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71.
荷载对钻孔应变测值影响的实验及力学解析 总被引:1,自引:0,他引:1
介绍了弦频钻孔应变仪和体积式应变仪二次地表荷载试验的结果。根据弹性力学的理论和方法,对钻孔地壳应变测量及荷载试验的力学模型、边界条件等予以简化,使得经典的集中力作用于半无限弹性体表面的布辛奈斯克(Boussinesq)解,可有条件地运用于钻孔应变测量中地表荷载变化问题的定量分析研究。所给出的实验方法、研究思路及计算方法等,对定量研究钻孔应变测量中的荷载干扰、研究岩石力学性质、制定台站钻孔应变观测技术标准及观测规范等具有一定意义。 相似文献
72.
地应力场的不均匀分布是地球科学非常关心的问题,远场差异构造应力及介质本身的不均匀性对地应力场的不均匀分布都有重要影响.本文利用弹性力学理论,以地球科学的包体-地层系统为例,推导了边界差异构造应力条件下包体-地层系统位移场和应力场的解析表达式.将远场差异构造应力分解为均匀构造应力和偏构造应力两部分,通过边值问题的一般求解方法,分别得出了这两种情况下的理论解.通过将两部分理论解叠加,得到了边界差异构造应力条件下包体-地层系统的位移场、应力场和连接载荷.通过推导的解析解与有限元数值解进行比较,两者非常一致.通过分析包体-地层系统、材料参数、几何尺寸、远场构造应力的大小和方向等因素对包体-地层位移场和应力场分布的影响,可以用于探讨钻孔应变等包体应力(应变)计观测的地震应变阶、慢地震、地震孕育、火山喷发、地球自由振荡、地震波等现象的地球动力学机制.结果表明,远场地应力的分布主要受控于边界构造应力的大小和方向.在包体内部,应力场基本是均匀分布的;而在包体附近,由于介质差异,地应力场的不均匀性非常显著,并且有一定的优势方向,对地应力集中部位的分析为钻孔应变观测等地球动力学研究手段提供了基础理论参考. 相似文献
73.
Yuanqiang Li Jingye Li Xiaohong Chen Jian Zhang Xin Bo 《Geophysical Prospecting》2020,68(7):2009-2026
The conventional impedance inversion method ignores the attenuation effect, transmission loss and inter-layer multiple waves; the smooth-like regularization approach makes the corresponding impedance solution excessively smooth. Both fundamentally limit the resolution of impedance result and lead to the inadequate ability of boundary characterization. Therefore, a post-stack impedance blocky inversion method based on the analytic solution of viscous acoustic equation is proposed. Based on the derived recursive formula of reflections, the 1D viscous acoustic wave equation is solved analytically to obtain zero-offset full-wave field response. Applying chain rule, the analytical expression of the Fréchet derivative is derived for gradient-descent non-linear inversion. Combined with smooth constraints, the blocky constraints can be introduced into the Bayesian inference framework to obtain stable and well-defined inversion results. According to the above theory, we firstly use model data to analyse the influence of incompleteness of forward method on seismic response, and further verify the effectiveness of the proposed method. Then the Q-value sensitivity analysis of seismic trace is carried out to reduce the difficulty of Q-value estimation. Finally, the real data from Lower Congo Basin in West Africa indicate that the proposed approach provide the high-resolution and well-defined impedance result. As a supplement and development of linear impedance inversion method, the non-linear viscous inversion could recover more realistic and reliable impedance profiles. 相似文献
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75.
Kojitani H. Nishimura K. Kubo A. Sakashita M. Aoki K. Akaogi M. 《Physics and Chemistry of Minerals》2003,30(7):409-415
Raman spectroscopy of calcium ferrite type MgAl2O4 and CaAl2O4 and heat capacity measurement of CaAl2O4 calcium ferrite were performed. The heat-capacity of CaAl2O4 calcium ferrite measured by a differential scanning calorimeter (DSC) was represented as CP(T)=190.6–1.116 × 107T–2 + 1.491 × 109T–3 above 250 K (T in K). The obtained Raman spectra were applied to lattice dynamics calculation of heat capacity using the Kieffer model. The calculated heat capacity for CaAl2O4 calcium ferrite showed good agreement with that by the DSC measurement. A Kieffer model calculation for MgAl2O4 calcium ferrite similar to that for CaAl2O4 calcium ferrite was made to estimate the heat capacity of the former. The heat capacity of MgAl2O4 calcium ferrite was represented as CP(T)=223.4–1352T –0.5 – 4.181 × 106T –2 + 4.300 × 108T –3 above 250 K. The calculation also gave approximated vibrational entropies at 298 K of calcium ferrite type MgAl2O4 and CaAl2O4 as 97.6 and 114.9 J mol–1 K–1, respectively. 相似文献
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79.
地面磁共振法(MRS)因具有定性、定量分析地下水能力,而备受关注.传统磁共振地层含水量反演多采用均匀半空间模型,忽略电阻率分布信息对结果的影响.针对这一问题,本文基于多层电介质中磁共振响应理论,提出MRS与瞬变电磁(TEM)联合反演方法,通过电阻率分布信息对含水量反演过程的实时修正,提高了解释结果的准确度.反演算法采用自适应遗传算法(AGA)进行,基于繁殖规则,动态调整交叉概率和变异概率,解决了标准遗传算法易未成熟收敛而难以得到全局最优解问题.模型数据表明,含噪10%情况下,联合反演仍能较准确地反映地下含水单元模型结构,对比MRS单独反演优势明显.同时,内蒙古白旗野外观测数据联合反演结果与钻井资料基本一致,充分验证了AGA反演算法的实用性及MRS-TEM联合反演的实际意义. 相似文献
80.
Optically stimulated luminescence (OSL) dating has been applied to determine the burial age of sediment horizons within a sequence containing Lower Palaeolithic artefacts on an upland site associated with a solution feature (doline) at West Cliffe, located on the North Downs in Kent, UK. The study makes use of a novel extension of the single aliquot OSL measurement procedure to investigate the nature of significant overdispersion in equivalent dose values with very small aliquots of quartz inclusions, enabling single grain resolution to be approached with ∼90 μm diameter quartz extracted from the relatively fine-grained brickearth. A detailed examination of the uniformity of the distribution of radionuclide sources in the sampled volumes was also performed and this included the application of a spatially-resolved technique for beta dose rate measurement. The OSL ages, obtained for the burial of brickearth positioned stratigraphically below and above a clay and flint clast layer containing the artefacts and debitage, place the deposition of the artefacts to between ca 140 and 80 ka ago. This is significantly later than indicated by the artefact typology (>300 ka) and contrary to the expectation of in situ burial indicated by earlier research in this region. If displacement occurred on other upland sites this finding has important implications for establishing the timing of hominin use of the upland areas which, beyond broad attribution to Lower or Middle Palaeolithic origin, is uncertain and similar doubts apply to the interpretation of the environments that prevailed. 相似文献