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41.
Carmelo Ferlito Marco Viccaro Eugenio Nicotra Renato Cristofolini 《Bulletin of Volcanology》2012,74(2):533-543
Mount Etna volcano (Italy) during the period 2001–2005 has undergone a period of intense eruptive activity marked by three
large eruptions (2001, 2002–2003 and 2004–2005). These eruptions encompassed diverse eruptive styles and regimes: from intensely
explosive, during 2001 and 2002–2003 eruptions, to exclusively effusive in the 2004–2005 event. In this work, we put forward
the idea that these three eruptions are the response of the progressive arrival into the uppermost segment of the open-conduit
system of a new magma, which was geochemically distinct in terms of trace element and Sr–Nd–Pb isotope signature from the
products previously emitted by the Etnean volcano. The magma migrated upwards mainly through a peripheral tectonic system,
which can be considered as eccentric in spite of its relative proximity to the main system. The ingress of the new magma and
its gradual displacement from the eccentric system into the uppermost sector of the open-conduit gave rise to different eruptive
behaviours. At the beginning, the ascent of the undegassed magma, able to exsolve a gas phase at depth, and its interaction
with closed-system magma reservoirs less than 10 km deep gave rise to the explosive events of 2001 and 2002–2003. Later, when
the same magma entered into the open-conduit system, it took part in the steady-state degassing and partially lost its volatile
load, leading to a totally effusive eruption during the 2004–2005 event. One further consideration highlighted here is that
in 2001–2005, migration of the feeding axis from an eccentric and peripheral position towards the main open-conduit has led
to the development of a new vent (South East Crater 2) located at the eastern base of the South East Crater through which
most of the subsequent Etnean activity occurred. 相似文献
42.
The rational use of pesticides generates an impact which is normally reversed and eliminated by the environment itself. However, the indiscriminate use of pesticides makes its natural degradation rhythm difficult, prolonging their presence in the soil for a great deal of time. Aiming towards a decrease in the environmental impact of pesticides, soil microorganisms capable of degrading pesticides, such as propanil, were investigated. An Enterobacter cloacae strain, isolated from rice field soil, was exposed to the herbicide propanil alone and in a mixture containing also bentazone, clomazone, quinclorac, and 2,4‐D. This bacterium was able to eliminate 100% of the applied propanil in 28 days. Propanil degradation in the 5‐herbicide mixture was much lower than that of individual pesticide degradation. The aeration of the system helped to degrade propanil and its subproduct 3,4‐dichloroaniline much faster. LC with UV detection was used to determine the remaining concentrations of the herbicides and their subproducts. 相似文献
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44.
Aline Nogueira da Silveira Renato Silva Jorge Rubio 《International Journal of Mineral Processing》2009,93(2):103-109
This work describes AMD techniques of neutralization, with lime, flocculation of the precipitates and comparative flocs/liquid separation by flotation with microbubbles or by lamellar settling (LS). The AMD treated water was characterized by its quality for recycling in terms of inorganic or organic elements, suspended or dissolved solids, among others. Two types of flocs were formed, “aerated” or not, in a special flocculation reactor, patented by this research group (RGF®). Aerated flocs formed (within seconds) entered into contact with microbubbles under high shearing and raised-up at rates > 120 mh− 1 allowing a rapid solid–liquid separation by flotation (HR-high rate), at about 13–15 m3m− 2 h− 1 loading capacity. Conversely, the non-aerated flocs settled at about 5–6 m h− 1 in a lamella settler. Both AMD treatment techniques showed similar efficiencies (removal of ions > 90%) but the separation by lamella settling presented advantages, namely less reagents (no flotation collector required), lower power requirements and easier to operate. The operating costs (approximate values) of the AMD treatment by LS at pH 9 reaches about 0.3 US$ m− 3 against 0.6 US$ m− 3 for the HR-flotation process. Results found were proved to be similar to those found in recent ADM treatment installations in South Brazil. The quality of the treated water is fairly good, nearly free of heavy metals ion, low BOD (biological oxygen demand) and TOC (total organic content), low solids content and may be readily reused for irrigation, industrial processes and as wash water (among others, streets, vehicles, dust control). However, there is a need to extend the use of this treated water resource, but this, at least in Brazil, has not been legislated properly. It is concluded that this research will contribute in the discussion of this old and complex problem in acid mining effluents worldwide. 相似文献
45.
Quantifying rock fall probabilities and their temporal distribution associated with weather seasonality 总被引:1,自引:1,他引:0
Renato Macciotta Michael Hendry David M. Cruden Andrée Blais-Stevens Tom Edwards 《Landslides》2017,14(6):2025-2039
Quantifying rock fall hazards requires information about their frequency and volumes. Previous studies have focused on quantifying rock fall volume–frequency relationships or the weather conditions antecedent to rock fall occurrences, and their potential use as prediction tools. This paper is focused on quantifying rock fall occurrence probabilities and presents approaches for quantifying rock fall temporal distributions. In particular, von Mises distributions allow direct correlation between seasonal weather variations and rock fall occurrences. The approaches are illustrated using a rock fall database along a railway corridor in the Canadian Cordillera, in which rock fall occurrences were correlated to the morphology and lithology. A Binomial probability distribution applied to the annual rock fall frequency suggests an average daily rock fall probability of 1 × 10?2 across the study area. However, circular (von Mises) distributions associated with weather trends in the area, and fitted to monthly rock fall records, allow estimation of daily rock fall probabilities in different months. This approach allows a direct correlation between rock fall frequencies and seasonal variations in weather conditions. The results suggest daily rock fall probabilities between 4 × 10?3 and 8 × 10?3 for April through July and up to 2.1 × 10?2 in October. Moreover, local peaks in rock fall monthly records are quantitatively explained through the seasonality of weather conditions. Similar values are obtained when applying the Binomial distribution to monthly records. However, this last approach does not show strong distribution fits and does not allow a correlation between rock fall frequencies and seasonal weather variations. 相似文献
46.
Biochemical and microbial features of shallow marine sediments along the Terra Nova Bay (Ross Sea,Antarctica) 总被引:1,自引:0,他引:1
Franco Baldi Davide Marchetto Francesco Pini Renato Fani Luigi Michaud Angelina Lo Giudice Daniela Berto Michele Giani 《Continental Shelf Research》2010
Shallow marine sediments were collected from seven stations (three of which located at Gerlache Inlet, two at Tethys Bay, one at Adelie Cove and one just beneath the Italian Research Base) along the Terra Nova Bay coast (Ross Sea, Antarctica). Their chemical, biochemical and microbiological properties were studied in order to provide further insights in the knowledge of this Antarctic benthic ecosystem. Overall, the organic carbon (OC) represented the major fraction of total carbon (TC) and displayed concentrations similar to or slightly lower than those previously measured in Antarctic bottom sediments. The biopolymeric carbon within OC ranged from 4.1% to 19.9% and showed a wide trophic range (65–834 μg g−1 d.w.). Proteins (PRT) represented on average the main biochemical class contributing to labile organic carbon, followed by lipids (LIP) and carbohydrates (CHO). The activity of aminopeptidase, β-d-glucosidase, alkaline phosphatase and esterase was checked, giving the highest values at Tethys Bay and at the deepest water sediments. The principal component analysis, which was computed considering physical, chemical (elemental and biochemical sedimentary composition) and microbiological parameters (including bacterial abundance, ectoenzymatic activities, T-RFs richness and diversity indices), allowed to obtain two main clusters (“Tethys Bay” and “other stations”). Based on data obtained, two representative 16S rRNA clone libraries using samples from Tethys Bay and Gerlache Inlet were constructed. The sequences of 171 clones were compared to those available in public databases to determine their approximate phylogenetic affiliations. Both aerobic and anaerobic bacteria were disclosed, with the majority of them affiliated with the Gamma- and Deltaproteobacteria, Bacteroidetes and Acidobacteria. The occurrence of strictly anaerobic bacteria suggests that sediments might also undergo anoxic conditions that, in turn, could favor the accumulation of PRT in respect to CHO, assuming that fermentation of amino acids is slower than that of sugars from decomposing polysaccharides. 相似文献
47.
48.
重点介绍和讨论了中性条件下旋转扰动流体中边界层强迫不稳定及其相关的一些问题,阐述了旋转体系中切变驱动边界层不稳定的动力学特征.这些不稳定状态的研究在大气物理学、流体动力学、海洋学等多个领域中引起科学家极大的兴趣,近年来在实验和理论研究中都得到了不断的发展.意大利都灵大学基础物理系地球科学实验组通过水槽旋转实验方法,不断改变水槽启动或结束时的旋转运动速度,以及底部壁面粗糙度等要素,所得到的实验结果与SDBL理论非常一致. 相似文献
49.
Although failures and successes in fisheries management are related to decision making processes, these are rarely analyzed in detail and even less often following quantitative or semi-quantitative approaches. Herein, we study the decision making process for Chile's most important fisheries using a binary decision model. This model evaluates the probability that an annual total allowable catch (TAC) will or will not be modified by the National Fisheries Council (NFC) based on biological, economic, and social factors. We also analyze some aspects of individual voting, particularly whether the members vote against or abstain from voting on the proposed TAC and if they prioritize resource conservation objectives. Our results indicate that the risk of over exploitation for many important stocks in Chile is aggravated by failures at the decision making level: the scientifically recommended TACs for those fisheries that generate higher levels of employment and have greater economic value are normally increased. This analysis shows that the NFC has clearly prioritized short-term economic and social objectives over resource conservation goals. We discuss the need to adjust the composition and functioning of the NFC in order to ensure long-term sustainability of the fisheries. 相似文献
50.
Late Quaternary environmental and climate changes registered in lacustrine sediments of the Serra Sul de Carajás,south‐east Amazonia
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