science-chemistry: command not found

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/bin/science-chemistry - from package: science-chemistry

You may install the required package with command apt-get install {package}

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