I still find the section of the source text quoted a little difficult to understand (but then I find impact factors generally a bit difficult). However, I think this is probably what they're referring to. My reservation is that they seem to be talking about the "ventana de exposición" of a particular article, whereas "publication window" normally applies to a period of publication of a journal, whereby all the articles published during that period are taken into account. The other standard "window", the citation window, is the period during which citations are counted. The point is that in calculating impact factors, there's no point in counting citations of an article as soon as it is published, because obviously it will take a while, a year or two, before people start citing it. But also you don't make the publication window too long, because it's considered that after a certain amount of time an article is no longer making a real impact on the field.

Anyway, the English terms first:

Jo Cross (Market Research Manager, Taylor & Francis/Routledge), "Impact Factors – Back to Basics", Editors’ Bulletin, Vol. 1, No. 2, 23–30, July 2005.
"[...]
Calculating an impact factor requires a denominator (the total number of articles published) and a numerator (the total number of citations received by those articles). A time period, or ‘window,’ needs to be defined for both these variables.
The publication window is the period during which the articles included in the calculation were published. The citation window is the period during which citations to these articles were counted."
https://www.tandfonline.com/doi/pdf/10.1080/1752174070169589...

"Exposición" is a very unusual word to use in this field. Here is an example from an article in Spanish, "El Factor de Impacto: su popularidad, sus impactos y la necesidad de preservación del proceso de generación del conocimiento científico", by a Brazilian author; I don't know whether there's interference here from Brazilian Portuguese:

"Utilizar el Factor de Impacto en evaluaciones significa basarse en un análisis restringido a las citaciones a los periódicos indexados en la Web of Science (interfaz web que tiene acceso no solo al SCI como a sus bancos complementarios en ciencias sociales, artes y humanidades). Se añade a ello la restricción a las citaciones a los artículos recientes, ya que considera su primero y segundo años de exposición, es decir, si un periódico tiene sus artículos de determinado año citados después de dos años, no se está considerando el impacto de ese periódico."
http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0080...

I think it's clear that "años de exposición" here means "years of publication", and I believe it's the same in your text.

But "years of publication" can be applied to a particular article, meaning the number of years since it was published, which is the sense in your text:

"Article influence: a measure of the average influence per article of papers in the journal in the first five years of publication."
http://rsfs.royalsocietypublishing.org/citation-metrics

The "first five years of publication" here must mean the first five years after publication.

So I think that "ventana de exposición" means "publication window", although the term is apparently being used in a slightly unusual way.