with the same tongue and lips position they different only by the power of vocal cords, i'm not sure but mandarin may have positional variants of "p", "t" and "k" letters, that is intervocal position and position after n and ng, when "p", "t" and "k" become voiced, and sound pretty close to Russian "б", "д" and "л". You can try to feel the difference by put a hand on laryngeal prominence, strong vibration should appear during voiced consonants pronounciation.

"Д" and "Б" are voiced consonants. "Т" and "П" are voiceless consonants. In Russian, there is a clear difference between them, if there is a vowel after them. You can type "балка палка бочка почка забор запор" into the Google translate service, type the loudspeaker icon and listen to these words. Then you can type "дочка точка плоды плоты сдал стал" into the Google translate service, type the loudspeaker icon and listen to these words. However, in some conditions they are pronounced identically. At the end of a word both are pronounced as voiceless. Before voiceless consonants both are pronounced as voiceless. Before voiced consonants both are pronounced as voiced.

Are you familiar with whisper? When you whisper, you speak with airflow only, without the voice. That's how sounds P, T, K, F are produced. When you add voice, you get B, D, G, V.

Д - close - like in word - Deep, Dollar :) Т - close - like in word - Tell, Talk, Time... Try to say Dime :) Spasibo - its different P and B // Pain/Boat. Anyway - here many autotraslators with sound files - http://www.translate.ru/