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991.
J. A. Combi J. F. Albacete Colombo L. Pellizza J. López-Santiago G. E. Romero J. Martí A. J. Muñoz-Arjonilla E. Sánchez-Ayaso P. L. Luque-Escamilla J. R. Sánchez-Sutil 《Astrophysics and Space Science》2011,331(1):53-61
We present a catalog of cross-correlated radio, infrared and X-ray sources using a very restrictive selection criteria with
an IDL-based code developed by us. The significance of the observed coincidences was evaluated through Monte Carlo simulations
of synthetic sources following a well-tested protocol. We found 3320 coincident radio/X-ray sources with a high statistical
significance characterized by the sum of error-weighted coordinate differences. For 997 of them, 2MASS counterparts were found.
The percentage of chance coincidences is less than 1%. X-ray hardness ratios of well-known populations of objects were used
to provide a crude representation of their X-ray spectrum and to make a preliminary diagnosis of the possible nature of unidentified
X-ray sources. The results support the fact that the X-ray sky is largely dominated by Active Galactic Nuclei at high galactic
latitudes (|b|≥10°). At low galactic latitudes (|b|≤10°) most of unidentified X-ray sources (∼94%) lie at |b|≤2°. This result suggests that most of the unidentified sources found toward the Milky Way plane are galactic objects. Well-known
and unidentified sources were classified in different tables with their corresponding radio/infrared and X-ray properties.
These tables are intended as a useful tool for researchers interested in particular identifications. 相似文献
992.
R. Chandra B. Schmieder C. H. Mandrini P. Démoulin E. Pariat T. Török W. Uddin 《Solar physics》2011,269(1):83-104
We present and interpret observations of two morphologically homologous flares that occurred in active region (AR) NOAA 10501
on 20 November 2003. Both flares displayed four homologous Hα ribbons and were both accompanied by coronal mass ejections
(CMEs). The central flare ribbons were located at the site of an emerging bipole in the centre of the active region. The negative
polarity of this bipole fragmented in two main pieces, one rotating around the positive polarity by ≈ 110° within 32 hours.
We model the coronal magnetic field and compute its topology, using as boundary condition the magnetogram closest in time
to each flare. In particular, we calculate the location of quasi-separatrix layers (QSLs) in order to understand the connectivity between the flare ribbons. Though several polarities were present in AR 10501,
the global magnetic field topology corresponds to a quadrupolar magnetic field distribution without magnetic null points.
For both flares, the photospheric traces of QSLs are similar and match well the locations of the four Hα ribbons. This globally
unchanged topology and the continuous shearing by the rotating bipole are two key factors responsible for the flare homology.
However, our analyses also indicate that different magnetic connectivity domains of the quadrupolar configuration become unstable
during each flare, so that magnetic reconnection proceeds differently in both events. 相似文献
993.
994.
Martin Nekola René Hudec Martin Jelínek Matůš Kocka Petr Kubánek Filip Münz Cyril Polášek Vojtěch Šimon Jan Štrobl 《Experimental Astronomy》2010,28(1):79-85
We report on two small aperture robotic telescopes called BART and D50 operated in Ondřejov. Both telescopes are capable of
automatic observation of gamma ray burst (GRB) optical afterglows. Coordinates of GRBs are taken from alerts distributed via
Internet. Telescopes observe other interesting high energy sources when there is not any alert. The smaller telescope BART
has aperture D = 254 mm. The bigger telescope D50 has a primary mirror of diameter D = 500 mm. Both telescopes are controlled
by free software package RTS2 and are accessible through Internet. We describe the two telescopes and related software and
show some results such as our first observed optical counterpart of GRB. 相似文献
995.
Vladimír Skalský 《Astrophysics and Space Science》2010,330(2):373-398
Assuming that the relativistic universe is homogeneous and isotropic, we can unambiguously determine its model and physical properties, which correspond with the Einstein general theory of relativity (and with its two special partial solutions: Einstein special theory of relativity and Newton gravitation theory), quantum mechanics, and observations, too. 相似文献
996.
C. Rodríguez-López A. Moya R. Garrido J. MacDonald R. Oreiro A. Ulla 《Astrophysics and Space Science》2010,329(1-2):205-209
Mode trapping of high-radial order gravity modes was found for a particular sdO model. The trapping is caused by the change in composition from the helium radiative shell to the hydrogen burning shell. A non-adiabatic effect of this trapping is the higher tendency to instability of the trapped modes. Low- to intermediate-radial order pressure modes (in sdO models they correspond to mixed modes with most nodes in the P-mode region) are found to be trapped by the chemical transition from the carbon-oxygen core to the He burning shell. As the trapping is produced in the deep interior of the star, where energy interchange is negligible at the p-mode frequencies, it has no particular effect on the driving. 相似文献
997.
We calculate NLTE models of stellar winds of hot compact stars (central stars of planetary nebulae and subdwarf stars). The studied range of subdwarf parameters is selected to cover a large part of these stars. The models predict the wind hydrodynamical structure and provide mass-loss rates for different abundances. Our models show that CNO elements are important drivers of subdwarf winds, especially for low-luminosity stars. We study the effect of X-rays and instabilities on these winds. Due to the line-driven wind instability, a significant part of the wind could be very hot. 相似文献
998.
The north – south asymmetries (NSA) of three solar activity indices are derived and mutually compared over a period of more
than five solar cycles (1945 – 2001). A catalogue of the hemispheric sunspot numbers, the data set of the coronal green line
brightness developed by us, and the magnetic flux derived from the NSO/KP data (1975 – 2001) are treated separately within
the discrete low- and mid-latitude zones (5° – 30°, 35° – 60°). The calculated autocorrelations, cross-correlations, and regressions
between the long-term NSA data sets reveal regularities in the solar activity phenomenon. Namely, the appearance of a distinct
quasi-biennial oscillation (QBO) is evident in all selected activity indices. Nevertheless, a smooth behavior of QBO is derived
only when sufficient temporal averaging is performed over solar cycles. The variation in the significance and periodicity
of QBO allows us to conclude that the QBO is not persistent over the whole solar cycle. A similarity in the photospheric and
coronal manifestations of the NSA implies that their mutual relation will also show the QBO. A roughly two-year periodicity
is actually obtained, but again only after significant averaging over solar cycles. The derived cross-correlations are in
fact variable in degree of correlation as well as in changing periodicity. A clear and significant temporal shift of 1 – 2
months in the coronal manifestation of the magnetic flux asymmetry relative to the photospheric manifestation is revealed
as a main property of their mutual correlation. This shift can be explained by the delayed large-scale coronal manifestation
in responding to the emergence of the magnetic flux in the photosphere. The reliability of the derived results was confirmed
by numerical tests performed by selecting different numerical values of the used parameters. 相似文献
999.
Zdeněk ?vestka 《Solar physics》2010,267(2):235-250
I recount my career in solar physics beginning at Ondřejov Observatory in 1948 and ending with my ∼30 year stay at the Laboratory
of Space Research in Utrecht. 相似文献
1000.