As a rule of thumb, a cup of filter coffee contains about 80mg of caffeine.凭经验估计，一杯过滤咖啡约含80毫克咖啡因。As a rule of thumb , the minimum device feature is about 4 times the beam diameter.一般来说, 最小器件图形大约是电子束直径的4倍.A rule of thumb ...

a rule of thumb的音标：a rule of thumb的英式发音音标为：[ə ru:l ɔv θʌm]a rule of thumb的美式发音音标为：[e rul ʌv θʌm]...

概测法...