[误] His theory has no scientific base.

[正] His theory has no scientific basis.

注：base 和 basis 虽然都有“基础”的含义，但 base 指物质上的、具体的“基础”，常表示“基地”或“根据地”，如：After bombing the targets, the planes returned safely to their base;而 basis 则指理论、信念、思想或某项工作所依据的抽象的“基础”或“根据”。