zhè / zhǒng / tóng / wèi / sù / de / fàng / shè / xìng / huó / dù / huì / suí / shí / jiān / zhú / jiàn / jiàng / dī

这种同位素的放射性活度会随时间逐渐降低。

The radioactive activity of this isotope gradually decreases over time.