Numerical search tags can be applied to the following values: attack, health, mana, and owned. Examples of some of the types of searches you can do can be found below:

attack:1Only find cards with an attack value of 1
health:7+Only find cards with a health value of 7 or greater
mana:5-Only find cards with a mana cost of 5 or less
attack:3-5Only find cards with an attack value between 3 and 5, inclusive
owned:1Only find cards that you own a single copy of
mana:oddOnly find cards with an odd mana cost
mana:evenOnly find cards with an even mana cost
rarity:<value>(free, common, rare, epic, legendary)
type:<value>(minion, spell, weapon, hero)

We’ve also added a few special keywords to help you better filter your Collection:Keep in mind you can use the same numerical parameters for any of the four search tags mentioned above.

extraShow all cards you have more than 2 copies of, including golden cards
goldenShow only golden cards
missingShow any cards you don’t have (only works in Card Crafting mode)
newShow any “New” cards in your collection
has:textfor example: “battlecry”

You can also combine these tags to make your search even more specific. Find all minions with 3-attack and 3-health by using the attack:3 health:3 search tag combination. Admire all of your golden epics with a golden epic search. Or use extra rare to look for extra rare cards you can disenchant to craft some new cards.

Source: https://playhearthstone.com/en-us/news/20056284