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171.
A self-similar solution to the problem of the implosion of a cylindrical shock wave in the presence of a magnetic field has been investigated. A strong shock wave in a cylindrically-symmetric flow travels to the axis of symmetry through a gas of uniform initial density 0 and zero-pressure. A comparative study has been made between the results obtained in ordinary gasdynamics and magnetogasdynamics with transverse and axial components of the magnetic field. The value of similarity exponent has been assigned from that found in the paper of Whitham (1958). 相似文献
172.
Evidence is presented to show that during epochs of high sunspot activity, the duration of manifestation of equatorial spread-F (ESF) irregularities in the Earth's equatorial ionosphere undergoes a systematic modulation around the times of crossing of the heliospheric current sheet by the Earth. The modulation which is assessed as an indirect and geomagnetic activity-associated effect, is characterised by an enhancement in the duration of ESF conditions prior to the current sheet crossing and a reduction thereafter. It is suggested that the observed response of the equatorial ionosphere to the current sheet passage is primarily a manifestation of the geomagnetic activity related modifications in the equatorial east-west electric field in the post-sunset period. 相似文献
173.
The analysis of the fine structure of the Asteroidal Belt evidenciates a group of asteroids next to the resonance 4/9 with Jupiter. In this group and in other groups associated to the Hirayama families there are indications that their orbital parameters can be represented by quantum numbers as defined here and in two of our previous works. Together with this the distribution of the eccentricities and inclinations of the orbital planes of short period comets and diverse type of asteroids indicates that they can be classified as objects with e > sin i and objects with e > sin i with a limit e = sin i which determinates geometrical properties of the orbits related with discrete states in the solar system. This study lets open the possibility of following studies in order to confirm the quantum characteristics of the Asteroidal Belt being these characteristics common to all the solar system and depending of the same fundamental constant of action per mass unit H
0 = 1/2
0 × T
0 (potential × time) because only a small part of all the available data in the Asteroid Belt is used here. 相似文献
174.
Profiles of the O i 7773 triplet obtained at a spatial resolution 0.5 are analyzed using spectral line inversion techniques. Inferences are made about departures from LTE, convective velocity fields, and solar temperature fluctuations. 相似文献
175.
J. L. Halbwachs 《Astrophysics and Space Science》1985,110(1):149-152
The frequency of binaries with degenerate secondary components was evaluated according to the spectral types of the primaries. It appears that this proportion is 25% for binaries with giant primary components, and less than about 17% for dwarfs.Communication presented at the International Conference on Astrometric Binaries, held on 13–15 June, 1984, at the Remeis-Sternwarte Bamberg, Germany, to commemorate the 200th anniversary of the birth of Friedrich Wilhelm Bessel (1784–1846). 相似文献
176.
J. B. Zirker 《Solar physics》1985,102(1-2):33-40
An analysis of prominence hydrogen lines is presented in the spectral band 10–20 . The results are consistent with earlier work.Operated by the Association of Universities for Research in Astronomy, Inc., under contrast AST 84-18716 with the National Science Foundation. 相似文献
177.
"An attempt is made in the light of an analysis of population changes occurring in several sub-districts of Greater Santiago in the period between the last population censuses of 1970 and 1982, based on small-area census units (distritos and communas) to draw attention to the effects on the spatial growth of the city resulting from changed conditions in the political and juridical sphere since the change of power in 1973." The effect of changes in government policy concerning the liberalization of the property market and the illegal occupation of land are noted. (summary in ENG) 相似文献
178.
Radio and X-ray observations are presented for three flares which show significant activity for several minutes prior to the main impulsive increase in the hard X-ray flux. The activity in this ‘pre-flash’ phase is investigated using 3.5 to 461 keV X-ray data from the Solar Maximum Mission, 100 to 1000 MHz radio data from Zürich, and 169 MHz radio-heliograph data from Nançay. The major results of this study are as follows:
- Decimetric pulsations, interpreted as plasma emission at densities of 109–1010 cm?3, and soft X-rays are observed before any Hα or hard X-ray increase.
- Some of the metric type III radio bursts appear close in time to hard X-ray peaks but delayed between 0.5 and 1.5 s, with the shorter delays for the bursts with the higher starting frequencies.
- The starting frequencies of these type III bursts appear to correlate with the electron temperatures derived from isothermal fits to the hard X-ray spectra. Such a correlation is expected if the particles are released at a constant altitude with an evolving electron distribution. In addition to this effect we find evidence for a downward motion of the acceleration site at the onset of the flash phase.
- In some cases the earlier type III bursts occurred at a different location, far from the main position during the flash phase.
- The flash phase is characterized by higher hard X-ray temperatures, more rapid increase in X-ray flux, and higher starting frequency of the coincident type III bursts.
179.
It is proposed that the solar flare phenomenon can be understood as a manifestation of the electrodynamic coupling process of the photosphere-chromosphere-corona system as a whole. The system is coupled by electric currents, flowing along (both upward and downward) and across the magnetic field lines, powered by the dynamo process driven by the neutral wind in the photosphere and the lower chromosphere. A self-consistent formulation of the proposed coupling system is given. It is shown in particular that the coupling system can generate and dissipate the power of 1029 erg s#X2212;1 and the total energy of 1032 erg during a typical life time (103 s) of solar flares. The energy consumptions include Joule heat production, acceleration of current-carrying particles along field lines, magnetic energy storage and kinetic energy of plasma convection. The particle acceleration arises from the development of field-aligned potential drops of 10–150 kV due to the loss-cone constriction effect along the upward field-aligned currents, causing optical, X-ray and radio emissions. The total number of precipitating electrons during a flare is shown to be of order 1037–1038. 相似文献
180.
The data such as the H-spectrum-spectroheliographic (SSHG) observations, the H-chromospheric observations, etc., of a flare loop prominence which occurred on the western solar limb on 1981 April 27 have been obtained at Yunnan Observatory. The distribution of the internal motions and the macroscopical motion of the flare loop prominence with time and space in the course of its eruption and ascension is derived from the comprehensive analysis of the data. The possible physical pictures and the instability of the motions of the loop are inferred and discussed. 相似文献