"has been frequently reported" is grammatically correct and it can be used in written English.
For example, "An increase in cases of the flu virus has been frequently reported over the past few weeks."
Nanocrystallization of amorphous alloys induced by electronic energy deposition has been frequently reported in recent years.
Air pollution with high ambient concentrations of particulate matter (PM) has been frequently reported in China.
It has been frequently reported that a major problem of Internet business models is that they lack transaction profitability.
The unreliability of the distal skin component of the gracilis myocutaneous free flap has been frequently reported.
Generation of charged nanoparticles in the gas phase has been frequently reported during the synthesis of thin films and nanostructures, such as nanowires, using chemical vapor deposition (CVD).
Moreover, the side effect detrimental to the system's operational stability when TVC is adopted for the MED plant has been frequently reported.
In the literature, it has been frequently reported that PV sleeves possess intrinsic spontaneous pacemaking activity and triggered activity in normal dogs and rabbits.
Apical root resorption has been frequently reported in the maxillary incisor region [28].
Direct discharge of MSW into surface waters has been frequently reported [14, 15].
A correlation between migraine and panic disorder has been frequently reported [14 19] with a bidirectional association [20].
The adhesion of nanoparticles to test organisms has been frequently reported [e.g., 1, 2, 10, 13, 16, 38, 39, 55, 66; Sørensen et al. 2015; 81].
