全文获取类型
收费全文 | 1002篇 |
免费 | 35篇 |
国内免费 | 6篇 |
专业分类
测绘学 | 17篇 |
大气科学 | 75篇 |
地球物理 | 258篇 |
地质学 | 354篇 |
海洋学 | 39篇 |
天文学 | 227篇 |
综合类 | 1篇 |
自然地理 | 72篇 |
出版年
2021年 | 9篇 |
2020年 | 10篇 |
2019年 | 18篇 |
2018年 | 15篇 |
2017年 | 17篇 |
2016年 | 21篇 |
2015年 | 14篇 |
2014年 | 21篇 |
2013年 | 37篇 |
2012年 | 28篇 |
2011年 | 27篇 |
2010年 | 26篇 |
2009年 | 47篇 |
2008年 | 35篇 |
2007年 | 29篇 |
2006年 | 42篇 |
2005年 | 36篇 |
2004年 | 34篇 |
2003年 | 29篇 |
2002年 | 28篇 |
2001年 | 24篇 |
2000年 | 14篇 |
1999年 | 20篇 |
1998年 | 11篇 |
1997年 | 17篇 |
1996年 | 16篇 |
1995年 | 26篇 |
1994年 | 25篇 |
1993年 | 13篇 |
1992年 | 13篇 |
1991年 | 22篇 |
1990年 | 15篇 |
1989年 | 12篇 |
1988年 | 11篇 |
1987年 | 15篇 |
1986年 | 10篇 |
1985年 | 13篇 |
1984年 | 22篇 |
1983年 | 23篇 |
1982年 | 14篇 |
1981年 | 9篇 |
1980年 | 19篇 |
1979年 | 15篇 |
1978年 | 12篇 |
1977年 | 17篇 |
1976年 | 7篇 |
1975年 | 14篇 |
1974年 | 12篇 |
1973年 | 24篇 |
1971年 | 8篇 |
排序方式: 共有1043条查询结果,搜索用时 32 毫秒
1.
Arnold Gucsik Christian Koeberl Franz Brandsttter Eugen Libowitzky Wolf Uwe Reimold 《Meteoritics & planetary science》2003,38(8):1187-1197
Abstract— We studied unshocked and experimentally (at 12, 25, and 28 GPa, with 25, 100, 450, and 750°C pre‐shock temperatures) shock‐metamorphosed Hospital Hill quartzite from South Africa using cathodoluminescence (CL) images and spectroscopy and Raman spectroscopy to document systematic pressure or temperature‐related effects that could be used in shock barometry. In general, CL images of all samples show CL‐bright luminescent patchy areas and bands in otherwise nonluminescent quartz, as well as CL‐dark irregular fractures. Fluid inclusions appear dominant in CL images of the 25 GPa sample shocked at 750°C and of the 28 GPa sample shocked at 450°C. Only the optical image of our 28 GPa sample shocked at 25°C exhibits distinct planar deformation features (PDFs). Cathodoluminescence spectra of unshocked and experimentally shocked samples show broad bands in the near‐ultraviolet range and the visible light range at all shock stages, indicating the presence of defect centers on, e.g., SiO4 groups. No systematic change in the appearance of the CL images was obvious, but the CL spectra do show changes between the shock stages. The Raman spectra are characteristic for quartz in the unshocked and 12 GPa samples. In the 25 and 28 GPa samples, broad bands indicate the presence of glassy SiO2, while high‐pressure polymorphs are not detected. Apparently, some of the CL and Raman spectral properties can be used in shock barometry. 相似文献
2.
Radiative Transfer (RT) codes with image capability are a fundamental tool for preparing interferometric observations and
for interpreting visibility data. In view of the upcoming VLTI facilities, we present the first comparison of images/visibilities
coming from two 3D codes that use completely different techniques to solve the problem of self-consistent continuum RT. In
addition, we focus on the astrophysical case of a disk distorted by tidal interaction with by-passing stars or internal planets
and investigate for which parameters the distortion can be best detected in the mid-infrared using the mid-infrared interferometric
device MIDI.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
3.
It has been found that the near-infrared flux variations of Seyfert galaxies satisfy relations of the form Fi ≈α i j +β i j Fj , where Fi , Fj are the fluxes in filters i and j ; and α i , j , β i , j are constants. These relations have been used to estimate the constant contributions of the non-variable underlying galaxies. The paper attempts a formal treatment of the estimation procedure, allowing for the possible presence of a third component, namely non-variable hot dust. In an analysis of a sample of 38 Seyfert galaxies, inclusion of the hot dust component improves the model fit in approximately half the cases. All derived dust temperatures are below 300 K, in the range 540–860 K or above 1300 K. A noteworthy feature is the estimation of confidence intervals for the component contributions: this is achieved by bootstrapping. It is also pointed out that the model implies that such data could be fruitfully analysed in terms of principal components. 相似文献
4.
5.
6.
Fred L. Whipple 《Earth, Moon, and Planets》1996,72(1-3):69-78
This study is based primarily on the calculations of comet orbits over ~ 106 years for 160 short-period comets by Harold F. Levison and Martin J. Duncan from which there are calculated “ablation AGES”. There are positive statistical correlations (having many deviations) with radial nongravitational forces, comet activity measures, and dust-to-gas ratios in the spectra, in the sense that comets of greater “AGES” tend to be less active and to show less dust in their spectra than comets of lesser “AGES”. 相似文献
7.
8.
This study uses 2 years of data from a detailed weekly water sampling programme in a 11·4 km2 upland peat catchment in the Northern Pennines, UK. The sampling comprised precipitation, soil‐water samples and a number of streams, including the basin outlet. Samples were analysed for: pH, conductivity, alkalinity, Na, K, Ca, Mg, Fe, Al, Total N, SO4, Cl and colour. Principal component analysis (PCA) was used to identify end‐members and compositional trends in order to identify controls on the development of water composition. The study showed that the direct use of PCA had several advantages over the use of end‐member mixing analysis (EMMA) as it combines an analysis of mixing and evolving waters without the assumption of having to know the compositional sources of the water. In its application to an upland peat catchment, the study supports the view that shallow throughflow at the catotelm/acrotelm boundary is responsible for storm runoff generation and shows that baseflow is controlled by cation exchange in the catotelm and mixing with a base‐rich groundwater. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
9.
10.
Detlef Wolf 《Geophysical Journal International》1985,80(1):275-279
Summary. Boussinesq's problem is solved for a uniform and incompressible Maxwell half-space subject to an external gravity field. The solution is based on momentum equations which account for stress advection in the hydrostatically pre-stressed continuum during its deformation. The analysis shows that disregarding the pre-stress term renders the theoretical stress distribution incorrect and the deformation singular in the inviscid limit of the Maxwell continuum. Our solution is contrasted with a recently published alternative solution of the same problem, where regularity in the inviscid limit was forced by modified boundary conditions. 相似文献