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521.
Elizabeth A. Wentz Donna J. Peuquet Sharolyn Anderson 《International journal of geographical information science》2013,27(9):1309-1325
The availability of spatial data on an unprecedented scale as well as advancements in analytical and visualization techniques gives researchers the opportunity to study complex problems over large urban and regional areas. Nevertheless, few individual data sets exist that provide both the requisite spatial and/or temporal observational frequency to truly facilitate detailed investigations. Some data are collected frequently over time but only at a few geographic locations (e.g., weather stations). Similarly, other data are collected with a high level of spatial resolution but not at regular or frequent time intervals (e.g., satellite data). The purpose of this article is to present an interpolation approach that leverages the relative temporal richness of one data set with the relative spatial richness of another to fill in the gaps. Because different interpolation techniques are more appropriate than others for specific types of data, we propose a space–time interpolation approach whereby two interpolation methods – one for the temporal and one for the spatial dimension – are used in tandem to increase the accuracy results. We call our ensemble approach the space–time interpolation environment (STIE). The primary steps within this environment include a spatial interpolation processor, a temporal interpolation processor, and a calibration processor, which enforces phenomenon-related behavioral constraints. The specific interpolation techniques used within the STIE can be chosen on the basis of suitability for the data and application at hand. In this article, we first describe STIE conceptually including the data input requirements, output structure, details of the primary steps, and the mechanism for coordinating the data within those steps. We then describe a case study focusing on urban land cover in Phoenix, Arizona, using our working implementation. Our empirical results show that our approach increased the accuracy for estimating urban land cover better than a single interpolation technique. 相似文献
522.
523.
Pele has been the most intense high-temperature hotspot on Io to be continuously active during the Galileo monitoring from 1996-2001. A suite of characteristics suggests that Pele is an active lava lake inside a volcanic depression. In 2000-2001, Pele was observed by two spacecraft, Cassini and Galileo. The Cassini observations revealed that Pele is variable in activity over timescales of minutes, typical of active lava lakes in Hawaii and Ethiopia. These observations also revealed that the short-wavelength thermal emission from Pele decreases with rotation of Io by a factor significantly greater than the cosine of the emission angle, and that the color temperature becomes more variable and hotter at high emission angles. This behavior suggests that a significant portion of the visible thermal emission from Pele comes from lava fountains within a topographically confined lava body. High spatial resolution, nightside images from a Galileo flyby in October 2001 revealed a large, relatively cool (<800 K) region, ringed by bright hotspots, and a central region of high thermal emission, which is hypothesized to be due to fountaining and convection in the lava lake. Images taken through different filters revealed color temperatures of 1500±80 K from Cassini ISS data and 1605±220 and 1420±100 K from small portions of Galileo SSI data. Such temperatures are near the upper limit for basaltic compositions. Given the limitations of deriving lava eruption temperature in the absence of in situ measurement, it is possible that Pele has lavas with ultramafic compositions. The long-lived, vigorous activity of what is most likely an actively overturning lava lake in Pele Patera indicates that there is a strong connection to a large, stable magma source region. 相似文献
524.
XMM–Newton surveys of the Canada–France Redshift Survey fields – I. The submillimetre/X-ray relation
525.
Paul F. Scott Pedro Carreira Kieran Cleary Rod D. Davies Richard J. Davis Clive Dickinson Keith Grainge Carlos M. Gutiérrez Michael P. Hobson Michael E. Jones Rüdiger Kneissl Anthony Lasenby Klaus Maisinger Guy G. Pooley Rafael Rebolo José Alberto Rubiño-Martin † Pedro J. Sosa Molina Ben Rusholme ‡ Richard D. E. Saunders Richard Savage Ane Slosar Angela C. Taylor David Titterington Elizabeth Waldram Robert A. Watson § Althea Wilkinson 《Monthly notices of the Royal Astronomical Society》2003,341(4):1076-1083
526.
Gilles Fontaine Elizabeth M. Green Pierre Brassard Stéphane Charpinet Pierre Chayer Malvina Billères Suzanna K. Randall Ben Dorman 《Astrophysics and Space Science》2004,291(3-4):379-386
We briefly review the recent advances that have been made on the front of pulsating subdwarf B (sdB) stars. The first family of sdB pulsators, the EC 14026 stars, was discovered a few years ago and consists of short-period (~100?200 s) p-mode variables. The second type of pulsating sdB’s consists of the PG 1716+426 stars, a group of variables showing long-period (~1 h) g-mode pulsations. The existence of the latter was first reported less than a year ago. While the two types of sdB pulsators differ markedly in their observational characteristics, we recently found a unifying property in the sense that the observed modes in these objects are excited through the same driving process, a classic kappa mechanism associated with the radiative levitation of iron in the stellar envelope. 相似文献
527.
J. E. Smith A. Robinson † S. Young D. J. Axon † Elizabeth A. Corbett 《Monthly notices of the Royal Astronomical Society》2005,359(3):846-864
We present detailed scattering models confirming that distinctive variations in polarization across the broad Hα line, which are observed in a significant fraction of type 1 Seyfert galaxies, can be understood in terms of a rotating line-emitting disc surrounded by a coplanar scattering region (the equatorial scattering region). The predicted polarization properties are: (i) averaged over wavelength, the position angle (PA) of polarization is aligned with the projected disc rotation axis and hence also with the radio source axis; (ii) the polarization PA rotates across the line profile, reaching equal but opposite (relative to the continuum PA) rotations in the blue and red wings; and (iii) the degree of polarization peaks in the line wings and passes through a minimum in the line core. We identify 11 objects that exhibit these features to different degrees. In order to reproduce the large-amplitude PA rotations observed in some cases, the scattering region must closely surround the emission disc and the latter must itself be a relatively narrow annulus – presumably the Hα-emitting zone of a larger accretion disc. Asymmetries in the polarization spectra may be attributable to several possible causes, including bulk radial infall in the equatorial scattering region, or contamination by polar scattered light. The broad Hα lines do not, in general, exhibit double-peaked profiles, suggesting that a second Hα-emitting component of the broad-line region is present, in addition to the disc. 相似文献
528.
529.
Elizabeth R. Stanway Andrew Bunker Richard G. McMahon 《Astrophysics and Space Science》2003,284(2):381-384
Photometric redshifts have proven a powerful tool in identifying galaxies over a large range of lookback times. We have been
generalising this technique to incorporate the selection of candidate high redshift QSOs. We have applied this to a large
optical/near-infrared imaging survey in 6 wavebands aiming to push farther in redshift (and fainter in luminosity) than previous
studies. We believe that study of these very faint and distant objects provides valuable insights into galaxy formation and
evolution. Here we present work in progress and preliminary results for a catalogue of objects detected as part of the Las
Campanas Infrared Survey. This is a stepping stone to the type of survey data that will become available in the next few years
from projects such as UKIDSS and VISTA.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
530.
Source subtraction for the extended Very Small Array and 33-GHz source count estimates 总被引:1,自引:0,他引:1
Kieran A. Cleary † Angela C. Taylor ‡ Elizabeth Waldram Richard A. Battye Clive Dickinson § Rod D. Davies Richard J. Davis Ricardo Genova-Santos Keith Grainge Michael E. Jones ¶ Rüdiger Kneissl G. G. Pooley Rafael Rebolo José Alberto Rubiño-Martín Richard D. E. Saunders Paul F. Scott Ane Slosar David Titterington Robert A. Watson 《Monthly notices of the Royal Astronomical Society》2005,360(1):340-353
We describe the source subtraction strategy and observations for the extended Very Small Array (VSA), a cosmic microwave background interferometer operating at 33 GHz. A total of 453 sources were monitored at 33 GHz using a dedicated source subtraction baseline. 131 sources brighter than 20 mJy were directly subtracted from the VSA visibility data. Some characteristics of the subtracted sources, such as spectra and variability, are discussed. The 33-GHz source counts are estimated from a sample selected at 15 GHz. The selection of VSA fields in order to avoid bright sources introduces a bias into the observed counts. This bias is corrected and the resulting source count is estimated to be complete in the flux-density range 20–114 mJy. The 33-GHz source counts are used to calculate a correction to the VSA power spectrum for sources below the subtraction limit. 相似文献