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71.
Synergy and fusion of optical and synthetic aperture radar satellite data for underwater topography estimation in coastal areas 总被引:1,自引:1,他引:0
Andrey Pleskachevsky Susanne Lehner Thomas Heege Claudius Mott 《Ocean Dynamics》2011,61(12):2099-2120
A method to obtain underwater topography for coastal areas using state-of-the-art remote sensing data and techniques worldwide
is presented. The data from the new Synthetic Aperture Radar (SAR) satellite TerraSAR-X with high resolution up to 1 m are
used to render the ocean waves. As bathymetry is reflected by long swell wave refraction governed by underwater structures
in shallow areas, it can be derived using the dispersion relation from observed swell properties. To complete the bathymetric
maps, optical satellite data of the QuickBird satellite are fused to map extreme shallow waters, e.g., in near-coast areas.
The algorithms for bathymetry estimation from optical and SAR data are combined and integrated in order to cover different
depth domains. Both techniques make use of different physical phenomena and mathematical treatment. The optical methods based
on sunlight reflection analysis provide depths in shallow water up to 20 m in preferably calm weather conditions. The depth
estimation from SAR is based on the observation of long waves and covers the areas between about 70- and 10-m water depths
depending on sea state and acquisition quality. The depths in the range of 20 m up to 10 m represent the domain where the
synergy of data from both sources arises. Thus, the results derived from SAR and optical sensors complement each other. In
this study, a bathymetry map near Rottnest Island, Australia, is derived. QuickBird satellite optical data and radar data
from TerraSAR-X have been used. The depths estimated are aligned on two different grids. The first one is a uniform rectangular
mesh with a horizontal resolution of 150 m, which corresponds to an average swell wavelength observed in the 10 × 10-km SAR
image acquired. The second mesh has a resolution of 150 m for depths up to 20 m (deeper domain covered by SAR-based technique)
and 2.4 m resolution for the shallow domain imaged by an optical sensor. This new technique provides a platform for mapping
of coastal bathymetry over a broad area on a scale that is relevant to marine planners, managers, and offshore industry. 相似文献
72.
The Totalp-Platta-Malenco ophiolites in the Eastern Central Alps offer a unique opportunity to study the behaviour of Li, Be and B in ultramafic rocks in response to serpentinization and to progressive Alpine metamorphism. These units represent the remnants of a former ocean-continent transition that was intensely serpentinized during exposure on the Jurassic seafloor of the Ligurian Tethys. From north to the south, three isograd reactions (lizardite⇒antigorite+brucite;lizardite+talc⇒antigorite;lizardite+tremolite⇒antigorite+diopside) have been used to quantify the evolution of the light element content of metamorphic minerals. We determined the Li, Be and B concentrations in major silicate minerals from the ultramafic bodies of Totalp, Platta and Malenco by secondary ion mass spectrometry. Mantle minerals have Be concentrations (e.g. <0.001-0.009 μg/g in olivine) similar to the metamorphic minerals that replace them (e.g. <0.001-0.016 μg/g in serpentine). The mantle signature of Be is thus neither erased during seafloor alteration nor by progressive metamorphism from prehnite-pumpellyite to epidote-amphibolite facies. In contrast, the Li and B inventories of metamorphic minerals are related to the lizardite-to-antigorite transition. Both elements display higher concentrations in the low-temperature serpentine polymorph lizardite (max. 156 μg/g Li, max. 318 μg/g B) than in antigorite (max. 0.11 μg/g Li, max. 12 μg/g B). Calculated average B/Li ratios for lizardite (∼1395) and antigorite (∼115) indicate that Li fractionates from B during the lizardite-to-antigorite transition during prograde metamorphism in ultramafic rocks. In subduction zones, this signature is likely to be recorded in the B-rich nature of forearc fluids.Relative to oceanic mantle the Be content of mantle clinopyroxene is much higher, but similar to Be values from mantle xenoliths and subduction-related peridotite massifs. These data support previous hypothesis that the mantle rocks from the Eastern Central Alps have a subcontinental origin. We conclude that Be behaves conservatively during subduction metamorphism of ultramafic rocks, at least at low-temperature, and thus retains the fingerprint of ancient subduction-related igneous events in mantle peridotites. 相似文献
73.
The study of re-homogenized melt inclusions in the same growth planes of quartz of pegmatites genetically linked to the Variscan
granite of the Ehrenfriedersdorf complex, Erzgebirge, Germany, by ion microprobe analyses has determined high concentrations
of Be, up to 10,000 ppm, in one type of melt inclusion, as well as moderate concentrations in the 100 ppm range in a second
type of melt inclusion. Generally, the high Be concentrations are associated with the H2O- and other volatile-rich type-B melt inclusions, and the lower Be concentration levels are connected to H2O-poor type-A melt inclusions. Both inclusion types, representing conjugate melt pairs, are formed by a liquid–liquid immiscibility
separation process. This extremely strong and very systematic scattering in Be provides insights into the origin of Be concentration
and transport mechanisms in pegmatite-forming melts. In this contribution, we present more than 250 new analytical data and
show with ion microprobe and fs-LA-ICPMS studies on quenched glasses, as well as with confocal Raman spectroscopy of daughter
minerals in unheated melt inclusions, that the concentrations of Be may achieve such extreme levels during melt–melt immiscibility
of H2O-, B-, F-, P-, ± Li-enriched pegmatite-forming magmas. Starting from host granite with about 10 ppm Be, melt inclusions with
10,000 ppm Be correspond to enrichment by a factor of over 1,000. This strong enrichment of Be is the result of processes
of fractional crystallization and further enrichment in melt patches of pegmatite bodies due to melt–melt immiscibility at
fluid saturation. We also draw additional conclusions regarding the speciation of Be in pegmatite-forming melt systems from
investigation of the Be-bearing daughter mineral phases in the most H2O-rich melt inclusions. In the case of evolved volatile and H2O-rich pegmatite systems, B, P, and carbonates are important for the enrichment and formation of stable Be complexes. 相似文献
74.
The Portneuf–Mauricie Domain (PMD), located in the south-central part of the Grenville province, contains Mesoproterozoic
Ni–Cu ± platinum-group element (PGE) prospects hosted in a variety of plutonic intrusions (layered, with simple structures,
or zoned) and emplaced in a mature island arc setting. A two-stage model is envisaged to explain the formation of magmatic
sulfides. An early loss of a small amount of sulfides in the conduits of primitive, hydrous mantle-derived melts under high
fO2, resulted in depletion of the magmas in chalcophile and precious metals (Cu/Pd ratios vary from initial mantle values up
to 1.6 × 106). Then, nearer the mineralized zones, the magmas interacted with sulfide-bearing country rocks, resulting in felsification
of the magmas, assimilation of crustal sulfur (δ
34S values up to +5.5‰), and the formation of an immiscible sulfide liquid. Liquid-sulfide formation was followed by variable
interactions between the silicate and sulfide magmas, which were responsible for the enrichment of sulfides in Ni, Cu, and,
locally, PGE. Indeed, low R factors are found for prospects hosted in intrusions with a simple internal structure and in layered intrusions whereas high
R factors are found for prospects hosted in zoned intrusions. Finally, sulfide melt may have been partly incorporated into
later pulses of magma and injected into shallow magma chambers to form the PMD prospects. The PMD prospects share common characteristics
with other well-known deposits (Aguablanca, Vammala, Stormyrplunen, and deposits in Alaskan/Ural-type intrusions), attesting
to the Ni, Cu, and PGE potential of deposits associated with subduction-zone settings. 相似文献
75.
Woodrow B. Thompson Carol B. Griggs Norton G. Miller Robert E. Nelson Thomas K. Weddle Taylor M. Kilian 《Quaternary Research》2011,75(3):552-565
Excavations in the late-glacial Presumpscot Formation at Portland, Maine, uncovered tree remains and other terrestrial organics associated with marine invertebrate shells in a landslide deposit. Buds of Populus balsamifera (balsam poplar) occurred with twigs of Picea glauca (white spruce) in the Presumpscot clay. Tree rings in Picea logs indicate that the trees all died during winter dormancy in the same year. Ring widths show patterns of variation indicating responses to environmental changes. Fossil mosses and insects represent a variety of species and wet to dry microsites. The late-glacial environment at the site was similar to that of today's Maine coast. Radiocarbon ages of 14 tree samples are 11,907 ± 31 to 11,650 ± 50 14C yr BP. Wiggle matching of dated tree-ring segments to radiocarbon calibration data sets dates the landslide occurrence at ca. 13,520 + 95/−20 cal yr BP. Ages of shells juxtaposed with the logs are 12,850 ± 65 14C yr BP (Mytilus edulis) and 12,800 ± 55 14C yr BP (Balanus sp.), indicating a marine reservoir age of about 1000 yr. Using this value to correct previously published radiocarbon ages reduces the discrepancy between the Maine deglaciation chronology and the varve-based chronology elsewhere in New England. 相似文献
76.
Jan P. Amend Thomas M. McCollom Wolfgang Bach 《Geochimica et cosmochimica acta》2011,75(19):5736-5748
Active deep-sea hydrothermal vents are hosted by a range of different rock types, including basalt, peridotite, and felsic rocks. The associated hydrothermal fluids exhibit substantial chemical variability, which is largely attributable to compositional differences among the underlying host rocks. Numerical models were used to evaluate the energetics of seven inorganic redox reactions (potential catabolisms of chemolithoautotrophs) and numerous biomolecule synthesis reactions (anabolism) in a representative sampling of these systems, where chemical gradients are established by mixing hydrothermal fluid with seawater. The wide ranging fluid compositions dictate demonstrable differences in Gibbs energies (ΔGr) of these catabolic and anabolic reactions in three peridotite-hosted, six basalt-hosted, one troctolite-basalt hybrid, and two felsic rock-hosted systems. In peridotite-hosted systems at low to moderate temperatures (<∼45 °C) and high seawater:hydrothermal fluid (SW:HF) mixing ratios (>10), hydrogen oxidation yields the most catabolic energy, but the oxidation of methane, ferrous iron, and sulfide can also be moderately exergonic. At higher temperatures, and consequent SW:HF mixing ratios <10, anaerobic processes dominate the energy landscape; sulfate reduction and methanogenesis are more exergonic than any of the aerobic respiration reactions. By comparison, in the basalt-hosted and felsic rock-hosted systems, sulfide oxidation was the predominant catabolic energy source at all temperatures (and SW:HF ratios) considered. The energetics of catabolism at the troctolite-basalt hybrid system were intermediate to these extremes. Reaction energetics for anabolism in chemolithoautotrophs—represented here by the synthesis of amino acids, nucleotides, fatty acids, saccharides, and amines—were generally most favorable at moderate temperatures (22-32 °C) and corresponding SW:HF mixing ratios (∼15). In peridotite-hosted and the troctolite-basalt hybrid systems, ΔGr for primary biomass synthesis yielded up to ∼900 J per g dry cell mass. The energetics of anabolism in basalt- and felsic rock-hosted systems were far less favorable. The results suggest that in peridotite-hosted (and troctolite-basalt hybrid) systems, compared with their basalt (and felsic rock) counterparts, microbial catabolic strategies—and consequently variations in microbial phylotypes—may be far more diverse and some biomass synthesis may yield energy rather than imposing a high energetic cost. 相似文献
77.
Nicolas D. Greber Beda A. Hofmann Igor M. Villa Thomas F. Nägler 《Geochimica et cosmochimica acta》2011,75(21):6600-6609
We analyzed the molybdenum (Mo) isotope compositions (IC) of 59 samples from two molybdenite mineralizations (Alpjahorn and Grimsel) and from a Mo-rich hydrothermal breccia (Grimsel) from the Aar Massif, Switzerland. The formation temperature of the Late Paleozoic Mo mineralizations (300-600 °C) is much higher than that of the Pliocene breccia (100-160 °C). The Mo IC of the molybdenites varies over 1.35‰. Even in a single hand specimen it spans 0.45‰, indicating that fractionation processes during molybdenite precipitation can vary on a cm scale. The Mo IC of most molybdenites analyzed here are significantly heavier than that of the host rock (δ98/95Mo = (0.05 ± 0.1)‰) and show a bimodal distribution centered around δ98/95Mo ≈ 1.1‰ and 0.2‰. This result rules out single stage Rayleigh fractionation as the relevant formation mechanism and instead, redox variations are suggested to be a main factor controlling the Mo IC of the studied high-temperature Mo deposits. The range of the Mo IC in one single deposit, the Alpjahorn, overlaps with the variation range of almost all other published values for Mo IC in Mo deposits. Compared to the molybdenites, the breccia shows an even wider variation of 3.0‰ (δ98/95Mo between −1.6‰ and +1.4‰). In contrast to the high-T molybdenite deposits, here the Mo was transported via oxidized surface waters into the breccia system, where it was reduced and precipitated. This indicates that oxidation and reduction of Mo complexes may lead to highly variable Mo IC in hydrothermal systems. 相似文献
78.
79.
The leaching behaviour of electrostatic precipitator dust from the Mufulira Cu smelter (Copperbelt, Zambia) was studied using a 48-h pH-static leaching experiment (CEN/TS 14997). The release of metals (Cd, Co, Cu, Ni, Pb and Zn) and changes in mineralogical composition using X-ray diffraction and PHREEQC-2 modelling were investigated in the pH range of 3–7. The highest concentrations of metals were released at pH 3–4.5, which encompasses the natural pH of the dust suspension (~4.3). About 40% of the total Cu was leached at pH 3, yielding 107 g/kg. Chalcanthite (CuSO4·5H2O), magnetite (Fe3O4) and delafossite (CuFeO2) represented the principal phases of the studied dust. In contact with water, chalcanthite was dissolved and hydrated Cu sulphates precipitated at pH 4–7. Gypsum (CaSO4·2H2O) and secondary Fe or Al phases were observed in the leached residues. Serious environmental impact due to leaching may occur in dust-contaminated soil systems in the vicinity of the smelting plants. 相似文献
80.
Atlantic croaker is one of the most abundant demersal fish in Chesapeake Bay. Until recently, when substantial declines in
abundance have occurred, high biomass supported elevated fisheries landings. Therefore, study of the diet of Atlantic croaker
is important to understand its own dynamics and its role in the Chesapeake Bay ecosystem. Patterns in the diet of croaker
varied annually, seasonally, and spatially, but were not strongly correlated with any measured environmental variables. Although
the majority of the diet of croaker consisted of polychaetes and other benthic items, about 20% of the croaker diet by weight
consisted of anchovy and other fishes. Croaker consumption of anchovy is likely a result of crepuscular feeding that has not
been captured in previous studies that sampled during the day and with bottom trawls. Thus, croaker influences both the benthic
and pelagic components of the Chesapeake Bay food web and incorporating such diel patterns in diet may increase the reliability
of fishery ecosystem models. 相似文献