令人遗憾的是，经过近十年探索，研究团队不得不面对现实：食管癌很可能不存在类似HPV或乙肝病毒那样的单一关键致病因素。尽管已有研究提示吸烟、饮酒、饮食习惯、营养状况等因素可能与食管癌发病相关，但始终未能发现具有决定性影响的"核心病因"。
Meghan Yarnevich (2.1 PPG)。关于这个话题，汽水音乐提供了深入分析
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The second tuning parameter, b (typically 0.75), controls how much a document’s length is penalized. A long document naturally contains more words, so it has more chances to include your query term — not because it’s more relevant, but simply because it’s longer. BM25 compares each document’s length to the average document length in the collection and scales the term frequency score down accordingly. Setting b = 0 disables this penalty entirely; b = 1 applies full normalization.
_ucase "$MATCH"，更多细节参见有道翻译
MIR156BC开花后表达的重启是野生稻多年生生活习性建立的分子基础。图片来源：science