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741.
742.
Images from three filters of the Voyager 1 wide-angle camera were used to measure the continuum reflectivity and spectral gradient near 6000 Å and the 6190-Å band methane/continuum ratio for a variety of cloud features in Jupiter's atmosphere. The dark “barge” features in the North Equatorial Belt have anomalously strong positive continuum spectral gradients suggesting unique composition, probably not elemental sulfur. Methane absorption was shown at unprecedented spatial scales for the Great Red Spot and its immediate environment, for a dark barge feature in the North Equatorial Belt, and for two hot spot and plume regions in the North Equatorial Belt. Some small-scale features, unresolvable at ground-based resolution, show significant enhancement in methane absorption. Any enhancement in methane absorption is conspicuously absent in both hot spot regions with 5-μm brightness temperature 255°K. Methane absorption and 5-μm emission are correlated in the vicinity of the Great Red Spot but are anticorrelated in one of the plume hot spot regions. Methane absorption and simultaneously maps of 5-μm brightness temperature were quantitatively compared to realistic cloud structure models which include multiple scattering at 5 μm as well as in the visible. A curve in parameter space defines the solution to any observed quantity, ranging from a shallow atmosphere and thin NH3 cloud to a deep atmosphere with a thick ammonia cloud. Without additional constraints, such as center-to-limb information, it is impossible to specify the NH3 cloud optical depth and pressure of a deeper cloud top independently. Variability in H2 quadrupole lines was also investigated and it was found that the constancy of the 4-0 S(1)-line equivalent width is consistent with the constancy of the methane 6190-Å band equivalent width at ground-based resolution, but the much greater variability of the 3-0 S(1) line is inconsistent with either the methane band or 4-0 S(1) line. In hot spot regions the 255°K brightness temperature requires a cloud optical depth of about 2 or less at 5 μm in the NH3 cloud layer. To be consistent with the observed 6190-Å methane absorption in hot spot regions, the NH3 cloud optical depth in the visible is about 7.5, implying that aerosols in hot spot regions have effective radii near 1 μm or less. 相似文献
743.
Monte Carlo radiative transfer techniques are used to develop a height-dependent spicule model based upon a more realistic configuration than has hitherto been considered. The spicule is represented by a uniform cylinder, of finite length, standing vertically upon a plane chromosphere. The observed, limb-darkened, anisotropic chromospheric flux incident upon the cylinder is incorporated into the transfer calculations.The resulting model is characterized by a random, line broadening velocity of 20 km/sec, with electron temperature increasing from 6 × 103 K at the base to about 1.5 × 104 K at 11500 km above the solar surface. The corresponding values of electron density are 8 × 1011 cm-3 and 4 × 1010 cm-3. Contrast curves of the spicule model against the chromospheric background are computed and indicate that spicules should appear both bright and dark on the disk, depending upon their position with respect to the limb, the spectral frequency of observation and the viewing height.This work is based on a Ph.D. thesis submitted to the Department of Astro-Geophysics, University of Colorado.The National Center for Atmospheric Research is sponsored by the National Science Foundation. 相似文献
744.
The Nazareth(b) meteorite is a medium octahedrite found in 1968 near Nazareth, Texas. It contains 8.75% nickel and large schreibersite inclusions 相似文献
745.
746.
747.
The history of the definition of salinity and the methods of computing It are traced from the beginning of the twentieth century until the present. Difficulties that have arisen in existing practices are discussed, in particular, the situation regarding reduction of in-situ CTD observations. The Practical Salinity Scale 1978 is an attempt to remove the shortcomings; it has been recommended for international acceptance. The basis for this new scale is an equation relating the ratio of the electrical conductivity of the seawater sample to that of a standard potassium chloride solution (KCI) at15deg C atmospheric pressure. The samples used were prepared from standard seawater diluted with distilled water or evaporated by weight. Finally, the set of new equations for CTD data reduction is given, based upon the work of authors whose papers are appearing elsewhere in this volume. 相似文献
748.
749.
Yu Jingjing Li Xiao-Feng Lewis Elizabeth Blenkinsop Stephen Fowler Hayley J. 《Climate Dynamics》2020,54(5):2919-2940
Climate Dynamics - There is an urgent need for high-quality and high-spatial-resolution hourly precipitation products around the globe, including the UK. Although hourly precipitation products... 相似文献
750.
Helen J. Fraser Suzanne E. Bisschop Klaus M. Pontoppidan Alexander G. G. M. Tielens Ewine F. van Dishoeck 《Monthly notices of the Royal Astronomical Society》2005,356(4):1283-1292
A solid-state feature was detected at around 2175 cm−1 towards 30 embedded young stellar objects in spectra obtained using the Infrared Spectrometer and Array Camera at the European Southern Observatory Very Large Telescope. We present results from laboratory studies of CO adsorbed at the surface of zeolite wafers, where absorption bands were detected at 2177 and 2168 cm−1 (corresponding to CO chemisorbed at the zeolite surface) and 2130 cm−1 (corresponding to CO physisorbed at the zeolite surface), providing an excellent match to the observational data. We propose that the main carrier of the 2175-band is CO chemisorbed at bare surfaces of dust grains in the interstellar medium. This result provides the first direct evidence that gas–surface interactions do not have to result in the formation of ice mantles on interstellar dust. The strength of the 2175-band is estimated to be ∼4 × 10−19 cm molecule−1 . The abundance of CO adsorbed at bare grain surfaces ranges from 0.06 to 0.16 relative to H2 O ice, which is, at most, half of the abundance (relative to H2 O ice) of CO residing in H2 O-dominated ice environments. These findings imply that interstellar grains have a large (catalytically active) surface area, providing a refuge for interstellar species. Consequently, the potential exists for heterogeneous chemistry to occur involving CO molecules in unique surface chemistry pathways not currently considered in gas grain models of the interstellar medium. 相似文献