全文获取类型
收费全文 | 73篇 |
免费 | 6篇 |
专业分类
测绘学 | 12篇 |
大气科学 | 17篇 |
地球物理 | 16篇 |
地质学 | 10篇 |
海洋学 | 4篇 |
综合类 | 3篇 |
自然地理 | 17篇 |
出版年
2023年 | 1篇 |
2022年 | 1篇 |
2021年 | 4篇 |
2020年 | 1篇 |
2019年 | 1篇 |
2018年 | 1篇 |
2017年 | 2篇 |
2014年 | 6篇 |
2013年 | 4篇 |
2012年 | 5篇 |
2011年 | 6篇 |
2010年 | 5篇 |
2009年 | 3篇 |
2008年 | 9篇 |
2007年 | 7篇 |
2006年 | 3篇 |
2005年 | 1篇 |
2004年 | 4篇 |
2003年 | 6篇 |
2001年 | 2篇 |
2000年 | 3篇 |
1998年 | 1篇 |
1996年 | 1篇 |
1991年 | 1篇 |
1990年 | 1篇 |
排序方式: 共有79条查询结果,搜索用时 29 毫秒
71.
Nasr Yousef M. J. Omar M. Radzi Bin Abas Noorsaadah A. Rahman Norhayati Mohd. Tahir Ahmed I. Rushdi Bernd R. T. Simoneit 《Environmental Geology》2007,52(8):1485-1500
The concentrations of n-alkanes, unresolved complex mixture (UCM), petroleum molecular markers, other tracers of cooking and burning emissions, and
natural background in atmospheric particles and roadside dust particles were measured at eight locations in the city center
and the suburbs of Kuala Lumpur, Malaysia. Atmospheric particles were collected using high-volume filtration (PM-10, GFF)
over 24 h average periods. Road dusts were swept up, dried and sieved. Both types of samples were extracted with dichloromethane/methanol
mixture (3:1 v/v) by ultrasonic agitation. The extracts were then fractionated by column chromatography and the alkanes subjected
to gas chromatography–mass spectrometry (GC–MS). Total extracts were also analyzed directly by GC–MS after silylation. The
molecular distributions of compounds as well as diagnostic geochemical ratios were determined in order to identify the sources
of the organic compounds. Samples collected from a rural area and lubricating oils were also analyzed for comparisons. Anthropogenic
and biogenic sources such as vehicular emissions, waxes of higher plants, food cooking operations, and biomass and domestic
refuse burning processes contributed to the organic matter content of atmospheric and to lesser extent, roadside dust particles. 相似文献
72.
In November 2004–January 2005, a micro orifice uniform deposit impactor (MOUDI) and a Nanometer (nanometer)-MOUDI were used in the center of Taiwan to measure particle size (18 nm particle size 18 μm) distributions of atmospheric aerosols at a traffic site during the winter period. The average Mass in Media Aerodynamic Diameter (MMAD) of suspended particles is 0.99 μm this study. As for the ultra fine and nanometer (nanometer) particle mode, the composition order for these major ions species was SO42− NH4+ NO3− Mg2+ Ca2+ Na+ K+ Cl−. An ion Chromatography (DIONEX-100) was used to analyze major anion species, Cl−, NO3−, SO42− and cation species, NH4+Na+, K+, Ca2+Mg2+. Their concentrations were also extracted from various particles size modes (nanometer (nanometer), ultra fine, fine and coarse). The results obtained in this study also indicated that the average portions for the major ionic species (SO42−, NH4+ and Mg2+) in the nanometer (nanometer), ultra fine, fine and coarse particulate modes are about 34%, 37%, 63% and 30%, respectively at this traffic sampling site during the winter period. 相似文献
73.
城市低层大气臭氧生成的模拟研究 总被引:7,自引:0,他引:7
利用一个城市边界层臭氧模式,以南京市为对象,研究了臭氧在城市低层大气中的形成机制和规律,得出了南京市18个交通点的日臭氧浓度最大值的分布图。结果表明,南京市白天有相当长的时间是处于臭氧超标的状态,不少交通点的日最大臭氧浓度值是标准的2-3倍。文章还模拟了PAN,OH自由基和HCHO这三种重要物种的日变化规律。同时,本文选择南京市东郊的紫金山风景区,实次探讨了植物排放有机物对臭氧生成的贡献。从模式的模拟研究可得,与人为因素相比,植物排放对臭氧生成的作用也是不可忽视的,值得作深入一步的探讨。 相似文献
74.
城市交通信息系统动态管理模块设计研制* 总被引:4,自引:0,他引:4
本文以北京交通信息系统的开发研制为例,着重阐述了城市交通信息系统中交通动态管理模块的设计与实施。 相似文献
75.
江苏省长江沿岸港口群体的功能,格局与发展研究 总被引:9,自引:3,他引:9
本文论述了江苏省长江沿岸港口群体的交通区位优势和战略地位,分析了港口群体的现代发展特征、职能结构以及主要存在问题,提出了港口群体的发展构思。 相似文献
76.
In this paper, a numerical approach for the prediction of vibrations induced in buildings due to railway traffic in tunnel is proposed. The numerical method is based on a sub-structuring approach, where the train is simulated by a multi-body model; the track–tunnel–ground system is modeled by a 2.5D FEM–PML approach; and the building by resource to a 3D FEM method. The coupling of the building to the ground is established taking into account the soil–structure-interaction (SSI). The methodology proposed allows dealing with the three-dimensional characteristics of the problem with a reasonable computational effort. Using the proposed model, a numerical study is developed in order to better discern the impact of the use of floating slabs systems for the isolation of vibrations in the tunnel on the dynamic response of a building located in the surrounding of the tunnel. The comparison between isolated and non-isolated scenarios allowed concluding that the mats stiffness is a key parameter on the efficiency of floating slab systems. Furthermore, it was found that the selection of the stiffness of the mats should be performed carefully in order to avoid amplification of vertical vibrations of the slabs of the building. 相似文献
77.
Local and global shape functions in a boundary element formulation for the calculation of traffic induced vibrations 总被引:1,自引:1,他引:1
This paper compares the use of local and global shape functions in a boundary element method that is used in a prediction model for traffic induced vibrations. The boundary element formulation describes the interaction problem between a linear elastic layered half-space and a longitudinally invariant structure representing a road or a railway track. The boundary element formulation in the frequency–wavenumber domain is obtained by means of a weighted residual method. Constant element shape functions, as well as Legendre and Chebyshev shape functions are considered. Their effect on both accuracy and computational effort is investigated. The presence of a singularity in the Chebyshev based shape functions allows to obtain a better approximation for the soil tractions. The theory is applied to road traffic induced vibrations where the response is calculated in a large number of output points. 相似文献
78.
79.