spontaneouslyadv.自发地；自生地；自然产生地spontaneousadj.自发的，自然的，本能的；自然产生的spontaneous scattering自发散射spontaneous conception自然妊娠spontaneous hydrolysis自发水解spontaneous regression自发性回归spontaneous hemothorax自发性血胸spontaneous adsorption自发吸附现象spontaneous ionization自然电离spontaneous nucleation自然结晶spontaneous thick seam易燃厚煤层spontaneous background自然本底