“刻苦钻研”可以翻译为 “study assiduously/diligently” 或 “delve deeply into（something）with great perseverance” 。
“study assiduously/diligently” 强调以专注、勤奋的态度进行学习或研究，突出“刻苦”和“钻研”的持续性和专注性。例如：He has been studying assiduously to improve his skills.（他一直在刻苦钻研以提高自己的技能。）
“delve deeply into（something）with great perseverance” 侧重于深入探究某一领域或问题，体现出不畏艰难、持续探索的精神，更加强调“钻研”的深度和决心。例如：She delves deeply into ancient history with great perseverance.（她刻苦钻研古代历史 。）