行政調查 職權調查主義 自由心證 舉證責任 舉證責任之分配 職權調查之範圍 決定重要性 證據必要性 比例原則 當事人協力義務 Administrative investigation Administrative authority investigation Burden of proof Doctrine of distribution of the burden of proof Importance of decision Evidence necessary Principle of proportionality Duty of cooperation