он наверное где-нибудь на лингве или на прозе тот же вопрос перезадал, а ответы - сюда ))

Мало изучены:
Rotary dressing, although becoming widely used, is not well understood.

Изучен недостаточно полно:
This is a partial EHD film regime and little is understood of the damping characteristics of such films.

Наименее изучены:
The lubrication related failures are least understood.

Не полностью изучен:
Many aspects of ionic behaviour in biochemical systems are still not fully (or completely) understood.

Недостаточно исследован:
The region very near the wall has not been
adequately explored (or investigated, or studied).
The mechanism of the process is as yet imperfectly (or little) understood.
The factors influencing gas release are still not clearly understood.

Полностью не изучен:
The factors influencing gas release are (still) not clearly (or completely) understood.

Мало изучен:
These processes are scantily (or poorly) known.