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311.
圆轨道锥束重建精度与锥角关系的研究 总被引:5,自引:1,他引:5
目的:深入研究Radon空间的数据缺失与锥角的关系改进算法。方法:相对于二维CT重建,锥束重建有着诸多优势,因此目前得到越来越广泛的应用。圆轨道锥束重建,因为算法上的简洁性以及工程实现的可行性,成为了锥束重建比较乐于采用的形式。但是由于圆轨道几何结构的限制,使其不能够得到完备的锥束重建数据,只有在锥角较小的情况下才能得到,因此深入研究Radon空间的数据缺失与锥角的关系以改进算法。结果:通过一定的近似得到了一个它们之间比较简单的关系。结论:基于这一关系提出了改进算法 相似文献
312.
Multilinear Regression Analysis for Seismic Response and Engineering Properties of Liquefiable Coromandel Coastal Soil Deposits 总被引:1,自引:0,他引:1
S. Senthamilkumar C. Natarajan K. Muthukumaran 《Geotechnical and Geological Engineering》2009,27(3):439-453
This paper investigates the seismic characteristics and geotechnical properties with respect to the liquefaction potential
of the deposits in the Coromandel coastal line of Nagapattinam town, Tamilnadu, India. A series of field tests were conducted
using standard penetration test, cone penetration test and plate load test. Laboratory tests were conducted on the collected
samples. From the results, a microzonation map was developed for the liquefaction potential and settlements. Some multilinear
regression models between permeability, fines content, relative density, coefficient of curvature, coefficient of uniformity,
mean particle size, factor of safety, settlement, standard penetration test values and cone penetration test values were developed.
The shear wave velocity and shear modulus were calculated from the field penetration tests and correlations between the normalized
values of peak ground accelerations, velocities and displacements, which were obtained from the equivalent linear ground motion
analysis using SHAKE software, with other parameters of soil. From the results, it was found that at some of the areas are
vulnerable to high amplification of waves even for small earthquake. 相似文献
313.
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315.
粉喷桩对桩间土性状的影响 总被引:2,自引:0,他引:2
粉喷桩处理软土地基已在国内外得到较为广泛的应用,作为一种复合地基,对其工作机理仍有进一步研究的必要。本文利用实际工程标准贯入测试的结果,分析了粉喷桩对桩间可液化土层性状的影响;利用静力触探测试数据,讨论了粉喷桩施工前后桩间上端阻力和侧摩阻力的变化规律。 相似文献
316.
The Senyama volcanic products of the late Pliocene to early Pleistocene O’e Takayama volcano overlie a 100-m-thick, late Pliocene
coastal quartz-sandstone and are intruded by an early Pleistocene dacite dome. The Senyama volcanic products are the remains
of a cone that retains a basal part 1.5 km across and 150–250 m high from the substrate. The cone comprises dacite block-and-ash
flow deposits and minor base-surge deposits occur at the base. Single beds of the block-and-ash flow deposits are 1–16 m thick
and dip inward 20–40° at the base of the cone and inward or outward 10–20° at the summit. Juvenile fragments in the block-and-ash
flow deposits are non- to poorly vesicular and commonly have curviplanar surfaces and prismatic joints extending inward from
the surfaces, which imply quenching and brittle fracturing of dacite lava. They are variably hydrothermally altered. Nevertheless,
juvenile blocks appear to retain a uniform direction of the magnetization vector residual during thermal demagnetization between
280°C and 625°C. At the time of the eruption, the well-sorted sand of the substrate was at the coast and a good aquifer that
facilitated explosive interaction of water and the ascending dacite lava. The mechanism of the explosion perhaps involved
thermal contraction cracking of the dacite lava, water-inflow into the interior of the lava, and explosive expansion of the
water. Initial phreatomagmatic explosions opened the vent. Succeeding phreatomagmatic or phreatomagmatic–vulcanian explosions
produced block-and-ash flow deposits around the vent. Hydrothermal silver-ore deposits and manganese-oxide deposits occur
in the Senyama volcanic products and the underlying sandstone, respectively. They could represent post-eruptive activity of
the hydrothermal system developed in and around the cone. 相似文献
317.
We describe two small scoria cone volcanoes, Hidden Cone and Little Black Peak (ages between ~320–390 ka), in the Southwestern
Nevada Volcanic Field and discuss their eruption mechanisms and inferences about their plumbing systems. Cone-forming pyroclastic
deposits are consistent with eruptive styles ranging from Strombolian to violent Strombolian, and lavas emanated from near
the bases of the cones. The volcanoes are monogenetic (rather than polycyclic, as allowed by previous geomorphic interpretations).
Vents at each volcano appear to coincide with pre-existing normal faults, consistent with observations at older, deeply eroded
volcanoes in the region. The existence of these two volcanoes on a topographically high area (particularly Hidden Cone) provides
evidence for short feeder dike lengths (~500 m at the surface). We infer that this short length reflects the small length
scale of the mantle source region that was tapped to feed each volcano.
Editorial responsibility: J Stix 相似文献
318.
Visual Modflow在建立长春市地下水开采预警系统中的应用 总被引:5,自引:0,他引:5
采用Visual Modflow对长春城区的地下水位、Cl^-浓度进行模拟和预报,在此基础上,应用Visual Modflow软件的系统化和可视化特点以及所拥有的强大模拟功能,建立长春城区地下水开采预警系统。研究结果表明:长春城区浅层水水位略有上升趋势,深层水漏斗中心水位呈下降趋势,个别超采漏斗出现预警水位;Cl^-浓度变化的幅度很小,水位和Cl^-浓度的幅度均在允许范围。 相似文献
319.
The felsic dikes of La Gomera (Canary Islands): identification of cone sheet and radial dike swarms 总被引:1,自引:0,他引:1
E. Ancochea J. L. Brndle M. J. Huertas C. R. Cubas F. Hernn 《Journal of Volcanology and Geothermal Research》2003,120(3-4):197-206
On the northern part of La Gomera there exists a great abundance of trachytic–phonolitic dikes showing a broad diversity in dip and strike. Several methods have been applied in order to separate these dikes in different sets, localise the area from where they derive, and reconstruct the geometry of the swarms. The oldest dikes correspond to a radial swarm dated at 8 Ma. The felsic activity migrated then southwestwards and a second radial swarm and a cone sheet complex were developed between 7.5 and 6.4 Ma ago. The cone sheet complex is 10 km in diameter and shared its centre with that of the second radial structure. The cone sheets exhibit an outward decrease of dip angle whilst every individual sheet maintains a constant inclination. This geometry reflects the existence of an ancient single dome-shaped shallow magma chamber situated some 1650 m below present sea level. The eastern radial swarm represents a felsic episode that could mark the ending of the Lower Old Basalts, the earlier subaerial activity of La Gomera. The two other dike swarms represent a younger episode coeval with the Upper Old Basalts. 相似文献
320.