intersci: command not found

Have You tried accessing the binary with the full path?

Maybe Your $PATH variable doesn't contain the default paths? echo $PATH should give something like:

[root@server ~]# echo $PATH
/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin

If it's empty, You may set the PATH variable with this command

export PATH="/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin"

On Debian possible default full paths are:

/usr/lib/debug/usr/bin/intersci - from package: scilab-full-bin-dbg
/usr/bin/intersci - from package: scilab-full-bin

You may install the required package with command apt-get install {package}
Error in other languages:
intersci: bevel nie gevind nie
intersci: comandă negăsită
intersci: comando não encontrado
intersci: commande introuvable
intersci: command not found
intersci: käsku ei ole
intersci: không tìm thấy lệnh
intersci: komanda nerasta
intersci: Kommando nicht gefunden.
intersci: kommandot finns inte
intersci: komut yok
intersci: nie znaleziono polecenia
intersci: níor aimsíodh an t-ordú
intersci: no se encontró la orden
intersci: no s'ha trobat l'ordre
intersci: opdracht niet gevonden
intersci: parancs nem található
intersci: perintah tidak ditemukan
intersci: príkaz nenájdený
intersci: příkaz nenalezen
intersci: команда не найдена
intersci: командата не е открита
intersci: 命令找不到
intersci: コマンドが見つかりません