全文获取类型
收费全文 | 377篇 |
免费 | 4篇 |
专业分类
测绘学 | 6篇 |
大气科学 | 11篇 |
地球物理 | 204篇 |
地质学 | 43篇 |
海洋学 | 1篇 |
天文学 | 109篇 |
综合类 | 1篇 |
自然地理 | 6篇 |
出版年
2018年 | 4篇 |
2017年 | 4篇 |
2016年 | 6篇 |
2015年 | 4篇 |
2014年 | 6篇 |
2013年 | 11篇 |
2011年 | 8篇 |
2010年 | 10篇 |
2009年 | 11篇 |
2008年 | 6篇 |
2007年 | 5篇 |
2006年 | 5篇 |
2005年 | 7篇 |
2004年 | 4篇 |
2001年 | 7篇 |
2000年 | 4篇 |
1999年 | 9篇 |
1997年 | 4篇 |
1996年 | 12篇 |
1995年 | 6篇 |
1994年 | 9篇 |
1993年 | 7篇 |
1992年 | 10篇 |
1991年 | 5篇 |
1990年 | 13篇 |
1989年 | 19篇 |
1988年 | 13篇 |
1987年 | 6篇 |
1986年 | 7篇 |
1985年 | 10篇 |
1984年 | 8篇 |
1983年 | 9篇 |
1982年 | 5篇 |
1981年 | 9篇 |
1980年 | 8篇 |
1978年 | 10篇 |
1977年 | 5篇 |
1976年 | 5篇 |
1975年 | 5篇 |
1974年 | 4篇 |
1973年 | 5篇 |
1971年 | 8篇 |
1970年 | 6篇 |
1969年 | 6篇 |
1966年 | 4篇 |
1963年 | 4篇 |
1962年 | 3篇 |
1960年 | 5篇 |
1959年 | 3篇 |
1957年 | 5篇 |
排序方式: 共有381条查询结果,搜索用时 318 毫秒
61.
The influence of temperature changes in circumstellar silicate-like envelopes upon the polarization effects is investigated. It is shown that under the assumption that ΔT g>50° and conductivity of silicate grains is indirectly proportional toT g this mechanism can be responsible for the observed dependence of intensity vs polarization in some late-type stars, e.g. V CVn. The same effects can be produced by dirty ices and graphite grains. It is suggested that irradiation by electrons and/or protons can affect the circumstellar envelopes in a similar way, especially those of early-type stars, and irradiation by neutrons can exert an influence on the envelopes of supernovae. 相似文献
62.
The probability that γ-ray bursts may be generated by the infall of comet-like objects on the neutron stars, as recently proposed by Harwit and Salpeter (1973), is reexamined. Although hypothetical cometary clouds around the parent star may survive the supernova outburst virtually untouched, the frequency of γ-outbursts due to the comet impact on the neutron star or white dwarf is only about 10?3 of the observed occurrence. A considerably higher rate of comets passing per year at critical periastron distance must be assumed if the γ-ray outbursts are to be due to the collision of coments with compact stars. 相似文献
63.
There are many aspects of observational evidence that cometary nuclei have irregular or nonspherical shape. The triaxial figure of the Halley's Comet nucleus is a well known fact. Therefore, the nucleus shape plays a significant role in consideration of the formation and evolution of comets and several attempts have been made to explain their nonsphericity. These studies were mainly based on the random-walk schemes for the aggregation processes. Although some results indeed lead to irregularities and deviation from sphericity, the spherical or irregular shape seem to be prevailing results. On the other hand the triaxial figure can be formed by the tidal and rotational forces. Thus, the assumption that the shape of the cometary nucleus due to some of these effects is in principle acceptable. In here assumed scenario already evolved cometary nucleus is situated as a satellite in the gravitation field of a planetary-like body. Since the rigidity of the nucleus is low, it may be easily transferred in the state of a synchronous satellite and in its shape could be imprinted the dynamical effects from this epoch. Here presented results indicate, that such a possibility should be seriously considered. The theory of this process is applied to the nucleus of comet Halley. It is shown, that the nucleus might be synchronously orbiting around a planetary-like hypothetical body with a period of 0.7 days. The minimal bulk tensile strength of the cometary material of about 102 N m–2 is estimated. 相似文献
64.
The paper presents a new method of the estimation of spatial variations of the magnetic field and superthermal electron distribution
in solar cm-radio burst sources. The method is based on minimization of the difference between the theoretical and observed
radio fluxes and on the analysis of several burst spectra recorded in different moments of time. Several solar cm-radio bursts
are analyzed by this method. It is found that the measure of the spatial variations of the superthermal electron distribution
in the radio source is always larger than that for the magnetic field. 相似文献
65.
We report exceptional fireball activity of the Orionid meteor shower in 2006. During four nights in October 2006 the autonomous
fireball observatories of the Czech part of the European Fireball Network (EN) recorded 48 fireballs belonging to the Orionids.
This is significantly more than the total number of Orionids recorded during about five decades long continuous operation
of the EN. Based on precise multi-station photographic and radiometric data we present accurate atmospheric trajectories,
heliocentric orbits, light curves and basic physical properties of 10 Orionid fireballs with atmospheric trajectories that
were long enough and, with one exception, were observed from at least three stations. Seven were recorded in within a 2-h
interval in the night of 20/21 October. Their basic parameters such as radiant positions and heliocentric orbits are very
similar. This high fireball activity originated from a very compact geocentric radiant defined by α = 95.10° ± 0.10° and
δ = 15.50° ± 0.06°. These fireballs most likely belonged to a distinct filament of larger meteoroids trapped in 1:5 resonance
with Jupiter. From detailed light curves and basic fireball classification we found that these meteoroids appertain to the
weakest component of interplanetary matter. 相似文献
66.
Miroslav Šifta Pavel Chromý 《Norsk geografisk tidsskrift. Norwegian journal of geography》2017,71(2):98-113
The aim in the article is to conceptualize the general foundations of research on the importance of regional symbolism in the process of region and regional identity formation. The article is founded on a critical analysis of works pertaining not only to the field of the new regional geography, but also to the field of regional marketing and/or branding, sociology, and semiology. The authors focus on meanings attributed to symbols and symbolism in literature, and observe which elements are viewed as regional symbols and how these symbols contribute to the process of regional development and institutionalization, especially in the formation of its symbolic shape. They examine the thematic and theoretical grounds, looking at identity, regional identity, and regional institutionalization. Next, regional symbols are defined and classified according to their types and forms, and their importance in the process of regional formation and institutionalization is discussed. The results show that symbols of any type can play an important role in a region’s marketing, and become the key image associated with a region. The authors conclude that regional symbols are a significant feature of the formation of a region and its identity, both outwardly (the external image of a region) and inwardly (concerning the inhabitants’ relationships with their region). 相似文献
67.
68.
Kryštof Verner Jiří Žák Jaroslava Pertoldová Josef Šrámek Jiří Sedlák Jakub Trubač Patricie Týcová 《International Journal of Earth Sciences》2009,98(3):517-532
The Plechy pluton, southwestern Bohemian Massif, represents a late-Variscan, complexly zoned intrusive center emplaced near
the crustal-scale Pfahl shear zone; the pluton thus provides an opportunity to examine the interplay among successive emplacement
of large magma batches, magmatic fabric acquisition, and the late-Variscan stress field associated with strike-slip shearing.
The magmatic history of the pluton started with the emplacement of the porphyritic Plechy and Haidmühler granites. Based on
gravity and structural data, we interpret that the Plechy and Haidmühler granites were emplaced as a deeply rooted, ∼NE–SW
elongated body; its gross shape and internal fabric (steep ∼NE–SW magmatic foliation) may have been controlled by the late-Variscan
stress field. The steep magmatic foliation changes into flat-lying foliation (particularly recorded by AMS) presumably as
a result of divergent flow. Magnetic lineations correspond to a sub-horizontal ∼NE–SW finite stretch associated with the divergent
flow. Subsequently, the Třístoličník granite, characterized by steep margin-parallel magmatic foliation, was emplaced as a
crescent-shaped body in the central part of the pluton. The otherwise inward-younging intrusive sequence was completed by
the emplacement of the outermost and the most evolved garnet-bearing granite (the Marginal granite) along the southeastern
margin of the pluton.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
69.
70.
Vlastislav Červený 《Studia Geophysica et Geodaetica》2013,57(2):267-275
Recently, several expressions for the two-point paraxial travel time in laterally varying, isotropic or anisotropic layered media were derived. The two-point paraxial travel time gives the travel time from point S′ to point R′, both these points being situated close to a known reference ray Ω, along which the ray-propagator matrix was calculated by dynamic ray tracing. The reference ray and the position of points S′ and R′ are specified in Cartesian coordinates. Two such expressions for the two-point paraxial travel time play an important role. The first is based on the 4 × 4 ray propagator matrix, computed by dynamic ray tracing along the reference ray in ray-centred coordinates. The second requires the knowledge of the 6 × 6 ray propagator matrix computed by dynamic ray tracing along the reference ray in Cartesian coordinates. Both expressions were derived fully independently, using different methods, and are expressed in quite different forms. In this paper we prove that the two expressions are fully equivalent and can be transformed into each other. 相似文献