patzer2: Curious game! The move 38...Qd4+! would have given Black a three-fold repetition of moves for a draw. However, I don't know if Black overlooked it or over-estimated his chances with the inferior 38...Qg7? .
Either way, White demonstrates superb technique in punishing this mistake in the strong continuation after 39. Kg2! . After the unusual pinning move 44. Qe6! (Queen pinning a Queen), Black's position is hopelessly lost.
Black resigned in the final position, I suppose, because he correctly figured White would bring up his King and eventually win the pawn on h6 with a won endgame. However, the win is not so easy and Black might have held out a few more moves to see if White would find the winning line(s).
In any event, here's my analysis of the final position, as a win for White:
<52. Ng4 Nf8 1-0> Black resigns in lieu of such possibilities as 53. Nh6+ Kh8 54. Bf7!
[Not 54. Nf7+? Kg8 55. Nh6+ (Certainly Not 55. Nxd6?? Nxg6 , which allows Black to turn the tables and win.) 55... Kh8 56. Nf7+ Kg8 57. Nh6+ = with only a draw by repetition]
54... Kh7 (54... Nd7 55. Kf3 Kh7 56. Ng8 Bf8 57. Kg4 Kh8 58. Kg5 Nb6 ) 55. Ng8 Bd8 56. Kg4! (Not 56. Bxd6?? Nf5+ ) 56... Ng6 57. Bxg6+ Kxg6 58. Bxd6 Kf7 59. Nh6+ Kg6 60. Bf4 Nh5 61. Be3 Nf6+ 62. Kf3 Bb6 63. Ng4 Nxg4 64. Kxg4 Kf7 65. Kf5 Ke7 66. Bf4 Kd7 67. d6 Bd8 68. Bg5 Bb6 69. Ke5 Ba7 70. Kd5 Bb8 71. Bf4 Ba7 72. Be3 Bb6 73. Bxc5 Bd8 74. Bd4 Kc8 75. c5 .