Is the phrase "We can see that ..." appropriate in research papers?
The goal of scientific writing is to transfer knowledge and information with high degree of clarity, precision, conciseness, and a reasonably natural tone. When editing written work, a quick litmus test is to slash away each phrase then evaluate if the sentence can do without it. "We can see that..." is a very popular candidate to be slashed because in 99% of the cases, the sentence's meaning wouldn't change:


  "We can see in Table 1 that the average age is 56 years old with a standard
  deviation of 7 years."
  
  "The average age is 56 years old with a standard deviation of 7
  years (Table 1)."


When describing graphs or illustration, we tend to see "We can see that..." a lot more frequently than in other plain text; most of these can also be deleted:


  "In Figure 1, we can see that females are the majority (67%)."
  
  "Females are the majority (67%, Figure 1)."


... or replaced by the graphical components on which that the viewers should focus.


  "In Figure 2, we can see that the sales of graphic novel have been
  steadily increasing since 2011."
  
  "The sales of graphic novel have been steadily increasing since 2011,
  as indicated by the dotted line in Figure 2." OR
  
  "The sales of graphic novel (dotted line in Figure 2) have been
  steadily increasing since 2011"




And a few random thoughts from also an ESL:


I tend to focus on how efficient the sentence is rather than how formal the sentence is. I will, on any day, take a PhD candidate who writes clearly than one who writes formally. "Formal" bad writing scratches the inside of my cranium.
When it comes to writing, I tend to gear away from pragmatic advices that say "You always have to..." or "You never should..." Languages and usages change along time; it's more important to be able to tell my ideas to the current crowd, than to be able to write an ancient script. Beginning learners should feel free to stick to a handful of "rules of thumb," but as the learning progresses they should develop their own judgment and some flexibility.
A journal is only as formal as the editors of that journal go. Check the guideline to authors, read the specified style manual, and read a few current issues for an overall landscape, and then write. Leave all other "formal this" and "formal that" behind.