全文获取类型
收费全文 | 425篇 |
免费 | 9篇 |
专业分类
测绘学 | 12篇 |
大气科学 | 31篇 |
地球物理 | 97篇 |
地质学 | 183篇 |
海洋学 | 19篇 |
天文学 | 66篇 |
自然地理 | 26篇 |
出版年
2023年 | 2篇 |
2021年 | 7篇 |
2020年 | 10篇 |
2019年 | 10篇 |
2018年 | 13篇 |
2017年 | 14篇 |
2016年 | 16篇 |
2015年 | 24篇 |
2014年 | 18篇 |
2013年 | 26篇 |
2012年 | 17篇 |
2011年 | 33篇 |
2010年 | 36篇 |
2009年 | 27篇 |
2008年 | 21篇 |
2007年 | 12篇 |
2006年 | 27篇 |
2005年 | 12篇 |
2004年 | 20篇 |
2003年 | 6篇 |
2002年 | 14篇 |
2001年 | 10篇 |
2000年 | 9篇 |
1999年 | 2篇 |
1998年 | 5篇 |
1997年 | 3篇 |
1996年 | 3篇 |
1995年 | 1篇 |
1994年 | 3篇 |
1993年 | 3篇 |
1992年 | 1篇 |
1991年 | 1篇 |
1989年 | 2篇 |
1988年 | 1篇 |
1986年 | 3篇 |
1985年 | 2篇 |
1984年 | 1篇 |
1981年 | 2篇 |
1980年 | 1篇 |
1978年 | 2篇 |
1977年 | 3篇 |
1976年 | 3篇 |
1974年 | 1篇 |
1973年 | 2篇 |
1972年 | 1篇 |
1971年 | 3篇 |
1963年 | 1篇 |
排序方式: 共有434条查询结果,搜索用时 0 毫秒
111.
Claudio Zanni Attilio Ferrari Silvano Massaglia Gianluigi Bodo Paola Rossi 《Astrophysics and Space Science》2004,293(1-2):99-106
We present a 2.5D magnetohydrodynamic (MHD) simulation of the acceleration of a collimated jet from a magnetized accretion disk. We employ a MHD Adaptive Mesh Refinement (AMR) code (FLASH—University of Chicago). Thanks to this tool we can follow the evolution of the system for many dynamical timescales with a high-spatial resolution. Assuming an initial condition in which a Keplerian disk, thus with no accretion motions, is threaded by a uniform poloidal magnetic field, we show how both the accretion flow and the acceleration of the outflow occur, and we present in detail which are the forces responsible for the jet launching and collimation. Our simulation also shows how the collimating forces due to the self-generated toroidal magnetic field can produce some peculiar knotty features. 相似文献
112.
Claudio Bastos Pereira 《Astrophysics and Space Science》1996,240(1):1-11
EG And is a S-type symbiotic star. Presented are UV observations made by IUE from 1978 to 1991. From these observations the electron density and the electron temperature were obtained. The size of the Heii emitting region was estimated as 7.3R. Line and continuum variations confirm the binary nature of EG And. 相似文献
113.
114.
We present the second part of a complete theory for the plasma and field structure of a cool coronal arch, corresponding to those observed in the EUV from Skylab. The global magneto-hydrodynamic (MHD) stability of a previously described equilibrium-loop model is evaluated, and compared with that of an unmodified ambient force-free field. The influence of the photospheric boundary condition is also evaluated, producing a specification of stability limits which depend on the relative field and plasma pressures and scale widths. The resulting restrictions on the allowable field configuration of a coronal loop are then compared with observed values. The implications of this general method for deducing small-scale coronal magnetic-field structure from the measured plasma profile of an emissive feature are also described. 相似文献
115.
We consider a restricted three-body problem where the primaries are moving in an elliptic collision orbit and the infinitesimal
mass moves in a three dimensional space. This paper is devoted to prove analytically the existence of several families of
symmetric periodic solutions as continuation of Keplerian circular orbits. In our approach the perturbing parameter is related
with the energy of the primaries. 相似文献
116.
It is shown that the combined use of radio observations of the quiet Sun and UV line intensities allows to compute the absolute coronal abundance of the elements. The abundances found by this method agree very well with the most recent determinations. A model of the transition region and corona in hydrostatic equilibrium is also presented. Similarities and differences with models based on UV observations are discussed. 相似文献
117.
118.
We present analytical formulas to estimate the variation of achieved deflection for an Earth-impacting asteroid following a continuous tangential low-thrust deflection strategy. Relatively simple analytical expressions are obtained with the aid of asymptotic theory and the use of Peláez orbital elements set, an approach that is particularly suitable to the asteroid deflection problem and is not limited to small eccentricities. The accuracy of the proposed formulas is evaluated numerically showing negligible error for both early and late deflection campaigns. The results will be of aid in planning future low-thrust asteroid deflection missions. 相似文献
119.
Mirko Carlini Alessandro Chelli Roberto Francese Serena Giacomelli Massimo Giorgi Andrea Quagliarini Andrea Carpena Claudio Tellini 《Landslides》2018,15(2):283-296
This paper investigates the role played by geomorphological and tectonic processes affecting a portion of an active mountain belt in causing the occurrence of different types of landslides developed in flysch bedrock. The adopted multidisciplinary approach (geomorphology, geology and geophysics) allowed to recognize in a portion of the Northern Apennines of Italy different types of landslides that developed in response to slope dynamics, in turn dependent on broader regional-scale tectonic processes. Sedimentary bed attitude, local tectonic discontinuities and lithology only partially influenced the type of landslides, which have been deeply affected by the activity of regional-scale antiform that controlled the hillslope geomorphic evolution in different ways. The growth of this structure and the tilting of its forelimb produced gently dipping slopes that approached the threshold angle that can cause the occurrence of (mainly) translational rockslides. Conversely, high-angle normal faulting parallel to the antiform axis (related to a later stage of activity of the antiform itself) strongly controlled the stream network evolution and caused the watercourses to deeply incise portions of their valleys. This incision produced younger steep valley slopes and caused the development of complex landslides (roto-translational slides-earth/debris flow). The results of the integrated study presented in this paper allowed to distinguish two main types of landslides whose development reflects the events that led to the geomorphological and geological evolution of the area. In this perspective, within the study area, landslides can be regarded and used as indicators of broader-scale recent tectonic processes. 相似文献
120.
SiGOG: simulated GPS observation generator 总被引:3,自引:0,他引:3