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71.
One of the primary threats to ocean ecosystems from plastic pollution is ingestion by marine organisms. Well-documented in seabirds, turtles, and marine mammals, ingestion by fish and sharks has received less attention until recently. We suggest that fishes of a variety of sizes attack drifting plastic with high frequency, as evidenced by the apparent bite marks commonly left behind. We examined 5518 plastic items from random plots on Kamilo Point, Hawai’i Island, and found 15.8% to have obvious signs of attack. Extrapolated to the entire amount of debris removed from the 15 km area, over 1.3 tons of plastic is attacked each year. Items with a bottle shape, or those blue or yellow in color, were attacked with a higher frequency. The triangular edges or punctures left by teeth ranged from 1 to 20 mm in width suggesting a variety of species attack plastic items. More research is needed to document the specific fishes and rates of plastic ingestion. 相似文献
72.
Fernanda Imperatrice Colabuono Satie Taniguchi Rosalinda Carmela Montone 《Marine pollution bulletin》2010,60(4):630-634
The occurrence of plastic objects in the digestive tract was assessed in eight species of Procellariiformes collected in southern Brazil and the occurrence of polychlorinated biphenyls (PCBs) and organochlorine pesticides (OCPs) in the ingested plastics pellets and plastic fragments was evaluated. PCBs were detected in plastic pellets (491 ng g−1) and plastic fragments (243-418 ng g−1). Among the OCPs, p,p′-DDE had the highest concentrations, ranging from 68.0 to 99.0 ng g−1. The occurrence of organic pollutants in post-consumer plastics supports the fact that plastics are an important source carrying persistent organic pollutants in the marine environment. Although transfer through the food chain may be the main source of exposure to POPs to seabirds, plastics could be an additional source for the organisms which ingest them, like Procellariiformes which are the seabirds most affected by plastic pollution. 相似文献
73.
Microplastics pose a threat to coastal environments due to their capacity to adsorb persistent organic pollutants (POPs). These particles (less than 5 mm in size) are potentially dangerous to marine species due to magnification risk over the food chain. Samples were collected from two Portuguese beaches and sorted in four classes to relate the adsorption capacity of pollutants with color and age. Polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs) and DDTs were analysed on pellets through gas chromatography mass spectrometry (GC-MS), and types of plastic were identified using Fourier transformed infra-red spectroscopy (micro-FTIR). Microplastics were mostly polyethylene and polypropylene. Regarding sizes, some fibres ranged from 1 to 5 μm in diameter and were 500 μm in length. The majority of samples collected had sizes above 200 μm. Black pellets, unlike aged pellets, had the highest concentrations of POPs except for PAHs in Fonte da Telha beach. PAHs with higher concentrations were pyrene, phenantrene, chrysene and fluoranthene. Higher concentrations of PCBs were found for congeners 18, 31, 138 and 187. Further investigation is necessary to understand the relationship between plastic degradation and adsorption for different pollutants. 相似文献
74.
玻璃钢夹砂管在土木水利工程领域得到了愈来愈广泛的应用,但现有的埋地管道地震响应分析模型大多不考虑管-土动力相互作用,且多针对均质材料管道,无法应用于具有明显层状复合材料结构特征的玻璃钢夹砂管。基于玻璃钢夹砂管的层状复合材料结构特征,建立了完整的埋地玻璃钢夹砂管地震响应分析模型,在数值分析模型中,考虑了管-土间复杂的动力相互作用,以及地震散射波从有限域向无限域的传播。算例分析表明,所建立的埋地玻璃钢夹砂管地震响应分析模型可合理地分析埋地玻璃钢夹砂管在地震荷载作用下的动力响应。 相似文献
75.
76.
We have studied the plastic deformation of Mg2SiO4 wadsleyite polycrystals. Wadsleyite was synthesized from a forsterite powder in a multianvil apparatus. It was then recovered
and placed in a second multianvil assembly designed to induce plastic deformation by compression between two hard alumina
pistons. After the deformation experiment, the microstructures are characterized by transmission electron microscopy (TEM)
and large-angle convergent beam electron diffraction (LACBED). Deformation experiments have been carried out at 15–19 GPa
and at temperatures ranging from room temperature to 1800–2000 °C. Five different dislocation types have been identified by
LACBED: [100], 1/2〈111〉, [010], 〈101〉 and [001]. The [001] dislocations result from dislocation reactions and not from activation
of a slip system. The [010] dislocations are activated under high stresses at the beginning of the experiments and further
relax by decomposition into 1/2〈111〉 dislocations or by dissociation into four 1/4[010] partial dislocations. The following
slip systems have been identified: 1/2〈111〉{101}, [100](010), [100](001), [100]{011}, [100]{021}, [010](001), [010]{101} and
〈101〉(010).
Received: 15 July 2002 / Accepted: 14 February 2003
Acknowledgements High-pressure experiments were performed at the Bayerisches Geoinstitut under the EU IHP – Access to Research Infrastructures
Programme (Contract no. HPRI-1999-CT-00004 to D.C. Rubie). P.C. has benefited from a Congé thématique pour recherche from
the University of Lille, and would like to thank warmly all the people in Bayreuth who contributed to this work by daily assistance
and discussions: Nathalie Bolfan-Casanova, Daniel Frost, Jed L. Mosenfelder and Brent Poe. The quality of the preparation
of the TEM specimens by H. Schultze is greatly appreciated. 相似文献
77.
We have studied the dislocation microstructures that develop in (Mg0.9Fe0.1)2SiO4 wadsleyite deformed by simple shear at high pressure. The experiments were performed in a multianvil apparatus with the shear
assembly designed by Karato and Rubie (1997). The samples were synthesized in a separate experiment from high-purity oxides.
The deformation experiments were carried out at 14 GPa and 1300 °C with time durations ranging from 1 to 8 h leading to plastic
shear strains of 60 and 73%, respectively. The microstructures investigated by transmission electron microscopy (TEM) show
that dislocation glide is activated under these conditions over the whole experimental time. The easy slip systems at 1300
°C involve 1/2<111> dislocations gliding in {101} as well as [100] dislocations gliding in (010) and {011}.
Received: 15 July 2002 / Accepted: 14 February 2003
Acknowledgements High-pressure experiments were performed at the Bayerisches Geoinstitut under the EU IHP — Access to Research Infrastructures
Programme (Contract no. HPRI-1999-CT-00004 to D.C. Rubie). The quality of the preparation of the TEM specimens by H. Schultze
is greatly appreciated. 相似文献
78.
迄今,矿山开采沉陷领域的研究者们在采煤引起的地表移动规律研究及共服务于生产方面已经取得了令人膛目的成就,但是在复杂构造条件下采煤引起的特殊地表移动现象研究方面尚无明显进展。本文运用现代工程地质学理论和现代变形力学理论,对一个复杂的摺皱断裂十分发育的条件下采取露天和井下联合开采方式所引起的特殊地表移动现象及其规律作了分析,取得了预测规律与实际情况一致的结果。 相似文献
79.
Reaction-induced weakening of plagioclase–olivine composites 总被引:1,自引:0,他引:1
The localisation of strain into natural ductile shear zones is often associated with the occurrence of metamorphic reactions. In order to study the effects of solid–solid mineral reactions on plastic deformation of rocks, we have investigated the shear deformation of plagioclase–olivine composites during the reaction plagioclase + olivine → orthopyroxene + clinopyroxene + spinel (± garnet). Microstructures of plagioclase–olivine composites were studied after shear deformation experiments in a Griggs apparatus. Experiments were performed on anorthite–forsterite (An–Fo) and labradorite–forsterite (Lab–Fo) composites at 900 °C, confining pressures between 1000–1600 MPa and with constant shear strain rates of 5 × 10−5 s−1.In absence of reaction, Lab–Fo composites are stronger than pure olivine and labradorite end-members that deform with a high temperature plasticity mechanism. Lab–Fo composites strain–harden due to the inhibition of extensive recrystallisation by interphase boundaries.In An–Fo composites, the reaction induces strain weakening by a switch from dislocation creep to grain size sensitive deformation mechanisms through the development of fine-grained (size < 0.5 μm) polyphase reaction products. Interconnecting layers of reaction products accommodate most of the applied strain by grain size sensitive creep. Recovery processes are pronounced during syndeformational reaction: original anorthite and olivine dynamically recrystallise by subgrain rotation and bulging recrystallisation. Presumably, the dynamic recrystallisation is caused by reduced stress conditions and partitioning of strain and strain rates between the new reaction products and the relict An–Fo grains. The results of our experiments are in good agreement with natural observations of shear localisation in the lower crust and upper mantle, and imply that anhydrous mineral reactions can be important causes for localisation of deformation. 相似文献
80.