全文获取类型
收费全文 | 798篇 |
免费 | 140篇 |
国内免费 | 196篇 |
专业分类
测绘学 | 119篇 |
大气科学 | 206篇 |
地球物理 | 158篇 |
地质学 | 294篇 |
海洋学 | 133篇 |
天文学 | 25篇 |
综合类 | 67篇 |
自然地理 | 132篇 |
出版年
2024年 | 7篇 |
2023年 | 8篇 |
2022年 | 27篇 |
2021年 | 31篇 |
2020年 | 27篇 |
2019年 | 46篇 |
2018年 | 24篇 |
2017年 | 51篇 |
2016年 | 35篇 |
2015年 | 46篇 |
2014年 | 65篇 |
2013年 | 82篇 |
2012年 | 41篇 |
2011年 | 49篇 |
2010年 | 50篇 |
2009年 | 66篇 |
2008年 | 47篇 |
2007年 | 58篇 |
2006年 | 61篇 |
2005年 | 44篇 |
2004年 | 46篇 |
2003年 | 45篇 |
2002年 | 33篇 |
2001年 | 17篇 |
2000年 | 19篇 |
1999年 | 16篇 |
1998年 | 11篇 |
1997年 | 13篇 |
1996年 | 14篇 |
1995年 | 6篇 |
1994年 | 9篇 |
1993年 | 6篇 |
1992年 | 12篇 |
1991年 | 1篇 |
1989年 | 9篇 |
1988年 | 2篇 |
1987年 | 3篇 |
1985年 | 2篇 |
1984年 | 2篇 |
1983年 | 1篇 |
1982年 | 2篇 |
排序方式: 共有1134条查询结果,搜索用时 882 毫秒
591.
Modeling Full Seismogram Envelopes Using Radiative Transfer Theory with Born Scattering Coefficients
The equation of radiative transfer is used to model the transport of seismic energy in 2-D and 3-D acoustic random media.
Monte-Carlo solutions of this equation using non-isotropic Born scattering coefficients are compared to three analytical solutions:
Markov approximation, radiative transfer theory with isotropic scattering coefficients, and diffusion approximation. Additionally,
we compare to finite differences solutions of the full wave equation in 2-D. We find a good correspondence of radiative transfer
theory to Markov approximation for the case of multiple forward scattering. The comparison to radiative transfer theory with
isotropic scattering coefficients, a model frequently used in data analysis, demonstrates that in the case of forward scattering
the isotropic scattering model is not better than a diffusion approach. To compare radiative transfer theory with non-isotropic
scattering coefficients to finite differences solutions of the full wave equation, the finite source duration and the bandpass
filter process as well as the normalization of absolute amplitudes are explicitely taken into account. We find a good coincidence
of both theories for scattering parameters, which are realistic for usual Earth crust. The theory correctly describes the
unscattered direct wavefront, the envelope broadening caused by multiple forward scattering, as well as the late coda caused
by multiple wide angle scattering. For strong scattering, which can be expected for very heterogeneous media such as strato
volcanoes, the solutions of radiative transfer differ from the more complete solutions of the full wave equation. 相似文献
592.
593.
Categorical maps, comparisons, and confidence 总被引:2,自引:0,他引:2
The comparison of categorical maps is a common problem in several different contexts. Differences between categorical maps can be characterized and measured in a variety of ways. In 2004 we invited individuals from remote sensing, geographical information analysis, spatial modelling, and landscape ecology to participate in a virtual workshop in order to compare strategies for comparison. This revealed that the key dimensions of comparison relate to (1) the map characteristics considered, (2) the nature of the comparison, (3) the handling of geographical space, (4) the units of computed measures, and (5) the tests of significance.Ferko Csillag deceased 相似文献
594.
595.
太行山嶂石岩地貌与云台山地貌特征 总被引:3,自引:0,他引:3
太行山中南段地区旅游地质资源十分丰富,其中河北嶂石岩国家级地质公园和河南云台山世界级地质公园旅游地质地貌特征最具特色,分别代表了本区砂岩和碳酸盐岩独特地貌景观。 相似文献
596.
Based on temperature reconstruction and proxy data from 14 sites in the Northern Hemisphere, this paper focused on comparing the cycles of temperature variations between the Arctic and other areas, including Atlantic, Europe, China, Asia, Pacific, Indian Ocean, and America during the transition from the last Interstade to the Last Glacial Maximum, from the Last Glacial Maximum to megathermal period in Holocene and the transition of the Little Ice Age (LIA) by the methods of Singular Spectrum Analysis (SSA) and Maximum Entropy Spec-trum (MES). The results showed that environmental changes in the Arctic are most similar to that in the North American and better similar to Asia, Atlantic and Pacific, the least similar to Indian Ocean and Europe. The 1500-year oscillation of temperature existed both in Arctic and Europe. 相似文献
597.
598.
李满洲 《水文地质工程地质》2007,34(2):125-128
本文针对饱和粘性土地基,分别采用振击、锤击两种技术方法、工艺对其进行加固处理。结果表明:在相同布桩方案和用料条件下,振动(φ550)沉管桩较锤击(φ377)沉管桩加固效果更好。同原天然地基土相比,二者处理后的复合地基承载力和变形模量提高幅度分别为94.0%5、2.9%和65.0%、21.5%。主要因为前者有利于地基土颗粒之间的剪切与重组及其土的三维结构改变,有利于桩间土排水固结和挤密作用的发挥,且置换因素亦有较大作用;而后者不利于地基土颗粒之间的剪切与重组及其土的三维结构改变,虽然成桩密度较大,但该致密桩体却不利于超孔隙水压力的消散与桩间土排水固结作用的发挥,且由于所成桩径较小,桩体置换作用和径向挤密作用相对均较弱。 相似文献
599.
《The Professional geographer》1983,35(2):230-260
Book Reviewed in this article: Rabat: Urban Apartheid in Morocco . Janet Abu -Lughod . Marketplaces in a Developing Country: The Case of Western Nigeria . Isaac Ayinde Adalemo . Farming Development and Space: A World Agricultural Geography . Bernd Andreae . Section and Party: A Political Geography of American Presidential Elections, from Andrew Jackson to Ronald Reagan . J. Clark Archer and Peter J. Taylor . Women and Space: Ground Rules and Social Maps . Shirley Ardener , ed. European Progress in Spatial Analysis . R. J. Bennett , ed. The Origins of Academic Geography in the United States . Brian W. Blouet Geographic Perspectives on Global Problems . Ronald Reed Boyce . Seasonal Dimensions to Rural Poverty . Robert Chambers , Richard Longhurst and Arnold Pacey eds. The New Nationalism and the Use of Common Spaces: Issues in Marine Pollution and the Exploitation of Antarctica . Jonathan I. Charney , ed. Communications Tomorrow: The Coming of the Information Society . Edward Cornish , ed. The Design of Suburbia . Arthur Edwards . Explorer on the Northern Plains: Lieutenant Gouverneur K. Warren's Preliminary Report of Explorations in Nebraska and Dakota in the Years 1855–56–57. With an Introduction by Frank N. Schubert . The Changing Climate: Responses of the Natural Flora and Fauna . Michael J. Ford . Essentials of Physical Geography . Robert E. Gabler , Robert J. Sager , Sheila Brazier , and Daniel L. Wise. The Road to Jaramillo . William Glen . Valued Environments . John R. Gold and Jacquelin Burgess , eds. Proximity and Preference: Problems in the Multidimensional Analysis of Large Data Sets . Reginald G. Golledge and John N. Rayner , eds. A Search for Common Ground . Peter Gould and Gunnar Olsson , eds. Geography: Its History and Concepts . Arild Holt -Jensen . A Population Geography . Huw R. Jones . The Human Mosaic: A Thematic Introduction to Cultural Geography, 3rd ed. Terry G. Jordan and Lester Rowntree . Urban Social Geography: An Introduction . Paul Knox . The Anatomy of Job Loss: The How, Why and Where of Employment Decline . Doreen Massey and Richard Meegan . The Information Society as Post-Industial Society . Yoneji Masuda . Map Librarianship, 2nd ed. Harold Nichols . India: Cultural Patterns and Processes . Allen G. Noble and Ashok K. Dutt , eds. The God that Limps: Science and Technology in the Eighties . Colin Norman . Geography: An Introductory Perspective . Robert E. Norris , Keith D. Harries and John D. Vitek . The Politics of Technology Assessment . David M. O'Brien and Donald A. Marchand . Ethnic Segregation in Cities . Ceri Peach , Vaughan Robinson and Susan Smith , eds. Churches and Church Membership in the United States, 1980 . Bernard Quinn , Herman Anderson , Martin Bradley , Paul Goetting and Peggy Shriver . Energy in Australia: Politics and Economics . Hugh Saddler . Development from Above or Below? The Dialectics of Regional Planning in Developing Countries . Walter B. Stóuhr and D. R. Fraser Taylor , eds. Human Impact on the Ecosystem . Joy Tivy and Greg O'Hare . Plants and People: Vegetation Change in North America . Thomas R. Vale . The Mapmakers: The Story of the Great Pioneers in Cartography from Antiquity to the Space Age . John Noble Wilford . 相似文献
600.