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91.
Evidence is presented of a periodic component in the inter-annual variability of precipitation and pressure data for India
during June, the month of the onset of the Indian southwest monsoon. Two frequencies that explain a statistically significant
percent of the variance in these data sets are the same as the two that explain most of the variance of the average monthly
lunar tidal potential for June. Not only are the frequencies the same but they are also in phase which strongly suggests that
lunar tides in the atmosphere do, in fact, produce an element of climatic variability. The amplitude of the atmospheric response
to this periodic forcing was not constant in time but was found to be related to the long term change in northern hemispheric
surface temperature. This susceptibility of the atmosphere to an external forcing results in a nonlinear relationship between
forcing and response. As a result, nonlinear regression had to be used in order to adequately define the magnitude of the
response at a given frequency. The ramifications of this nonlinear response are discussed. The nonlinear interaction of the
northern hemisphere temperature and the 18.6 year lunar nodal cycle results in a modulation of the frequency which appears
in a linear spectral analysis near 22 years. Thus, the 22-year cycle often found in meteorological data sets may instead be
the result of the modulated nodal cycle. 相似文献
92.
月球地形测绘和月球大地测量(5) 总被引:8,自引:1,他引:8
主要介绍月球地形测绘和月球大地测量的情况。第一部分论述了月球大地测量(Selenodesy)的定义和方法。月球大地测量的一个特点是它的观测数据绝大部分都要依靠航天探测器或环月、绕月卫星来获取。月球大地测量的内容可以考虑有三个方面:一是在月球上给出一个有确定定义的坐标参考系,并在其中布测一个控制网;二是确定这一月球参考系的大地测量几何和物理常数;三是求定月球的外部重力场。第二部分介绍月球地形测绘。重点介绍了月球地形的特点,它大体分为月海、月陆、环形山等三种类型。 相似文献
93.
V. V. Ivashkin 《Journal of Earth System Science》2005,114(6):613-618
The Moon-to-Earth low energy trajectories of ‘detour’ type are found and studied within the frame of the Moon-Earth-Sun-particle
system. These trajectories use a passive flight to the Earth from an initial elliptic selenocentric orbit with a high aposelenium.
The Earth perturbation increases the particle selenocentric energy from a negative value first to zero and then to a positive
one and therefore leads to a passive escape of the particle motion from the Moon attraction near the translunar libration
pointL
2. This results in the particle flight to a distance of about 1.5 million km from the Earth where the Sun gravitation decreases
the particle orbit perigee distance to a small value that leads to the particle approaching the Earth vicinity in about 100
days of the flight. A set of the Moon-to-Earth ‘detour’ trajectories is defined numerically. Characteristics of these trajectories
are presented. The ‘detour’ trajectories give essential economy of energy (about 150 m/s in Delta V) relative to the usual
ones. 相似文献
94.
Abhijit Basu 《Journal of Earth System Science》2005,114(3):375-380
Back scattered electron and transmission electron imaging of lunar soil grains reveal an abundance of submicrometer-sized
pure Fe0 globules that occur in the rinds of many soil grains and in the submillimeter sized vesicular glass-cemented grains called
agglutinates. Grain rinds are amorphous silicates that were deposited on grains exposed at the lunar surface from transient
vapors produced by hypervelocity micrometeorite impacts. Fe0 may have dissociated from Fe-compounds in a high temperature (>3000°C) vapor phase and then condensed as globules on grain
surfaces. The agglutinitic glass is a quenched product of silicate melts, also produced by micrometeorite impacts on lunar
soils. Reduction by solar wind hydrogen in agglutinitic melts may have produced immiscible droplets that solidified as globules.
The exact mechanism of formation of such Fe0 globules in lunar soils remains unresolved. 相似文献
95.
E. M. Galimov 《Journal of Earth System Science》2005,114(6):801-806
The Russian Luna-Glob project has been conceived with a view to understand the origin of the Earth-Moon system. The objectives
and main features of the Luna-Glob mission, which will mainly study the internal structure of the Moon by seismic instruments,
are described in the context of the past and current program of lunar exploration in Russia. 相似文献
96.
Numerical investigations have been carried out to analyse the evolution of lunar circular orbits and the influence of the
higher order harmonics of the lunar gravity field. The aim is to select the appropriate near-circular orbit characteristics,
which extend orbit life through passive orbit maintenance. The spherical harmonic terms that make major contributions to the
orbital behaviour are identified through many case studies. It is found that for low circular orbits, the 7th and the 9th
zonal harmonics have predominant effect in the case of orbits for which the evolution is stable and the life is longer, and
also in the case of orbits for which the evolution is unstable and a crash takes place in a short duration. By analysing the
contribution of the harmonic terms to the orbit behaviour, the appropriate near-circular orbit characteristics are identified. 相似文献
97.
Yu. ShkuratovA. Ovcharenko E. ZubkoO. Miloslavskaya K. MuinonenJ. Piironen R. NelsonW. Smythe V. RosenbushP. Helfenstein 《Icarus》2002,159(2):396-416
To better understand the negative polarization and brightness opposition effects observed on airless celestial bodies, we carried out simultaneous photometric and polarimetric measurements of laboratory samples that simulate the structure of planetary regoliths. Computer modeling of shadow-hiding and coherent backscatter in regolith-like media are also presented. The laboratory investigations were carried out with a photometer/polarimeter at phase angles covering 0.2°-4° and wavelengths of 0.63 and 0.45 μm. We studied samples that characterize a variety of microscopic structures and albedos. A particle-size dependence of the negative branch of polarization for powdered dielectric surfaces was found. Colored samples such as a powder Fe2O3 exhibit a very prominent wavelength dependence of the photometric and polarimetric opposition phenomena. Metallic powders usually exhibit a wide branch of the negative polarization independent of the size of particles. For fine dielectric powders, both opposition phenomena become more prominent when the samples were compressed. Our computer modeling based on ray tracing in particulate media shows that shadow-hiding affects the negative polarization only in combination with the coherent backscatter enhancement. Modeling reveals that scattering orders higher than second contribute to negative polarization even in dark particulate surfaces. Our model qualitatively reproduces the effects of varying sample-compression that we observed in the laboratory. Our experimental and computer modeling studies mutually confirm that the degree of polarization for highly reflective dielectric surfaces depends not only on phase angle but also on surface tilt. Even at exactly zero phase the degree of polarization for tilted surfaces can be nonzero. A tilt of the surface normal to the scattering plane gives a parallel shift of the negative polarization branch to large values of |P|. The tilt in the perpendicular plane gives the same shift in the direction of positive polarization. At exactly zero phase angle, a celestial body of irregular shape can exhibit nonzero polarization even in integral polarimetric observations. 相似文献
98.
High speed photometry during the lunar occultation of a stellar system provides an effective means of achieving high angular
resolution in one dimension at the sub arc second level which is well suited for resolving close binary projected separations
in the range of 10–100 milliarc seconds. An optical fast photometer designed for such a purpose is described and some results
from the initial observations taken with the system including the resolution of a projected separation of 55 milli arcsecond
in one binary system are detailed. 相似文献
99.
100.
LIU Jiyu School of Geodesy Geomatics Wuhan University Luoyu Road Wuhan China. 《地球空间信息科学学报》2007,10(1):1-3
According to our engineering research on satellite-borne laser retroreflector array, some suggestions are proposed on how to manufacture a new Apollo LLRA that can make us measure one illuminating point and unilluminating area on the moon's surface. These suggestions are: to control the dihedral angle offset within ± 0.1″; to use the larger aperture of the transparent face of cube corner prisms; to investigate how to separate out Apollo's reflected laser from mixed beam hitting on the LLR system. 相似文献