全文获取类型
收费全文 | 413篇 |
免费 | 15篇 |
国内免费 | 1篇 |
专业分类
测绘学 | 7篇 |
大气科学 | 17篇 |
地球物理 | 85篇 |
地质学 | 126篇 |
海洋学 | 38篇 |
天文学 | 125篇 |
综合类 | 1篇 |
自然地理 | 30篇 |
出版年
2021年 | 5篇 |
2020年 | 3篇 |
2019年 | 6篇 |
2018年 | 7篇 |
2017年 | 9篇 |
2016年 | 9篇 |
2015年 | 5篇 |
2014年 | 12篇 |
2013年 | 24篇 |
2012年 | 4篇 |
2011年 | 13篇 |
2010年 | 13篇 |
2009年 | 18篇 |
2008年 | 16篇 |
2007年 | 13篇 |
2006年 | 14篇 |
2005年 | 14篇 |
2004年 | 24篇 |
2003年 | 25篇 |
2002年 | 15篇 |
2001年 | 13篇 |
2000年 | 15篇 |
1999年 | 11篇 |
1998年 | 17篇 |
1997年 | 6篇 |
1996年 | 4篇 |
1995年 | 3篇 |
1994年 | 4篇 |
1993年 | 7篇 |
1992年 | 7篇 |
1991年 | 9篇 |
1990年 | 4篇 |
1989年 | 8篇 |
1988年 | 3篇 |
1987年 | 9篇 |
1985年 | 7篇 |
1984年 | 10篇 |
1983年 | 6篇 |
1982年 | 3篇 |
1981年 | 4篇 |
1980年 | 3篇 |
1979年 | 3篇 |
1978年 | 6篇 |
1976年 | 2篇 |
1975年 | 3篇 |
1974年 | 2篇 |
1970年 | 1篇 |
1968年 | 1篇 |
1967年 | 2篇 |
1966年 | 3篇 |
排序方式: 共有429条查询结果,搜索用时 15 毫秒
411.
412.
Itziar Aretxaga David H. Hughes Kristen Coppin Angela M. J. Mortier Jeff Wagg James S. Dunlop Edward L. Chapin Stephen A. Eales Enrique Gaztañaga Mark Halpern Rob J. Ivison Eelco van Kampen Douglas Scott Stephen Serjeant Ian Smail Thomas Babbedge rew J. Benson Scott Chapman David L. Clements Loretta Dunne Simon Dye Duncan Farrah Matt J. Jarvis Robert G. Mann Alexandra Pope Robert Priddey Steve Rawlings Marc Seigar Laura Silva Chris Simpson Mattia Vaccari 《Monthly notices of the Royal Astronomical Society》2007,379(4):1571-1588
413.
Earth, Moon, and Planets - 相似文献
414.
Volume Contents
Contents to Volume 9 相似文献415.
J. Faulkner 《Astrophysics and Space Science》2003,285(2):339-339
The impact of Fred Hoyle's work on the structure and evolution of red giants, particularly his breakthrough contribution with
Martin Schwartzschild (1955), is described and assessed. Working with his students in the early 1960s, Hoyle presented new
physical ways of understanding some of the approximations used, and results obtained, in that seminal paper. His initial viewpoint
on the critical role of the outer surface boundary condition was replaced by a more subtle, if related one, which emphasized
the peculiar difficulty of storing much mass outside a dense stellar core. That viewpoint that – low-mass red giants are essentially
white dwarfs with a serious mass-storage problem – is still extremely fruitful. Recently, I have extended Hoyle's approach
to explain not only many of the structural properties of red giants themselves, but also to link and unify the structures
of low-mass stars from the main sequence through both the red giant and horizontal branch phases of evolution. Many aspects
of these stars that had remained mysterious for decades have now fallen into place, and some questions have been answered
that were not even posed before. With red giants as the simplest example, this recent work emphasizes that stars, in general,
may have at least two distinct but very important centres: (i) a geometrical centre, and (ii) a separate nuclear centre, residing in a shell outside a zero-luminosity dense core for example. This two-centre perspective leads to an explicit,
analytic, asymptotic theory of low-mass red giant structure. In this theory, there arises a naturally important in situ measure of central compactness: the parameter
. That parameter, like others, is derived self-consistently and explicitly, and can be used to show how close a given model's
properties are to ultimate asymptotic relationships. The results obtained also imply that the problem of understanding why
such stars become red giants is one of anticipating a remarkable yet natural structural bifurcation which occurs in them.
In the resulting theory, both the ratio
and products like
prove to be important, self-consistently derived quantities. Two striking theorems involving such quantities express between
them the very essence of red giant behaviour, proving analytically for the first time that stars with dense cores are necessarily
(i) extremely luminous, and (ii) very large. Perhaps the most astonishingly unexpected single result is that for the very
value Nature provides for the relevant nuclear energy-generating temperature exponent (CNO's η=15), ρsh and
behave in a well-defined, precisely inverse manner. This emphasizes that the internal behaviour of such stars is definitely anti-homologous rather than homologous, thus showing how very unfortunate the term `shell homology' is. Finally, I sketch a viewpoint which (i) links the structural
and evolutionary behaviour of stars from the main-sequence through horizontal branch phases of evolution, and also (ii) has
implications for post-main-sequence developments in more massive stars.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
416.
Hazel Faulkner 《水文研究》1992,6(4):397-416
A kinematic flood routing procedure has been devised for a small dendritic headwater gully network on the Western slope of Colorado. the program is spatially-distributed, incorporating lateral inflows from 103 field sites on the network for which channel geometry variables are known. This model, in which a lateral inflow algorithm for the sideslopes between each channel site is convoluted into a Freeze-type (1978) numerical scheme, is fully developed in this paper. Although the field basis of the lateral inflow algorithm has been tested elsewhere (Faulkner, 1990), sensitivity tests were needed for the roughness and hillslope velocity estimates used in the routing procedure. After these successful tests, a suitably precalibrated run of the model was compared with a field-monitored runoff event on the watershed, and results again were encouraging. However, peak attentuation downstream was more pronounced in reality than on the simulation, so the model was also modified by inclusion of allowances for transmission loss. the tendency that the model had displayed for peak size attenuation downstream was considerably enhanced. Using the model, the geomorphic role of the flashfloods which affect the watershed in the summer months is briefly considered by applying the model to existing records of local summer storm rainfall events as a basis for event simulation. These simulations show that downstream attenuation of the flood wave on concave networks in steep semiarid terrain was likely to be a common occurrence, possibly resulting in down-net deposition and differences in geomorphic behaviour between upstream and downstream sites. the discussion is finally broadened to consider the relative importance of ‘common’ as compared to ‘freak’ watershed events in maintaining these differences. 相似文献
417.
Ian J. Duncan 《Journal of Geodynamics》1985,2(1):1-21
A new analysis of the isotope systematics of sulphide common leads can be made on the basis of examining the deriations of the data from a simple single-stage evolution. Δt, the age discrepancy between the single-stage lead model age and the geologic age, increases systematically from 3.8 Ga to the present. This trend appears to reflect an increase in the μ of the primitive mantle due to incorporation of a large portion of the earth's lead into the core, early in the earth's evolution. Leads associated with shale-hosted lead-zinc deposits show a rapid increase in Δt beginning at 2.5 to 2.0 Ga. This deviation of shale-hosted leads from the general trend is interpreted as a response to concentration of uranium in organic-rich shales subsequent to the evolution of an oxidizing atmosphere. Comparison of common leads in alkali feldspars with the volcanogenic sulphide data suggests that they have a similar evolution of Δt with time. Numerical simulations reveal that even substantial increases in real μ over the last 2.0 Ga are not reflected in significant increases in the single-stage model μs. 相似文献
418.
The theory of consolidation is extended to partly saturated clay soils, and formulated for finite element analyses. This formulation couples the effects of both stress and flow. It takes account of variations of this permeability of the soil and compressibility of the pore fluid with changes in void ratio, and the non-linear stress–strain behaviour of soil. The Cam Clay model is revised to model the stress–strain behaviour of compacted soils. The compressibility of pore fluid is derived using Boyle's Law and Henry's Law, taking into account the effect of surface tension. An empirical equation is developed for permeability of pore fluid. An example of settlement of a footing on partly saturated soil is described and discussed. 相似文献
419.
The fundamental plane of isolated early-type galaxies 总被引:1,自引:0,他引:1
420.
Diana Hannikainen Duncan Campbell-Wilson Richard Hunstead Vince McIntyre Jim Lovell John Reynolds Tasso Tzioumis Kinwah Wu 《Astrophysics and Space Science》2001,276(1):45-48
In 1998 September, the X-ray transient XTE J1550–564 underwent amajor outburst in soft and hard X-rays, followed by a radio flare. Australian Long Baseline Array imagesobtained shortly after the peak in the radio flare showed evolving structure.The components observed have an apparent separation velocity of >2c. 相似文献