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41.
Response of Reactive Phosphorus Burial to the Sedimentary Transition from Cretaceous Black Shales to Oceanic Red Beds in Southern Tibet 下载免费PDF全文
The mechanism of sedimentary transition from the Cretaceous black shales to the oceanic red beds is a new and important direction of Cretaceous research. Chemical sequential extraction is applied to study the burial records of reactive phosphorus in the black shale of the Gyabula Formation and oceanic red beds of the Chuangde Formation, Southern Tibet. Results indicate that the principal reactive phosphorus species is the authigenic and carbonate-associated phosphorus (CaP) in the Gyabula Formation and iron oxides-associated phosphorus (FeP) in the Chuangde Formation which accounts for more than half of their own total phosphorus content. While the authigenic and carbonate-associated phosphorus (CaP) is almost equal in the two Formations; the iron oxides-associated phosphorus is about 1.6 times higher in the Chuangde Formation than that in the Gyabula Formation resulting in a higher content of the total phosphorus in the Chuangde Formation. According to the observations on the marine phosphorus cycle in Modern Ocean, it is found that preferential burial and regeneration of reactive phosphorus corresponds to highly oxic and reducing conditions, respectively, leading to the different distribution of phosphorus in these two distinct type of marine sediments. It is the redox-sensitive behavior of phosphorus cycle to the different redox conditions in the ocean and the controlling effects of phosphorus to the marine production that stimulate the local sedimentary transition from the Cretaceous black shale to the oceanic red beds. 相似文献
42.
近年来的观测结果显示北极对流层臭氧发生亏损的同时 ,大气中的气态汞浓度也急剧下降。这种现象的发生被认为是大气中活性卤素物种的增多而引起的。活性的卤素物种例如Br/Cl与臭氧作用 ,一方面导致臭氧亏损 ,同时 ,生成BrO/ClO氧化大气中的Hg0 ,使Hg0 转化为活性汞 (RGM)而沉降。北极地区大气中活性卤素物种主要来自海洋大型藻类释放的卤代烃分解和海盐的贡献。在过去的几十年里 ,随气候变暖 ,北极海冰变薄 ,面积减少 ,海洋排放的活性卤素物种浓度增加 ,从而使北极地区大气中的汞沉降通量增加 ,加剧了北极生物圈中的汞污染。由于北极海冰减少变薄趋势还在持续 ,因此 ,北极大气中汞亏损引起的沉降通量增加对生态圈的影响应该引起广泛重视。本文在综述这方面研究的最新进展基础上 ,提出了今后的研究方向。 相似文献
43.
阴离子交换色谱-电感耦合等离子体质谱联用技术用于面粉中溴形态分析 总被引:1,自引:0,他引:1
建立的阴离子交换色谱-电感耦合等离子体质谱联用技术用于测量面粉中的痕量 BrO3-及Br-。使用DIONEX CarBoPac PA-100(4 mm×250 mm,i.d.)色谱柱,在流速1 mL/min 及5 mmol/L NH4NO3淋洗液下分离BrO3-和Br-。该方法在100μL进样量下BrO3-的检出限为 0.0027 μmoL/L(0.22μg/L),Br-为0.0067 μmoL/L(0.54μg/L)。对市场上部分面粉类样品的分析结果表明,所选面粉只有一种检出有BrO3-,其他样品中的BrO3-均低于检出限。方法的回收率可达到98%-109%。 相似文献
44.
In this study, the decolorization, dearomatization, and mineralization efficiencies of different advanced oxidation processes (AOPs; namely O3, O3/Fe(II), O3/Fe(II)/UVA, and O3/TiO2/UVA) were investigated for the azo dye C.I. Reactive Red 194 (RR194). The effects of pH (3–11), amount of TiO2 (0.05–1 g/L), and concentration of Fe(II) (0.1–1.6 mM) were investigated for the applied methods. The decolorization and mineralization efficiencies of the photocatalytic ozonation system (O3/TiO2/UVA) were increased by decreasing the pH of the dye solution in contrast to the ozonation system (O3). Decolorization of RR194 was increased in the photocatalytic ozonation system with an increasing amount of catalyst however, a decreasing was occurred for the homogeneous catalytic system (O3/Fe(II)) when increasing the concentration of catalyst. The decolorization efficiency of the homogeneous catalytic system (O3/Fe(II)) was enhanced when combined with UVA light. In our study, the most efficient method for dearomatization and mineralization was the O3/TiO2/UVA among the applied AOPs. 相似文献
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Reactive transport codes that use a Gibbs Energy Minimization (GEM) to solve chemical equilibria are uncommon. We present a new coupling of the Richards flow module of the Finite Element (FE) based OpenGeoSys code with the GEM based chemical solver GEMS3K. The coupled code is highly parallelized using an overlapping domain decomposition approach in combination with execution of multiple threads that solve chemical equilibria in parallel. FE reactive transport schemes are often affected by spurious concentration oscillations. We effectively suppress these oscillations with a linearized algebraic flux corrected transport (FCT) algorithm. An application example is presented which investigates the evolution of material interfaces in a deep geological repository for nuclear waste. The example uses all features of the new coupled code: flow and multi-component transport in variably saturated media, and a very complex chemical setup which makes extensive use of (non-linear) solid solution formulations for mineral phases. 相似文献
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49.
This work presents analytical models which are able to predict contours of concentrations and isotope ratios of organic pollutants in homogeneous aquifers. Four analytical solutions of the advective–dispersive transport equation for reactive transport from the literature differing in assumptions regarding biodegradation kinetics were used. Stable isotope ratios are computed after modelling the individual reactive transport of isotopic species in the aquifer, which respond differently to fractionation by biodegradation or sorption. The main finding of this study is that the isotope ratios in the plumes are very sensitive to the assumptions underlying the biodegradation kinetics in the models. When biodegradation occurs throughout the core of the plume as first-order reaction, the transversal gradients in isotope ratios are smooth. When biodegradation occurs in a bi-molecular reaction with an electron acceptor (modelled by double-Monod kinetics), steep transversal isotope gradients are predicted. When the reaction rates approach instantaneous reaction along the plume fringes, isotope shifts in the core of the plume disappear. A model incorporating plume and fringe degradation produces the most plausible predictions of isotope ratios in this study. It is shown furthermore that isotope fractionation by sorption causes an even different pattern of isotope ratios, with positive shifts restricted to near the forerunning front of an expanding plume. The models developed in this work can serve for the validation of numerical models and may be incorporated in natural attenuation support systems such as e.g. BIOSCREEN. 相似文献
50.
Sahadevan Renganathan Jayabalan Kalpana Mahendradas Dharmendira Kumar Manickam Velan 《洁净——土壤、空气、水》2009,37(11):901-907
Nymphaea rubra stem was used as a low cost and easily available biosorbent for the removal of Reactive Red 2 dye from an aqueous solution. Initially, the effects of biosorbent dosage (0.2–1.0 g L–1), pH (1–6), and dye concentration (30–110 mg L–1) on dye removal were studied. Batch experiments were carried out for biosorption kinetics and isotherm studies. The results showed that dye uptake capacity was found to increase with a decrease in biosorbent dosage. Equilibrium uptake capacity was found to be greatest at a pH value of 2.0, when compared to all other pH values studied. The equilibrium biosorption isotherms were analyzed by the Freundlich and Langmuir models. The equilibrium data was found to fit very well with the Freundlich isotherm model when compared to the Langmuir isotherm model. The kinetic data was analyzed using pseudo-first order and pseudo-second order kinetic models. From the results, it was observed that the kinetic data was found to fit the pseudo-second order kinetic model very well. The surface morphology of the stem of the N. rubra biosorbent was exemplified by scanning electron microscopy. Fourier transform infrared analysis was employed to confirm the existence of an amine group in the stem of N. rubra. 相似文献