全文获取类型
收费全文 | 2478篇 |
免费 | 143篇 |
国内免费 | 11篇 |
专业分类
测绘学 | 206篇 |
大气科学 | 176篇 |
地球物理 | 670篇 |
地质学 | 883篇 |
海洋学 | 139篇 |
天文学 | 406篇 |
综合类 | 25篇 |
自然地理 | 127篇 |
出版年
2024年 | 5篇 |
2023年 | 12篇 |
2022年 | 22篇 |
2021年 | 42篇 |
2020年 | 58篇 |
2019年 | 45篇 |
2018年 | 144篇 |
2017年 | 112篇 |
2016年 | 178篇 |
2015年 | 152篇 |
2014年 | 168篇 |
2013年 | 198篇 |
2012年 | 168篇 |
2011年 | 162篇 |
2010年 | 138篇 |
2009年 | 133篇 |
2008年 | 104篇 |
2007年 | 82篇 |
2006年 | 76篇 |
2005年 | 51篇 |
2004年 | 65篇 |
2003年 | 47篇 |
2002年 | 50篇 |
2001年 | 44篇 |
2000年 | 32篇 |
1999年 | 20篇 |
1998年 | 45篇 |
1997年 | 29篇 |
1996年 | 19篇 |
1995年 | 22篇 |
1994年 | 21篇 |
1993年 | 10篇 |
1992年 | 19篇 |
1991年 | 12篇 |
1990年 | 21篇 |
1989年 | 11篇 |
1988年 | 9篇 |
1987年 | 7篇 |
1985年 | 10篇 |
1983年 | 10篇 |
1982年 | 9篇 |
1981年 | 6篇 |
1980年 | 9篇 |
1978年 | 6篇 |
1977年 | 4篇 |
1975年 | 4篇 |
1972年 | 9篇 |
1968年 | 3篇 |
1965年 | 3篇 |
1950年 | 4篇 |
排序方式: 共有2632条查询结果,搜索用时 0 毫秒
191.
Joaquin Bastias Mauricio Calderón Lea Israel Francisco Hervé Richard Spikings Robert Pankhurst 《International Geology Review》2020,62(11):1467-1484
ABSTRACT This paper addresses the Jurassic–Cretaceous stratigraphic evolution of fore-arc deposits exposed along the west coast of the northern Antarctic Peninsula. In the South Shetland Islands, Upper Jurassic deep-marine sediments are uncomformably overlain by a Lower Cretaceous volcaniclastic sequence that crops out on Livingston, Snow and Low islands. U-Pb zircon ages are presented for the upper Anchorage Formation (153.1 ± 1.7 Ma) and the Cape Wallace granodiorite of Low Island (137.1 ± 1.7 Ma) as well as 40Ar/39Ar ages of 136–139 Ma for Low Island andesites. Data are also presented for a U-Pb age of 109.0 ± 1.4 Ma for the upper volcanic succession of Snow Island. In combination with published stratigraphy, these data provide a refined chrono- and litho-stratigraphic framework for the deposits herein referred to as the Byers Basin. Tentative correlation is explored with previously described deposits on Adelaide and Alexander islands, which could suggest further continuation of the Byers Basin towards the south. We also discuss possible correlation of the Byers Basin with the Larsen Basin, a sequence that shows the evolution of foreland to back-arc deposits more or less contemporaneously with the fore-arc to intra-arc evolution of the Byers Basin. 相似文献
192.
The effect of equilibrium flow on linear Alfvén resonances in coronal loops is studied in the compressible viscous MHD model. By means of a finite element code, the full set of linearised driven MHD equations are solved for a one-dimensional equilibrium model in which the equilibrium quantities depend only on the radial coordinate. Computations of resonant absorption of Alfvén waves for two classes of coronal loop models show that the efficiency of the process of resonant absorption strongly depends on both the equilibrium parameters and the characteristics of the resonant wave. We find that a steady equilibrium shear flow can also significantly influence the resonant absorption of Alfvén waves in coronal magnetic flux tubes. The presence of an equilibrium flow may therefore be important for resonant Alfvén waves and coronal heating. A parametric analysis also shows that the resonant absorption can be strongly enhanced by the equilibrium flow, even up to total dissipation of the incoming wave. 相似文献
193.
194.
195.
A. Marco G. Bernabeau J.M. Torrejón J. Fabregat 《Astrophysics and Space Science》1998,263(1-4):299-302
We are developing a long term programme to determine abundances of peculiar stars, as a function of age, in open clusters
with ages ≤ 5 × 107 yr. A fundamental part will be to deduce the ages and physical properties of these clusters with higher accuracy than in
previous studies. As part of this effort we present here CCD uvbyβ photometry of two open clusters, NGC 884 and NGC 869.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
196.
197.
198.
Leónidas Slaucitajs 《Pure and Applied Geophysics》1964,59(1):75-83
Resumen Se aplica el análisis de energía de espectro a los datos de la variación secular geomagnética para tres observatorios del Hemisferio Sur: Pilar, Amberley, Mauritius. Las figuras 2–10 indican generalmente tres tipos de picos: a) de periodos de menos de 10 años; b) del periodo aproximado de la actividad solar de 10–11 años; c) de una fluctuación de 40–60 años. Los coeficientes de la expansión esférico-armónica de la variación secular muestran también una fluctuación del último tipo.
Summary The power spectrum analysis is applied to geomagnetic secular variation data of three southern magnetic observatories: Pilar, Amberley, Mauritius. The figures 2–10 indicate in general three types of peaks: a) of periods less than 10 years; b) of approximately solar activity cycle; c) of 40–60 years fluctuation. Also the coefficients of spherical harmonic expansion of SV show the last type fluctuation.相似文献
199.
200.