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261.
Rock coatings are frequent on natural rock outcrops and even more on stone surfaces of historical buildings and monuments. They are interesting as some of them have a protective effect against erosion. In the last 30 years, research on rock coatings has been performed separately on either buildings or natural outcrops. This paper studies and compares thin coatings found on granitic rock surfaces of historical buildings with coatings found on natural granite outcrops in a same climatic area (NW Spain) by analysing their surface and cross-sections. As rock surfaces of buildings have known age they can be used to assess rates of weathering and coating growth. This is the first comparative study of formation of coatings on natural and built surfaces in the same region. Both endogenous (rock characteristics) and exogenous factors (climatic conditions, air pollution) that could affect the coatings formation are considered to assess the origin and formation of coatings. X-Ray Diffraction (XRD) and X-Ray Fluorescence (XRF) analyses of the underlying rocks, XRD analyses of the coatings and Scanning Electron Microscopy (SEM) observations of surface and cross-sections of the coatings, performing Energy Dispersive Spectrometry (EDS) and X-ray maps, were carried out to establish their composition. Fieldwork and results indicate that natural outcrops are widely covered by biological coatings or coatings formed due to rock weathering, while coatings found on rock ashlars are highly variable with air pollution, other building materials, organic droppings and micro-environmental factors contributing to coatings on rock ashlars in a more significant way than substrate characteristics and exposure time. 相似文献
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264.
Michael Wiedenbeck 《Geostandards and Geoanalytical Research》2010,34(4):387-394
Secondary ion mass spectrometry (SIMS or ion microprobe) remains one of the most powerful techniques in the analytical geochemist’s toolkit. The key strength of SIMS is its capacity to provide trace element and isotope data at sampling sizes which are not approached by other methods. As compared with the main competing technique of laser ablation-ICP-MS, SIMS commonly provides a total sampling mass some 10 to 500 times smaller; this feature can be the deciding factor as to whether an analytical objective is technically achievable. Additional strengths of SIMS lie in the areas of depth profiling and trace element imaging. Though perhaps not as commonly used in the geosciences, these two operational modes represent unique capabilities of SIMS. 相似文献
265.
E. SKRZYPEK K. SCHULMANN P. ŠTÍPSKÁ F. CHOPIN J. LEHMANN O. LEXA J. HALODA 《Journal of Metamorphic Geology》2011,29(4):473-496
In a Barrovian metamorphic sequence, garnetiferous mica schists document a heterogeneously developed superposition of sub‐orthogonal fabrics and multiple garnet growth episodes. In the variably deformed domains, four types of garnet porphyroblasts have been defined based on inclusion trail patterns. Modelled garnet zoning in the MnNCKFMASHTO system indicates a prograde evolution from 4–4.5 kbar and 490–510 °C to 5–6 kbar and 520–550 °C in the earliest subhorizontal fabric progressing towards 6.5–7.5 kbar and 560–590 °C in the subsequent subvertical foliation. This fabric is heterogeneously deformed into a shallow‐dipping retrograde foliation associated with garnet resorption. In situ electron backscatter diffraction measurements of ilmenite inclusions in individual garnet grains yield precise data on included planar and linear elements. Consistent orientations of internal foliations, lineations and foliation intersection axis sets indicate a superposition of three sub‐orthogonal foliation systems. Weak variations of internal records with increasing intensity of deformation suggest that a moderate buckling stage occurred, but apparent lack of porphyroblast rotation is interpreted as a result of dominant passive flow. Coupling the orientation of internal fabric sets with P–T estimates is used to complement the tectono‐metamorphic evolution of the thickened crust. We demonstrate that garnet porphyroblasts preserve features which reflect large‐scale tectonic processes in orogens. 相似文献
266.
本文对北大别西部的湖北英山万家老屋、罗田七道河尹家店和安徽金寨丁埠乡李集3个片麻岩样品中锆石进行了BSE显微结构分析,并在此基础上对锆石进行了离子探针U-Pb年龄测定。结果表明北大别存在两种类型的片麻岩,它们的原岩分别形成于晋宁期和燕山期,其中英山万家老屋片麻岩的形成年龄为794Ma,后期地质事件对其锆石U-Pb年龄造成的影响较小;七道河尹家店片麻岩的形成年龄为730Ma,并可能受到燕山期岩浆事件的影响,得到了140Ma左右的变质年龄;丁埠乡李集片麻岩的形成年龄为140Ma。结合已有的年代学结果,北大别地体广泛存在晋宁期的岩浆事件,表明其可能为扬子板块的北缘。 相似文献
267.
论证了柴里矿区现代地应力场为大地静力场型,指出地应力研究的工程意义,通过层位,实践,经济效益几方面的对比,指出三灰是二水平主干岩层位选择的最佳层位。 相似文献
268.
层序地层与煤层气关系探讨 总被引:2,自引:0,他引:2
从层序地层的角度,对煤层气的生、储和保存进行了论述,试图找出层序地层与煤层气之间的联系,并对体系域与煤层气之间的关系作了探讨。 相似文献
269.
Ludmila A. Pavlova Ludmila Ph. Paradina Olga Yu. Belozerova 《Geostandards and Geoanalytical Research》2001,25(2-3):333-344
In this paper we report the results of electron probe X-ray microanalysis (EPMA) that was used to study environmental materials. The mode of preparation and certification of reference samples based on a basaltic glass matrix for environmental applications of EPMA is described. These samples were prepared containing scandium, strontium and barium (from 0.03 up to 7% m/m) and an evaluation was made of homogeneity, their stability to local heating, followed by analysis by independent methods for certification of composition. Matrix correction procedures for the EPMA technique have been developed for particles having a size commensurable with the volume of X-ray generation. An analytical equation for the size factor is proposed and two techniques for selecting optimum conditions for the analysis of environmental samples by EPMA are reported. These procedures provided satisfactory results when utilized in analysing sediments recovered from snow, coal fly ash and the bones of animals and fish, results from which can be used as indicators for evaluating the pollution level of the lower atmosphere, surface and ground water, as well as revealing pollution mechanisms. 相似文献
270.