The phrase "almost not visible" is correct and usable in written English.
It can be used to describe something that is very difficult to see or barely perceptible.
Example: "The stars were almost not visible due to the thick clouds covering the night sky."
Alternatives: "barely visible" or "hardly noticeable".
They are very thiny and small, almost not visible for human eye and they are responsible for transferring the cerebrospinal fluid from brain convexity into dural vein sinuses.
Two women, one staring at the viewer and one whose head is covered in a shawl (and is almost not visible) are presented with texts regarding equality of pay in the workforce.
This is almost not visible in the 3d-animation, because the 3d display is done with a color-map with transparency-parameter.
For five of the 11 species in Table 1, queens have a reduced T1, almost not visible in dorsal view.
Furthermore, it was found in an animal study that near-infrared autofluorescence associated with RPE melanin was observable in a pigmented rat retina and almost not visible in the albino rat retina [ 52].
MA protein is not detected at all in viral particles, and the differences in CA level are almost not visible, going against the whole proposed mechanism that AMOT is able to surpass the lack of PTAP in crippled HIVGag.
The process was hazardous: semantic forms are almost by definition not visible on the surface, and there is no purely syntactic form that guarantees validity of an argument.
In other realms, we're already moving toward a future when the most dazzling and successful technologies are not visible and work almost by magic.
The results showed that, for stoichiometric rutile, the optical absorption in the visible region is almost not influenced by proton implantation but that in ultraviolet region is influenced.
This deformation is observed with almost the same magnitude in three independent interferograms but is not visible in any pre-seismic interferograms.
Robert Musil wrote that nothing is as invisible as a monument; this un-monumental memorial was distinctly visible, and yet so discreet as to be almost not there.
