在英文论文中，表示某一特征的“存在”或“出现”可以用以下词汇和短语：
- Occurrence: 表示某事的发生或存在。
- 例句：The occurrence of the mutation was confirmed in multiple samples.
- Existence: 表示某物的存在。
- 例句：The existence of the protein was verified through Western blot analysis.
- Presence: 表示某物的存在或出现。
- 例句：The presence of the marker indicates a positive response to the treatment.
- Appear: 动词，表示出现。
- 例句：The results showed that the symptom appeared in the early stages of the disease.
- Detected: 表示被检测到或存在。
- 例句：The biomarker was detected in all patient samples.
- Manifestation: 表示特征或症状的显现。
- 例句：The manifestation of the disease varies among different patients.
- Observed: 表示被观察到的存在或出现。
- 例句：An increase in cell proliferation was observed after the treatment.
- Identified: 表示被识别或存在的特征。
- 例句：Several key genes were identified in the pathway analysis.
通过这些词汇和短语，可以在英文论文中准确表达某一特征的存在或出现。