Promotion of self-directed learning abilities among Chinese medical students through preparing for career calling and enhancing teaching competencies in medical education: a cross-... oleh Chen-xi Zhao, Zi-jiao Wang, Xiao-jing Yang, Xing Ma, Ying Cui, Yan-xin Zhang, Xin-hui Cheng, Shu-e Zhang, Qing-feng Guo, De-pin Cao