Free indirect discourse is constructed by the substitution of those subjects, and the rules of substitution coincide with general grammar.
自由间接引语即由潜在的多个主体之间的代换而构成，而且代换规则与一般语法规则一致。
2
The reactivities and selectivities of aliphatic and aromatic free-radical(substitution)reactions were explained semi-quantitatively by the perturbation molecular orbital theory.
从而用微扰分子轨道理论半定量地解释了脂肪族的游离基取代和芳香族的游离基取代反应的反应性和选择性。
3
Due to the consideration of environmental protection, the substitution of lead-containing solder with lead-free solder has become an inevitable trend in the 21st century.