Jiefang Ribao is included in WiseSearch (https://wisesearch6.wisers.net/) from Wisers in Hong Kong starting from the issues August 2000 onwards. Many libraries subscribe to this database.
You can also try the 全国报刊索引 (https://www.cnbksy.com). They have indexed 解放日报(上海) 1955-2019 (but I am not sure how complete the index is). You can order individual articles for scanning. Some libraries offer to cover this for their readers.
Best wishes,
Joshua Seufert
Chinese Studies Librarian
East Asian Library
Princeton University
email: jseufert@princeton.edu