社区的工作对知识的全面积累是否有很大的贡献，这一点是值得怀疑的。

And whether the community's work contributes much to an overall accumulation of knowledge is doubtful.

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平面中的通量和空间中的通量有很大区别，在平面中，通量仅仅是线积分的另一种形式，而在空间中，它表现为曲面积分。

Flux looks quite different in the plane and in space because, in the plane, it is just another kind of line integral, while in space it is a surface integral.

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然而，由于各岛屿国家的陆地面积、1人口密度、气候、地理地形条件等有很大差异，它们的森林覆盖程度也有很大差别。

However, due to a considerable variation in land area, 1 population density and climatic, geological and topographical conditions, the extent of forest cover differs greatly among the island states.

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