全文获取类型
收费全文 | 4117篇 |
免费 | 1212篇 |
国内免费 | 571篇 |
专业分类
测绘学 | 591篇 |
大气科学 | 305篇 |
地球物理 | 1880篇 |
地质学 | 1735篇 |
海洋学 | 310篇 |
天文学 | 28篇 |
综合类 | 408篇 |
自然地理 | 643篇 |
出版年
2024年 | 13篇 |
2023年 | 42篇 |
2022年 | 118篇 |
2021年 | 170篇 |
2020年 | 170篇 |
2019年 | 220篇 |
2018年 | 167篇 |
2017年 | 222篇 |
2016年 | 215篇 |
2015年 | 264篇 |
2014年 | 279篇 |
2013年 | 257篇 |
2012年 | 257篇 |
2011年 | 257篇 |
2010年 | 197篇 |
2009年 | 250篇 |
2008年 | 234篇 |
2007年 | 282篇 |
2006年 | 253篇 |
2005年 | 205篇 |
2004年 | 215篇 |
2003年 | 183篇 |
2002年 | 162篇 |
2001年 | 123篇 |
2000年 | 113篇 |
1999年 | 118篇 |
1998年 | 122篇 |
1997年 | 117篇 |
1996年 | 115篇 |
1995年 | 94篇 |
1994年 | 65篇 |
1993年 | 94篇 |
1992年 | 61篇 |
1991年 | 54篇 |
1990年 | 45篇 |
1989年 | 37篇 |
1988年 | 35篇 |
1987年 | 27篇 |
1986年 | 20篇 |
1985年 | 4篇 |
1982年 | 2篇 |
1980年 | 4篇 |
1979年 | 4篇 |
1974年 | 1篇 |
1954年 | 13篇 |
排序方式: 共有5900条查询结果,搜索用时 203 毫秒
11.
模糊划分矩阵在岩土参数概率分布中的应用 总被引:1,自引:0,他引:1
讨论如何在小样本条件下用已有的过程经验与试验资料确定岩土参数概率分布,用模糊划分矩阵与BAYES方法相结合,给出由小样本试验数据确定岩土参数的概率分布。 相似文献
12.
13.
关于非球形粒子光散射的T-矩阵数值计算方法的研究 总被引:1,自引:0,他引:1
首先介绍了无规取向轴对称非球形粒子光散射的T-矩阵数值方法。然后,进一步研究了T-矩阵计算的收敛问题,提出了一种新的关于无规取向无吸收非线形散射物体的物理收敛方法,我们研究了椭球粒子的收敛问题,结果表明我们的数值方法和T-矩阵计算程序是有效的, 收敛精度与粒子的尺度和形状有很强的依赖性,在一定的条件下,我们的物理收敛速度优于NASA Mishchenko的数学收敛速序。 相似文献
14.
提要 本文详细讨论了一种三维重力位场快速正反演方法。作者在前人工作的基础上,对算法作了行之有效的改进,通过对反演中的不稳定因素进行各种理论模型试算,得出保证迭代反演稳定收敛的准则,编制出可在微型机IBM—PC上运行的人机对话式自动正反演程序。本文还对各种不均质模型进行了模似计算并将该方法应用于某含油气沉积盆地的双层界面构造研究,揭示出了储油有利地段。 相似文献
15.
Summary. Multiparameter inversions of multimode dispersion data are performed for two large regions: the Pacific Ocean and North America. Anisotropy is taken into account by considering transversely isotropic structures with a vertical axis of symmetry. Two fundamental questions are studied in detail: (1) how to make the inverted models consistent when using different sets of parameters, (2) what is the significance of transversely isotropic inversion for the actual Earth's structure? It is proved that full consistency of the inverted models can be achieved by properly taking into account some a priori informations on the model and it is shown that the use of transversely isotropic models with vertical axis of symmetry does not cause severe limitations when interpreting the data. The models we have obtained are discussed in the light of these investigations. Considering an olivine-rich upper mantle, we make a tentative interpretation of these models in terms of preferred orientation of the a -axis of the crystals in one fixed horizontal direction. 相似文献
16.
17.
Aimed at promoting regional coalitions and expanding the approach to economic links, this paper puts forward some new concepts
such as link intensity and receiving coefficient, expounds the indexes of quantitative analysis of economic links and establishes
the quantitative-analysis model of economic links. With help of the model, this paper calculates the values of the link intensities
between Su-Xi-Chang (Suzhou-Wuxi-Changzhou) region and Shanghai, and analyzes the regional difference of the economic links. 相似文献
18.
19.
《The Professional geographer》1987,39(1):85-94
Reviews of geographic software in this article: DEMO-GRAPHICS: WORLD POPULATIONS AND PROJECTIONS. ESP GAUSS. CEMODEL S. Damus LIMDEP. William H. Greene MICROSTAT 4.1 OTIS PCIPS. (Personal Computer Image Processing System) . H.J. Meyers and R. Bernstein. REGRESSION ANALYSIS OF TIME SERIES (RATS) SPSS/PC+ URBAN DATA MANAGEMENT SOFTWARE (UDMS) 相似文献
20.
Jorge Luis De Souza 《Pure and Applied Geophysics》1991,136(2-3):245-264
The Rayleigh wave phase and group velocities in the period range of 24–39 sec, obtained from two earthquakes which occurred in northeastern brazil and which were recorded by the Brazilian seismological station RDJ (Rio de Janeiro), have been used to study crustal and upper mantle structures of the Brazilian coastal region. Three crustal and upper mantle models have been tried out to explain crustal and upper mantle structures of the region. The upper crust has not been resolved, due basically to the narrow period range of the phase and group velocities data. The phase velocity inversions have exhibited good resolutions for both lower crust and upper mantle, with shear wave velocities characteristic of these regions. The group velocity data inversions for these models have showed good results only for the lower crust. The shear wave velocities of the lower crust (3.86 and 3.89 km/sec), obtained with phase velocity inversions, are similar to that (=3.89 km/sec) found byHwang (1985) to the eastern South American region, while group velocity inversions have presented shear velocity (=3.75 km/sec) similar to that (=3.78 km/sec) found byLazcano (1972) to the Brazilian shield. It was not possible to define sharply the crust-mantle transition, but an analysis of the phase and group velocity inversions results has indicated that the total thickness of the crust should be between 30 and 39 km. The crustal and upper mantle model, obtained with phase velocity inversion, can be used as a preliminary model for the Brazilian coast. 相似文献