The knowledge which is praised by Allaah in the Qur’aan and Sunnah
Question

                They are many ahadeeths describing the importance of elm(science) and that scientists will have a great reward, so what's meant by elm? is it just the forensic elm that's mentioned in ahadeeths or could it be any kind of elm like biology, physics, electronics etc?
Praise be to Allah.The 
          knowledge mentioned here is the knowledge of sharee’ah which is derived 
          from the Qur’aan and Sunnah. This is the legacy of the Prophets, for 
          the Prophets did not leave behind dirhams and dinars (money), rather 
          they only left behind knowledge. Whoever learns it gains a great deal. 
          When the texts commend knowledge, what is meant is knowledge of the 
          Qur’aan, Sunnah and sharee’ah. This also includes knowledge of nahw 
          (grammar), i.e., the Arabic language, because it is the language of 
          the Qur’aan: knowledge of how inheritances are to be shared out (faraa’id); 
          acts of worship (‘ibaadaat); interactions with others (mu’aamalaat); 
          punishments prescribed in sharee’ah (hudood); the shar’i literature 
          and Arabic literature, for it is the biography of the close friends 
          (awliya’) of Allaah and His righteous slaves. Similarly it is important 
          to know the means to this knowledge, such as Usool al-Fiqh, tawheed, 
          ‘Aqeedah, the basic principles of Islam, etc. With regard to other, 
          worldly sciences which the Muslims need to know, there is no doubt that 
          they come under the heading of fard kifaayah (communal obligation, i.e., 
          if some of the community does it, the rest are absolved of the obligation); 
          those who are able to learn them are obliged to do so, thus fulfilling 
          the obligation of fard kifaayah, because the people are in need of that, 
          so long as that does not prevent them from learning the things that 
          they are obliged to know. Undoubtedly there is benefit in sciences such 
          as biology, chemistry, etc. Many of the scholars were of the view that 
          it is obligatory to learn necessary crafts and industries, and there 
          should be enough people who have these skills, such as blacksmiths, 
          tailors, barbers, etc. 
 Shaykh 
          ‘Abd-Allaah ibn Jibreen 
 And 
          the sciences which Muslims are in need of, such as military skills, 
          are even more essential and more obligatory. And Allaah knows best.