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801.
我国西南山区各种山地灾害(暴雨、崩塌、滑坡、泥石流与洪水)往往彼此相伴生,而成串联式链状结构。以泥石流为主害灾种的灾链演变有五个阶段。据灾链演化区域分异性,分出四个大区九个灾区。 相似文献
802.
A method for modelling mass balance in partial melting and anatectic leucosome segregation 总被引:1,自引:0,他引:1
F. BEA 《Journal of Metamorphic Geology》1989,7(6):619-628
A method is proposed for adjusting the mass balance to characterize quantitatively the behaviour of minerals in anatexis. The method is based on an unconstrained simple mixing model that can be expressed as: where B , A 0, and A 1-n, are compositional vectors of segregate, source rock and source minerals, respectively. The most important concepts are: (1) degree of partial fusion: FMM= 1/a0; (2) mineral fractionation index: and (3) plagioclase differentiation index: . For a given mineral, the MFI values have the following meaning: (a) MFI <0: residual phase originated, at least partly, as a product of incongruent melting; (b) 0 > MFI <1: preferential retention in the residue; (c) MFI= 1: identical modal fraction in source and melt; (d) a0 > MFI > 1: preferential incorporation into the segregate, and (e) MFI > a0: external contribution to the anatectic system defined by a0 A 0. To test the method and illustrate its use, it was applied to two real problems of partial melting in the Peña Negra Anatectic Complex (Central Spain). The first is a very simple case of segregation of a diktyonitic neosome from an orthogneiss through partial melting located in vertical shear zones. This process is characterized by: (1) FMM= 0.51; (2) active incorporation of K-feldspar, plagioclase and biotite into the segregate; (3) disequilibrium melting of plagioclase; (4) residual behaviour of quartz and ilmenite. The second case concerns the formation of a cordierite-bearing granite from granodioritoid diatexites through an anatectic process, whose most salient characteristics are: (1) FMM= 0.45; (2) incongruent melting of biotite; (3) residual behaviour of plagioclase, which melted with a PDI of 1.22; (4) preferential incorporation of quartz into the segregate; (5) total extraction of K-feldspar from the residue. 相似文献
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805.
Luo Jinfa Xia Zenglu 《地理学报(英文版)》1996,(2)
1CriticalconcentrationofpollutedheaVyn1etalsish1eallowableconcel1trationofheavymetalsinsoilsItisnotonIythecriticalindexofvanousbiologicalandenvironmentalehaofmetalelementsinsoils,blltalsothebasisforworkingoutti1estandardofsoilenvirorunatalquality,anddefilungthesoilenvironn1entalconcentration.Attentionwasthuspaidtoenvironmotalconservationathomeandabroad.Althoughtherearen1anyrePorts[2-4]oneffeCtsofsinglesoilpollutant,yCttherearefewrePoftsoncompansonsofn1etalelema1tcnticalconcatrationinsoilsofd… 相似文献
806.
莫来铁尖晶岩的发现和玄武岩浆的深部分异作用 总被引:3,自引:0,他引:3
莫来铁尖晶岩是首次发现的一种新型火山岩,由铁尖晶石、莫来石、铁板钛矿和火山玻璃组成,其平均化学成分相当于一个简化的SiO_2-FeO~*—Al_2O_3三元系。莫来铁尖晶岩浆是原始岩浆深部分异的结果。原始玄武岩浆在地幔深处分离结晶出富含硬玉分子的斜方辉石、单斜辉石,进化岩浆向富Al、Fe而贫Si的方向演化,最终产生莫来铁尖晶岩浆。后者喷出地表,冷凝结晶形成莫来铁尖晶岩。 相似文献
807.
地下水中铀的油气化探意义及其应用 总被引:2,自引:1,他引:2
经过20多年的实验研究,逐渐认识了地下水中铀的油气化探意义和特性,从而掌握了它对油气的指标意义,并在油气化探中得到了应用。油田水和深层地下水由于处在还原和弱还原环境中,铀的浓度分异效应不显著;潜水处于氧化环境中,铀的浓度分异效应显著,储集着与油气有关的信息。文章阐述了油气藏上方潜水中铀的异常特征,接着论述了铀指标的特性,即稳定性、直观性和单一性。最后以松辽中央拗陷南部和东濮凹陷为例,介绍了应用实例。 相似文献
808.
Brian J. Shaw 《The Australian geographer》1993,24(2):39-49
The study of residential differentiation in nineteenth‐century cities has generally been pursued without reference to Australian examples due to a lack of suitable data sources and a tendency to assume ‘New World’ models for the antipodean case. This study of late nineteenth‐century Fremantle, Western Australia, utilises data drawn from contemporary municipal ratebooks in a comprehensive analysis of residential space at the micro‐scale of individual lots. Conducted at three time intervals during a period of in‐migration and urban transformation, the analysis reveals the distinctiveness of one Australian urban experience during an era of ‘compressed development’. Residential differentiation is shown to exist both between and within occupational status groups, reflecting subtle differences in tenancy status, dwelling type and lot densities. With population increase and the onset of industrialisation, many of these differentials can be seen to disappear, particularly between middling status groups. Drawing upon additional evidence from other researchers, it is possible to construct a schematic model of antipodean urban development to represent more precisely the period in Australian cities prior to large‐scale suburbanisation. 相似文献
809.
810.
本区段S3盐层晶间卤水在铅直方向上的均一性,是用瓦里亚什科(М.Г.ВаЯШКО)的“重力垂直分异”观点解释本湖晶间卤水分异问题时,遇到的不可克服的困难之一.本文用统计分析和系统理论的方法,研究了本地段S3盐层晶间卤水分异特征及成因,结论表明:“阶段性淡化”说在本区段也是成立的. 相似文献