全文获取类型
收费全文 | 3073篇 |
免费 | 107篇 |
国内免费 | 40篇 |
专业分类
测绘学 | 67篇 |
大气科学 | 223篇 |
地球物理 | 790篇 |
地质学 | 1004篇 |
海洋学 | 312篇 |
天文学 | 604篇 |
综合类 | 10篇 |
自然地理 | 210篇 |
出版年
2021年 | 27篇 |
2020年 | 39篇 |
2019年 | 46篇 |
2018年 | 58篇 |
2017年 | 51篇 |
2016年 | 88篇 |
2015年 | 60篇 |
2014年 | 67篇 |
2013年 | 158篇 |
2012年 | 82篇 |
2011年 | 119篇 |
2010年 | 123篇 |
2009年 | 125篇 |
2008年 | 126篇 |
2007年 | 140篇 |
2006年 | 125篇 |
2005年 | 92篇 |
2004年 | 87篇 |
2003年 | 88篇 |
2002年 | 92篇 |
2001年 | 74篇 |
2000年 | 82篇 |
1999年 | 56篇 |
1998年 | 61篇 |
1997年 | 60篇 |
1996年 | 47篇 |
1995年 | 58篇 |
1994年 | 49篇 |
1993年 | 31篇 |
1992年 | 48篇 |
1991年 | 39篇 |
1990年 | 60篇 |
1989年 | 44篇 |
1988年 | 41篇 |
1987年 | 39篇 |
1986年 | 36篇 |
1985年 | 39篇 |
1984年 | 57篇 |
1983年 | 44篇 |
1982年 | 33篇 |
1981年 | 52篇 |
1980年 | 36篇 |
1979年 | 50篇 |
1978年 | 42篇 |
1977年 | 34篇 |
1976年 | 23篇 |
1975年 | 23篇 |
1974年 | 22篇 |
1973年 | 23篇 |
1972年 | 18篇 |
排序方式: 共有3220条查询结果,搜索用时 15 毫秒
11.
M. A. Iatì C. Cecchi-Pestellini D. A. Williams F. Borghese P. Denti R. Saija S. Aiello 《Monthly notices of the Royal Astronomical Society》2001,322(4):749-756
Recent observations of stellar composition suggest that elements in the Sun are significantly more abundant than in other stars. The reduction in the available element budget implies a drastic revision in current models of interstellar dust. Theoretical models are therefore exploring fluffy, porous physical structure for the grain material. Since a detailed exact treatment of extinction cross-sections is mandatory for a correct understanding of the nature of interstellar dust, we present a technique based on the multipole expansions of the electromagnetic field, which has proven to be general, flexible and powerful in treating scattering of light by porous, composite, arbitrarily shaped particles. The results of this study speak in favour of core–mantle structures characterized by the presence of porosities. 相似文献
12.
David A. Williams 《Planetary and Space Science》1992,40(12):1683-1693
We review the present understanding of interstellar CH+. We show that the essential chemistry was correctly identified by Bates and Spitzer in 1951. More recent work has been concerned with defining appropriate venues within which this chemistry can function efficiently. This process had led to a much fuller understanding of the nature of the interstellar medium. 相似文献
13.
14.
M. A. P. Torres J. Casares I. G. Martínez-Pais P. A. Charles 《Monthly notices of the Royal Astronomical Society》2002,334(1):233-240
We present a library of 47 open-cluster integrated spectra, mostly obtained at CASLEO (San Juan, Argentina) in the range 3600 < λ < 7400 Å , which are made available at CDS. The data are combined with previous spectra to obtain 10 high signal-to-noise ratio basic templates in the young and intermediate-age domains, which are also provided in the library. These Galactic disc templates represent the increased time resolution spectral evolution of a stellar population unit around the Solar metallicity level. The improved signal-to-noise ratio of the present templates with respect to previous template lists, together with their increased time resolution, allowed us to improve the fundamental parameters of some open clusters. The present spectral library will be useful for several astrophysical applications, particularly for population syntheses of star-forming giant galaxies. 相似文献
15.
Report of the International Astronomical Union Division I Working Group on Precession and the Ecliptic 总被引:1,自引:0,他引:1
J. L. Hilton N. Capitaine J. Chapront J. M. Ferrandiz A. Fienga T. Fukushima J. Getino P. Mathews J.-L. Simon M. Soffel J. Vondrak P. Wallace J. Williams 《Celestial Mechanics and Dynamical Astronomy》2006,94(3):351-367
The IAU Working Group on Precession and the Equinox looked at several solutions for replacing the precession part of the IAU
2000A precession–nutation model, which is not consistent with dynamical theory. These comparisons show that the (Capitaine
et al., Astron. Astrophys., 412, 2003a) precession theory, P03, is both consistent with dynamical theory and the solution most compatible with the IAU 2000A
nutation model. Thus, the working group recommends the adoption of the P03 precession theory for use with the IAU 2000A nutation.
The two greatest sources of uncertainty in the precession theory are the rate of change of the Earth’s dynamical flattening,
ΔJ2, and the precession rates (i.e. the constants of integration used in deriving the precession). The combined uncertainties
limit the accuracy in the precession theory to approximately 2 mas cent−2.
Given that there are difficulties with the traditional angles used to parameterize the precession, zA, ζA, and θA, the working group has decided that the choice of parameters should be left to the user. We provide a consistent set of parameters
that may be used with either the traditional rotation matrix, or those rotation matrices described in (Capitaine et al., Astron.
Astrophys., 412, 2003a) and (Fukushima Astron. J., 126, 2003).
We recommend that the ecliptic pole be explicitly defined by the mean orbital angular momentum vector of the Earth–Moon barycenter
in the Barycentric Celestial Reference System (BCRS), and explicitly state that this definition is being used to avoid confusion
with previous definitions of the ecliptic.
Finally, we recommend that the terms precession of the equator and precession of the ecliptic replace the terms lunisolar precession and planetary precession, respectively. 相似文献
16.
The spectra of active galaxies and their nuclei are rich in emission and absorption line features. A major aim of present
research is the development of self-consistent hydrodynamic models for the production of the line-forming regions. We here
review such modelling and stress the central role played by shock phenomena induced by winds and explosions on scales ranging
from the circumstellar to the intergalactic. 相似文献
17.
This paper presents two and three dimensional simulations of the interaction of shocks with media with large numbers of dense
inclusions. An approximate model of the interaction of a starburst wind with the surrounding galactic ISM illustrates issues
which must be addressed in global models of ISM dynamics. As a step towards developing the sub-grid model of multiphase turbulence,
we define and study a form of ‘multiphase Riemann problem’. This allows us to develop macroscopic characteristics of the flows
which may be compared to such subgrid models. 相似文献
18.
19.