"it is however clear" is correct and usable in written English.
You can use this phrase when you want to emphasize that a situation is clear despite any uncertainty or ambiguity that may have preceded it. For example: "The legal ramifications of this case are complex, it is however clear that the matter must be resolved in court."
It is, however, clear that some reacceleration is unavoidable in the turbulent interstellar medium.
It is, however, clear that the dark spots must be produced by some active mechanism.
It is, however, clear that the 1970 amendment broadened rather than restricted the Board's discretion to determine whether nonbanking activities are significantly related to banking.
This reform has been judged in many ways, favourably and unfavourably; it is, however, clear that Akhenaton's theology, if not fully monotheistic, in any case strongly tends toward monotheism.
It is, however, clear that until they are the American political class will look less like the elders of the shining city on the hill they claim to be and rather more like kids in a kindergarten playground waiting for an adult to intervene.
It is, however, clear that these interactions are largely predicated on the detergent character of HAs.
It was, however, clear that the classes themselves imperfectly captured patterns of overstory community composition for a number of reasons.
It was, however, clear that already 3 h after PM+Mg2+ exposure a large number of white matter cells (with pyknotic nucleus) were positive to TRPM7.
It was, however, clear that the early response to Fe deficiency was initiated between 1 and 6 h of growth under Fe-deficient conditions.
It is, however, not clear what the Bayesian approach really means.
It is however not clear by which molecular mechanisms ZNF804A increases disease risk.
