全文获取类型
收费全文 | 215篇 |
免费 | 25篇 |
国内免费 | 106篇 |
专业分类
测绘学 | 7篇 |
地球物理 | 19篇 |
地质学 | 88篇 |
海洋学 | 172篇 |
综合类 | 30篇 |
自然地理 | 30篇 |
出版年
2023年 | 6篇 |
2022年 | 7篇 |
2021年 | 11篇 |
2020年 | 18篇 |
2019年 | 7篇 |
2018年 | 23篇 |
2017年 | 7篇 |
2016年 | 7篇 |
2015年 | 10篇 |
2014年 | 13篇 |
2013年 | 32篇 |
2012年 | 12篇 |
2011年 | 20篇 |
2010年 | 17篇 |
2009年 | 15篇 |
2008年 | 12篇 |
2007年 | 15篇 |
2006年 | 5篇 |
2005年 | 14篇 |
2004年 | 12篇 |
2003年 | 10篇 |
2002年 | 9篇 |
2001年 | 12篇 |
2000年 | 3篇 |
1999年 | 10篇 |
1998年 | 7篇 |
1997年 | 2篇 |
1996年 | 3篇 |
1995年 | 1篇 |
1994年 | 4篇 |
1993年 | 4篇 |
1992年 | 1篇 |
1991年 | 2篇 |
1990年 | 2篇 |
1989年 | 2篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1982年 | 1篇 |
1977年 | 1篇 |
1976年 | 2篇 |
1973年 | 3篇 |
1971年 | 2篇 |
排序方式: 共有346条查询结果,搜索用时 15 毫秒
31.
Concentrations of some heavy metals and trace elements such as Cr, Ga, Ni, Zn, Mo, Cu, Pb, Yb, Y, Nb, Ti, Sr, Ba, Mn, Sc, Co, V, Zr, Fe, Al, W, Se, Bi, Sb, As, Cd in recent mollusk shells and factors affecting their distribution and deposits collected from various depths in the southern and southwestern parts of the Marmara Sea are investigated. The distribution of the elements in the shells is categorized into four groups. Of these, concentrations of 12 elements (As, Bi, Cd, Co, Ga, Mo, Nb, Sb, Se, Sc, W and Yb) are below zero [(0.053-0.79)×10^-6]; concentrations of seven elements (Cr, Ni, Pb, V, Y, Zr and Cu) are (1.0-6.0)×10^-6; concentrations of four elements (Ti, Mn, Ba and Zn) are 10- 20×10^-6; and concentrations of five elements (Si, Al, Fe, Mg and Sr) are (47.44-268.11)×10^-6. The taxonomic characteristics of the 29 elements were studied separately in mollusk shells such as Chamalea gallina (Linn6), Pitar rudis (Poli), Nassarius reticulatus (Linn6), Venerupis senescens (Coocconi), Mytilus galloprovincialis (Lamarck), Mytilaster lineatus (Gemelin in Linne) and Chlamys glabra. It was found that, in mollusk taxonomy, the elements have unique values. In other words, element concentrations in various mollusk shells depend mainly on the taxonomic characteristics of mollusks. In various bionomic environments different element distributions of the same species are attributed to the different geochemical characters of the each environment. Data obtained in this study indicate that the organisms are the most active and deterministic factors of the environment. 相似文献
32.
A. J. B. Anderson 《Mathematical Geology》1971,3(1):1-14
Numerical methods for the examination of multivariate soil samples are presented in geometric terms. Techniques of coordinate representation by principal components, by nonmetric scaling, and by a new method are discussed, as are techniques for agglomerative hierarchic cluster analysis. These are illustrated by two sets of previously published data. 相似文献
33.
34.
Boriana Deliiska 《Transactions in GIS》2007,11(4):637-651
Geoinformatics is a comparatively new interdisciplinary science and as a part of space informatics uses methods and terminology of informatics and many natural sciences. An ontology of geoinformatics is discussed in the paper, especially concerning its structure, relationships with other ontologies, resources for development and utilization. The ontology of geoinformatics is a kind of domain ontology and has a layered structure consisting of syntactic and semantic layers. The corpus of this ontology is an existing multilingual dictionary of geographical information systems (GIS) enriched with terminology from other external sources. The building of the ontology is preceded by the development of a taxonomy and thesaurus of geoinformatics. The thesaurus database is converted into an OWL ontology by a Visual Basic application. The reusing of the ontology is proposed by its transformation in application ontologies for geoinformatics education. 相似文献
35.
Analysis of subfossil remains of larval Chironomidae in 38 surface-sediment samples from between 53 and 189 meter depth in Lake Tanganyika (East Africa) yielded 77 morphotypes, among which 7 Tanypodinae, 19 Orthocladiinae, and 51 Chironominae. Character-state differences between these morphotypes resemble differences at the species level in the better-known Holarctic fauna, hence we consider most of our Lake Tanganyika morphotypes equivalent to morphological species. Individual morphotypes were identified to species, genus, or tribe level depending on current alpha-taxonomic knowledge on the larvae of the group concerned, and the taxonomic resolution of preserved diagnostic features. This paper presents taxon diagnoses and an illustrated key to the Chironominae (Chironomini and Tanytarsini) in this collection. As the living chironomid fauna of Lake Tanganyika has never been comprehensively studied, we also briefly discuss faunistic aspects, and the ecology of the recovered species and genera in relation to benthic habitat diversity in Lake Tanganyika. 相似文献
36.
37.
38.
39.
Heikki Simola 《Journal of Paleolimnology》1991,6(3):257-260
The utility of classifying chrysophyte stomatocysts by their characteristic honeycomb and ridge patterns is questioned, because a strikingly similar expanding pattern appears on the surface of ionized polymer gels during osmotical swelling as a result of simple physical forces. The rapid accumulation of silicate into a spherical cyst inside a chrysophyte cell appears to be as a physical process sufficiently similar to result in an analogous pattern in microscopic scale. Chrysophyte stomatocysts that possess honeycomb or ridge patterns could be regarded as frozen moments of the pattern evolution during the silicate gel phase. As a consequence, such structures should have little taxonomical value. 相似文献
40.
Dave Lazarus 《Mathematical Geology》1994,26(7):817-832
Marine micropaleontology must in the future provide more precise chronologic and paleoenvironmental information, which in turn must be based on better, more consistent taxonomic and distributional data. Better tools for synthesis and standardization of this data are needed, as the ever expanding published literature is rapidly becoming unmanageable by purely manual compilation methods. The micropaleontology group at the ETH has developed a large relational database of marine microfossil data to partially meet this need. It currently contains biogeographic data on the distribution in Deep Sea Drilling Project (DSDP) and Ocean Drilling Program (ODP) holes of nearly 8,000 species of Cenozoic planktonic foraminifera, radiolaria, diatoms and calcareous nannofossils. The database also includes full stratigraphic occurrence (range chart) data for these fossil groups from more than 100 selected Neogene holes. A particular feature of the database is that all sample information and species names in the original reports are linked to newly created, updatable, comprehensive age models and synonymy lists which reflect modern chronology and taxonomic usage. Searches of the database automatically make use of this information in producing reports. Species ' occurrences, including first and last occurrence information, can be further analyzed using external spreadsheet and statistics packages; plotted by mapping programs; or displayed by a new program which creates composite age-range charts. 相似文献