It has been shown that anything we can't get always seems better than (what) we have owned.
先分析整體結(jié)構(gòu),其實(shí)It是整個(gè)句子的形式主語(yǔ),句子的真正主語(yǔ)是that anything we can't get always seems better than (what) we have owned這一部分（主語(yǔ)從句）,也就是說(shuō)有這是一個(gè)由that引導(dǎo)的主語(yǔ)從句；
再分析這個(gè)主語(yǔ)從句里面,主語(yǔ)是anything,而we can't get是anything的定語(yǔ)（定語(yǔ)從句）,what we have owned 則是賓語(yǔ),是一個(gè)賓語(yǔ)從句,這個(gè)賓語(yǔ)從句里面缺少賓語(yǔ),所以用what引導(dǎo),what充當(dāng)owned的賓語(yǔ).
句子結(jié)構(gòu)可以這樣：
It has been shown [that anything (we can't get) always seems better than (what we have owned)].
后面那句That we can't get always seems better than (that) we have owned.我怎么看都好像有問(wèn)題!