Frequency of quotation is an important index to measure the social prominence and academic influence of a paper in document metrology Through measuring the times being quoted after the paper is published, appraisal by frequency of quotation evaluates research achievement in the form of academic papers It is a way to evaluate periodicals, disciplines (majors), countries (districts) and units (individuals) related to certain academic papers Appraisal by frequency of quotation is a research achievement appraisal system with academic papers as its carrier advocated by American Scientific Information Research Institute and widely acknowledged in the world Nowadays it seems to be the only method to appraise the quality of papers published in journals and the academic standard of a discipline (major), a country (district) and a unit (individual) Actually, appraisal by frequency of quotation is not omnipotent; it has its own range of application It can be applied to basic research but not to development research It has its limitation when applied to application research In one word, appraisal by frequency of quotation has its adaptability, limitation and irrationality