全文获取类型
收费全文 | 406篇 |
免费 | 30篇 |
专业分类
测绘学 | 8篇 |
大气科学 | 31篇 |
地球物理 | 180篇 |
地质学 | 105篇 |
海洋学 | 14篇 |
天文学 | 88篇 |
自然地理 | 10篇 |
出版年
2022年 | 7篇 |
2021年 | 5篇 |
2020年 | 4篇 |
2019年 | 6篇 |
2018年 | 19篇 |
2017年 | 18篇 |
2016年 | 16篇 |
2015年 | 19篇 |
2014年 | 26篇 |
2013年 | 23篇 |
2012年 | 13篇 |
2011年 | 11篇 |
2010年 | 18篇 |
2009年 | 12篇 |
2007年 | 10篇 |
2006年 | 5篇 |
2005年 | 3篇 |
2004年 | 8篇 |
2003年 | 5篇 |
2002年 | 13篇 |
2001年 | 4篇 |
2000年 | 6篇 |
1999年 | 5篇 |
1998年 | 9篇 |
1997年 | 5篇 |
1996年 | 6篇 |
1995年 | 3篇 |
1994年 | 5篇 |
1993年 | 4篇 |
1991年 | 5篇 |
1990年 | 12篇 |
1989年 | 4篇 |
1988年 | 7篇 |
1987年 | 8篇 |
1986年 | 4篇 |
1985年 | 7篇 |
1984年 | 5篇 |
1983年 | 8篇 |
1982年 | 9篇 |
1981年 | 6篇 |
1980年 | 4篇 |
1979年 | 7篇 |
1978年 | 6篇 |
1977年 | 5篇 |
1974年 | 4篇 |
1973年 | 4篇 |
1972年 | 7篇 |
1971年 | 8篇 |
1964年 | 3篇 |
1960年 | 3篇 |
排序方式: 共有436条查询结果,搜索用时 15 毫秒
431.
Stable isotopic and elemental characteristics of recent tufa from a karstic Krka River (south‐east Slovenia): useful environmental proxies? 下载免费PDF全文
Tufa samples from 16 consecutive barrages along a 13 km section of the groundwater‐fed Krka River (Slovenia) were analysed for their petrographical, mineralogical, elemental and stable carbon (δ13C) and oxygen (δ18O) isotope composition, to establish their relation to current climatic and hydrological conditions. Waters constantly oversaturated with calcite and the steep morphology of the Krka riverbed stimulate rapid CO2 degassing and subsequent tufa precipitation. The carbon isotope fractionation (Δ13C) between dissolved inorganic carbon and tufa in the Krka River evolves towards isotopic equilibrium being controlled by continuous CO2 degassing and tufa precipitation rate downstream. The Δ13C increased from 1·9 to 2·5‰ (VPDB); however, since tufa precipitation rates remain similar downstream, the major controlling factor of carbon isotope exchange is most probably related to the continuous 12CO2 degassing downstream leaving the carbon pool enriched in 13C. In the case of oxygen, the isotope fractionation (Δ18O) was found to be from 1·0 to 2·3‰ (VSMOW) smaller than reported in the literature. The observed discrepancies are due to different precipitation rates of calcite deposits because Krka tufas on cascades grow relatively faster compared to slowly precipitated calcite deposits in cave or stream pools. Due to non‐equilibrium oxygen isotope exchange between Krka tufa and water, the δ18O proxy showed from 1·2 to 8·2°C higher calculated water temperatures compared to measured water temperatures, demonstrating that δ18O proxy‐based temperature equations are not reliable for water temperature calculations of fast‐growing tufa on cascades. Because Mg is bound to the terrigenous dolomite fraction in the Krka tufa samples, the Mg/Ca was also found to be an unreliable temperature proxy yielding over up to 20°C higher calculated water temperatures. 相似文献
432.
Soejono Igor Janoušek Vojtěch Žáčková Eliška Sláma Jiří Konopásek Jiří Machek Matěj Hanžl Pavel 《International Journal of Earth Sciences》2017,106(6):2109-2129
International Journal of Earth Sciences - Cadomian magmatic complexes of the Brunovistulian Domain crop out at the eastern termination of the Bohemian Massif. However, the age, nature and... 相似文献
433.
Snežana S. Nenadović Ljiljana M. Kljajević Maja A. Nešić Marijana Ž. Petković Katarina V. Trivunac Vladimir B. Pavlović 《Environmental Earth Sciences》2017,76(2):79
The paper presents chemical and structural analysis of geopolymer materials which are obtained by alkali-activated calcined clay (metakaolin) originated from Serbia under strictly defined conditions. Characterization of the metakaolin and geopolymers molecular structure has been done using X-ray diffraction, scanning electron microscope, Fourier transform infrared spectroscopy and matrix-assisted laser desorption ionization time-of-flight mass spectrometry. The paper presents the possibility of obtaining geopolymer structure and differences in chemical and structural characterization of these materials taking into account the concentration of NaOH as a variable parameter. The results of MALDI analysis of metakaolin and synthesized geopolymer structures using various matrix system: 2,4,6 trihydroxyacetophenone (THAP), α-cyano-4-hydroxycinnamic, 2,6 dihydroxyacetophenone and laser desorption/ionization, have shown that THAP matrix is the most appropriate for analysing these aluminosilicate materials. 相似文献
434.
Karel Hron Peter Filzmoser Patrice de Caritat Eva Fišerová Alžběta Gardlo 《Mathematical Geosciences》2017,49(6):797-814
The log ratio methodology converts compositional data, such as concentrations of chemical elements in a rock, from their original Aitchison geometry to interpretable real orthonormal coordinates, thereby allowing meaningful statistical processing and visualization. However, it must be taken into account that the original concentrations can be flawed by detection limit or imprecision problems that can severely affect the resulting coordinates. This paper aims to construct such orthonormal log ratio coordinates, called weighted pivot coordinates, that capture the relevant relative information about an original component and treat the redundant information in a controlled manner. Theoretical developments are supported by a thorough simulation study. Weighted pivot coordinates are then applied to the geochemical mapping of catchment outlet sediments from the National Geochemical Survey of Australia illustrating their advantage over possible alternatives. 相似文献
435.
Shatsillo A. V. Rud’ko S. V. Latysheva I. V. Rud’ko D. V. Fedyukin I. V. Malyshev S. V. 《Izvestiya Physics of the Solid Earth》2019,55(6):841-863
Izvestiya, Physics of the Solid Earth - Abstract—Paleo- and rock magnetic, sedimentological, and isotope geochemical study is carried out for the carbonate member of Late Neoproterozoic... 相似文献
436.
Tiiu Elbra Petr Schnabl Kristýna Čížková Petr Pruner Šimon Kdýr Jacek Grabowski Daniela Reháková Andrea Svobodová Camille Frau William A.P. Wimbledon 《Studia Geophysica et Geodaetica》2018,62(2):323-338
Palaeo- and rock-magnetic investigations of the St Bertrand’s Spring (Le Ravin de Font de St Bertrand) locality in France were carried out in order to contribute to, and improve, the stratigraphy of the Jurassic-Cretaceous boundary interval. Magnetic susceptibility shows slightly diamagnetic behaviour in the lowermost part of the profile and an increase (paramagnetic) towards its middle and upper parts. Rock-magnetic measurements throughout the section show magnetite as the main magnetic fraction, together with traces of hematite. Additionally, thermal demagnetization indicates the presence of goethite. Our magnetostratigraphy indicates three normal/reversed polarity sequences; possibly encompassing the magnetozones M19r to the M17n. This suggests that the St Bertrand section straddles the Tithonian/Berriasian boundary and reaches the middle Berriasian sensu lato. 相似文献