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871.
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Detecting colour changes of a gravitational microlensing event induced by the limb-darkened extended source effect is important for obtaining useful information about both the lens and the source star. However, precise measurements of the colour changes are hampered by blending, which also causes colour changes of the event. In this paper, we show that although the colour change measured from the subtracted image by using the recently developed photometric method of the 'difference image analysis' (DIA) differs from the colour change measured by using the conventional method based on the extraction of the individual source stars' point spread functions, the curve of the colour changes (colour curve) constructed by using the DIA method enables one to obtain the same information about the lens and source star, but with significantly reduced uncertainties due to the absence of blending. We investigate the patterns of the DIA colour curves for both single lens and binary lens events by constructing colour change maps. 相似文献
873.
P. M. Phillips I. W. A. Browne P. N. Wilkinson 《Monthly notices of the Royal Astronomical Society》2001,321(2):187-198
We present the results of an unbiased radio search for gravitational lensing events with image separations between 15 and 60 arcsec, which would be associated with clusters of galaxies with masses >1013–14 M⊙ . A parent population of 1023 extended radio sources stronger than 35 mJy with stellar optical identifications was selected using the FIRST radio catalogue at 1.4 GHz and the APM optical catalogue. The FIRST catalogue was then searched for companions to the parent sources stronger than 7 mJy and with separation in the range 15 to 60 arcsec. Higher-resolution observations of the resulting 38 lens candidates were made with the VLA at 1.4 and 5 GHz, and with MERLIN at 5 GHz in order to test the lens hypothesis in each case. None of our targets was found to be a gravitational lens system. These results provide the best current constraint on the lensing rate for this angular scale, but improved calculations of lensing rates from realistic simulations of the clustering of matter on the relevant scales are required before cosmologically significant constraints can be derived from this null result. We now have an efficient, tested observational strategy with which it will be possible to make an order-of-magnitude larger unbiased search in the near future. 相似文献
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Naoki Seto 《Monthly notices of the Royal Astronomical Society》2002,333(2):469-474
The binary confusion noise spectrum in the Laser Interferometer Space Antenna ( LISA ) band depends strongly on the observational period and abundance of Galactic close white dwarf binaries (CWDBs). We have investigated how the number of the resolved Galactic CWDBs varies with the operation period of LISA , and found that the resolved number would typically grow by a factor of 5 when the operation period increases from 1 to 10 yr. We have also made a similar estimation for the number of CWDBs, the chirp signal of which can be measured using matched filtering analysis. 相似文献
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Catherine Heymans Michael L. Brown Marco Barden John A. R. Caldwell Knud Jahnke Chien Y. Peng Hans-Walter Rix y Taylor Steven V. W. Beckwith Eric F. Bell rea Borch Boris Häußler Shardha Jogee Daniel H. McIntosh Klaus Meisenheimer Sebastian F. Sánchez Rachel Somerville Lutz Wisotzki Christian Wolf 《Monthly notices of the Royal Astronomical Society》2005,361(1):160-176
879.
C. J.Fluke R. L.Webster D. J.Mortlock 《Monthly notices of the Royal Astronomical Society》2002,331(1):180-196
Using the ray-bundle method for calculating gravitational lens magnifications, we outline a method by which the magnification probability may be determined specifically in the weak lensing limit for cosmological models obtained from N -body simulations.
16 different models are investigated, which are variations on three broad classes of cold dark matter model: the standard model with (Ω0 , λ 0 )=(1.0,0.0) , the open model with (Ω0 , λ 0 )=(0.3,0.0) and the lambda model, which is a flat model with a cosmological constant (Ω0 , λ 0 )=(0.3,0.7) .
The effects of varying the Hubble parameter, H0 , the power spectrum shape parameter, Γ, and the cluster mass normalization, σ 8 , are studied. It is shown that there is no signature of these parameters in the weak lensing magnification distributions. The magnification probability distributions are also shown to be independent of the numerical parameters such as the lens mass and simulation box size in the N -body simulations. 相似文献
16 different models are investigated, which are variations on three broad classes of cold dark matter model: the standard model with (Ω
The effects of varying the Hubble parameter, H
880.