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431.
ZHAO Guiping LIU Shuwen LIU Xiaohan Computational Geodynamics Laboratory Graduate School of Chinese Academyof Sciences Beijing School of Earth Space Sciences Peking University Beijing Institute of Geology Geophysics Chinese Academy of Sciences Beijing 《《地质学报》英文版》2004,78(1):186-190
Although porphyroblast microstructures play an important role in structural and metamorphic studies, there are still controversies in the interpretation. The focus is how porphyroblasts grow during deformation and metamorphism. In this paper, we introduce a new approach, the Synchrotron Radiation X-Ray Fluorescence, to a hemi-quantitative interpretation of the growth mode of porphyroblasts. The analysis was done at the Beijing Synchrotron Radiation Facility. The specimens were sampled from metapelite of the Baoyintu Group, northern Urad Middle Banner, Inner Mongolia. The new method is successful for determining the microscopic distribution of trace elements in porphybroblasts. The results support the theory of deformation partition, which has been brought forth by Bell and his colleagues, and demonstrate the existence of porphyroblast growth phases and the growth mode of porphyroblasts by hemi-quantitative mineral chemical analysis. The porphyroblast grows stage by stage in the manner of the distribution 相似文献
432.
1IntroductionMostgeologistshaveacceptedthattheQinling Dabieorogenicbeltistheproductofcontinentaldeepsubduction (Okayetal.,1993;Cong ,B .etal.,1995 ;Hackeretal.,1995 ;DongShuwenetal.,1993) .Butasthebiggest scaleUHPmetamorphicbeltintheworld ,thereactionbetweenthecrustandthemantleatthepost orogenicstageandtheexhumation ,upliftinganddenudationoftheorogenicbeltarethecomplexdynamicprocesses .ItwasreportedpreviouslythatsomeCretaceousvolcanicrocksexistinthemiddleoftheDabieMountains (GuanYuncaiet… 相似文献
433.
发育在大别造山带东部的假玄武玻璃是区域内NE-SW向断裂带快速滑移形成的构造岩。地质产状、显微构造及岩石化学研究表明,这些假玄武玻璃主要由超碎裂岩化作用所形成。假玄武玻璃及围岩的全岩(包括部分单矿物)K-Ar年龄测定表明,大别造山带的假玄武玻璃形成于81~93Ma之间。本文同时测定了叠加在假玄武玻璃基质之上的多硅白云母的激光^40Ar/^39Ar年龄为78.9Ma。显微构造及所获得的年龄数据显示,这些沿NE-SW向断裂发育的假玄武玻璃是在晚白垩世(80~90Ma)时期伴随着大别造山带整体隆升过程形成的,而与早期板块俯冲过程无关。同时,不同定年方法在数据上的一致性还表明,全岩K-Ar方法在确定某些假玄武玻璃及含假玄武玻璃的断裂构造年代时,可能仍然是一种行之有效的的方法。 相似文献
434.
大别山榴辉岩的包裹体研究 总被引:2,自引:0,他引:2
本文对大别山榴辉岩流体包裹体进行了研究。包裹体成分以NaCl-H2O、H2O、NaCl-CO2-H2O为主,是在退变质的角闪岩相和绿片岩相条件下捕获的。从变质高峰期至退变质晚期,包裹体成分演化由氧化向还原转化。熔融包裹体的发现,说明榴辉岩在形成过程中伴随局部深熔作用。通过流体包裹体研究,对大别山榴辉岩抬升过程p-T-t轨迹进行了探讨,认为是一等温降压过程。 相似文献
435.
本文运用社会学、社会心理学的有关基本理论。提出了震灾中情感互动、邻里互动、团体互动和社会互动的基本概念;分析了震灾中由上述互动方式构成的社会救灾体系或网络,探讨了震灾中超常行为和从众行为的二重性及其扬抑对策。 相似文献
436.
通过英云闪长质片麻岩变质结构的研究,把变质作用分为四个演化阶段,用三组分五个矿物相ACF体系P-T成因格子表示了这个演化过程。四个变质阶段矿物地质温度和压力计算结果构成了逆时针P-T-t轨迹。角闪石生成二辉石的平衡反应计算表明,主期变质水活度明显高于峰期变质水活度。水活度越高角闪石向二辉石转化温度越高,因此水活度是麻粒岩相变质作用的独立因素之一。 相似文献
437.
DONG Shuwen 《《地质学报》英文版》2009,83(4)
Abstract: On May 12th, 2008, the Mw7.9 Wenchuan earthquake ruptured the Beichuan, Pengguan and Xiaoyudong faults simultaneously along the middle segment of the Longmenshan thrust belt at the eastern margin of the Tibetan plateau. Field investigations constrain the surface rupture pattern, length and offsets related to the Wenchuan earthquake. The Beichuan fault has a NE-trending right-lateral reverse rupture with a total length of 240 km. Reassessment yields a maximum vertical offset of 6.5±0.5 m and a maximum right-lateral offset of 4.9±0.5 m for its northern segment, which are the largest offsets found; the maximum vertical offset is 6.2±0.5 m for its southern segment. The Pengguan fault has a NE-trending pure reverse rupture about 72 km long with a maximum vertical offset of about 3.5 m. The Xiaoyudong fault has a NW-striking left-lateral reverse rupture about 7 km long between the Beichuan and Pengguan faults, with a maximum vertical offset of 3.4 m and left-lateral offset of 3.5 m. This pattern of multiple co-seismic surface ruptures is among the most complicated of recent great earthquakes and presents a much larger danger than if they ruptured individually. The rupture length is the longest for reverse faulting events ever reported. 相似文献
438.
LI Qiugen CHEN Xu LIU Shuwen WANG Zongqi ZHOU Yingkui ZHANG Jian WANG Tao 《《地质学报》英文版》2009,83(3):550-561
Abstract:In this study, whole-rock geochemical and Nd isotopic data, as well as detrital zircon Hf isotopes of Palaeoproterozoic metasedimentary rocks from the Jiangxian Group are presented to evaluate the characteristics of their provenance and the tectonic history. The major and trace element compositions are comparable to Post-Archean upper continental crust (PA-UCC), but have slight enrichment in the LILE, with the exception of Cs and Sr, and a slight depletion in ferromagnesian elements, HFS elements, such as Nb and Ta, and some major elements, such as CaO and Na2O. The geochemical data reveal that the collected metasedimentary rocks have experienced intermediate source weathering with chemical index of alteration values ranging from 72 to 78, varying degrees of K-metasomatism, and post-depositional loss of Na, as well as negligible sorting, and are derived from the weathering of mostly felsic and non-mafic rocks. The selected Lu–Hf isotopic analysis on detrital zircon points to both the Trans-North China Orogen and Eastern Block of the north China craton as the most likely sources for the metasedimentary rocks of the Jiangxian Group. However, a contribution of detritus from the Western Block of the north China craton can be ruled out. The sediments were probably deposited in a back-arc basin within an active continental margin setting. 相似文献
439.
440.
Polar Mohr diagram method and its application in calculating the shear displacements of general shear zones with volume loss 总被引:2,自引:0,他引:2
The main problem, in determining the shear displacement of a general shear zone with volume change using the available formula,
is that it is hard to know the initial angle between the planes (or lines) in the plane of shear. A planar deformation analysis
of this kind of ductile shear zone is carried out with the polar Mohr diagram. If the volume change is induced by homogeneous
contraction in the Z direction of the shear zone, there are sufficient conditions for constructing a polar Mohr diagram regardless
of sequence of the simple shear and volume change. Therefore, the angle between a line and the shear direction before and
after the deformation can be measured. Making use of these lines the shear strain and the volume change can be calculated
and the shear displacement can be determined. 相似文献