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211.
C. John Mann 《Mathematical Geology》1988,20(5):589-601
Although risk analysis today is considered to include three separate aspects (1) identifing sources of risk, (2) estimating probabilities quantitatively, and (3) evaluating consequences of risk, here only estimation of probabilities for natural geologic events, processes, and phenomena is addressed. Ideally, evaluation of potential future hazards includes an objective determination of probabilities that have been derived from past occurrences of identical events or components contributing to complex processes or phenomena. In practice, however, data which would permit objective estimation of those probabilities of interest may not be adequate, or may not even exist.Another problem that arises normally, regardless of the extent of data, is that risk assessments involve estimating extreme values. Probabilities are required for events that are the greatest or rarest because they commonly will have the greatest consequences; the largest, or rarest, events always fall in tails of frequency distributions. Rarely are extreme values accurately predictable even when an empirical frequency distribution is established well by data.In the absence of objective methods for estimating probabilities of natural events or processes, subjective probabilities for the hazard must be established through Bayesian methods, expert opinion, or Delphi methods. Alternative solutions may involve consequence analysis which may demonstrate that, although an event may occur, its consequences are sufficiently small that it safely may be ignored or by establishing bounds which may demonstrate that although probabilities are not known they cannot exceed a maximum value that is sufficiently small so that associated risk may be considered to be negligible.Uncertainty of every probability determination must be stated for each component of an event, process, or phenomenon. These uncertainties also must be propagated through the quantitative analysis so that a realistic estimate of total uncertainty can be associated with each final probability estimate for a geologic hazard.This paper was presented (by title) at Emerging Concepts, MGUS-87 Conference, Redwood City, California, 13–15 April 1987. 相似文献
212.
Itziar Aretxaga David H. Hughes Kristen Coppin Angela M. J. Mortier Jeff Wagg James S. Dunlop Edward L. Chapin Stephen A. Eales Enrique Gaztañaga Mark Halpern Rob J. Ivison Eelco van Kampen Douglas Scott Stephen Serjeant Ian Smail Thomas Babbedge rew J. Benson Scott Chapman David L. Clements Loretta Dunne Simon Dye Duncan Farrah Matt J. Jarvis Robert G. Mann Alexandra Pope Robert Priddey Steve Rawlings Marc Seigar Laura Silva Chris Simpson Mattia Vaccari 《Monthly notices of the Royal Astronomical Society》2007,379(4):1571-1588
213.
214.
Summary. It is confirmed that even when disturbance variations are taken into account, the spatial scale of day-to-day variability of Sq is local, that is, of the order of one or two thousand kilometres, rather than globally correlated. 相似文献
215.
The origin of high dissolved manganese concentrations in slightly acidic mine runoff from a surface mine operated by the Cumberland Coal Company in eastern Tennessee was investigated. Mineralogical and chemical analyses were performed on 31 samples of sandstone, shale, coal, and mudstone from the mine to identify the sources and stratigraphic distribution of high extractable manganese contents in the spoil materials. The samples were analyzed for their bulk mineral content by X-ray diffraction, net acid-base potential, and reaction to 2 or 4 chemical extraction procedures. A limited number of samples were analyzed for petrographic characteristics, clay mineral composition by X-ray diffraction, and mineral compositions by electron microprobe. Analysis of the data and consideration of the geochemical conditions at the mine were used to identify probable sources for the high extractable manganese contents.The results indicate 2 prominent, independent sources of extractable manganese. The first source is exchangeable manganese on clay minerals (mainly illite + muscovite and chlorite) and is concentrated in shale and mudstone rock types. The second and more significant source is manganese in siderite concretions and cement, mainly in shale and mudstone. Comparison to other coal-bearing strata indicates that manganese-rich siderite is common in fresh- to brackish-water subaqueous sediments that overlie coal. This is especially the case for coals formed in wet, tropical environments.Ratios of manganese to calcium and magnesium in mine runoff suggest that manganese from siderite is the major cause of the high dissolved manganese contents. A conceptual model is developed to explain the high manganese contents of the mine runoff. Oxidation of pyrite creates mildly acidic waters that are subsequently partially neutralized by reaction with impure siderite. Solubilized manganese remains dissolved in the slightly acidic runoff water, whereas dissolved iron precipitates as ferric hydroxide or goethite. Consideration of data from other coal mining regions suggests that similar reactions involving impure siderite may be responsible for high manganese concentrations in acidic to slightly acidic mine runoff. Geochemical reaction path modeling of pyrite and impure siderite with rainwater illustrate how resulting water compositions may vary depending on pyrite to siderite ratios in spoil materials. Spoil water compositions from the Cumberland mine are largely consistent with reaction of pyrite and impure siderite in proportions observed in the sediments; however, deviations may be explained by minor mixing with waters that reacted only with impure siderite or clay mineral exchange reactions. 相似文献
216.
A. Vaivads G. Andersson S. D. Bale C. M. Cully J. De Keyser M. Fujimoto S. Grahn S. Haaland H. Ji Yu. V. Khotyaintsev A. Lazarian B. Lavraud I. R. Mann R. Nakamura T. K. M. Nakamura Y. Narita A. Retinò F. Sahraoui A. Schekochihin S. J. Schwartz I. Shinohara L. Sorriso-Valvo 《Experimental Astronomy》2012,33(2-3):491-527
We describe the mission concept of how ESA can make a major contribution to the Japanese Canadian multi-spacecraft mission SCOPE by adding one cost-effective spacecraft EIDO (Electron and Ion Dynamics Observatory), which has a comprehensive and optimized plasma payload to address the physics of particle acceleration. The combined mission EIDOSCOPE will distinguish amongst and quantify the governing processes of particle acceleration at several important plasma boundaries and their associated boundary layers: collisionless shocks, plasma jet fronts, thin current sheets and turbulent boundary layers. Particle acceleration and associated cross-scale coupling is one of the key outstanding topics to be addressed in the Plasma Universe. The very important science questions that only the combined EIDOSCOPE mission will be able to tackle are: 1) Quantitatively, what are the processes and efficiencies with which both electrons and ions are selectively injected and subsequently accelerated by collisionless shocks? 2) How does small-scale electron and ion acceleration at jet fronts due to kinetic processes couple simultaneously to large scale acceleration due to fluid (MHD) mechanisms? 3) How does multi-scale coupling govern acceleration mechanisms at electron, ion and fluid scales in thin current sheets? 4) How do particle acceleration processes inside turbulent boundary layers depend on turbulence properties at ion/electron scales? EIDO particle instruments are capable of resolving full 3D particle distribution functions in both thermal and suprathermal regimes and at high enough temporal resolution to resolve the relevant scales even in very dynamic plasma processes. The EIDO spin axis is designed to be sun-pointing, allowing EIDO to carry out the most sensitive electric field measurements ever accomplished in the outer magnetosphere. Combined with a nearby SCOPE Far Daughter satellite, EIDO will form a second pair (in addition to SCOPE Mother-Near Daughter) of closely separated satellites that provides the unique capability to measure the 3D electric field with high accuracy and sensitivity. All EIDO instrumentation are state-of-the-art technology with heritage from many recent missions. The EIDOSCOPE orbit will be close to equatorial with apogee 25-30 RE and perigee 8-10 RE. In the course of one year the orbit will cross all the major plasma boundaries in the outer magnetosphere; bow shock, magnetopause and magnetotail current sheets, jet fronts and turbulent boundary layers. EIDO offers excellent cost/benefits for ESA, as for only a fraction of an M-class mission cost ESA can become an integral part of a major multi-agency L-class level mission that addresses outstanding science questions for the benefit of the European science community. 相似文献
217.
The growth rate of speckled snapper Lutjanus rivulatus was investigated using data from a long-term tag-recapture study conducted in the St Lucia Marine Reserve within the iSimangaliso Wetland Park, a World Heritage Site in northern KwaZulu-Natal, South Africa. A total of 1 429 L. rivulatus were tagged and 453 (31.7%) individual fish were recaptured one or more times. Growth rates were modelled from the tag-recapture data using a maximum-likelihood approach. It is shown that L. rivulatus is a slow-growing species with L∞ = 918?mm FL, K = 0.06 and phi-prime (Ø, the growth index) = 2.69. The effects of deep-hooking and multiple captures were tested and this revealed that there was no significant impact on the growth of L. rivulatus. The growth index was lower than that recorded in many other similar congeneric species. Slow growth, coupled with high levels of residency and site fidelity, suggest that this species is vulnerable to exploitation and that a precautionary approach towards future management is appropriate. 相似文献
218.
Stephen Serjeant Seb Oliver † Michael Rowan-Robinson Hans Crockett Vasilis Missoulis Tim Sumner Carlotta Gruppioni Robert G. Mann Nick Eaton David Elbaz David L. Clements Amanda Baker reas Efstathiou Catherine Cesarsky Luigi Danese Alberto Franceschini Reinhardt Genzel y Lawrence Dietrich Lemke Richard G. McMahon George Miley Jean-Loup Puget Brigitte Rocca-Volmerange 《Monthly notices of the Royal Astronomical Society》2000,316(4):768-778
219.
Necessary technical experience is being gained from successful construction and deployment of current prototype detectors to search for UHE neutrinos in Antarctica, Lake Baikal in Russia, and the Mediterranean. The prototype detectors have also the important central purpose of determining whether or not UHE neutrinos do in fact exist in nature by observation of at least a few UHE neutrino-induced leptons with properties that are not consistent with expected backgrounds. We discuss here the criteria for a prototype detector to accomplish that purpose in a convincing way even if the UHE neutrino flux is substantially lower than predicted at present. 相似文献
220.
Matthew E. Brueseke Jeffrey A. Benowitz Alexander T. Bearden Michael Everett Mann Daniel P. Miggins 《地学学报》2023,35(1):49-57
Distinguishing the initiation of actual collision from flat-slab subduction of oceanic buoyant highs along convergent margins is elusive because both can lead to inboard deformation and disrupt magmatic arcs. Volcanoes with nascent tear magmatic signatures provide a means to document both the occurrence and timing of actual oceanic buoyant high collision. There is a ~40-year debate on when the true collision of the Yakutat plateau began in Alaska. Three newly identified ca. 1 Ma volcanoes with a north-to-south trench perpendicular orientation, nascent tear geochemical signatures, overlaying an imaged Yakutat slab tear, provide constraints on the timing of Yakutat collision and slab tearing. The ca. 1 Ma slab tear is coincident with Yakutat slab segmentation, northern continental Aleutian Arc rejuvenation, cessation of Wrangell Arc magmatism, increased collisional zone exhumation and eastern Yakutat trench abandonment. The documentation of nascent slab tear volcanoes may help resolve similar debates in other convergent margin settings. 相似文献