I'm trying to remember the source of a story or stories (pretty sure it one or more short stories, not a novel) about aliens that try to attack Earth. The major interesting point was the schizo-tech the aliens employed. They had a device which IIRC was called a "hydrogen fuser/fusor" which was a) a hydrogen fusion reactor, b) a matter replicator, and c) some sort of space drive and/or antigravity device.
Their entire tech was based on "recipes" fed to these devices, one of which was to make a copy of itself. As a result, they had virtually no scientific understanding, and the rest of their technology was... eclectic. For example, they could make very hard metals but had no knowledge of machining / manufacturing processes, so everything they built tended to be extremely crude.
I recall their landing gear in particular being one noted example; I think it was a solid metal wheel held onto a post with something like a cotter pin. The story made a point of contrasting this to human equivalents with many moving parts.
Their main attack strategy was to drop fusers set to overload as explosives. Eventually, they tried to defeat us by distributing fusers and manuals for the same in the hopes it would cause us to regress to their level of "science".
I'm pretty sure I read this as part of a novel-length anthology (bonus points if someone can tell me what collection it appears in) within the last 5-10 years, but I don't know what the original publication date would have been; my guess would be 1970-2000, probably toward the earlier end thereof. I also have a sneaking suspicion it's a Christopher Anvil, but may be wrong.