根据gensim文档中的 .show_topics()方法，其默认 num_topics 参数值(要返回的主题数")为10:

According to the gensim documentation for the .show_topics() method, its default num_topics parameter value ("Number of topics to be returned") is 10:

https://radimrehurek.com/gensim/models/ldamulticore.html#gensim.models.ldamulticore.LdaMulticore.show_topics

如果希望它返回10以上，请为该方法的 num_topics 参数提供首选的非默认值.例如:

If you want it to return more than 10, supply your preferred non-default value for that method's num_topics parameter. For example:

len(lda_sentence_model.show_topics(formatted=False, num_topics=15))