全文获取类型
| 收费全文 | 6472篇 |
| 免费 | 21篇 |
| 国内免费 | 23篇 |
专业分类
| 测绘学 | 35篇 |
| 大气科学 | 1124篇 |
| 地球物理 | 1519篇 |
| 地质学 | 3526篇 |
| 海洋学 | 80篇 |
| 天文学 | 151篇 |
| 综合类 | 4篇 |
| 自然地理 | 77篇 |
出版年
| 2013年 | 107篇 |
| 2009年 | 63篇 |
| 2006年 | 61篇 |
| 2005年 | 54篇 |
| 2004年 | 48篇 |
| 2002年 | 48篇 |
| 1997年 | 52篇 |
| 1996年 | 93篇 |
| 1995年 | 53篇 |
| 1994年 | 52篇 |
| 1993年 | 70篇 |
| 1992年 | 161篇 |
| 1991年 | 170篇 |
| 1990年 | 165篇 |
| 1989年 | 152篇 |
| 1988年 | 145篇 |
| 1987年 | 198篇 |
| 1986年 | 143篇 |
| 1985年 | 126篇 |
| 1984年 | 180篇 |
| 1983年 | 185篇 |
| 1982年 | 202篇 |
| 1981年 | 204篇 |
| 1980年 | 167篇 |
| 1979年 | 202篇 |
| 1978年 | 178篇 |
| 1977年 | 160篇 |
| 1976年 | 120篇 |
| 1975年 | 150篇 |
| 1974年 | 146篇 |
| 1973年 | 149篇 |
| 1972年 | 142篇 |
| 1971年 | 146篇 |
| 1970年 | 157篇 |
| 1969年 | 104篇 |
| 1968年 | 139篇 |
| 1967年 | 131篇 |
| 1966年 | 89篇 |
| 1965年 | 96篇 |
| 1964年 | 108篇 |
| 1963年 | 44篇 |
| 1962年 | 94篇 |
| 1960年 | 110篇 |
| 1957年 | 47篇 |
| 1955年 | 48篇 |
| 1954年 | 68篇 |
| 1952年 | 58篇 |
| 1951年 | 41篇 |
| 1950年 | 63篇 |
| 1949年 | 48篇 |
排序方式： 共有6516条查询结果，搜索用时 31 毫秒
1.
2.
Jacques Henrard 《Celestial Mechanics and Dynamical Astronomy》1996,64(1-2):107-114
The dynamical behavior of asteroids inside the 2:1 and 3:2 commensurabilities with Jupiter presents a challenge. Indeed most of the studies, either analytical or numerical, point out that the two resonances have a very similar dynamical behavior. In spite of that, the 3:2 resonance, a little outside the main belt, hosts a family of asteroids, called the Hildas, while the 2:1, inside the main belt, is associated to a gap (the Hecuba gap) in the distribution of asteroids.In his search for a dynamical explanation for the Hecuba gap, Wisdom (1987) pointed out the existence of orbits starting with low eccentricity and inclination inside the 2:1 commensurability and going to high eccentricity, and thus to possible encounters with Mars. It has been shown later (Henrard et al.), that these orbits were following a path from the low eccentric belt of secondary resonances to the high eccentric domain of secular resonances. This path crosses a bridge, at moderate inclination and large amplitude of libration, between the two chaotic domains associated with these resonances.The 3:2 resonance being similar in many respects to the 2:1 resonance, one may wonder whether it contains also such a path. Indeed we have found that it exists and is very similar to the 2:1 one. This is the object of the present paper. 相似文献
3.
V. Delouille J. De Patoul J. F. Hochedez L. Jacques J. P. Antoine 《Solar physics》2005,228(1-2):301-321
The extreme ultraviolet imaging telescope (EIT) of SOHO offers a unique record of the solar atmosphere for its sampling in
temperature, field of view, resolution, duration, and cadence. To investigate globally and locally its topology and evolution
during the solar cycle, we consider a multi-scale approach, and more precisely we use the wavelet spectrum.
We present three results among the applications of such a procedure. First, we estimate the typical dimension of the supergranules
as seen in the 30.4 nm passband, and we show that the evolution of the characteristic network scale is almost in phase with
the solar cycle. Second, we build pertinent time series that give the evolution of the signal energy present in the corona
at different scales. We propose a method that detects eruptions and post-flaring activity in EUV image sequences. Third, we
introduce a new way to extract active regions in EIT images, with perspectives in, e.g., long-term irradiance analysis. 相似文献
4.
Experimental results are presented from the extensive program of drained plane strain compression tests on sand carried out in Grenoble over the last two decades. Systematic analysis of photographs of the deforming specimen allowed for measuring deformations and determining strain fields throughout the test, that is: prior to, at, and after the onset of strain localization. The principles, details and accuracy of the procedure are described, as well as its suitability to properly depict the patterns of deformation. Findings concerning the occurrence and progression of strain localization are discussed. The issues of shear band orientation and thickness are addressed, as well as temporary and persistent complex localization patterns, and the volumetric behaviour inside a band after its formation. The influence of such variables as initial state of the sand (effective stress and relative density), specimen size and slenderness, as well as grain size, is discussed. Copyright © 2004 John Wiley & Sons, Ltd 相似文献
5.
6.
7.
8.
9.
10.
Jacques Laskar 《Celestial Mechanics and Dynamical Astronomy》1993,56(1-2):191-196
Frequency analysis is a new method for analyzing the stability of orbits in a conservative dynamical system. It was first devised in order to study the stability of the solar system (Laskar, Icarus, 88, 1990). It is a powerful method for analyzing weakly chaotic motion in hamiltonian systems or symplectic maps. For regular motions, it yields an analytical representation of the solutions. In cases of 2 degrees of freedom system with monotonous torsion, precise numerical criterions for the destruction of KAM tori can be found. For a 4D symplectic map, plotting the frequency map in the frequency plane provides a clear representation of the global dynamics and describes the actual Arnold web of the system. 相似文献