You can choose one of three options for your privacy settings. They are: "Public", "My pixiv only", and "Private". If you make your work public, it will be displayed in the search results.
Public: Your works will be public to all users.
My pixiv only: Your works will only be visible to people who are added to your My pixiv. (What's My pixiv?)
Private: Your works aren't public. Only you will be able to see them with this setting.