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81.
82.
We applied a tomographic method to image an aseismic strike–slip fault in North Morocco and found that the occurrence of earthquakes is not only controlled by the state of tectonic stress but also by material heterogeneity in the crust. We have constructed an integrated model of seismic, electric, magnetic and heat flow properties across northeastern Morocco primarily based on a tomography inversion of local earthquake arrival times. The seismic images obtained show a pronounced low-velocity zone at 5 km depth parallels to the Nekor fault, coinciding with an anomalously high conductive and low gravity structure, which is interpreted as a fault gouge zone and/or a fluid-filled subsurface rock matrix. Below 10 km depth, a weak positive velocity zone indicates that the fault gouge is stable. The seismicity and the seismic velocity results for the Al-Hoceimas region show that the concentrations of earthquakes are confined in the high velocity area. This anomaly is interpreted to be a brittle and competent layer of the upper crust that sustains seismogenic stress. On the eastern coast line of Morocco, we infer that a high density, high velocity body exists in the shallowest layers of the upper crust, probably formed by Miocene volcanic rocks. 相似文献
83.
利用新疆及邻区2万多条Pn射线的走时资料,采用层析成像的方法反演该地区上地幔顶部的Pn速度结构.主要结果是:①新疆地区平均h速度为.2km/s,高于中国大陆地区的平均值(.0km/s),速度变化量从-0.3km/s到0.2km/s.②准噶尔盆地是明显的高Pn速度区,高速区与地貌形状吻合较好,最大值达.4km/s;塔里木盆地整体上呈现高速异常二者都可能与盆地是稳定地块、构造活动和变形较弱有关.③在盆地与山脉的交接带即主要的构造活动带,存在较低的Pn速度,可达7.9km/s.④塔里木南缘中部存在一显著的低速区,可能与岩浆活动和构造活动较强有关.⑤上地幔顶部波速各向异性整体上盆地中心较弱,边缘地带较强.新疆南部波速的各向异性可能是因印度板块对欧亚大陆的碰撞使地幔物质向北蠕动的结果. 相似文献
84.
电阻率三维反演方法研究进展 总被引:6,自引:7,他引:6
系统分析了当前几种主要的电阻率三维反演方法,重点讨论高密度电阻率方法,论述了每种方法的优缺点及最新研究进展状况,提出了进一步研究的方向。 相似文献
85.
多层螺旋CT在复杂部位骨折检查中的应用 总被引:1,自引:0,他引:1
目的:探讨多层螺旋CT(MSCT)在颜面部位骨折,关节内骨折,脊柱骨折中的检查价值,材料和方法:选择29例复杂部位骨折病人,应用GELight Speed,Plus型MSCT机检查及ADW4.0型工作站进行图像处理。结果:MSCT可逼真显示复杂结构的解剖及病理解剖,对隐匿性骨折线及小骨片的移位显示优于其它影像学检查。结论:MSCT在复杂部位骨折检查中有明显优势。 相似文献
86.
Colliding Blast Waves Driven by the Interaction of a Short-Pulse Laser with a Gas of Atomic Clusters
Roland A. Smith James Lazarus Matthias Hohenberger Alastair S. Moore Joseph S. Robinson Edward T. Gumbrell Mike Dunne 《Astrophysics and Space Science》2007,307(1-3):131-137
Collisions between shocks are commonly found in many astrophysical objects, however robust numerical models or laboratory
analogues of these complex systems remain challenging to implement. We report on the development of scaled laboratory experiments
which employ new techniques for launching and diagnosing colliding shocks and high Mach number blast waves, scalable to a
limited subset of astrophysically-relevant regimes. Use of an extended medium of atomic clusters enables efficient (>80%)
coupling of 700 fs, 1 J, 1054 nm laser pulses to a “cluster” gas with an average density of ≈1019 particles cm−3, producing an initial energy density >105 J cm−3, equivalent to ≈5×109 J/g. Multiple laser foci are used to tailor the spatial profile of energy deposition, or to launch pairs of counter-propagating
cylindrical shocks which then collide. By probing the collision interferometrically at multiple view angles in 5^ increments and applying an inverse Radon transform to the resulting phase projections we have been able to tomographicall
reconstruct the full three-dimensional, time-framed electron density profile of the system. 相似文献
87.
88.
Shear zones in porous sand: Insights from ring-shear experiments and naturally deformed sandstones 总被引:2,自引:1,他引:2
In a high-resolution small-scale seismic experiment we investigated the shallow structure of the Wadi Araba fault (WAF), the principal fault strand of the Dead Sea Transform System between the Gulf of Aqaba/Eilat and the Dead Sea. The experiment consisted of 8 sub-parallel 1 km long seismic lines crossing the WAF. The recording station spacing was 5 m and the source point distance was 20 m. The first break tomography yields insight into the fault structure down to a depth of about 200 m. The velocity structure varies from one section to the other which were 1 to 2 km apart, but destinct velocity variations along the fault are visible between several profiles. The reflection seismic images show positive flower structures and indications for different sedimentary layers at the two sides of the main fault. Often the superficial sedimentary layers are bent upward close to the WAF. Our results indicate that this section of the fault (at shallow depths) is characterized by a transpressional regime. We detected a 100 to 300 m wide heterogeneous zone of deformed and displaced material which, however, is not characterized by low seismic velocities at a larger scale. At greater depth the geophysical images indicate a blocked cross-fault structure. The structure revealed, fault cores not wider than 10 m, are consistent with scaling from wear mechanics and with the low loading to healing ratio anticipated for the fault. 相似文献
89.
利用中美合作Hi-Climb项目北段吉隆-鲁谷剖面的天然地震探测数据,拾取2004~2005年期间5级以上地震事件的P波与4级以上地震的Pn波震相的走时,通过多震相层析成像反演获得青藏高原腹地的地下500 km以上的P波速度扰动结构.结果表明雅江地区为北向倾斜的低速扰动,班公-怒江断裂下方存在向南俯冲并被印度板块俯冲挤压而回折的高速体,建立了印度板块在冈底斯地块下方拆沉并被雅江低速体穿越的构造样式.说明印度板块俯冲在到达班公-怒江缝合带之前已经开始消减,与拆沉位置对比发现,印度板块的前锋深部呈现多期多级次特征,并受到地幔热循环作用的影响. 相似文献
90.