The only year Bonds missed significant time to injury was 1999. That was also when he stopped stealing so many bases, changed his swing, bulked up, and his AB/HR ratio started to drop below 10, where it's been since 2000.
Even before that, though, Bonds was one of the most consistent home run hitters in baseball history. He's now on a ML record tying (with Jimmie Foxx) streak of 12 consecutive seasons with 30 or more homers, going back to 1992.
Several things happened in 2001 to enable Bonds to break the record, including having the then-reigning MVP, Jeff Kent, hitting behind him, and Rich Aurillia having a career year (37 hrs) ahead of him. Bonds and Aurillia combined for 110 homers, more than Ruth and Gehrig's 107 in 1927, and second only to Maris and Mantle's 115 in 1961.