全文获取类型
收费全文 | 30篇 |
免费 | 6篇 |
国内免费 | 7篇 |
专业分类
测绘学 | 2篇 |
大气科学 | 10篇 |
地球物理 | 4篇 |
地质学 | 15篇 |
海洋学 | 8篇 |
天文学 | 4篇 |
出版年
2024年 | 1篇 |
2020年 | 1篇 |
2019年 | 2篇 |
2017年 | 1篇 |
2016年 | 6篇 |
2014年 | 2篇 |
2013年 | 2篇 |
2012年 | 2篇 |
2011年 | 1篇 |
2009年 | 1篇 |
2008年 | 4篇 |
2007年 | 1篇 |
2006年 | 1篇 |
2004年 | 3篇 |
2003年 | 1篇 |
2001年 | 3篇 |
2000年 | 1篇 |
1999年 | 1篇 |
1998年 | 2篇 |
1997年 | 2篇 |
1996年 | 1篇 |
1994年 | 2篇 |
1993年 | 1篇 |
1984年 | 1篇 |
排序方式: 共有43条查询结果,搜索用时 31 毫秒
11.
In a high-level radioactive waste (HLW) repository, pH has an impact on the solubility, migration, and adsorption of radionuclides. Thus, understanding the effects of pH on the diffusion of radionuclides is essential for long-term disposal of HLW. In this work, the diffusion behaviors of Re(VII) and Se(IV) in compacted Gaomiaozi (GMZ) bentonite at different pH have been investigated by a through-diffusion method. The effective diffusion coefficient, i.e., De values of Re(VII) and Se(IV) were in the range of (1.0–2.4) × 10−11 m2/s at pH 3.0–10.0 and (0.38–2.3) × 10−11 m2/s at pH 3.0–9.0. In the case of Re(VII), the De values remained almost unchanged probably because ReO4− was the dominant species in the pH range of 3.0–10.0. In the case of Se(IV), whose predominant species were HSeO3− at pH < 9.0 and SeO32− at pH ≥ 9.0, the De values decreased by a factor of 3–6 at pH 9.0, i.e., De (pH < 9.0)/De (pH 9.0) ≈ 3–6, implying that the species with a higher valence state had a stronger anion exclusion effect. The decrease in De values can be explained by the diffusion species of Se(IV). Additionally, the rock capacity factor α decreased with the increase of pH. HSeO3− was absorbed on GMZ bentonite with distribution coefficient Kd values in the range of (1.0–2.5) × 10−4 m3/kg at pH ≤ 8.0, whereas SeO32− was negligibly sorbed at pH > 8.0. 相似文献
12.
13.
The reactivity of dissolved iron compounds towards different pollutants and photooxidants in atmospheric liquid water depends upon the oxidation state and speciation of iron. Our measurements of the oxidation state of dissolved iron eluted from aerosol particles (Dae: 0.4–1.6 m) collected in the urban atmosphere of Ljubljana showed that a large fraction of the iron content is present as Fe(II). The concentration ratio [Fe(II)]/[Fe(III)] varied between 0.9 and 3.1. The kinetics of S(IV) autoxidation catalyzed by Fe(II) under the conditions representative for acidified atmospheric liquid water and the influence of oxalate on this reaction under dark conditions was investigated. The reaction rate is the same if Fe(II) or Fe(III) is used as a catalyst under the condition that Fe(II) can be oxidized in Fe(III), which is the catalytically active species. Oxalate has a strong inhibiting effect on the S(IV) autoxidation in the presence of Fe(II). The reaction is autocatalytic with an induction period, that increases with higher concentrations of oxalate. The inhibiting effect of oxalate differs according to whether iron is initially in the Fe(II) or Fe(III) state. However, in both cases the inhibition by oxalate is a result of the formation of complexes with the catalyst. 相似文献
14.
Krzysztof J. Rudzinski 《Journal of Atmospheric Chemistry》2004,48(2):191-216
Autoxidation of S(IV) initiated by manganese sulphate or potassium peroxydisulphate in alkaline aqueous solutions was significantly slowed down by dissolved isoprene, which decayed in the process. The laboratory experiments were carried out in a batch, perfectly mixed reactor, which had no gas space. The concentration–time profiles of oxygen were measured with a Clark-type electrode. The profiles of sulphite species and of isoprene were evaluated from the UV spectra of solutions. The kinetic analysis indicated that isoprene reacted directly with sulphate radical anions produced during the S(IV) autoxidation. A relative second-order rate constant of (2.12 ± 0.37) × 109 M–1 s–1 was determined for this reaction at 25 °C, pH (8.0–8.5) and ionic strength of (1.7–4.9) × 10–3 M (the reference rate constant of the reaction of sulphate radical anions with sulphite ions equalled 3.4 × 108 M–1 s–1). A tentative mechanism of isoprene oxidation during S(IV) autoxidation, which included formation of isoprene – SO–
4 adduct, was based on the analogy to the gas-phase reactions of isoprene and to the liquid-phase reactions of sulphate radical anions with other compounds. Atmospheric significance of the aqueous-phase reaction of isoprene with sulphate radicals was discussed. Approximate analysis showed the reaction is a potential sink for isoprene in the aqueous phase and in the gas–liquid systems of high liquid water content (LWC > 10–5 m3 m–3). The aqueous-phase oxidation of isoprene can produce secondary pollutants, and influence transformation and the long-range transport of SO2 in the atmosphere. 相似文献
15.
海床冲淤变化对港口与航道工程建设非常重要。由于泥沙供给、人类活动和其他等因素的影响,海床冲淤变化非常复杂。洋山深水港是一个新兴的深水港口,是上海国际航运中心重要的组成部分,它的建设引起了各方的广泛关注。目前,洋山水深港一、二、三期港区在潮流运动和定期疏浚下保持着良好的水深。四期港区工程是世界上最大的全自动化深水码头,2017年12月以开港运行。本论文基于大量的地形资料、水文泥沙资料,分析了整个洋山深水港多年来的海床冲淤变化和近期四期工程海域海床冲淤变化。结果显示:1998-2010年整个洋山港区海床冲淤变化表现为较大幅度的冲淤,在洋山主通道内呈现为"南淤北冲"的格局,但是颗珠山汊道一直以来均表现冲刷的趋势;四期港区水域近一些年来也表现为一个冲刷的趋势,多年年均冲刷幅度0.7m左右;讨论了外界泥沙供给、港口工程陆域边界封堵、港池疏浚和由此带来的水流的变化以及泥沙水力特性等因素的对洋山港海域海床冲淤变化的影响,在众多因素中,颗珠山汊道的存在(或保留)对洋山西部水域或四期港区水域冲刷有着积极的作用,它的存在所产生的落潮作用对四期港区的水深维护起到重要的正面影响。 相似文献
16.
为了研究大黄鱼(Pseudosciana crocea)peroxiredoxin Ⅳ(Lyc-Prx Ⅳ)在细胞内的抗氧化功能,构建了表达大黄鱼Prx Ⅳ的重组质粒p CMV-Lyc-Prx Ⅳ,瞬时转染人胚肾细胞(HEK-293T),利用Western blotting方法检测转染后的细胞样品中Lyc-Prx Ⅳ的表达情况,并通过测定细胞内过氧化氢浓度来评价Lyc-Prx IV的体内抗氧化作用.结果显示,Lyc-Prx Ⅳ可在转染重组质粒p CMV-Lyc-Prx Ⅳ的HEK-293T细胞中表达,且细胞中A560处的吸光值在转染后6、12、24 h后分别为0.154、0.116以及0.162,而瞬时转染空载体p CMV后细胞样品在A560处的吸光值在转染后一直稳定在0.260左右,说明细胞中过氧化氢的浓度在转染后6、12、24 h时明显低于瞬时转染空载体p CMV细胞中的过氧化氢浓度(p〈0.01).表明Lyc-Prx Ⅳ在生物体内可以分解过氧化氢,参与生物体内氧化还原状况的调控. 相似文献
17.
18.
Irena Grgić Andreja Dovžan Gorazd Berčič Vida Hudnik 《Journal of Atmospheric Chemistry》1998,29(3):315-337
Laboratory experiments were conducted with real atmospheric aerosol particles as well as with synthetic solutions under dark conditions, to simulate some of the chemical features of aerosols. In solutions obtained by the leaching of aerosols (size range >D
ae: 0.4–1.6 m) that contained sufficient amounts of transition metal ions (e.g. Fe) and organic species (e.g. oxalate), S(IV) oxidation rates were significantly lower than those expected from the Fe-catalyzed S(IV) autoxidation in Milli-Q water. The results suggest that oxalate is responsible for much of the observed inhibition. Acetate and formate also inhibit the reaction, but to a much lesser extent. Oxalate has a strong inhibiting effect on the Fe-catalyzed S(IV) autoxidation at all investigated pH values (2.8, 3.7 and 4.5). It was established that Fe(III)-oxalato complexes affect the redox cycling of Fe(II)/Fe(III) and that the observed decrease of the reaction rate is caused by the reduced amount of catalytically active Fe(III) due to the complexation with oxalate. For the system Fe-S(IV)-O2-oxalate at initial pH 3.7 the reaction rate was calculated using exponential simplification to account for oxalate influence on the amount of free Fe(III) by the following equation:–rS(IV) = k · [S(IV)] · [Fe(III))] · e
-b·[Ox] 相似文献
19.
C. Simon Jeffery 《Monthly notices of the Royal Astronomical Society》1998,294(3):391-398
The optical spectrum of the early B hydrogen-deficient star LS IV+6°2 has been analysed. With T eff = 31000 K, log g = 4.05, n H ∼ 10−4 and n c ∼ 0.1 (relative abundances by number), it is the hottest high-gravity extreme helium star (EHe) yet studied. The He i spectrum shows all predicted permitted and forbidden transitions in absorption. LS IV+6°2 is a comparatively metal-rich EHe star; abundances of C, N, O, Ne, Mg, Al and P are typical of other EHes, whilst Si and S are somewhat deficient. With the surface parameters given, LS IV+6°2 lies close to the boundary of the helium star pulsation instability finger near T eff ∼ 27000 K. Available data indicate that the radial velocity is variable, but give no indication of amplitude or period. 相似文献
20.
Kaul Gena Hitoshi Chiba Katsuo Kase Kazuo Nakashima Daizo Ishiyama 《Resource Geology》2013,63(4):360-370
A sulfide chimney ore sampled from the flank of the active Tiger vent area in the Yonaguni Knoll IV hydrothermal field, south Okinawa trough, consists of anhydrite, pyrite, sphalerite, galena, chalcopyrite and bismuthinite. Electron microprobe analysis indicates that the chalcopyrite contains up to 2.4 wt% Sn, whereas bismuthinite contains up to 1.7 wt% Pt, 0.8 wt% Cu and 0.5 wt% Fe. The Sn‐rich chalcopyrite and Pt–Cu–Fe‐bearing bismuthinite are the first reported occurrence of such minerals in an active submarine hydrothermal system. The results confirm that Sn enters the chalcopyrite as a solid solution towards stannite by the coupled substitution of Sn4+Fe2+ for Fe3+Fe3+, whereas Pt, Cu and Fe enter the bismuthinite structure as a solid solution during rapid nucleation. The fluid inclusions homogenization temperatures in anhydrite (220–310°C) and measured end‐member temperature of the vent fluids on‐site (325°C) indicate that Sn‐bearing chalcopyrite and Pt–Cu–Fe‐bearing bismuthinite express the original composition of the minerals that precipitated as metastable phases at a temperature above 300°C. The result observed in this study implies that sulfides in ancient volcanogenic massive sulfide deposits have similar trace element distribution during nucleation but it is remobilised during diagenesis, metamorphism or supergene enrichment processes. 相似文献