When aiming for a scientific victory in Civilization 6, it is best to plan out which wonders you are going to be building towards that victory. There are three total that will help you reach this victory condition, but you'll be very lucky to get two of them in one playthrough, as competing civilizations will often get the other two before you can.
Wonder: Great Library
Required: Recorded History
Provides : +2 Science +1 Great Scientist point per turn and 2 Great Works of Writing slots
Receives boost to all Ancient and Classical era technologies.
Must be built on flat land adjacent to a Campus with a Library
Wonder: Oxford University
Required: Scientific Theory
Provides: +3 Great Scientist points per turn, +2 Great Works of writing slots +20% Science in city, and awards 2 randomly chosen free technologies when completed.
Must be built on flat Grasslands or Plains adjacent to a Campus district with a University.
Wonder: Oracle
Requires: Mysticism
Provides: +1 Culture +1 Faith Patronage of Great People cost 25% less Faith. Districts in this city provide +2 Great Person points of their type
Must be built on hills.
Keep in mind here that both the oracle and great library require civics to unlock them, but are early in the civics tech tree. This means that having a strong culture in the early game is actually going to help you with getting to those civics and unlocking them early to build these, and then you can start focusing on your science to rush to the scientific theory tech for the oxford university.
Wonder: Great Library
Required: Recorded History
Provides : +2 Science +1 Great Scientist point per turn and 2 Great Works of Writing slots
Receives boost to all Ancient and Classical era technologies.
Must be built on flat land adjacent to a Campus with a Library
Wonder: Oxford University
Required: Scientific Theory
Provides: +3 Great Scientist points per turn, +2 Great Works of writing slots +20% Science in city, and awards 2 randomly chosen free technologies when completed.
Must be built on flat Grasslands or Plains adjacent to a Campus district with a University.
Wonder: Oracle
Requires: Mysticism
Provides: +1 Culture +1 Faith Patronage of Great People cost 25% less Faith. Districts in this city provide +2 Great Person points of their type
Must be built on hills.
Keep in mind here that both the oracle and great library require civics to unlock them, but are early in the civics tech tree. This means that having a strong culture in the early game is actually going to help you with getting to those civics and unlocking them early to build these, and then you can start focusing on your science to rush to the scientific theory tech for the oxford university.