Search the Internet in the way of relevant documents， mostly input keywords to the search engine to query ， and then， according to the importance of search engine To show the relevant documents available to the user. Using this transfer System check mode， it is difficult to observe and keyword-related events Trend. However， most of the documents have TimeStamp， if we can use the TimeStamp of documents， We can observe the keyword to a different continuous time interval Number of occurrences， understanding and the keywords related events and trends. In this study， we use a technology of Inverted-Index like search engine to use， computing time for each word in each unit The number of occurrences， as the termhistory. On the other hand， the In a large number of documents dealing with the calculation and storage of facing the problem of We use the Divide and Conquer algorithm method， first a large number of original documents， according to the time divided into many smaller units of time (monthly) file， and then marge termhistory of small units into large units (annually) Order termhistory. In experiment， we use PubMed literature and will be a long time A lot of literature， the termhistory of keywords into the use of Can provide through the Google cloud computing the interface， Enter keywords used to query the historical series， converted into charts Presented in a way showed that the use of the historical sequence of keywords， We can observe the trend of events related to the change.
