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91.
While analyzing the archival data of the INTEGRAL observatory, we detected and localized a cosmic gamma-ray burst recorded on April 28, 2006, by the IBIS/ISGRI and SPI telescopes in their fields of view. Since the burst was not revealed by the INTEGRAL burst alert system (IBAS), information about its coordinates was not distributed in time and no search for its afterglow was conducted. The burst was recorded by the KONUS/WIND and RHES SI satellites. Its 20–200-keV fluence was 2.3 × 10?6 erg cm?2, the peak flux was 3.6 × 10?7 erg cm?2 s?1 (3.9 phot. cm?2 s?1). The burst had a complex multipeaked profile and stood out among typical bursts by an increase in its hardness with time. At the flux peak, the spectrum was characterized by a photon index α ? ?1.5 and a peak energy E p ? 95 keV. The burst lasted for ~12 s, after which its afterglow decaying as a power law with an index γ ~ ?4.5 was observed at energies 15–45 keV. The spectral hardness decreased noticeably during the afterglow. 相似文献
92.
S. L. Ginzburg V. F. D’yachenko V. V. Paleychik A. L. Sudarikov V. M. Chechetkin 《Astronomy Letters》2004,30(6):376-381
Based on the Maxwel-Vlasov equations, we consider the possible generation mechanisms of hard emission through the growth of plasma instabilities in a relativistic jet composed of electrons and protons. The accelerated material of the jet moves by inertia. When a small difference arises between the electron and proton velocities (which may result from the interaction of jet material with background plasma or from the acceleration mechanism) plasma instabilities can grow. The particle distribution functions, which were initially delta functions both in angle and in energy, transform into complex angular and energy dependences. In this case, the probability of collisions between high-energy particles in the jet increases, resulting in hard gamma-ray emission. 相似文献
93.
Aeolian soils in the Blayney district are characterised by having approximately 80% of their mass finer than 63 μm, Ti/Zr ratios of approximately 12, radioelement contents of 0.7% K, 2 ppm eU and 11 ppm eTh and a position high in the landscape. Their Ti/Zr ratio and abundant quartz content distinguishes them from soils derived from Tertiary basalts, which share some of the other characteristics. Many soils in the district have a partial aeolian contribution, which can be recognised by a Ti/Zr ratio that differs from that of the underlying rock. Abundance of an aeolian contribution suggests that airborne radiometric surveys should be very carefully interpreted. Ground studies suggest that high Th content in soils contrasted with low Th in adjacent rocks can be indicative of an aeolian contribution in soils. A substantial amount of fine material in a soil can also significantly dilute geochemical signatures if −63 μm (<80 mesh) samples are used for soil surveys during exploration. 相似文献
94.
Scientific objectives and payloads of Chang’E-1 lunar satellite 总被引:1,自引:0,他引:1
Sun Huixian Dai Shuwu Yang Jianfeng Wu Ji Jiang Jingshan 《Journal of Earth System Science》2005,114(6):789-794
China plans to implement its first lunar exploration mission Chang’E-1 by 2007. The mission objectives are
To achieve the above mission goals, five types of scientific instruments are selected as payloads of the lunar craft. These
include stereo camera and spectrometer imager, laser altimeter, microwave radiometer, gamma and X-ray spectrometers and space
environment monitor system. In order to collect, process, store and transmit the scientific data of various payloads a special
payload data management system is also included. In this paper the goals of Chang’E-1 and its payloads are described 相似文献
– | • to obtain a three-dimensional stereo image of the lunar surface, |
– | • to determine distribution of some useful elements and to estimate their abundance |
– | • to survey the thickness of lunar soil and to evaluate resource of3He and |
– | • to explore the environment between the Moon and Earth. |
95.
Gamma-ray spectrometer(GRS) is used to detect the elemental abundances and distributions on the lunar surface.To derive the elemental abundances,it is vital to acquire background gamma rays except lunar gamma rays.So GRS would observe background spectra in the course of earth-moon transfer on schedule.But in fact,GRS was not switched on in the course of flying toward the moon.After the CE-1 probe finished one-year mission,GRS car-ried out a test on background data on November 21?22,2008.The authors did conduct research on the methods of background deduction using 2105 hours of usable gamma-ray spectra acquired at the 200-km orbital height by the GRS and more than 5 hours of gamma-ray spectra acquired in the GRS background test.The final research results showed that the method of deducting the background using the minimum counts in the CE-1 GRS pixels is optimal for the elements,U,K and Th.The method applies to such a case that the elemental abundances in the pixel with the minimum counting rate are 0 μg/g and the continuum background counts are constant over the Moon.Based on the method of background deduction,the full energy peak counts of U,K,and Th are calculated. 相似文献
96.
由于地面γ能谱测量所反映的是表层土壤中的情况,因此地表影响因素,如介质的粒度、湿度及环境温度等成为不可忽视的干扰因素。经试验的数据曲线分析表明,介质粒度越大,其γ场降低,衰减率高;而介质的湿度越大,介质对射线的吸收量增高,衰减率增高。选择适当的季节,进行γ能谱测量也是很重要的。 相似文献
97.
Xiao-Hong Zhao Jin-Ming Bai 《中国天文和天体物理学报》2007,7(4):503-508
A Gamma-ray burst (GRB) is generally believed to be a jet with a small opening angle, this opening angle is usually derived with the afterglow light curve break time using an analytical method. Here we show that the method is not accurate. Using the set of equations of hydrodynamic evolution with the sideways expansion at the local sound speed derived by previous authors and the observed light curve break times, we numerically derive the initial opening angles. Then the collimation-corrected energies (Eγ) for a sample of GRBs are calculated. They are found to show a wide spread, suggesting that the previously declared clustering by some authors may not exist. Also, the Epeak -Eγ relation, claimed by some other authors (Epeak is the spectral peak energy), is found still to hold, with a slightly stronger correlation. 相似文献
98.
99.
Juan Cortina 《Astrophysics and Space Science》2005,297(1-4):245-255
The 17 m Major Atmospheric Gamma Imaging Cherenkov (MAGIC) telescope for gamma-ray astronomy between 30 and 300 GeV started
operations in its final configuration in October 2003 and is currently well into its calibration phase. Here I report on its
present status and its first gamma-ray source detections. 相似文献
100.
I. A. Grenier M. M. Kaufman Bernadó G. E. Romero 《Astrophysics and Space Science》2005,297(1-4):109-118
A subset of the unidentified EGRET γ-ray sources with no active galactic nucleus or other conspicuous counterpart appears
to be concentrated at medium latitudes. Their long-term variability and their spatial distribution indicate that they are
distinct from the more persistent sources associated with the nearby Gould Belt. They exhibit a large scale height of 1.3
± 0.6 kpc above the Galactic plane. Potential counterparts for these sources include microquasars accreting from a low-mass
star and spewing a continuous jet. Detailed calculations have been performed of the jet inverse Compton emission in the radiation
fields from the star, the accretion disc, and a hot corona. Different jet Lorentz factors, powers, and aspect angles have
been explored. The up-scattered emission from the corona predominates below 100 MeV whereas the disc and stellar contributions
are preponderant at higher energies for moderate (∼15∘) and small (∼1∘) aspect angles, respectively. Yet, unlike in the high-mass, brighter versions of these systems, the external Compton emission
largely fails to produce the luminosities required for 5 to 10 kpc distant EGRET sources. Synchrotron-self-Compton emission
appears as a promising alternative. 相似文献