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61.
We present an analysis of the spatial orientations of 1315 galaxies in 10 Abell clusters of BM type II–III (type II–III in the Bautz–Morgan system). It is found that the spin-vector orientations of the galaxies in six clusters (Abell 168, 426, 1035, 1227, 1367 and 1904) tend to lie parallel to the Local Supercluster (LSC) plane. The spin-vector projections of galaxies in six clusters (Abell 168, 1020, 1035, 1227, 1904 and 1920) are found to be oriented perpendicular with respect to the direction of the LSC centre. Three clusters (Abell 1920, 2255 and 2256) show a bimodal orientation: spin vectors tend to be oriented both parallel and perpendicular to the LSC plane. No dependence of radial velocity, distance and cluster magnitude on galaxy orientation is noticed. In a comparison with previous work, we noticed that the anisotropy might increase from early-type (BM type I) to late-type (BM types II–III and III) clusters. We notice a vanishing angular momentum for the less massive galaxy clusters (richness class 0). A significant alignment of the angular momenta of galaxies for massive clusters, e.g. the core of the Shapley Supercluster (richness class 4, M > 1015 M⊙ ), is found. 相似文献
62.
63.
M. G. Abrahamyan 《Astrophysics》2005,48(4):514-531
The classical Riemann S-ellipsoids are generalized to account for a Ferrers inhomogeneity in the mass distribution, a three-dimensional
anisotropy of the velocity dispersions, and the gravitation of a spheroidal halo. The Ferrers inhomogeneity does not affect
the equilibrium and stability conditions for the ellipsoids, but only changes the numerical coefficients in the equilibrium
parameters. The anisotropy of the velocity dispersions changes both the equilibrium conditions and the criterion for stability
of the ellipsoids, either extending or limiting the region in which the ellipsoids exist. A halo extends this region in all
cases and stabilizes the ellipsoids. The observed of the velocity dispersions of stars in the neighborhood of the sun are
obtained using the inhomgeneous model.
__________
Translated from Astrofizika, Vol. 48, No. 4, pp. 613–632 (November 2005). 相似文献
64.
N. Voglis P. Tsoutsis C. Efthymiopoulos 《Monthly notices of the Royal Astronomical Society》2006,373(1):280-294
In the presence of a strong m = 2 component in a rotating galaxy, the phase-space structure near corotation is shaped to a large extent by the invariant manifolds of the short-period family of unstable periodic orbits terminating at L 1 or L 2 . The main effect of these manifolds is to create robust phase correlations among a number of chaotic orbits large enough to support a spiral density wave outside corotation. The phenomenon is described theoretically by soliton-like solutions of a Sine–Gordon equation. Numerical examples are given in an N -body simulation of a barred spiral galaxy. In these examples, we demonstrate how the projection of unstable manifolds in configuration space reproduces essentially the entire observed bar–spiral pattern. 相似文献
65.
We suggest a new method for estimating the fractal dimension of the spatial distribution of galaxies: the method of selected cylinders. We show the capabilities of this method by constructing a two-point conditional column density for galaxies with known redshifts from the LEDA database. The fractal dimension of a sample of LEDA and EDR SDSS galaxies has been estimated to be 2.1±0.1 for cylinder lengths of 200 Mpc. A major advantage of the suggested method is that it allows scales comparable to the catalog depth to be analyzed for galaxy surveys in the form of conical sectors and small fields in the sky. 相似文献
66.
Observations in the submillimetre (submm) waveband have recently revealed a new population of luminous sources. These are proposed to lie at high redshift and to be optically faint because of their high intrinsic dust obscuration. The presence of dust has been previously invoked in optical galaxy count models which use the Bruzual & Charlot evolution models with an exponential τ =9 Gyr star formation rate (SFR) for spirals, and these fit the count data well from U to K . We now show that by using either a 1/ λ or Calzetti absorption law for the dust and re-distributing the evolved spiral galaxy ultraviolet (UV) radiation into the far-infrared (FIR), these models can account for all of the 'faint' ( 1 mJy) 850-μm galaxy counts, but fail to fit 'bright' ( 2 mJy) sources, indicating that another explanation for the submm counts may apply at brighter fluxes, e.g., quasi-stellar objects (QSOs) or ultraluminous infrared galaxies (ULIRGs). We find that the main contribution to the faint, submm number counts is in the redshift range 0.5< z <3, peaking at z ≈1.8. The above model, using either dust law, can also explain a significant proportion of the extragalactic background at 850 μm, as well as producing a reasonable fit to the bright 60-μm IRAS counts. 相似文献
67.
Xiaolei Zhang 《Astrophysics and Space Science》2002,281(1-2):281-284
One of the important consequences of a newly discovered secular dynamical evolution process of spiral galaxies (Zhang, 1996,
1998, 1999) is that the orbiting disk matter receives energy injection each time it crosses the spiral density wave crest.
This energy injection has been shown to be able to quantitatively explain the observed age-velocity-dispersion relation of
the solar neighborhood stars. We demostrate in this paper that similar energy injection into the interstellar medium could
serve as the large-scale energy source to continuously power the observed interstellar turbulence and to offset its downward
cascade tendency.
This revised version was published online in September 2006 with corrections to the Cover Date. 相似文献
68.
69.
Søren S. Larsen Duncan A. Forbes Jean P. Brodie 《Monthly notices of the Royal Astronomical Society》2001,327(4):1116-1126
We explore the rich globular cluster (GC) system of the nearby Sa galaxy M104, the 'Sombrero' (NGC 4594), using archive Wide Field Planetary Camera 2 data. The GC colour distribution is found to be bimodal at the >99 per cent confidence level, with peaks at and . The inferred metallicities are very similar to those of GCs in our Galaxy and M31. However, the Sombrero reveals a much enhanced number of red (metal-rich) GCs compared to other well-studied spirals. Because the Sombrero is dominated by a huge bulge and only has a modest disc, we associate the two subpopulations with the halo and bulge components, respectively. Thus our analysis supports the view that the metal-rich GCs in spirals are associated with the bulge rather than with the disc. The Sombrero GCs have typical effective (half-light) radii of ∼2 pc with the red ones being ∼30 per cent smaller than the blue ones. We identify many similarities between the GC system of the Sombrero and those of both late-type spirals and early-type galaxies. Thus both the GC system and the Hubble type of the Sombrero galaxy appear to be intermediate in their nature. 相似文献
70.
We are conducting a systematic study of a carefully selected sampleof nearby E/S0 galaxies and Sa bulges using the unique
panoramic integral-fieldspectrograph SAURON, mounted at the WHT. The goal of the SAURON projectis to fully map the gaseous/stellar
kinematics and the stellar populations of a representative sample of 80 early-type galaxies up to 1 Re,probing different environments
(clusters, field). These data, used in combination with existing ground-based and HST observations, and fed to the theoretical
machinery we have developed, will allow to determine theintrinsic dynamical structure of the galaxies. We will also measure
the masses of central black holes, relate the internal dynamics to the ageand metallicity of the stellar populations, and
establish the historyof metal enrichment as a function of Hubble type and environment. Some brief results on two targets observed
during the SAURON campaign will serve as an illustration of the unique and high quality data we are currently gathering.
This revised version was published online in September 2006 with corrections to the Cover Date. 相似文献