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961.
962.
M. Mohr P. A. Kukla J. L. Urai G. Bresser 《International Journal of Earth Sciences》2005,94(5-6):917-940
The Central European Basin is a classic area of salt tectonics, characterized by heterogeneous structural evolution and complex
salt movement history. We studied an area on its SW margin, based on prestack depth-migrated 2D and 3D seismic data. We use
seismic interpretation and retro-deformation to obtain a better understanding of salt tectonics, structural control, and sedimentary
response in this region. The first phase of salt tectonic evolution started with two main events of NW–SE extension and rafting
in the Triassic before the Upper Bunter and before the Upper Muschelkalk. Rafting was accompanied by first salt diapirism
and an increased sedimentary thickness adjacent to the salt structure. After salt supply ceased updip to the salt structure,
a mini-basin grew in the intra-raft area. This sedimentary differential loading caused salt movement and growth of a pillow
structure basinward. The second phase of salt movement was initiated by the formation of a NNW–SSE striking basement graben
in the Middle Keuper that triggered reactive diapirism, the breakthrough of the pillow’s roof and salt extrusion. The following
downbuilding process was characterized by sedimentary wedges with basal unconformities, onlap structures and salt extrusions
that ceased in the Jurassic. The third and latest phase of salt tectonic evolution was activated in the Late Cretaceous to
Lower Tertiary by compressional tectonics indicated by salt rise and a small horizontal shortening of the diapir. The interpreted
salt tectonic processes and the resulting geometries can now be better tied in with the regional heterogeneous framework of
the basin.
Unfortunately, the entire article was originally published Online First with errors. The publishers wish to apologize for this mistake. The correct article is shown here.
The online version of the original article can be found at 相似文献
963.
964.
Tina Svan Hansen 《Singapore journal of tropical geography》2005,26(2):170-190
This paper focuses on the large‐scale land use and land cover changes that have taken place in Sarawak state, East Malaysia over the three decades of 1972‐2002. Results are presented from a detailed land use and cover change (LUCC) study in the Niah River catchment using satellite imagery, questionnaire surveys and interviews. Successive waves of land cover changes have taken place. Large forest areas have been logged and gradually replaced by oil palm plantations, which now occupy more than 40 per cent of the total land area in the catchment. Concurrently, small‐scale farming systems have also changed. Formerly dominant Iban shifting cultivation practices are increasingly being replaced by cash crop production on permanent fields and impacted by off‐farm activities involving many ethnic groups. It is argued that land cover changes are continuous and complex processes involving a large number of variables which can be analysed for different time periods at various scales. 相似文献
965.
西爪哇金矿位于印度尼西亚西角湾火山岩金、铅锌铜多金属成矿带,该区有众多金矿床(点)。出露的三叠系火山岩地层,以火山喷发沉积为主,岩性组合为安山岩、英安岩、流纹岩及火山角砾岩,具爆发-喷溢沉积的特点,总体表现为火山弧特征。断裂构造破碎带是该地区主要控矿、容矿构造。岩石蚀变强烈,硅化与金矿化关系密切。 相似文献
966.
构造应力是促进煤炭物理和化学变化的主要压力因素,造成地温局部升高,改变煤的结构。地温升高改变瓦斯动力机制,互相叠加后造成瓦斯含量、动力大幅度提高,给煤矿开采带来难度。 相似文献
967.
管道衬砌内水外渗对边坡稳定影响的数值模拟 总被引:6,自引:0,他引:6
根据钢筋混凝土受拉开裂特性,通过混凝土开裂后钢筋和混凝土联合承载原理,提出了在内水压作用下混凝土衬砌开裂的裂缝宽度估算公式。根据开裂衬砌内水外渗的规律,提出了高压管道内水外渗与混凝土衬砌裂缝宽度相互影响的有限元迭代计算分析方法。该方法将内水压荷载分解为起裂荷载和破坏荷载,对混凝土衬砌起裂荷载采用一次加载,对破坏荷载采用分级加载迭代,由此较好地反映衬砌开裂和渗流耦合作用效应。根据渗流荷载对边坡的破坏作用,提出了对边坡稳定判断的思路。通过对实际工程的分析计算,论证了高压管道内水外渗对边坡的稳定影响, 为内水外渗与应力场耦合分析提供了一种有效的计算方法。 相似文献
968.
The ore deposits of The Granites goldfield are shear-hosted within Palaeoproterozoic amphibolite facies metasedimentary rocks
in the Tanami Region, Northern Territory, Australia. The ore bodies are located within a 5- to 35-m thick sequence of steeply
dipping unit of metamorphosed iron-rich metasedimentary rocks. Deformation at The Granites was complex and is characterized
by five successive deformation phases (D1–5). Shear veins (central and oblique) are the dominant type of vein geometry, with minor development of extensional veins and
reverse-fault related veins. Four generations of syn-tectonic veins, corresponding to D1, D3, D4, and D5, have been recognized and are comprised of quartz, quartz-carbonate, calc-silicate, and calcite. In addition, two generations
of disseminated sulfide–arsenide mineralization, dominated by pyrrhotite, arsenopyrite, and loellingite, with minor pyrite,
chalcopyrite and rare marcasite, formed syn-D1 and syn- to post-D3. Textural and structural evidence indicates deposition of gold was contemporaneous with the syn-D1 veins and sulfide–arsenide mineralization. Four hydrothermal phases are proposed for the formation of the veins and disseminated
sulfide–arsenide assemblages. The first phase (D1) was responsible for transport and deposition of the majority of the gold. Minor remobilization and deposition of gold occurred
during the D3 and D4 phases. Little is known about the nature of the D1 ore fluid, although a relatively low sulfur content is indicated by the assemblage pyrrhotite–arsenopyrite–loellingite+rare
pyrite. The growth of amphibolite facies metamorphic minerals andalusite and almandine garnet during D1 indicates a high temperature for the fluid. The D3 hydrothermal phase coincided with peak metamorphism. D4 fluids were hypersaline, high temperature, CO2-poor, and H2S-poor.
Editorial handling: L. Meinert 相似文献
969.
A spatial analysis of structural controls on Karst groundwater geochemistry at a regional scale 总被引:7,自引:0,他引:7
Danile Valdes Jean-Paul Dupont Benoît Laignel Sylvie Ogier Thierry Leboulanger Barbara J. Mahler 《Journal of Hydrology》2007,340(3-4):244-255
The coupled spatial investigation of the geometrical and geochemical properties of a chalk karstic aquifer provides information on the degree to which geologic structure controls aquifer functioning and groundwater quality. Major ion concentrations in the chalk aquifer of the Haute-Normandie region (France) were measured at a high spatial resolution (more than 100 sampling sites over a 6000 km2 area) and mapped. The first observation is a continuity of the geochemical properties, in spite of the karstic properties of the aquifer principal components analysis of geochemical maps revealed two types of spatial distributions: ions with an autochthonous origin (Ca2+, HCO3), and ions with a principally allochthonous origin (Cl−, Na+, , ). Mg2+ was categorised as both autochthonous (chalk dissolution) and allochthonous (brought in by infiltration of Tertiary deposits). To better understand the spatial distribution of the geochemistry, the aquifer geochemistry was compared to the physical properties of the aquifer, in particular aquifer thickness (representing aquifer geometry) and piezometric level (representing aquifer flow). Use of spatial correlation between the geochemical and the geometrical properties provided insight regarding the directional structure of the data and give evidence of directional relations between geochemical and geometrical properties. The degree of mineralisation (principally composed of Ca2+ and ions) increased along the direction of flow, corresponding to an increase in chalk dissolution rate along the flowpath. The steepest mineralisation gradients were related to an increase in the Mg/Ca ratio, evidence of longer residence times and corresponding to zones where aquifer flow capacity is limited because of a decrease of the thickness of the flow section (anticlines or faults). These results highlight the dominant role played by the geometry and the structural context in controlling aquifer geochemistry. 相似文献
970.
Electron Back-Scatter Diffraction (EBSD), which provides an easy way of acquiring large numbers of individual crystallographic orientation data from different phases, has been applied to the study of magmatic fabrics. Using this technique, the crystallographic preferred orientation (CPO) of plagioclase, biotite, orthopyroxene, hornblende and quartz in natural tonalites and quartzdiorites (from the Santa Olalla Igneous Complex, SW Iberia) deformed during the magmatic stage have been determined. Plagioclase is the coarser phase defining the main fabric in each sample, whereas biotite can display either the same fabric as plagioclase or a completely different one. The differences between these two phases occur because: (1) smaller phases interact with the larger ones to produce more random orientations, (2) under simple shear, finer phases can completely rotate giving a girdle included in the XZ plane, (3) finer phases can more easily preserve relict fabrics, while the coarser phases are completely reoriented by the last stress tensor. The last phases to crystallize show weak to completely random CPOs (hornblende) or completely random distributions (quartz). The study was completed with a shape preferred orientation analysis using the Intercept Method in order to detect weak magmatic lineations, and numerical modelling simulations of theoretically equivalent simple shear situations for each sample. 相似文献