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71.
72.
Recent spectroscopic observations of galaxies in the Fornax Cluster reveal nearly unresolved 'star-like' objects with redshifts appropriate to the Fornax Cluster. These objects have intrinsic sizes of ≈100 pc and absolute B -band magnitudes in the range −14< M B <−11.5 mag and lower limits for the central surface brightness μ B ≳23 mag arcsec−2 , and so appear to constitute a new population of ultracompact dwarf galaxies (UCDs). Such compact dwarfs were predicted to form from the amalgamation of stellar superclusters (by Kroupa) , which are rich aggregates of young massive star clusters (YMCs) that can form in collisions between gas-rich galaxies. Here we present the evolution of superclusters in a tidal field. The YMCs merge on a few supercluster crossing times. Superclusters that are initially as concentrated and massive as knot S in the interacting Antennae galaxies evolve to merger objects that are long-lived and show properties comparable to the newly discovered UCDs. Less massive superclusters resembling knot 430 in the Antennae may evolve to ω Cen-type systems. Low-concentration superclusters are disrupted by the tidal field, dispersing their surviving star clusters while the remaining merger objects rapidly evolve into the μ B − M B region populated by low-mass Milky Way dSph satellites. 相似文献
73.
In this paper the researchers collected 28 times of maximum light including 4 times of those observed at the Xinglong station,
the National Astronomical Observation of China between May 27, 2004 and June 1, 2004 and 1 time of maximum light from a 60
cm telescope on May 4, 1984. It found that the O-C point distribution was more completely compared than in any papers published
before. The period is decreasing at the rate of about (1.4±0.1)×10−8 per year, which should not be caused by stellar evolution. It might be only part of a binary orbital light-time variation
or other unknown reason. The time scale is longer than Pocs and Szeidl’s suggestion; the star needs more observations before
we can be certain of the exact light-time variation. 相似文献
74.
75.
76.
R. F. Griffin 《Journal of Astrophysics and Astronomy》1988,9(3):127-136
Photoelectric radial-velocity measurements show that HD 106947 is a double-lined spectroscopic binary. The components have
spectral types of about F6 V and G5 V and are in a 59-day orbit of moderate eccentricity. The system is a member of the Coma
Cluster. 相似文献
77.
Vanessa Doublier 《Astrophysics and Space Science》2002,281(1-2):211-212
Planetary Nebulae have proven to be an essential key to understand the long term chemical enrichment of the interstellar medium
due to low mass stars. They allow to study the original abundances of the star, and the effect of the star on the interstellar
medium. Blue compact dwarf galaxies are known to host violent star formation in very heavy element depleted environments.
They also show traces of past star formation (Doublier et al., 1999; 2001), including AGB starsand red giants which are responsible
for long term enrichment. However, models fails to reproduce the low metallicities observed if those stars are taken into
account. We observed PNe in BCDGs, and made a comparative study of the abundances in the HII regions and of the PNe.
This revised version was published online in September 2006 with corrections to the Cover Date. 相似文献
78.
79.
Summary The unprecedented quality of the IRAS data prompted a series of papers reinvestigating the origin of the galactic infrared/submillimeter radiation and the nature of the heating sources of the interstellar dust. The scope of this paper is to review the main results of these new studies. Sect. 1 contains a general introduction to the subject and an overview of the earlier work. In Sect. 2 and 3, we summarize our current knowledge on dust properties and on the interstellar radiation field. Then, we present the recent interpretations of the infrared emission of our Galaxy, which are based on the IRAS data: in Sect. 4 we present the results from the galactic disk; Sect. 5 covers the question of the contribution from small dust particles, and in Sect. 6 we describe the infrared radiation from the galactic center. The nature of the heating sources and the origin of the galactic infrared radiation is then discussed in Sect. 7. Finally, Sect. 8 presents a comparison of our Galaxy with external galaxies 相似文献
80.