A.PubMed
B.PMC
C.MeSH
D.Structure
E.All Databases
A.breastcancer[ti]ANDsurgery[ti]publisdinthelast5years
B.BreastNeoplasms/surgery[Mesh]publisdinthelast5years
C.BreastNeoplasms[Mesh]publisdinthelast5years
D.breastcancersurgery[ti]publisdinthelast5years
A.所有主题词按等级纳入到15个大类中,15个大类用字母A~N,Z表示
B.树状结构号后带有“+”表示该主题词还有下位概念
C.主题词按等级展开,展开的等级数最多可达9级
D.每一个主题词有一个树状结构号
A、MeSH Major Topic[MAJR]
B、MeSH Subheadings[SH]
C、Subset[SB]
D、MeSH Terms[MH]