语态指的是句子中的主语和谓语之间的关系。当句子的主语是谓语的执行者时，其谓语形式为主动语态(Active Voice)，当主语为谓语的承受者时，其谓语的形式为被动语态(Passive Voice)。
在被动语态的句子中，其主语往往是主动语态句子中谓语动词的宾语。因此，被动语态句子中的谓语动词必须是及物动词。
试比较：
We also determined four crystal structures of SPE 7 complexed with four different antigens.(主动语态)
Four crystal structures of SPE 7 complexed with four different antigens we alsodetermined.(被动词态)
语态决定于句子强调的是执行者还是承受者。当句子强调的是谓语动作的行者时，则采用主动语态。
To overcome these problems we have studied the biotransformation of foreign substrate by plant-cultured suspension cells.
当句子强调的是谓语动作的承受者时，则采用被动语态。
β-Lactams canbe transformed into valuable β-amino acid which are of immense interest from both pharmacological and chemical viewpoints.
在英语科技论文的表述中，被动语态的句子用得较多，但被动语态用词较多，使句子长或头重尾轻，故通常能用主动语态表述的内容可尽量不用被动语态表述。
A facile transformation of 3,4- -disubstituted 2-azetidinones to chiral 5,6- dihydro-2-pyridones, which can serve as valuablechiral intermediates for different piperidine and indolizidine alkaloids andazasugars, was reported by Lee et al.
此句明显头大尾小，给人一种句子不稳的感觉，若改成如下的主动句，则可克服这一毛病。
Lee et alreported a facile transformation of 3, 4-disubstituted 2-azetidinones to chiral 5, 6-dihydro-2-pyridones, which can serve as valuable chiral intermediates fordifferent piperidine and indolizidine alkaloids and azasugars.
在被动语态的句子中，凡是有动词时，则不用该动词相应的名词，以使句子简练。
Separation of the compounds was accomplished 可改成Thecompounds were separated.
科技英文论文的表述中，常见的这类名词及其相应的动词如下：
determination→determine,identification→identify,speculation→speculate , discussion→ discuss, description→describe , treatment→treat , assignment→assign ,interpretation→interpret , explanation→explain , calculation→calculate,differentiation→differentiate, synthesis→synthesiz, preparation→prepare,dissolution→dissolve,dilution→dilute,concentration→concetract,evaporation→evaporate,extraction→extract,analysis→analyze
由形式主语 it 代替主语从句先行所引出的被动句是常见的一种表述形式。
It has recently been reported by Mateo et al. that some immobilization methods can enhance the thermostability of an enzyme.
但在不影响句子表述内容的情况下可改成主动句：
Meteo et al. has recently reported that…
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