全面掌握GRE阅读的定位技巧_GRE经验技巧

全面掌握GRE阅读的定位技巧

　　Because of its accuracy in outlining the Earths subsurface, the seismic-reflection method remains the most important tool in the search for petroleum reserves. In field practice, a subsurface is mapped by arranging a series of wave-train sources, such as small dynamite explosions, in a grid pattern. As each source is activated, it generates a wave train that moves downward at a speed determined uniquely by the rocks elastic characteristics. As rock interfaces are crossed, the elastic characteristics encountered generally change abruptly, which causes part of the energy to be reflected back to the surface, where it is recorded by seismic instruments. The seismic records must be processed to correct for positional differences between the source and the receiver, for unrelated wave trains, and for multiple reflections from the rock interfaces. Then the data acquired at each of the specific source locations are combined to generate a physical profile of the subsurface, which can eventually be used to select targets for drilling.

　　按照文章的结构来分析，全文主要是针对一个观点进行论证，作者在文章的第一段的开头部分就给出明确的结论，即阐述某一个观点，而下文全是对此观点做出的解释说明和论证。黑斜体部分也是这篇短文的中心句，起到统领全文的作用。

　　三、转折词位

　　往往一篇文章中转折词的前后会成为阅读的出题点，这点我们必须时刻保持注意，转折词的前后往往阐述的内容或是对比，或是对立，或是让步，也或是为了铺垫和某个过渡。GRE阅读篇章中常常出现表示转折语气的词语包括：however, nonetheless, nevertheless, indeed, actually, in fact等等，对于这些词汇，我们定要时刻小心，遇到需作一下标记，而对与这些转折词前后内容之间的关系需要弄清楚。

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