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221.
Giuseppe Altavilla Maria Teresa Botticella Enrico Cappellaro Massimo Turatto 《Astrophysics and Space Science》2012,341(1):163-178
Despite decades of dedicated efforts there are still basic questions to answer with regard to Supernova progenitor systems and explosion mechanisms. In particular, in the last years a number of exceptionally bright objects and extremely faint events have demonstrated an unexpected large Supernova variety. 相似文献
222.
Teresa Moreno Fulvio Amato Xavier Querol Andrés Alastuey Josep Elvira Wes Gibbons 《Environmental Geology》2009,57(2):411-420
Given the relevance of desert aerosols to environmental issues such as dust storms, climate change and human health effects,
we provide a demonstration of how the bedrock geology of an arid area influences the mineralogy and geochemistry of even the
finest particulate matter (i.e., the inhalable fraction <10 μm in size: PM10). PM10 samples extracted from desert sediments at geologically contrasting off-road sites in central and southeastern Australia
(granitic, high grade metamorphic, quartzitic sandstone) were analyzed using X-ray diffraction (XRD), scanning electron microscopy
(SEM), inductively coupled plasma atomic emission spectrometry (ICP-AES) and inductively coupled plasma mass spectrometry
(ICP-MS). The “granitic” PM10 are highly alkali feldspathic and illitic, with a wide range of accessory minerals including rutile (TiO2), monazite [(Ce, La, Nd, Th, Y) PO4], xenotime (YPO4), apatite [Ca5(PO4)3 (F, OH, Cl)], hematite (Fe3O4), zircon (ZrSiO4) and thorite (ThSiO4). This mineralogy is reflected in the geochemistry which shows notable enrichments in rare earth elements (REE) and most
high field strength elements (both held in the accessory minerals), and higher than normal levels of low (<2.0) ionic potential
elements (Na, K, Li, Cs, Rb: held in alkali feldspar and illite). The “metamorphic” resuspended PM10 define a mineralogy clearly influenced by local exposures of pelitic and calc-silicate schists (sillimanite, muscovite, calcite,
Ca-amphibole), a dominance of monazite over other REE-bearing phases, and a geochemistry distinguished by enrichments in alkaline
earth metals (Ca, Mg, Ba, Sr) and depletion in heavy REE. The “quartzite” PM10, derived from rocks already recycled by Precambrian erosion and sedimentary transport, show a sedimentologically mature mineralogy
of mostly quartz and kaolinite, detrital accessory ilmenite, rutile, monazite and hematite, and the strongest geochemical
depletion (especially K, Rb, Cs, Na, Ca, Mg, Ba). 相似文献
223.
Geographical distribution of arsenic in sediments within the Rio Conchos Basin,Mexico 总被引:1,自引:0,他引:1
Melida Gutierrez M. Teresa Alarcón-Herrera Lucy M. Camacho 《Environmental Geology》2009,57(4):929-935
Arsenic (As) content of sediments from the Rio Conchos and Rio San Pedro in northern Mexico were measured to determine if
this toxic metalloid had accumulated to unsafe levels to humans and aquatic life. The spatial distribution of As in each of
the six clusters of river and arroyo sediments was analyzed to determine variations with respect to background levels and
to infer about potential As sources and sinks. In the northern part of the study area, background concentrations varied little
throughout the area and concentrations in river sediments were close to background levels. In the southern part, however,
the content of As in arroyo sediment contained a wider range of values and anomalous concentrations. The latter could be traced
in part to the presence of mine tailings. As concentrations were below the limit in all studied river stretches and thus do
not pose an immediate threat to the river environment, but As content in reservoir sediments exceeded the guideline values.
Reservoirs seem to act as a sink for As, warranting closer observation and monitoring. 相似文献
224.
Geomorphological heritage is a widely used term in European and North-American countries, but is still scarcely mentioned
in Africa. Nevertheless, the attractiveness of the African countries is often intimately connected to its breathtaking and
endless geological landscapes. Morocco is one of those countries that has the widest diversity in landscapes and landforms,
ranging from the Mediterranean and Atlantic coasts over the Rif, Middle Atlas, High Atlas and Anti-Atlas mountain chains to
the great rocky and sandy deserts in the South. A wide variety of geological units hosting different types of important economic
mineral deposits cover a temporal range from Late Precambrian to Quaternary. A detailed geomorphological study has been carried
out in the region of Ifrane and Azrou (Middle Atlas, Central Morocco) using a combination of high resolution satellite data
and direct field observations integrated by geological maps and scientific literature. In order to describe and evaluate the
geomorphological heritage of this area, 40 geomorphosites have been selected comprising springs, karst landforms (polje, dolines,
caves, sinkholes, stone forests, cryptokarstic dolines), carbonate depositional landforms (travertines and waterfalls), fluvial
landforms (meanders, canyons, palaeo-valleys, etc.), structural landforms (triangular facets, hogbacks, cuestas, residual
outcrops, etc.) and volcanic landforms (volcanoes, caldeira, pyroclastic cones, lava tube). The results of this research have
been summarised in a thematic map, representing the geomorphosites related to various landscape units. 相似文献
225.
Susana Serrano Peggy A. O’Day Maria Teresa García-González 《Geochimica et cosmochimica acta》2009,73(3):543-558
The bioavailability and fate of heavy metals in the environment are often controlled by sorption reactions on the reactive surfaces of soil minerals. We have developed a non-electrostatic equilibrium model (NEM) with both surface complexation and ion exchange reactions to describe the sorption of Pb and Cd in single- and binary-metal systems over a range of pH and metal concentration. Mineralogical and exchange properties of three different acidic soils were used to constrain surface reactions in the model and to estimate surface densities for sorption sites, rather than treating them as adjustable parameters. Soil heterogeneity was modeled with >FeOH and >SOH functional groups, representing Fe- and Al-oxyhydroxide minerals and phyllosilicate clay mineral edge sites, and two ion exchange sites (X− and Y−), representing clay mineral exchange. An optimization process was carried out using the entire experimental sorption data set to determine the binding constants for Pb and Cd surface complexation and ion exchange reactions.Modeling results showed that the adsorption of Pb and Cd was distributed between ion exchange sites at low pH values and specific adsorption sites at higher pH values, mainly associated with >FeOH sites. Modeling results confirmed the greater tendency of Cd to be retained on exchange sites compared to Pb, which had a higher affinity than Cd for specific adsorption on >FeOH sites. Lead retention on >FeOH occurred at lower pH than for Cd, suggesting that Pb sorbs to surface hydroxyl groups at pH values at which Cd interacts only with exchange sites. The results from the binary system (both Pb and Cd present) showed that Cd retained in >FeOH sites decreased significantly in the presence of Pb, while the occupancy of Pb in these sites did not change in the presence of Cd. As a consequence of this competition, Cd was shifted to ion exchange sites, where it competes with Pb and possibly Ca (from the background electrolyte). Sorption on >SOH functional groups increased with increasing pH but was small compared to >FeOH sites, with little difference between single- and binary-metal systems. Model reactions and conditional sorption constants for Pb and Cd sorption were tested on a fourth soil that was not used for model optimization. The same reactions and constants were used successfully without adjustment by estimating surface site concentrations from soil mineralogy. The model formulation developed in this study is applicable to acidic mineral soils with low organic matter content. Extension of the model to soils of different composition may require selection of surface reactions that account for differences in clay and oxide mineral composition and organic matter content. 相似文献
226.
Teresa A. Myers Matthew C. Nisbet Edward W. Maibach Anthony A. Leiserowitz 《Climatic change》2012,113(3-4):1105-1112
Communication researchers and practitioners have suggested that framing climate change in terms of public health and/or national security may make climate change more personally relevant and emotionally engaging to segments of the public who are currently disengaged or even dismissive of the issue. To evaluate these assumptions, using a nationally representative online survey of U.S. residents (N?=?1,127) conducted in December, 2010, we randomly assigned six previously identified audience segments on climate change to one of three experimental conditions. Subjects were asked to read uniquely framed news articles about climate change emphasizing either the risks to the environment, public health, or national security and the benefits of mitigation and adaptation-related actions. Results show that across audience segments, the public health focus was the most likely to elicit emotional reactions consistent with support for climate change mitigation and adaptation. Findings also indicated that the national security frame may possibly boomerang among audience segments already doubtful or dismissive of the issue, eliciting unintended feelings of anger. 相似文献
227.
An experimental investigation of antigorite dehydration in natural silica-enriched serpentinite 总被引:1,自引:0,他引:1
José Alberto Padrón-Navarta Jörg Hermann Carlos J. Garrido Vicente López Sánchez-Vizcaíno María Teresa Gómez-Pugnaire 《Contributions to Mineralogy and Petrology》2010,159(1):25-42
Piston cylinder experiments were performed to constrain the pressure and temperature conditions for two high-pressure antigorite
dehydration reactions found in silica-enriched serpentinites from Cerro del Almirez (Nevado–Filábride Complex, Betic Cordillera,
southern Spain). At 630–660°C and pressures greater than 1.6 GPa, antigorite first reacts with talc to form orthopyroxene ± chlorite + fluid.
We show that orthopyroxene + antigorite is restricted to high-pressure metamorphism of silica-enriched serpentinite. This
uncommon assemblage is helpful in constraining metamorphic conditions in cold subduction environments, where antigorite serpentinites
have no diagnostic assemblages over a large pressure and temperature range. The second dehydration reaction leads to the breakdown
of antigorite to olivine + orthopyroxene + chlorite + fluid. The maximum stability of antigorite is found at 680°C at 1.9 GPa,
which also corresponds to the maximum pressure limit for tremolite coexisting with olivine + orthopyroxene. The high aluminium
(3.70 wt% Al2O3) and chromium contents (0.59 wt% Cr2O3) of antigorite in the investigated starting material is responsible for the expansion of the serpentinite stability to 60–70°C
higher temperatures at 1.8 GPa than the antigorite stability calculated in the Al-free system. The antigorite from our study
has the highest Al–Cr contents among all experimental studies and therefore likely constraints the maximum stability of antigorite
in natural systems. Comparison of experimental results with olivine–orthopyroxene–chlorite–tremolite assemblages outcropping
in Cerro del Almirez indicates that peak metamorphic conditions were 680–710°C and 1.6–1.9 GPa. 相似文献
228.
Teresa Oberc-Dziedzic Ryszard Kryza Ksenia Mochnacka Alexander Larionov 《International Journal of Earth Sciences》2010,99(1):27-46
Approximately 500-Ma-old orthogneisses are widespread in the eastern part of the Variscan belt and are commonly interpreted
to have intruded mica-schist series of assumed Neoproterozoic age. New SHRIMP zircon ages of quartzofeldspathic metavolcanogenic
rocks of the mica schist series in the eastern part of the Karkonosze-Izera Massif (SW Poland) indicate that they are late
Cambrian/early Ordovician rather than Neoproterozoic in age, based on the zircon age spectra distributed mainly between ca.
500 and 660 Ma (with a few Proterozoic inherited minimum ages of ca. 970 and 1,825 Ma). Younger zircon dates, dispersed between
ca. 412 and 464 Ma, are interpreted as a result of Pb-loss likely caused by subsequent metamorphism. Consequently, the felsic
metavolcanogenic rocks appear to be roughly contemporaneous with the intrusion of ca. 500-Ma-old orthogneiss protoliths (with
the pooled concordia age of 487 ± 8 Ma interpreted as the best approximation of the protolith intrusive age). Field relationships,
petrological and geochemical features of the felsic and mafic rocks studied support a model in which the accompanying mica
schist series are not the original country rocks to the ca. 500 Ma granite intrusions, and indicate that their recent close
proximity is the result of tectonic juxtaposition. However, both the mica schists enclosing the bimodal metavolcanic rocks,
and the orthogneisses, are interpreted to represent a Cambro-Ordovician passive continental margin sequence being part of
the Saxothuringian domain. They are tectonically overlain to the east by HP/T metamorphic units, comprising MORB-type metaigneous
rocks, and delineating a tectonic suture separating the Saxothuringian block in the west from an assumed continental block
(Tepla-Barrandian) to the south-east. 相似文献
229.
This work aims to estimate the potential effects of the global warming projected for the twenty-first century on the biodiversity of a remote and pristine region of the Neotropics called Pantepui. Habitat loss and fragmentation by upward migration of bioclimatic conditions is analyzed using Species-Area Relationships (SAR) and Altitudinal Range Displacement (ARD) analysis. The ARD is a tool that uses the present-day lapse rate to estimate the upward migration of the species based on the global warming predicted by the IPCC. The results show that around 80% of the vascular flora, ca. 1,700 species of which up to 400 would be Pantepui endemics, are threatened of extinction. These estimates should be considered preliminary, but the danger is real. Therefore, suitable conservation or mitigation strategies are needed. 相似文献
230.