Passive voice is common in academic discourse since it is often felt necessary to shift the focus from human agency to the actions, processes and events being described. In academic writing in particular, foregrounding the writer/researcher in such processes is often felt to be inappropriate:

A total of 14 case studies were recorded. The data were analysed using principles of conversation analysis and thematic analysis set within a hermeneutic interpretative framework. In order to illuminate presentations of autonomy in practice, focus-group discussions with nurses and older people were useddiscuss the factors that prevented the operationalisation of an individualised rights-based concept of autonomy for older p as part of the interpretative process. I eople.

Note how the research process is described in the passive voice (were recorded, were analysed, were used), while the author changes to active voice (I discuss) when signposting the section dealing with personal stance and evaluation of the research.

Passive voice (along with the present tense) is particularly prevalent in abstracts to academic papers and articles:

The urban hierarchy of an English region in the period 1300-1540 is defined, using both documentary and archaeological evidence. The part of the East Midlands studied – Leicestershire, Northamptonshire and Rutland – contained twenty towns. ‘Benchmarks’ for placing towns in the hierarchy are explored. Including population, topography, social structure, occupational diversity, marketing and migratory networks, administration, and civic and material culture. The conclusion emphasizes the common urban characteristics of all of the towns studied, the compatibility of written an unwritten evidence, and the stability of the urban system.

Note here that active voice (emphasizes) occurs with the impersonal subject the conclusion (compare the alternative constructions which would foreground the researcher: I conclude/ I emphasize in the conclusion).

However, personal subjects and active voice verbs do occur frequently in academic discourse, particularly where a researcher is laying claim to a different or new approach to something, or contrasting their approach with that of others:

The acquisition of the English past tense inflection is the paradigm example of rule learning in the child language literature and has become something of a test case for theories of language development. This is unfortunate, as the idiosyncratic properties of the English system of marking tense make it a rather unrepresentative example of morphological development. In this paper, I contrast this familiar inflection with a much more complex morphological subsystem, the Polish genitive.

Personal subjects and active voice are also common where speakers/writers provide textual signposting:

Throughout the literature, these pedagogical themes emerge: build a large sight vocabulary, integrate new words with the old, provide a numbers of encounters with words, promote a deep level of processing, facilitate imaging and concreteness, use a variety of techniques, and encourage independent learner strategies. I will now discuss each item in turn.
(compare: Each item will now be discussed in turn.)

I think is less commonly used in academic writing than in everyday language, and expressions such as in my view / opinion, I would argue / suggest, it is reasonable to suppose / conclude / suggest / etc. are preferred when the writer is giving a personal opinion:

I would argue that different models are appropriate at different times.
(instead of I think that different models are appropriate at different times.)

Get-passives are very rare in academic writing, but are more frequent in spoken academic style:

[lecture about the alimentary system]
So particularly in middle-aged people who take Amatrozol, the"re at a great risk of food poisening because the bugs which the acid kills off don't get killed and they make it down through the gastrointestinal tract and five them a nasty case of food poisening.
('... are not killed' would be expected in written academic style)

Get-passives and be-passives may occur side by side in spoken academic style:

[microbiology lecture]
Many viruses get taken up by cells of the immune system of one sort or another. And they get transported to the lymph nodes and swollen lymph nodes is a common feature of many virus infections. And what's happening is that as the virus is taken to the lymph nodes, there is an intense immune response within the lymph nodes so the lymph node swells in an attempt to try and eliminate the virus infection.