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1.
Report of the International Astronomical Union Division I Working Group on Precession and the Ecliptic 总被引:1,自引:0,他引:1
J. L. Hilton N. Capitaine J. Chapront J. M. Ferrandiz A. Fienga T. Fukushima J. Getino P. Mathews J.-L. Simon M. Soffel J. Vondrak P. Wallace J. Williams 《Celestial Mechanics and Dynamical Astronomy》2006,94(3):351-367
The IAU Working Group on Precession and the Equinox looked at several solutions for replacing the precession part of the IAU
2000A precession–nutation model, which is not consistent with dynamical theory. These comparisons show that the (Capitaine
et al., Astron. Astrophys., 412, 2003a) precession theory, P03, is both consistent with dynamical theory and the solution most compatible with the IAU 2000A
nutation model. Thus, the working group recommends the adoption of the P03 precession theory for use with the IAU 2000A nutation.
The two greatest sources of uncertainty in the precession theory are the rate of change of the Earth’s dynamical flattening,
ΔJ2, and the precession rates (i.e. the constants of integration used in deriving the precession). The combined uncertainties
limit the accuracy in the precession theory to approximately 2 mas cent−2.
Given that there are difficulties with the traditional angles used to parameterize the precession, zA, ζA, and θA, the working group has decided that the choice of parameters should be left to the user. We provide a consistent set of parameters
that may be used with either the traditional rotation matrix, or those rotation matrices described in (Capitaine et al., Astron.
Astrophys., 412, 2003a) and (Fukushima Astron. J., 126, 2003).
We recommend that the ecliptic pole be explicitly defined by the mean orbital angular momentum vector of the Earth–Moon barycenter
in the Barycentric Celestial Reference System (BCRS), and explicitly state that this definition is being used to avoid confusion
with previous definitions of the ecliptic.
Finally, we recommend that the terms precession of the equator and precession of the ecliptic replace the terms lunisolar precession and planetary precession, respectively. 相似文献
2.
N. R. Sibgatullin 《Astronomy Letters》2001,27(12):799-808
The inclination of low-eccentricity orbits is shown to significantly affect orbital parameters, in particular, the Keplerian, nodal precession, and periastron rotation frequencies, which are interpreted in terms of observable quantities. For the nodal precession and periastron rotation frequencies of low-eccentricity orbits in a Kerr field, we derive a Taylor expansion in terms of the Kerr parameter at arbitrary orbital inclinations to the black-hole spin axis and at arbitrary radial coordinates. The particle radius, energy, and angular momentum in the marginally stable circular orbits are calculated as functions of the Kerr parameter j and parameter s in the form of Taylor expansions in terms of j to within O[j 6]. By analyzing our numerical results, we give compact approximation formulas for the nodal precession frequency of the marginally stable circular orbits at various s in the entire range of the Kerr parameter. 相似文献
3.
Stefano Casotto 《Celestial Mechanics and Dynamical Astronomy》1993,56(3):397-408
An analysis is presented of the orbital injection errors for the Lageos III satellite mission. Several methods are introduced for the solution of the Inverse Problem in the Theory of Errors. The novelty of the present approach consists in the use of the full geopotential covariance matrix in the error propagation equations. The GEM-T1 covariance matrix is used. It is found that by properly accounting for the correlation among the even zonal harmonic coefficients the acceptable error bounds increase by an order of magnitude with respect to the case when only the variances are used. The most stringent constraint, even when using the full covariance, is on inclination, whose nominal value must be realized within approximately 0.1° for the recovery of the Lense-Thirring precession to be successful at the 3% level (accounting only for injection errors). The associated tolerance in the semimajor axis is about 30 km while that in eccentricity is approximately 0.2. However, if the errors in semimajor axis and eccentricity can be kept to the routinely achievable levels respectively of 10 km and 0.004, then the tolerance in inclination can be relaxed to 0.2°. 相似文献
4.
5.
目的:总结正常软骨在改良脂肪抑制三维真实稳态自由进动序列上的表现,与传统序列对比研究软骨显像的图像质量,探讨经过改良以后的脂肪抑制三维真实稳态自由进动序列应用于软骨成像的可行性.方法:应用脂肪抑制三维快速小角度激发序列、三维双回波稳态序列、脂肪抑制快速自旋回波质子密度加权序列,以及经过改良以后的两个脂肪抑制三维真实稳态自由进动序列,对10名志愿者的膝关节进行扫描.测量各序列软骨及关节滑液的信号强度及背景噪声,计算各种方法所得图像的关节软骨的信噪比、关节软骨与滑液的对比噪声比及对比噪声比效率,比较各序列所得的信噪比、对比噪声比及对比噪声比效率之间有无统计学差异.结果:在改良的序列上软骨信号强度介于关节液与邻近骨质之间.6例信号均匀,4例软骨信号可见与脂肪抑制三维快速小角度激发序列相似的分层现象,各序列的信噪比、对比噪声比及对比噪声比效率差异具有显著性.采集次数为2次的脂肪抑制三维真实稳态自由进动序列的对比噪声比及对比噪声比效率优于其他序列.结论:经过改良后的真实稳态自由进动序列可以在保持关节软骨一定的信噪比的前提下在短时间内获得与关节滑液之间具有良好对比噪声比的图像.真实稳态自由进动序列可以用于关节软骨病变的诊断. 相似文献
6.
分量质子旋进磁力仪定向方法的研究 总被引:1,自引:0,他引:1
朱兆才 《地震地磁观测与研究》2000,21(5):16-20
根据分量质子旋进磁力仪补偿线圈电流允许误差 ,补偿线圈轴定向应满足的关系式和给出的允许误差 ,研究并给出了实现分量质子旋进磁力仪各定向标准的实用方法。 相似文献
7.
量子磁力仪研究和开发近况 总被引:11,自引:1,他引:11
介绍了核子旋进磁力仪、欧弗豪泽磁力仪、光泵磁力仪、超导磁力仪和原子磁力仪研究和开发近况, 提出了开展研究工作的建议。 相似文献
8.
Gabriella Della Penna 《Celestial Mechanics and Dynamical Astronomy》1999,75(2):103-124
A model for planetary precession is investigated using analytical and numerical techniques. A Hamiltonian function governing
the model is derived in terms of action-angle Andoyer-Déprit variables under the assumption of equatorial symmetry. As a first
approximation a simplified Hamiltonian with zero-eccentricity is considered and stability estimates are derived using KAM
theory. A validation of the analytical results is performed computing Poincaré surfaces of section for the circular and elliptical
model. We also investigate the role of the eccentricity and its connection with the appearance of resonances. Special attention
is devoted to the particular case of the Earth–Moon system.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
9.
10.
系统地介绍了DTZ系列质子旋进磁力仪的思路和性能特点,通过台站使用认为,DTZ系列仪器能满足地磁台观测精度的要求,具有实际使用的价值。 相似文献