GB国家标准 GB 7974-1987 纸及纸板白度测定法(漫射/垂直法) GB 7974-1987.Paper and board- Measurement of brightness(Diff/o-geometry). GB 7974以Ds光源、漫射/垂直照明观测条件下纸... 01月02日GB 7974 阅读全文