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391.
青岛花岗岩类复式岩基的古化石热水体系研究 总被引:3,自引:1,他引:3
对青岛花岗岩类复式岩基的氧同位素研究表明,各个岩体的氧同位素组成明显受水岩相互作用的影响。根据样品采集位置和氧同位素分析结果,可以恢复其中六个古化石水体系,它们包括两种类型;内高外低型和内低外高型,其形成可能与当时大气降水的循环方式密切相关,。近模拟计算表明,发生水岩作用的温度多在250-400℃之间,水岩比的变化较大(0.08%-0.3%)。研究还发现,曾发生过强烈去气作用的岩体与未经去气(或气 相似文献
392.
Reaction textures and fluid behaviour in very high pressure calc-silicate rocks of the Münchberg gneiss complex, Bavaria, Germany 总被引:2,自引:0,他引:2
Calc-silicate rocks occur as elliptical bands and boudins intimately interlayered with eclogites and high-pressure gneisses in the Münchberg gneiss complex of NE Bavaria. Core assemblages of the boudins consist of grossular-rich garnet, diopside, quartz, zoisite, clinozoisite, calcite, rutile and titanite. The polygonal granoblastic texture commonly displays mineral relics and reaction textures such as post kinematic grossular-rich garnet coronas. Reactions between these mineral phases have been modelled in the CaO-Al2O3-SiO2-CO2-H2O system with an internally consistent thermodynamic data base. High-pressure metamorphism in the calc-silicate rocks has been estimated at a minimum pressure of 31 kbar at a temperature of 630d? C with XH2, O ≥ 0.03. Small volumes of a CO2-N2-rich fluid whose composition was buffered on a local scale were present at peak-metamorphic conditions. The P-T conditions for the onset of the amphibolite facies overprint are about 10 kbar at the same temperature. XCo2 of the H2O-rich fluid phase is regarded to have been <0.03 during amphibolite facies conditions. These P-T estimates are interpreted as representing different stages of recrystallization during isothermal decompression. The presence of multiple generations of mineral phases and the preservation of very high-pressure relics in single thin sections preclude pervasive post-peak metamorphic fluid flow as a cause of a re-equilibration within the calc-silicates. The preservation of eclogite facies, very high-pressure relics as well as amphibolite facies reactions textures in the presence of a fluid phase is in agreement with fast, tectonically driven unroofing of these rocks. 相似文献
393.
大别山区变质岩中蓝晶石的几种退变质反应及其所指示的动力学过程 总被引:3,自引:2,他引:3
蓝晶石在大别山含柯石英和不含柯石英的榴辉岩、高压变质的副片麻岩、非高压变质的宿松群的变质沉积岩中都是重要的变质矿物。它们多有冠状或其它的变质反应结构,形成多样化的退变质反应矿物。有些退变质反应是十分罕见的。本文报道了8种蓝晶石的矿物组合和退变质反应,推测和计算了变质反应的温度-压力条件,从而探讨了它们代表的近等温降压、升温降压和流体为重要因素的降温降压的不同的动力学过程。这些数据与用其它变质矿物所得到的温度压力条件和PTt演化基本一致。为探讨大别山超高压变质带的构造演化提供了新的依据。 相似文献
394.
Melanoidin syntheses, which are carried out by preparing aqueous solutions of glucose and glycine, and glucose and alanine are examined with respect to variation of concentration of reactants, hydrogen ion concentration, molecular weights, functional groups and elemental compositions with increasing heating time at constant temperature (90°C). The experiments reveal that “melanoidins” consist of a mixture of fulvic acid-, humic acid- and kerogen-like polymers, with the initial formation of fulvic acid-, followed by humic acid- and kerogen-like polymers, but showing a period of coexistence of humic acid- and kerogen-like polymers. The kerogen-like polymers have elemental compositions similar to type II or II/III kerogens. The rate of melanoidin formation is much higher in the presence of montmorillonite. The CaCO3 association reactions of the same experiments, however, show extremely low rates of melanoidin formation. Laboratory simulations seem to be consistent with the observation that carbonate sediments usually contain small amounts of kerogens compared with clayey sediments, both Recent and ancient. 相似文献
395.
396.
The interaction between reaction and deformation: an experimental study using a biotite + plagioclase + quartz gneiss 总被引:3,自引:0,他引:3
Metamorphic reactions commonly accompany ductile deformation of crustal rocks. We performed an experimental study to determine: (i) the effect of syn-deformation reaction on strain weakening and localization, and (ii) the effect of crystal plastic deformation on reaction extent and distribution. Experiments were conducted on a fine-grained gneiss (58 vol.% quartz, forming the interconnected matrix, 13 vol.% biotite, 28 vol.% plagioclase and 1 vol.% garnet/Fe-Ti oxides). General shear experiments were performed at 745 and 800 °C, 1.5 GPa, two strain rates, and shear strain ( γ ) from 0.6 to 5, yielding three suites with initial phase strength contrast between the matrix quartz and weak biotite of 45×, 25× and 10×; hydrostatic experiments were performed on cores and powders at 750 and 800 °C and 1.5–2 GPa for the same times. At these conditions, biotite reacts with plagioclase and quartz to form garnet, K-feldspar and water (no melt was observed). Greater reaction extent was observed in deformed samples than in equivalent hydrostatic samples, because of the increased surface area and internal strain energy. In all of the deformed samples, reaction contributes to strain weakening, due principally to a switch to grain boundary sliding in the fine-grained reaction products. The degree to which syn-deformational reaction causes strain weakening and localization in this polyphase aggregate depends on the phase strength contrast and how it evolves. In samples with low-phase strength contrast, strain and reaction are homogeneously distributed; however, in samples with high-phase strength contrast, ductile strain and reaction interact positively to produce a narrow ductile shear zone. Similar concentration of reaction is observed in some natural ductile shear zones. 相似文献
397.
To evaluate the overall response of a structural system including its foundation and surrounding soil, an equivalent finite element model with reduced degrees of freedom using fibre theory‐based beam element was proposed. The proposed model was based on investigations of the subgrade soil reaction of a single‐layer model, and was verified for the cyclic behaviour of a laterally loaded single RC pile in terms of the load–displacement relationship, pile deformation, and soil pressures on the pile surface. Also investigated was the effect of the interfacial element between pile and soil on the behaviour of the laterally loaded pile. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
398.
Ali Bouafia 《Geotechnical and Geological Engineering》2007,25(3):283-301
Lateral load-deflection behaviour of single piles is often analysed in practice on the basis of methods of load-transfer P–Y curves. The paper is aimed at presenting the results of the interpretation of five full-scale horizontal loading tests of
single instrumented piles in two sandy soils, in order to define the parameters of P–Y curves, namely the initial lateral reaction modulus and the lateral soil resistance, in correlation with the pressuremeter
test parameters. P–Y curve parameters were found varying as a power of lateral pile/soil stiffness, on the basis of which hyperbolic P–Y curves in sand were proposed. The predictive capabilities of the proposed P–Y curves were assessed by predicting the soil/pile response in full-scale tests as well as in centrifuge tests and a very good
agreement was found between the computed deflections and bending moments, and the measured ones. Small-sized database of full-scale
pile loading tests in sand was built and a comparative study of some commonly used P–Y curve methods was undertaken. Moreover, it was shown that the load-deflection curves of these test piles may be normalised
in a practical form for an approximate evaluation of pile deflection in a preliminary stage of pile design. At last, a parametric
study undertaken on the basis of the proposed P–Y curves showed the significant influence of the lateral pile/soil stiffness on the non-linear load-deflection response. 相似文献
399.
Hf isotopic data of minerals in a mafic pyroxene granulite from the southern Bohemian Massif, together with their major and
trace element composition and petrological observations were used to decipher the metamorphic history and behaviour of zircon
in the granulite. The Hf isotopic composition in the minerals was used to estimate whether the decompression reaction, namely
the consumption of garnet and rutile, could have provided Zr for the formation of newly grown metamorphic zircon. The age
of the decompression reaction indicated by the evolution of Hf isotopes in garnet and orthopyroxene is between 333 and 331 Ma,
i.e. ca. 7 Ma younger than the available U–Pb zircon ages from the Moldanubian granulites and than the newly obtained 343 ± 2 Ma
laser ablation ICP-MS U–Pb age of zircons. The combination of bulk and in-situ Hf isotopic data, major and trace element composition
and petrological modeling of P–T evolution revealed that the formation of zircons can not be related to the decompression
phase of the evolution of the mafic granulites.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
400.