to no avail的用法和樣例：
例句
- His intervention was of no avail.
他的調停無(wú)效。 - His claim to ownership is invalid.
他的所有權是無(wú)效的。 - This is a subject into which many scientists have researched with no result.
這是一個(gè)雖經(jīng)很多科學(xué)家研究過(guò)但尚無(wú)結果的課題。 - Seven patients had abnormal urinalysis but no positive finding in culture.
七位病人之尿液常規檢查顯示白血球增多但培養無(wú)結果。
