必不可少

It is noted to that this binuclear nickel complex is able to catalyze ethylene polymerization as single-component catalyst.

值得注意的是，该化合物可以作为单组份催化剂催化乙烯聚合。

From the beginning of the use of bombax guitar to a professional Spain now playing with top-qin, have proved that China's market prospects for the guitar is remarkable.

从刚开始人们使用的红棉吉他到现在专业的西班牙顶级演奏用琴，无不证明了中国吉他市场的前景是令人瞩目的。