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121.
A newly developed direction finding (DF) technique for auroral hiss based on the measurement of time differences of wave arrival was carried out in 1978 at Syowa Station (geomag. lat. -70.4°), Antarctica and its two slave unmanned observing points located at about 20 km distances from Syowa. The auroral hiss signals (0.3–100 kHz) received at the two spaced points were transmitted to Syowa by a wide-band telemeter of 2 GHz. The arrival time difference of auroral hiss between Syowa and each spaced point was automatically determined by cross-correlating the waveforms of the received signals, and then the incident and azimuthal angles were measured with an accuracy of about 10°.It has been found that the new DF technique can determine localized exit regions at the ionospheric level which show rapid temporal movements. A comparison of the DF results with ground-based auroral data has shown that impulsive type auroral hiss with a wide-band frequency range has not emerged from the whole region of a bright aurora but from some localized regions of bright electron auroras at the ionospheric level, and that the arrival directions of auroral hiss change rapidly in accordance with the auroral movements. 相似文献
122.
Comprehensive global energetics analysis is carried out for the NCAR CCM2 with different horizontal resolutions of R15, T42,
T63, and T106 to assess the effect of various model truncations on the global energetics characteristics in climate models.
Both the energy levels and energy transformations are examined over the zonal wave number domain during a northern winter
and summer. In addition to the simulated atmosphere, the ECMWF global analysis during 1986 to 1990 is analyzed for comparison
using the same diagnostic scheme. Previous studies have revealed that zonal kinetic energy is supplied by synoptic disturbances
in terms of the zonal-wave interactions of kinetic energy. According to our result, however, such an energy flow from eddies
to zonal motions is valid only for zonal wave numbers up to about 30. We find that the zonal-wave interactions of kinetic
energy change sign beyond wave number 30 where the energy is transformed from zonal to eddies for both the ECMWF and CCM2-T106.
The large-scale zonal motions are diffusive against the short waves beyond wave number 30, which may well be parameterized
by various forms of the diffusion schemes. We suggest from this result that the atmospheric disturbances with wave numbers
lower than 30 are necessary to represent accurately the two-way interactions between zonal and eddy motions, because these
waves can actively influence the behavior of the zonal motions. Based on this finding, we suggest that the model resolution
of R15 is inadequate for climate studies from the energetics point of view, and that resolution of T42 is the minimum requirement
to represent the general circulation adequately. Some other discrepancies are discussed in detail for the coarse resolution
climate models.
Received: 15 July 1996/Accepted: 3 January 1997 相似文献
123.
124.
A. C. Brinkman J. Heise R. Mewe A. J. F. den Boggende J. Schrijver E. Gronenschild Y. Tanaka D. R. Parsignault J. Grindlay E. Schreier H. Schnopper H. Gursky 《Astrophysics and Space Science》1976,42(1):201-204
Measurements obtained with the Utrecht (1–8 keV) and Cambridge (1–28 keV) instruments on board the Astronomical Netherlands Satellite are discussed. Particularly, the 4.8 hr period is investigated.Paper presented at the COSPAR Symposium on Fast Transients in X- and Gamma-Rays, held at Varna, Bulgaria, 29–31 May, 1975. 相似文献
125.
126.
On the basis of observations (Zirin and Tanaka, 1973) inferring the presence of shear in magnetic fields, the amount of extractable energy stored in a class of force-free magnetic fields is evaluated for the flares of August 1972, using the formulations developed by Nakagawa and Raadu (1972). It is shown that the evaluated energy storage could be built up by the proper motions of sunspots in the active region McMath 11976 during July 31 and August 7. Then for the flare of August 7, a detailed analysis is made of the manner of energy release in the post maximum phases deduced from the configuration of flare loops. It is shown that the observed flare loops could be represented closely by the force-free magnetic fields and that the evaluated rate of energy release is consistent with observed rate given by the soft X-ray emission. The results of analysis suggest that the flare of August 1972 could be identified with the relaxation of an energetic force-free magnetic field towards lower energy states. The limitations and possible future extension of this type of analysis are discussed.Visiting scientist from the Tokyo Astronomical Observatory, Mitaka, Tokyo, Japan.The National Center for Atmospheric Research is sponsored by the National Science Foundation. 相似文献
127.
Using the results from special observations, the storm-time effects on whistler characteristics at low latitudes were examined and found to agree with previous statistical studies. A short discussion is made on the link between spread-F irregularities and magnetospheric whistler ducts. The enhanced whistler activity is explained as a consequence of the stable whistler duct region during spread-F conditions. 相似文献
128.
M. Matsuoka M. Fujii S. Miyamoto J. Nishimura M. Oda Y. Ogawara S. Hayakawa I. Kasahara F. Makino Y. Tanaka P. C. Agrawal B. V. Sreekantan 《Astrophysics and Space Science》1972,18(2):472-490
Simultaneous hard X-ray and optical observations of Sco X-1 were carried out on 1971 May 1 at Hyderabad, India, when Sco X-1 was optically bright. The X-ray intensity observed by balloon-borne counter telescopes increased in coincidence with optical enhancements, while the plasma temperature derived by fitting the X-ray spectrum in the energy range 20–40 keV to the thermal bremsstrahlung spectrum did not appreciably change over the whole period of observation. 相似文献
129.
Y. Fukada S. Hayakawa M. Ikeda I. Kasahara F. Makino Y. Tanaka 《Astrophysics and Space Science》1975,32(1):L1-L5
The energy spectrum of diffuse hard X-rays measured in the range 10–40 keV shows a rather sharp change of slope. The logarithmic derivative of the spectrum changes around 20–30 keV by the increment significantly greater than 0.5 within an interval smaller than 50 keV. 相似文献
130.
Based on the observations of the EUV spectroheliograms, the effective chromosphere-corona transition region is assumed to be restricted in a small volume element in the boundaries of the supergranular network. The center-to-limb variation of the quiet Sun at cm and dm wavelengths is analyzed to determine where the transition region is located in the network boundaries. Expressions are derived for the theoretical center-to-limb variation of the hypothetical brightness temperature only from the transition region, taking into account the orientation of the spicules. Comparison with the observations shows that the spicule-sheath model (Brueckner and Nicolas, 1973) and the hot plagette model (Foukal, 1974) are not compatible with the observations, because the limb brightening predicted by these models is too great. A new picture is therefore proposed that thin platelet transition regions are placed on top of the chromosphere and scattered between the network boundaries (the platelet transition-region model). This model is in accord with the observed center-to-limb variation of the radio emission. 相似文献