rates (up to 11 yr cm?1, ~5250 yr old, 42 14C dates) acted as a natural smoothing filter preventing the clear registration of some of the rapid climate change events. Not all the significant rises in water table registered in the peat bog archives of the British and Danish sites have been caused by solar forcing, and may be the result of other processes such as changes in other external forcing factors, the internal variability of the climate system or raised bog ecosystem. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
84.
The structure of the slow mode coupled with Alfvén mode in the axially symmetric magnetosphere is studied in the paper. Due to the coupling, the slow magnetosonic wave gets dispersion across magnetic shells and becomes not strictly guided. The slow mode is found to be captured between the resonant and cutoff surfaces, where the wave vector radial component goes to infinity and to zero, accordingly. The resonant surface is farther from the Earth than the cutoff surface. The slow mode resonance frequency is much lower than the Alfvén resonance frequency due to small value of the sound velocity near the equator. The maximum of the slow mode amplitude expressed in terms of the parallel magnetic field is concentrated near the equator, but expressed in hydromagnetic terms is concentrated near the ionospheres. 相似文献
85.
V. F. Pisarenko A. Sornette D. Sornette M. V. Rodkin 《Pure and Applied Geophysics》2008,165(5):847-888
We develop a new method for the statistical estimation of the tail of the distribution of earthquake sizes recorded in the
Harvard catalog of seismic moments converted to m
W
-magnitudes (1977–2004 and 1977–2006). For this, we suggest a new parametric model for the distribution of main-shock magnitudes,
which is composed of two branches, the pure Gutenberg-Richter distribution up to an upper magnitude threshold m
1, followed by another branch with a maximum upper magnitude bound M
max, which we refer to as the two-branch model. We find that the number of main events in the catalog (N = 3975 for 1977–2004 and N = 4193 for 1977–2006) is insufficient for a direct estimation of the parameters of this model, due to the inherent instability
of the estimation problem. This problem is likely to be the same for any other two-branch model. This inherent limitation
can be explained by the fact that only a small fraction of the empirical data populates the second branch. We then show that
using the set of maximum magnitudes (the set of T-maxima) in windows of duration T days provides a significant improvement, in particular (i) by minimizing the negative impact of time-clustering of foreshock/main
shock/aftershock sequences in the estimation of the tail of magnitude distribution, and (ii) by providing via a simulation
method reliable estimates of the biases in the Moment estimation procedure (which turns out to be more efficient than the
Maximum Likelihood estimation). We propose a method for the determination of the optimal choice of the T value minimizing the mean-squares-error of the estimation of the form parameter of the GEV distribution approximating the
sample distribution of T-maxima, which yields T
optimal = 500 days. We have estimated the following quantiles of the distribution of T-maxima for the whole period 1977–2006: Q
16%(M
max) = 9.3, Q
50%(M
max) = 9.7 and Q
84%(M
max) = 10.3. Finally, we suggest two more stable statistical characteristics of the tail of the distribution of earthquake magnitudes:
The quantile Q
T
(q) of a high probability level q for the T-maxima, and the probability of exceedance of a high threshold magnitude ρ
T
(m*) = P{m
k
≥ m*}. We obtained the following sample estimates for the global Harvard catalog and The comparison between our estimates for the two periods 1977–2004 and 1977–2006, where the latter period included the great
Sumatra earthquake 24.12.2004, m
W
= 9.0 confirms the instability of the estimation of the parameter M
max and the stability of Q
T
(q) and ρ
T
(m*) = P{m
k
≥ m*}. 相似文献
86.
El Chichón crater lake appeared immediately after the 1982 catastrophic eruption in a newly formed, 1-km wide, explosive crater. During the first 2 years after the eruption the lake transformed from hot and ultra-acidic caused by dissolution of magmatic gases, to a warm and less acidic lake due to a rapid “magmatic-to-hydrothermal transition” — input of hydrothermal fluids and oxidation of H2S to sulfate. Chemical composition of the lake water and other thermal fluids discharging in the crater, stable isotope composition (δD and δ18O) of lake water, gas condensates and thermal waters collected in 1995–2006 were used for the mass-balance calculations (Cl, SO4 and isotopic composition) of the thermal flux from the crater floor. The calculated fluxes of thermal fluid by different mass-balance approaches become of the same order of magnitude as those derived from the energy-budget model if values of 1.9 and 2 mmol/mol are taken for the catchment coefficient and the average H2S concentration in the hydrothermal vapors, respectively. The total heat power from the crater is estimated to be between 35 and 60 MW and the CO2 flux is not higher than 150 t/day or ~ 200 gm− 2 day− 1. 相似文献
87.
Valentina G. Batanova Jay M. Thompson Leonid V. Danyushevsky Maxim V. Portnyagin Dieter Garbe‐Schnberg Erik Hauri Jun‐Ichi Kimura Qing Chang Ryoko Senda Karsten Goemann Catherine Chauvel Sylvain Campillo Dmitri A. Ionov Alexander V. Sobolev 《Geostandards and Geoanalytical Research》2019,43(3):453-473
A new olivine reference material – MongOL Sh11‐2 – for in situ analysis has been prepared from the central portion of a large (20 × 20 × 10 cm) mantle peridotite xenolith from a ~ 0.5 My old basaltic breccia at Shavaryn‐Tsaram, Tariat region, central Mongolia. The xenolith is a fertile mantle lherzolite with minimal signs of alteration. Approximately 10 g of 0.5–2 mm gem quality olivine fragments were separated under binocular microscope and analysed by EPMA, LA‐ICP‐MS, SIMS and bulk analytical methods (ID‐ICP‐MS for Mg and Fe, XRF, ICP‐MS) for major, minor and trace elements at six institutions world‐wide. The results show that the olivine fragments are sufficiently homogeneous with respect to major (Mg, Fe, Si), minor and trace elements. Significant inhomogeneity was revealed only for phosphorus (homogeneity index of 12.4), whereas Li, Na, Al, Sc, Ti and Cr show minor inhomogeneity (homogeneity index of 1–2). The presence of some mineral and fluid‐melt micro‐inclusions may be responsible for the inconsistency in mass fractions obtained by in situ and bulk analytical methods for Al, Cu, Sr, Zr, Ga, Dy and Ho. Here we report reference and information values for twenty‐seven major, minor and trace elements. 相似文献
88.
Dmitri Rouwet Salvatore Inguaggiato Yuri Taran Nicholas Varley José A. Santiago S. 《Bulletin of Volcanology》2009,71(3):319-335
This study presents baseline data for future geochemical monitoring of the active Tacaná volcano–hydrothermal system (Mexico–Guatemala).
Seven groups of thermal springs, related to a NW/SE-oriented fault scarp cutting the summit area (4,100m a.s.l.), discharge
at the northwest foot of the volcano (1,500–2,000m a.s.l.); another one on the southern ends of Tacaná (La Calera). The near-neutral
(pH from 5.8 to 6.9) thermal (T from 25.7°C to 63.0°C) HCO3–SO4 waters are thought to have formed by the absorption of a H2S/SO2–CO2-enriched steam into a Cl-rich geothermal aquifer, afterwards mixed by Na/HCO3-enriched meteoric waters originating from the higher elevations of the volcano as stated by the isotopic composition (δD
and δ18O) of meteoric and spring waters. Boiling temperature fumaroles (89°C at ~3,600m a.s.l. NW of the summit), formed after the
May 1986 phreatic explosion, emit isotopically light vapour (δD and δ18O as low as −128 and −19.9‰, respectively) resulting from steam separation from the summit aquifer. Fumarolic as well as bubbling
gases at five springs are CO2-dominated. The δ13CCO2 for all gases show typical magmatic values of −3.6 ± 1.3‰ vs V-PDB. The large range in 3He/4He ratios for bubbling, dissolved and fumarolic gases [from 1.3 to 6.9 atmospheric 3He/4He ratio (R
A)] is ascribed to a different degree of near-surface boiling processes inside a heterogeneous aquifer at the contact between
the volcanic edifice and the crystalline basement (4He source). Tacaná volcano offers a unique opportunity to give insight into shallow hydrothermal and deep magmatic processes
affecting the CO2/3He ratio of gases: bubbling springs with lower gas/water ratios show higher 3He/4He ratios and consequently lower CO2/3He ratios (e.g. Zarco spring). Typical Central American CO2/3He and 3He/4He ratios are found for the fumarolic Agua Caliente and Zarco gases (3.1 ± 1.6 × 1010 and 6.0 ± 0.9 R
A, respectively). The L/S (5.9 ± 0.5) and (L + S)/M ratios (9.2 ± 0.7) for the same gases are almost identical to the ones calculated for gases in El Salvador, suggesting an
enhanced slab contribution as far as the northern extreme of the Central American Volcanic Arc, Tacaná. 相似文献
89.
Fjord exchange circulation and its response to abrupt changes in forcing is examined by means of an idealized modeling experiment. Puget Sound, a fjord-type estuary in western North America (State of Washington), is the main context for this study. Parameters of the idealized model are representative of the entrance sill at Admiralty Inlet and the Main Basin of Puget Sound. Sensitivity to some of the model parameters relevant to a 3D realistic model is discussed. An idealized tidal forcing with fortnightly modulation drives a qualitatively realistic cycle of exchange circulation while the other boundary conditions are kept fixed in time. The cycle is characterized by fortnightly pulses of deep water intrusions with a sharp front at the leading edge and reversed circulation cells below the sill depth developing between the intrusions. This basic state is then perturbed and response of the circulation to abrupt changes in oceanic salinity and river discharge is examined. 相似文献
90.
V. F. Pisarenko A. A. Lyubushin M. V. Bolgov T. A. Rukavishnikova S. Kanyu M. F. Kanevskii E. A. Savel’eva V. V. Dem’yanov I. V. Zalyapin 《Water Resources》2005,32(2):115-126
Methods used to analyze one type of nonstationary stochastic processes—the periodically correlated process—are considered. Two methods of one-step-forward prediction of periodically correlated time series are examined. One-step-forward predictions made in accordance with an autoregression model and a model of an artificial neural network with one latent neuron layer and with an adaptation mechanism of network parameters in a moving time window were compared in terms of efficiency. The comparison showed that, in the case of prediction for one time step for time series of mean monthly water discharge, the simpler autoregression model is more efficient.Translated from Vodnye Resursy, Vol. 32, No. 2, 2005, pp. 133–145.Original Russian Text Copyright © 2005 by Pisarenko, Lyubushin, Bolgov, Rukavishnikova, Kanyu, Kanevskii, Saveleva, Demyanov, Zalyapin. 相似文献