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551.
Carl B. Agee 《Physics of the Earth and Planetary Interiors》1997,100(1-4):41-47
Melting temperatures of the silicate fraction of the Allende CV3 meteorite, at upper mantle pressures, are several hundred degrees lower than that of fertile peridotite xenoliths or ‘pyrolite’. If the Earth accreted from material similar to chondrites, then deep mantle melting could have occurred with a relatively modest heat budget. It is concluded that initial chemical composition is an important variable in realistic magma ocean models. 相似文献
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553.
A Landscape Ecology Approach to Assessing Development Impacts in the Tropics: A Geothermal Energy Example in Hawaii 总被引:1,自引:0,他引:1
Jerry A. Griffith Carl C. Trettin & Robert V. O'Neill 《Singapore journal of tropical geography》2002,23(1):1-22
Geographic information systems (GIS) are increasingly being used in environmental impact assessments (EIA) because GIS is useful for analysing spatial impacts of various development scenarios. Spatially representing these impacts provides another tool for landscape ecology in environmental and geographical investigations by facilitating analysis of the effects of landscape pattern on ecological processes and examining change over time. Landscape ecological principles are applied in this study to a hypothetical geothermal development project on the Island of Hawaii. Some common landscape pattern metrics were used to analyse dispersed versus condensed development scenarios and their effect on landscape pattern. Indices of fragmentation and patch shape did not appreciably change with additional development. The amount of forest to open edge, however, greatly increased with the dispersed development scenario. In addition, landscape metrics showed that a human disturbance had a greater simplifying effect on patch shape and also increased fragmentation than a natural disturbance. The use of these landscape pattern metrics can advance the methodology of applying GIS to EIA. 相似文献
554.
The subsurface structure of Hagia Sophia, one of the oldest sacred monuments in the world built between 532–537 under the reign of Justinian in today's Istanbul, has been investigated by using two relative LaCoste-Romberg gravimeters in order to detect hidden cavities which have also served as earthquake dampers in similar constructions. On the building's ground floor a grid of 100 points with a grid size of about 4.m was measured. The mean gravimetric point error was ± 3.10–8 ms–2. The result of the examination is that cavities were not detected in the inner central part of Hagia Sophia with a larger diameter than 8.m down to a depth of about 20.m, and Hagia Sophia's foundation was found to be a slope of natural rock with a downward inclination to the East that has a small crest symmetrical to the building's East-West axis. 相似文献
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557.
G. de Vaucouleurs J. Blunck M. Davies A. Dollfus I.K. Koval G.P. Kuiper H. Masursky S. Miyamoto V.I. Moroz Carl Sagan Bradford Smith 《Icarus》1975,26(1):85-98
A new nomenclature for Martian regions and topographic features uncovered by Mariner 9, as officially adopted by the International Astronomical Union, is described. About 180 craters, generally of diameters >100 km, have been named, as well as 13 classes of topographic features designated catena, chasma, dorsum, fossa, labyrinthus, mensa, mons, patera, planitia, planum, tholus, vallis, and vastitas. In addition seven craters and the Kepler Dorsum are named on Phobos, and two craters on Deimos. Coordinates and maps of each named features are displayed. 相似文献
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559.
Carl Sagan 《Icarus》1973,18(4):649-656
Both non-gray radiative equilibrium and gray convective equilibrium calculations for Titan indicate that the discrepancy between the equilibrium temperature of an atmosphereless Titan and the observed infrared temperatures can be explained by a massive molecular hydrogen greenhouse effect. The convective calculations indicate a probable minimum optical depth of 14, corresponding to many tens of km-atm of H2, and total pressures of ~0.1 bar. The tropopause is several hundred km above the Titanian surface and at a temperature of about 90°K. Methane condensation is likely at this level. Such an atmosphere is unstable against atmospheric blow-off unless typical mesosphere scale heights are < 25km, an unlikely situation. Blow-off can also be circumvented by exospheric temperatures near the freezing point of hydrogen. It is considered more plausible that the present atmosphere is in equilibrium between outgassing and blow-off of the one hand and accretion from protons trapped in a hypothetical Saturnian magnetic field on the other; or exhibits uncompensated blow-off of outgassing products. To maintain the present blow-off rate without compensation for all of geological time requires an outgassing equivalent to the volatilization of a few km of subsurface ices. Photo-dissociation of these volatilized ices produces the observed high abundance of H2 as well as large quantities of complex organic chromophores which may explain the reddish coloration of the Titanian cloud deck. An extensive circum-Titanian hydrogen corona is postulated. Surface temperatures as high as 200°K are not excluded. Because of its high temperatures and pressures and the probable large abundance of organic compounds, Titan is a prime target for spacecraft exploration in the outer solar system. 相似文献
560.
The reflectivity of the Martian surface has been measured between 2.0 and 4.0 μ. A broad absorption band is observed which has a minimum at 2.85μm. The position and shape of the band is compared to features in numerous terrestrial minerals. Bound water in the Martian surface material is the most likely cause of the observed band. The strength of the observed band suggests a bound water content of approx. 1% by weight. The band is inconsistent with > a few % limonito or hydrated polymeric carbon suboxide. A mean particle radius ~100μm is deduced. The quality of bound water derived has a range of geological, climatic, and exobiological implications 相似文献