Is there a united resource or program to search public domain works?
By united I mean it searches in more than 1 website for my search term.
The internet archive https://archive.org/ lists both works they host as well as works in other libraries. While most (all?) of the ebook are available without cost the majority are public domain works, there are also many Create Commons & fair-use works. There is not a good way to search for only PD works, but due to the type of results returned that should not be an issue for most users. The works that are not PD, are mostly appropriate for attribution sharing, which mostly allowed.
(There are not any absolutes here)
Selecting texts will return everything that is mostly written words. From single page documents to books. This is approximately equal to 'ebooks'.
If you're looking specifically for public domain/open licensed works rather than simply works that are available for free, you can always use Google's Advanced Search options to find works that are filtered by usage rights--you can select:
- Free to use or share
- Free to use or share, even commercially
- Free to use, share, or modify
- Free to use, share, or modify, even commercially
It's not an ebook-specific search, but if you include the file format you're looking for, and perhaps a keyword like "download", you'll get reasonable results.
Apart from Internet Archive mentioned by Mr. Jenkins: https://archive.org/
You could try Project Gutenburg, which has a search bar on the top left hand corner:
Their site says:
Project Gutenberg offers over 42,000 free ebooks: choose among free epub books, free kindle books, download them or read them online.
We carry high quality ebooks: All our ebooks were previously published by bona fide publishers. We digitized and diligently proofread them with the help of thousands of volunteers.
Here is a list of their "Partners, Affiliates and Resources" which has listings for over 100,000 books:
As a last resort (unless you live in Australia) Project Gutenberg of Australia is good if you're looking for something that you cannot find elsewhere, or as the the above link explains:
As a general rule the works of authors who died before 1955 are in the public domain in Australia. Works by George Orwell (died 1950), Virginia Woolf (died 1941), and James Joyce (died 1941), just to name a few authors, are in the public domain in Australia.
This applies to just Australia, and they go on to say:
Works which are in the public domain in Australia may remain copyrighted in other Countries, even for several decades. People may not download, or read online, such works if they are in a country where they are still under copyright. That still leaves a lot of readers out there to enjoy etexts of some of the greatest literary works of the twentieth century.
Good Luck! :)