这个词是什么意思？
A group of elements that include SCANDIUM; YTTRIUM; and the LANTHANOID SERIES ELEMENTS. Historically, the rare earth metals got their name from the fact that they were never found in their pure elemental form, but as an oxide. In addition, they were very difficult to purify. They are not truly rare and comprise about 25% of the metals in the earth's crust.
中文名称索引；定义为 MeSH 英文原文，尚未逐条译审。MESH:D008674 · MeSH 2026。
Courtesy of the U.S. National Library of Medicine. Annual snapshot; later updates may not be reflected. NLM does not endorse this service.