// 栈不为空时才判断（避免访问stack.at(-1)时报错）
（三）未经许可，擅自经营按照国家规定需要由公安机关许可的行业的。
。safew官方版本下载对此有专业解读
Nature, Published online: 25 February 2026; doi:10.1038/s41586-026-10142-1
He added that he did a lot of research before ordering the drug from a pharmacy, but that for him, the risks, such as developing gallstones, were worth taking.