9. The speech recognition system according to claim 4 , wherein the degree of association calculation means calculates a degree of association on the basis of at least one of: the number of solutions in which individual solutions in the preceding N best solutions agree with individual solutions in the following N best solutions; differences between the ranks based on the recognition scores in the preceding N best solutions and the ranks based on the recognition scores in the following N best solutions, individual solutions in the preceding N best solutions being coincident with individual solutions in the following N best solutions; a time difference between time at which the preceding N best solutions have been output and time at which the following N best solutions have been output; differences between positions on the time series at which the plurality of groups of the preceding N best solutions appear and the positions on the time series at which the plurality of groups of the following N best solutions appear, in a case that a plurality of groups of the preceding N best solutions are obtained by comparing a first utterance with a plurality of recognition vocabularies, and a plurality of groups of the following N best solutions are obtained by comparing a second utterance made by a user who is different from a user of the first utterance with the plurality of recognition vocabularies.
11. The speech recognition system according to claim 9 , further comprising: a time information control means for assigning time information representing a current time to the N best solutions, and for writing the N best solutions including the time information assigned to the recognition result storage, wherein, the smaller the time difference between the current time represented by time information assigned to the preceding N best solutions and the current time represented by time information assigned to the following N best solutions, the higher the degree of association calculated by the degree-of-association calculation means.