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71.
To simultaneously evaluate the decay constant of 40K () and the age of a standard (t
std) using isotopic data from geologic materials, we applied a series of statistical methods. The problem of estimating the most probable intercept of many nonlinear curves in and t
std space is formulated by an errors-in-variables nonlinear regression model. Then a maximum likelihood method is applied to the model for a point estimate, which is equivalent to the nonlinear least square method when measurement error distributions are Gaussian. Uncertainties and confidence regions of the estimates can be approximated using three methods: the asymptotic normal approximation, the parametric bootstrap method and Bonferroni confidence regions. Five pairs of published data for samples with ages from 2 ka to 4.5 Ga were used to estimate and the age of Fish Canyon sanidine (t
FCs). The statistical procedure yields most probable estimates of (5.4755 ± 0.0170 × 10–10 (1)/year) and t
FCs (28.269 ± 0.0661 (1) Ma) which are in between previously published values. These results indicate the power of our approach to provide improved constraints on these parameters, although the preliminary nature of some of the input data require further review before the values can be adopted. 相似文献
72.
Adding Local Accuracy to Direct Sequential Simulation 总被引:3,自引:0,他引:3
Jef Caers 《Mathematical Geology》2000,32(7):815-850
Geostatistical simulations are globally accurate in the sense that they reproduce global statistics such as variograms and histograms. Kriging is locally accurate in the minimum local error variance sense. Building on the concept of direct sequential simulation, we propose a fast simulation method that can share these opposing objectives. It is shown that the multiple-point entropy of the resulting simulation is related to the univariate entropy of the local conditional distributions used to draw simulated values. Adding local accuracy to conditional simulations does not detract much from variogram reproduction and can be used to increase multiple-point entropy. The methods developed are illustrated using a case study. 相似文献
73.
基于Pro/E的渐开线圆柱齿轮参数化实体设计 总被引:1,自引:0,他引:1
在Pro/E环境下分析了渐开线圆柱齿轮三维造型的特征,应用Program模块进行二次开发,实现了全液压钻机回转器渐开线圆柱齿轮三维参数化实体设计,有效地提高了设计效率。 相似文献
74.
王蒙 《测绘与空间地理信息》2021,44(4):80-83,87
城市设计是控规中不可或缺的引导性内容。随着理论与编制方法的不断创新,城市设计已发展到了以形态整体性理论重构为目标的第四代范型,而三维形态不仅是城市设计的表现形式,也是揭示和把握城市演变进程特征和规律的重要手段,能够有效弥补和提高控制性详细规划指标在三维空间上的乏力和不足。本文以两个实验区为基础,尝试将控规指标作为参数导入CityEngine参数化建模软件中,再利用GIS平台对模型实施空间分析,实现了"建模—分析—编制"动态关联的参数化规划设计流程,使城市设计的引导性作用更加直观、高效。 相似文献
75.
介绍配套了气垫式保真筒的深海天然气水合物采样器的结构及其工作原理,同时为提升气垫式保真筒的保压性能,基于压降模型仿真分析了关键参数(预充压力、气腔长度、筒体长度、筒体内径和筒体壁厚)对采样终了筒内压降的影响。仿真研究结果表明:预充压力、气腔长度和筒体壁厚对气垫式保真筒的保压性能影响较大,且取值越大保压效果越好;筒体长度、筒体内径与筒内压降正相关且对其影响较小;同时综合保真筒的整体性能来讲,提高预充压力和增加气腔长度是提高气垫式保真筒的保压性能可选的有效方式。 相似文献
76.
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78.
基于结构弹性稳定理论,根据能量法推导出以位移为基本未知量的圆弧格构拱总势能,从Hamilton原理出发,建立了考虑剪切变形的圆弧格构拱的动力稳定微分方程.利用Galerkin方法将其转化为二阶常微分Mathieu型参数共振方程,求得周期解所包围的动力不稳定区域,探讨了圆弧格构拱发生参数共振的动力稳定性问题,分析了缀条面... 相似文献
79.
利用经实验验证过的ABAQUS有限元模型对轴力和弯矩共同作用下的约束钢柱进行了参数分析。以钢柱的屈曲温度和临界温度作为主要的评价指标,主要考虑了轴力荷载比、弯矩荷载比、轴向约束刚度比、转动约束刚度比、长细比和钢柱端部弯矩比等参数的影响,并且对不同参数之间的耦合性进行了分析。参数分析结果表明,轴向约束刚度的增大将会明显降低约束钢柱的屈曲温度,但是对其临界温度的影响相对较小;端部弯矩比对钢柱的临界温度影响很小;当钢柱的轴力荷载比和弯矩荷载比较小、轴向约束刚度比和长细比较大时,考虑屈曲后性能可以显著提高钢柱的抗火能力。 相似文献
80.
Sediments often occur as non‐normal size distributions composed of discrete, partially aggregated particle populations. These populations reflect provenance, dispersal pathways and their depositional environments. Recent experimental laboratory studies describing mud flocculation in turbulent marine systems prompted this investigation of the potential of aggregates to record size‐sensitive transport dynamics in a terrestrial fluvial system. Here, sediment‐size distributions in their natural condition of particle–aggregate mixtures are analysed by parametric statistics. A practical and freely available decompositional approach is outlined and field tested, which allows sediment to be viewed in both its conventional particulate form and as its naturally occurring mixture of transport‐stable aggregates and elementary particles. From a sequence of upward‐fining slack water couplets in the Flinders Ranges, South Australia, it is demonstrated that the characteristics, provenance and depositional history of fine‐grained sediments consisting of particle‐aggregate mixtures can best be understood fully by quantifying aggregation. 相似文献