Experiments have already been done in this field ,but only _a small scleA.at B.on C.in D.by

Experiments have already been done in this field ,but only _a small scleA.at B.on C.in D.by
Experiments have already been done in this field ,but only _a small scle
A.at B.on C.in D.by

Experiments have already been done in this field ,but only _a small scleA.at B.on C.in D.by
B on a small scle 是固定短语 是 小范围的