SAN FRANCISCO, Nov. 17 - Google Inc. plans to announce on Thursday that it is adding a new search service aimed at scientists and academic researchers.
 
Google Scholar, which was scheduled to go online Wednesday evening at scholar.google.com, is a result of the company's collaboration with a number of scientific and academic publishers and is intended as a first stop for researchers looking for scholarly literature like peer-reviewed papers, books, abstracts and technical reports.
 
Google executives declined to say how many additional documents and books had been indexed and made searchable through the service. While the great majority of recent scholarly papers and periodicals are indexed on the Web, many have not been easily accessible to the public.
 
The engineer who led the project, Anurag Acharya, said the company had received broad cooperation from academic, scientific and technical publishers like the Association of Computing Machinery, Nature, the Institute of Electrical and Electronics Engineers and the Online Computer Library Center.
 
The new Google service, which includes a listing of scientific citations as well as ways to find materials at libraries that are not online, will not initially include the text advertisements that are shown on standard pages for Google search results.
 
However, company executives say it is likely that advertisements will eventually accompany search results on Google Scholar. One academic publishing executive, John Sack, director of HighWire Press at Stanford University, said that such advertising could be quite profitable.
 
"The commercial reason for doing this is that you can target areas with high-quality, high-payback ads," Mr. Sack said. "An advertisement that goes next to an article on cloning techniques is probably going to be for services that are pretty expensive."
 
Mr. Acharya, who started the Google Scholar project, said his motivation, in part, had been a desire to help the academic community from which Google emerged.
 
"Google as a company has greatly benefited from academic research and this is one of the ways we can give back to the community," he said.
 
The project was also an effort, said Mr. Acharya, 39, to address a problem he confronted as an undergraduate in India. As a student he found materials in his college library, at times, to be significantly out of date.
 
Google Scholar will make the world's scientific literature universally accessible, he said.
 
"We don't know where the next breakthrough will come from," he said. "We want everyone to be able to stand on the shoulders of giants."
 
"Google's scientific search service is a significant step forward," said Danny Sullivan, editor of SearchEngineWatch, an online newsletter. He was quick to add, however, that Google was certain to have competition soon from Yahoo and others.
 
"We will continue to see an explosion of vertical search engines like this," he said of search services that focus on special collections.
 
Google Scholar is another reflection of changing habits in the academic world, said Mr. Sack of HighWire Press. In the past decade, students and researchers have begun to go to online search engines first.