Where can I find the complete tech tree?

Solution 1:

It's really great to know people are still playing SMAC! :)

• StrategyWiki contains a standard version of Tech Tree, with linked articles on facilities, units, and government types.
• This SMAX FAQ is also a great resource to get familiar with.

Another thing is that you should not look at Tech Tree as something ultimate. Depending on a faction you play, you should focus on different techs research order. CivGaming contains some great suggestions, let me just list the major ones:

• Unless playing Hive and Morgan, your goal is instant pop booming. So researching Ethical Calculus and Planetary Networks is almost an ultimate goal;
• If your strategy is builders, Industrial Automation is a must to build supply crawlers;
• Unless one of your opponents are University, try researching Secrets of the Human Brain as it gives an early free tech (Zak often researches it first);
• Your social economics settings, in a combination with faction profile, also highly impacts on what to research first;

Solution 2:

I'm unsure if this is a legal SE answer, but this thread has some links to PDFs that mimic the original game box's tech tree poster. It is the expansion's poster, hence the "ALIEN CROSSFIRE..." across the top. The technologies themselves appear correct.

The thread's comment points to this file, which is one big PDF, and this 4-page version.