全文获取类型
收费全文 | 458篇 |
免费 | 123篇 |
国内免费 | 87篇 |
专业分类
测绘学 | 15篇 |
大气科学 | 144篇 |
地球物理 | 167篇 |
地质学 | 191篇 |
海洋学 | 66篇 |
天文学 | 20篇 |
综合类 | 17篇 |
自然地理 | 48篇 |
出版年
2024年 | 1篇 |
2023年 | 4篇 |
2022年 | 14篇 |
2021年 | 4篇 |
2020年 | 6篇 |
2019年 | 15篇 |
2018年 | 16篇 |
2017年 | 16篇 |
2016年 | 15篇 |
2015年 | 16篇 |
2014年 | 25篇 |
2013年 | 24篇 |
2012年 | 30篇 |
2011年 | 30篇 |
2010年 | 24篇 |
2009年 | 34篇 |
2008年 | 40篇 |
2007年 | 52篇 |
2006年 | 30篇 |
2005年 | 32篇 |
2004年 | 23篇 |
2003年 | 15篇 |
2002年 | 27篇 |
2001年 | 29篇 |
2000年 | 11篇 |
1999年 | 22篇 |
1998年 | 16篇 |
1997年 | 21篇 |
1996年 | 17篇 |
1995年 | 9篇 |
1994年 | 9篇 |
1993年 | 8篇 |
1992年 | 7篇 |
1991年 | 5篇 |
1990年 | 4篇 |
1989年 | 3篇 |
1988年 | 4篇 |
1987年 | 3篇 |
1986年 | 1篇 |
1985年 | 3篇 |
1984年 | 1篇 |
1980年 | 2篇 |
排序方式: 共有668条查询结果,搜索用时 500 毫秒
31.
Angela Marinoni Paolo Laj Pierre Alexandre Deveau Federica Marino Grazia Ghermandi Fabien Aulagnier Hlne Cachier 《Atmospheric Research》2005,74(1-4):565-580
The physical and chemical properties of aerosol particles were investigated at Plan d'Aups, one of the ESCOMPTE sites located in the St. Baume mountain area (700 m a.s.l.), 50 km east of Marseilles (France). The site is ideally located for assessing the vertical and horizontal extent of the pollution plume from the Marseilles–Berre area.Our study showed that polluted air masses from the Marseilles–Berre area are advected to Plan d'Aups in the early afternoon. Average daily concentration of particles reaches up to 40 μg m−3 while 1-h average particle number concentration is greater than 30,000 cm−3. Most of the particle mass is composed of SO42− and organic carbon (OC). The chemical properties of the particles revealed that an additional source, possibly from the industrial area of Gardanne, contributes to the aerosol mass. This last source is characterised by significant emissions of elements, such as Zn, V, Al and Si.In addition to transport, we found that gas-to-particle conversion takes place at the interface between the free troposphere and the boundary layer. We estimated that on average, 30% of the particle number is accounted for by direct nucleation. This is potentially a major aerosol source to the free troposphere. 相似文献
32.
介绍滇中红层形成的地质历史背景,红层分布范围,主要地层岩性及区内地质构造。重点讨论滇中红层特别是红层软岩的岩体原生结构,及后期受构造改造的岩体结构特性,岩体风化特性,岩体水理作用特性,岩体物理力学性质等四方面的工程地质特性。 相似文献
33.
A. Foubert D. Van Rooij D. Blamart J.-P. Henriet 《International Journal of Earth Sciences》2007,96(1):141-158
Three provinces, characterized by the presence of carbonate mounds interpreted as cold-water coral banks have been reported
in Porcupine Seabight, SW of Ireland and were recently subjected to many detailed studies. This contribution discusses the
use of X-ray imagery and physical properties in deciphering palaeoceanographic, sedimentological and biological processes.
Physical property core logging and X-ray imagery are used to identify and describe sedimentation regimes and so their respective
palaeoceanographic and palaeoclimatological settings in two mound provinces, respectively the Belgica mound province and the
Magellan mound province. Both provinces show at present time clear differences in the hydrodynamic environment. This study
confirms that also during the past the oceanographic and sedimentological environment of both provinces differ clearly. Impacts
of glacial–interglacial variations and locally derived ice rafting events (IRE), comparable with the North Atlantic Heinrich
events (HE) have been recognized in both provinces. Moreover, the combination of X-ray imagery, magnetic susceptibility, gamma
density and P-wave velocity makes it possible to estimate the coral content and coral distribution in unopened cores localized
on top of carbonate mounds. A comparison between on-mound and off-mound cores in both provinces allowed revealing some mechanisms
of mound evolution and coral growth versus time. 相似文献
34.
35.
A hydrodynamic model is employed to derive the magnitude of on-shelf fluxes through a shelf-break canyon for a wide range of canyon sizes and ambient oceanic conditions. Predicted canyon-upwelling fluxes are of the order of 0.05–0.1 Sv (1 Sv=1 million m3/s), being several orders of magnitude greater than upslope fluxes in the bottom Ekman layer on the ambient continental slope. On the basis of ∼150 simulations conducted, a bulk formula of upwelling flux in a submarine canyon is derived. For typical conditions, the upwelling flux varies quadratically with forcing strength (speed of incident flow), linearly with canyon depth, and is inversely proportional to the buoyancy frequency of the density stratification inside the canyon. Other parameters such as density stratification above shelf-break depth and bottom friction are found to have minor influences on the resultant canyon-upwelling flux. 相似文献
36.
37.
大地震纬向分布的基本规律与动力学解释 总被引:2,自引:0,他引:2
统计了 1 90 0~ 1 999年全球大地震 (M≥ 7.0 )的纬向分布 ,进一步证实了全球大地震的分布的确存在不对称问题 ,北、南半球大地震发生的次数不对称 ,北半球多 ,南半球少 ;二个半球大地震集中分布的区域不对称 ,北半球大地震集中分布的区域为 1 5°~ 55°,南半球集中分布的区域为 0°~ 35°;北半球有 3个明显的大地震分布区间 ,即 1 5°~ 2 0°,35°~ 45°,50°~ 55°;两极地区无大地震。并且导出了计算日、月对地壳纬向水平引潮力达到极值的计算公式 ,根据日、月水平引潮力达到极值时的纬度分布的规律 ,较好地解释了全球大地震分布的不对称问题 相似文献
38.
Silke WIEPRECHT Department of Geology Groundwater Morphology German Federal Institute of Hydrology Koblenz Germany 《国际泥沙研究》2001,16(2)
1 INTRODUCTIONFor the pmpose of river restoration of the river Isar in the city area of Munich several inveshgationswere cAned out at the InshtUte for Hydrosciences, German Armed Forces University Munich. The calculation ofwater level for the differnt planned variants were realized by a 2d mathematical model. Although thesesimulahons were a very helpfol basis for fuIther planing, a physical model was constrUcted in order toinvestigate detalled problems.The main interest was focussed … 相似文献
39.
Jihn-Sung LAI Fi-John CHANG Assistant Research Fellow Hydrotech Research Institute National Taiwan University Taipei Taiwan Professor Department of Agriculture Engineering Hydrotech Research Institute National Taiwan University Taipe 《国际泥沙研究》2001,16(3)
1 INTRODUCTIONIn recent years, the concePt of long-term sustained use of reservoirs has been addressed because areservoir is very much considered to be a nonrenewable resource (Morris and Fan, l998). Technically,many options for reservoir sedAnentation control can be utlized to pursue the sustainable develoPment ofwater resources. In general, reduction of incoming sedimen yields from watersheds is often emPloyedin conjunction with hydraulic methods such as flushing or density currnt vot… 相似文献
40.
本文系统阐述了国家自然地图集Internet版的设计和研制过程中的若干问题,包括系统的概念设计、系统开发中的WebGIS技术和策略,系统的主要功能和特色,以及系统维护和更新方案等。本系统从概念设计来看分为服务器端软件模块、浏览器端软件模块、国家自然地图集数据库支持等几个部分。系统开发中采取的WebGIS技术和策略有:兼顾服务器端和客户端的综合型WebGIS策略,基于Java Applet的 WebGIS浏览器开发技术,基于Map Object(MO)的WebGIS服务器开发技术等3个方面。在系统的主要功能特色方面,本文从以下5个方面进行了论述:科学有序的内容结构、清晰精练并带导航的界面、富有特色的信息查询功能、多重表达的地图可视化效果、一定的空间信息分析和制图功能。在系统维护和更新方案上,本文从网络技术、数据更新、功能开发3个方面介绍了计划,并对今后的发展趋势进行了展望。 相似文献