We just came to look for a pencil and paper for Patros.

No venimos más que a buscar lápiz y papel para Patros.

—PÉREZ GALDÓS.

For you must know, my son, that the dreaming of the old is just remembering.

Porque has de saber, hijo mío, que el soñar de los viejos es sólo recordar.—MARTÍNEZ SIERRA.

It was just the door closing.

Era la puerta que se cerraba, nada más.

(b) Meaning at this or that moment, just is translated en este or ese mismo momento; or it may be implied in the present or imperfect tenses.

The door is just closing.Se cierra la puerta.
The door was just closing. Se cerraba la puerta.

The phrase en este mismo momento makes the just more emphatic.