Déguó lángquǎn shì chángjiàn de jǐngquǎn pǐnzhǒng.
The German Shepherd is a common police-dog breed.
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狼犬 and 狼狗 both cover wolf-like breeds (especially German Shepherds). 狼犬 sounds more formal/technical - preferred in breed names (德国狼犬, 捷克狼犬) and police-dog contexts; 狼狗 is the everyday word.