Who ya gonna trust -- "Science" with a capital S, or the Republicans? It's a bit silly as a question, because it's identifying two entities that won't fit entirely into a generalized judgment. But:
Scientific Misconduct
This has its own list on wikipedia. A lot of the examples come from medical research: fraudulent studies that claimed to show that ivermectin could treat covid; many other pharmacological studies; the recent concern that Alzheimer's research stemming from a 2006 study was falsified. Some of those who were shown to be guilty of falsifying results were found guilty of fraud and drew prison terms.
There are well-known examples in anthropology: Piltdown Man and, much more ludicrously, the Cardiff Giant, which can be seen in Cooperstown, NY.
And how were these cases brought to light? By researchers who attempted to duplicate the original studies. In the Alzheimer's case, Science magazine spent six months analyzing the data and images from the 2006 study.
The Repubs
Donald Trump spent 5 years spreading the Birther lie (2011-2016). In that time, how many Republicans came out and disputed his claims? When John Boehner, The GOP Speaker of the House, was asked if he would clear up the matter in a public statement, he made this statement:
"The American people have the right to think whatever they want to think...It's not my job to tell them."
Trump of course has told multiple thousands of lies -- didn't the tabulation get to 30,000 by the end of his Presidency? Just in the last two months he has unleashed these lies:
> American children are going to public school, where they get gender reassignment surgery without their parents' knowledge, and they come home with "brutal operations". (This one is so deranged that it should be made into a Harris ad -- Trump is clearly out of his mind.)
> Trump won the 2020 election AND Trump lost, but "by a whisker". (Again, it's deranged, and it shows the contempt he has for his audience, since he knows he can spout any amount of nonsense and still hold his followers under his spell.)
> The Haitians of Springfield, OH, are there illegally, and they are eating -- do I have to go on?
> The Biden administration has diverted FEMA disaster relief funds to housing for illegal aliens.
> Relief for hurricane victims is capped at $750.
> If you make a claim for relief, FEMA can and will claim your house and property.
Who is calling him out on these destructive lies? There are a few brave outliers in the GOP (Liz C.) who consistently tell the truth about Trump -- and of course Liz has been drummed out of the party. A few Republican governors and legislators have corrected the record on Springfield and on hurricane relief. But the party as a whole sustains Trump and is locked into a slavish relationship with him.
Scientists reform Science. Very few Republicans will tell the truth about Trump.