全文获取类型
收费全文 | 1524篇 |
免费 | 117篇 |
国内免费 | 147篇 |
专业分类
测绘学 | 178篇 |
大气科学 | 157篇 |
地球物理 | 332篇 |
地质学 | 443篇 |
海洋学 | 154篇 |
天文学 | 307篇 |
综合类 | 59篇 |
自然地理 | 158篇 |
出版年
2023年 | 17篇 |
2022年 | 24篇 |
2021年 | 26篇 |
2020年 | 33篇 |
2019年 | 56篇 |
2018年 | 36篇 |
2017年 | 37篇 |
2016年 | 40篇 |
2015年 | 46篇 |
2014年 | 72篇 |
2013年 | 74篇 |
2012年 | 49篇 |
2011年 | 64篇 |
2010年 | 40篇 |
2009年 | 84篇 |
2008年 | 76篇 |
2007年 | 114篇 |
2006年 | 84篇 |
2005年 | 87篇 |
2004年 | 79篇 |
2003年 | 72篇 |
2002年 | 59篇 |
2001年 | 55篇 |
2000年 | 63篇 |
1999年 | 48篇 |
1998年 | 56篇 |
1997年 | 36篇 |
1996年 | 30篇 |
1995年 | 27篇 |
1994年 | 15篇 |
1993年 | 23篇 |
1992年 | 26篇 |
1991年 | 17篇 |
1990年 | 15篇 |
1989年 | 17篇 |
1988年 | 8篇 |
1987年 | 15篇 |
1986年 | 7篇 |
1985年 | 9篇 |
1984年 | 3篇 |
1983年 | 3篇 |
1982年 | 5篇 |
1981年 | 2篇 |
1980年 | 3篇 |
1978年 | 3篇 |
1977年 | 3篇 |
1976年 | 6篇 |
1973年 | 4篇 |
1972年 | 10篇 |
1971年 | 7篇 |
排序方式: 共有1788条查询结果,搜索用时 15 毫秒
131.
132.
133.
J. Dommanget 《Journal of Astrophysics and Astronomy》2003,24(3-4):99-109
A research that we conducted in 1963 on the evolution of the binaries based on the available orbital data to obtain a philosophical
degree, led to the establishment of an interesting and new diagram between the logarithm of the total mass and a particular
parameterX, bound to the areal constant. This appeared to have a real physical significance but the basic observational material was
insufficiently extended to assure its undeniable existence. In 1981, a new research based on a more extended orbital material,
has confirmed this diagram. Presently, another important increase in the orbital material and the availability of highly accurate
trigonometric parallaxes produced by the Hipparcos satellite, gave us the opportunity to confirm once more the stability of
this diagram. This last research is here described. 相似文献
134.
M. V. Gyulzadyan J. A. Stepanian A. R. Petrosian D. Kunth B. McLean G. Comte 《Astrophysics》2003,46(2):131-143
The Second Byurakan Survey (SBS) is a well known combined survey, which uses the presence of UV-excess radiation in the continuum, or the presence of emission-lines in the spectra for the identification of active and star-forming galaxies. This paper reports on a comparative study of 77 galaxies identified with UV-excess, and 34 galaxies identified via emission-line techniques in the fields of the SBS. The spectroscopic parameters used for the comparison are the [OII]3727/H and [OIII]5007/H emission-lines ratios, the equivalent widths of [OII]3727, [OIII]5007 and H emission-lines, and the C
[OII]-C
H index. Spectroscopic parameters as well as new redshifts were determined from the spectra obtained with the 6m telescope of the Special Astrophysical Observatory (Russia). The main results are: 1) Galaxies discovered via UV-excess technique are preferably more active. 2) Galaxies discovered via emission-line technique are preferably high-excitation low-luminosity star-forming galaxies. 3) UV-excess galaxies with faintest UV-excess radiation are likely candidates to be LINER or Sy2 type objects. 相似文献
135.
136.
137.
We systematically investigate the encounters between the Sun and neighbouring stars and their effects on cometary orbits in the Oort cloud, including the intrinsic one with the star Gl 710 (HIP 89 825), with some implications to stellar and cometary dynamics. Our approach is principally based on the combination of a Keplerian‐rectilinear model of stellar passages and the Hipparcos Catalogue (ESA 1997). Beyond the parameters of encounter, we pay particular attention to the observational errors in parallaxes and stellar velocities, and their propagation in time. Moreover, as a special case of this problem, we consider the collision probability of a star passing very closely to the Sun, taking also into account the mutual gravitational attraction between the stars. In the part dealing with the influence of stellar encounters on the orbital elements of Oort cloud comets, we derive new simple formulae calculating the changes in the cometary orbital elements, expressed as functions of the Jeans impulse formula. These expressions are then applied to calculate numerical values of the element changes caused by close encounters of neighbouring stars with some model comets in the Oort cloud. Moreover, the general condition for an ejection of comets from the cloud effected by a single encounter is derived and discussed. 相似文献
138.
H. J. Martínez † A. Zandivarez† M. Domínguez‡ M. E. Merchán† D. G. Lambas† 《Monthly notices of the Royal Astronomical Society》2002,333(2):L31-L34
We estimate the fraction of star-forming galaxies in a catalogue of groups, constructed from the 2dF Galaxy Redshift Survey by Merchán & Zandivarez. We use the η spectral type parameter of galaxies and subdivide the sample of galaxies in groups into four types depending on the values of the η parameter following Madgwick et al. We obtain a strong correlation between the relative fraction of galaxies with high star formation and the parent group virial mass. We find that even in the environment of groups with low virial mass M ∼1013 M⊙ the star formation of their member galaxies is significantly suppressed. The relation between the fraction of early-type galaxies and the group virial mass obeys a simple power law spanning over three orders of magnitude in virial mass. Our results show quantitatively the way that the presence of galaxies with high star formation rates is inhibited in massive galaxy systems. 相似文献
139.
140.
The magnetosphere dynamics shows fast relaxation events following power-law distribution for many observable quantities during magnetic substorms. The emergence of such power-law distributions has been widely discussed in the framework of self-organized criticality and/or turbulence. Here, a different approach to the statistical features of these impulsive dynamical events is proposed in the framework of the thermodynamics of rare events [Lavenda, B.H., Florio, A., 1992. Thermodynamics of rare events, Int. J. Theor. Phys. 31, 1455–1475; Lavenda, B.H., 1995. Thermodynamics of Extremes. Albion]. In detail, an application of such a novel approach to the magnetospheric substorm avalanching dynamics as monitored by the auroral electroject index is discussed. 相似文献