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排序方式: 共有298条查询结果,搜索用时 203 毫秒
1.
李秀珍 《聊城大学学报(自然科学版)》1997,(3)
讨论了平面四次微分系统的特殊方向及在相平面上国成的角城内,奇点附近的轨线的分布;给出了右多端多项式系数构成的判别准则. 相似文献
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3.
邓勇 《达县师范高等专科学校学报》2006,16(5):25-26
利用数列的差分将常系数非齐次线性递归数列转化为常系数非齐次线性差分方程,从而得到一种求常系数非齐次线性递归数列特解的简易方法. 相似文献
4.
《特种建筑材料》双语教学的探索与实践 总被引:1,自引:0,他引:1
就《特种建筑材料》采用双语教学的教材、课件、教学形式、作业、考试等问题进行了探讨,并对《特种建筑材料》开展双语教学一年多来的成效进行了分析,希望对其他课程的双语教学开设有一定借鉴作用。 相似文献
5.
世界万物是由一种物质通过多种多样的运动形成的,很久以前有人称这种物质叫以太,请允许我在这里称其为动子。物质是由动子通过不同的群体运动形式表现出来,而物质之外的时间、空间等元素都是因动子的运动产生或改变。文章将初步建立一个由类似于相对论时空观的时间、空间模型,并用这个模型来辨析相对论的时空理论。通过建立的模型证实相对论的时空理论存在的局限性。 相似文献
6.
黑龙江省松嫩平原南部土地质量地球化学评价 总被引:1,自引:0,他引:1
以黑龙江省松嫩平原南部8.15万km^2范围表层土壤为研究对象,利用层次分析法、地统计学和模糊评价法从土地的肥力质量和环境质量进行评价,并利用地理信息系统(GIS)技术进一步分析研究区内地球化学质量的空间分布规律和变异性.研究结果表明,黑龙江省松嫩平原南部综合地球化学质量较好,土地的环境质量很高,土质非常清洁、安全.同... 相似文献
7.
What have recently been dubbed two ‘miracles’ of general relativity—(1) that all non-gravitational interactions are locally governed by Poincaré invariant dynamical laws; and (2) that, in the regime of experimental practice in which curvature effects may be ignored, the local Poincaré symmetries of the dynamical laws governing matter fields coincide with the local Poincaré symmetries of the dynamical metric field—remain unaccounted for in that theory. In this paper, I demonstrate that these two ‘miracles’ admit of a natural explanation in one particular successor theory to general relativity—namely, perturbative string theory. I argue that this point has important implications when considering both the ‘chronogeometricity’ (that is, the object in question being surveyed by rods and clocks built from matter fields) and spatiotemporal status of the dynamical metric field in both general relativity and perturbative string theory. 相似文献
8.
In this paper I argue that the case of Einstein׳s special relativity vs. Hendrik Lorentz׳s ether theory can be decided in terms of empirical evidence, in spite of the predictive equivalence between the theories. In the historical and philosophical literature this case has been typically addressed focusing on non-empirical features (non-empirical virtues in special relativity and/or non-empirical flaws in the ether theory). I claim that non-empirical features are not enough to provide a fully objective and uniquely determined choice in instances of empirical equivalence. However, I argue that if we consider arguments proposed by Richard Boyd, and by Larry Laudan and Jarret Leplin, a choice based on non-entailed empirical evidence favoring Einstein׳s theory can be made. 相似文献
9.
A part of the revival of interest in Mach׳s principle since the early 1960s has involved work by physicists aimed at calculating various sorts of frame-dragging effects by matter shells surrounding an interior region, and arguing that under certain conditions or in certain limits (ideally, ones that can be viewed as plausibly similar to conditions in our cosmos) the frame dragging becomes “complete” (e.g. Lynden-Bell, Katz, & Bičák, 1995) . Such results can bolster the argument for the satisfaction of Mach׳s principle by certain classes of models of GR. Interestingly, the frame-dragging “effect” of (say) a rotational movement of cosmic matter around a central point is argued by these physicists to be instantaneous—not an effect propagating at the speed of light. Not all physicists regard this as unproblematic. But rather than exploring whether there is something unphysical about such instantaneous “action at a distance”, or a violation of the precepts of Special Relativity, I am interested in exploring whether these physicists׳ calculations should be thought of as showing local inertia (resistance to acceleration) to be an effect, with distant matter distributions being the cause. I will try to apply some leading philosophical accounts of causation to the physical models of frame dragging, to see whether they imply that the frame dragging is superluminal causation. I will then offer reflections on the difficulties of applying causal talk in physical theories. 相似文献
10.
深圳特区报不断创新新闻理念,努力办成思想性、实用性的综合型党报;以建立现代企业制度为目标.创新报业经营管理体制,尝试现代企业法人治理结构的构建;以现代整合营销手段,实施差异化、分众化策略,提升报业的竞争力,成为我国地方党报做强做大的典范,被誉为“特区报现象”。解读特区报竞争力不断提升的奥秘,对其他地方党报的改革发展有着重要的启示作用。 相似文献