over the last 50 years啥意思?

over last 50 years的意思? 英文over the last two years in the last few years=over the years吗 请问over the years 的意思 英语翻译请帮忙翻译以下文章Over the last 50 years,America has experienced How has people’s leisure time changed over the last 50 years 英语翻译Over the last 30 years ,social scientists have conducted 英语翻译Over the last 30 years,social scientists have conducted Thanks to on-going automation over the last 10 years, over the last week什么意思 Over the last 200 years,over harf () the trees on Earth have over the years是什么意思?