1. 科技英语中的被动语态

据英国利兹大学John Swales 的统计，科技英语中的谓语至少三分之一是被动态。这是因为科技文章侧重叙事推理，强调客观准确。第一、二人称使用过多，会造成主观臆断的印象。因此尽量使用第三人称叙述，采用被动语态，例如：Attention must be paid to the working temperature of the machine.应当注意机器的工作温度。而很少说：You must pay attention to the working temperature of the machine .你们必须注意机器的工作温度。此外，如前所述，科技文章将主要信息前置，放在主语部份。这也是广泛使用被动态的主要原因。试观察并比较下列两段短文的主语。
We can store electrical energy in two metal plates separated by an insulating medium. We call such a device a capacitor, or a condenser, and its ability to store electrical energy capacitance .It is measured in farads.
电能可储存在由一绝缘介质隔开的两块金属极板内。这样的装置称之为电容器，其储存电能的能力称为电容。电容的测量单位是法拉。
这一段短文中各句的主语分别为：
Electrical energy
Such a device
Its ability to store electrical energy
It (Capacitance )
它们都包含了较多的信息，并且处于句首的位置，非常醒目。四个主语完全不同，避免了单调重复，前后连贯，自然流畅。足见被动结构可收简洁客观之效。

2. 被动语态的功能

1. functions of passive structure:

1) giving definition and stating rules or principles.

eg: The pressure that makes electrons flow along wires is called voltage.

2) describing prodedure in industrial production and scientific experiment.

3) reporting science news.

 The world’s first test-tube twins were born inMelbourne’sQueenVictoryHospitalat the weekend; it was announced here.

4)in written instructions, warnings and routines.

 Metal surface is prevented from coming into contacts.

3. 被动语态在科技英语中的应用

2. The use of By-phrase in the passive structure:

1) expressing ways and means

  eg: The problem was solved by       intensive research.

2) expressing non-person agent

  eg: The machine is driven by       electricity.

3) ........... standard

  eg: The fare of the transport

      is charged by weight.

4) ..... material force or          power

  eg: The damage was caused by       fire.

5) ... natural phenomena

  eg:  The growth of the plant      was affected by radiation

6) ... collective organization

  eg:  New techniques are       developed by the research        department.

       Large quantities of fuel        are used by modern        industry.