# 可用检索选项

创建在线数据库连接后，有些可用的检索选项

* 检索字段内容些许改变
* Match Case 和 Match Words **不可用**
* 不同数据库的字段(如 Author，Title，Keywords)不同，并且与本地搜索的字段也不同([在线数据库检索和本地数据搜索比较](https://app.gitbook.com/s/-LrgCHEEK5wsSALfCziF/online-databases/online-database-searching/Searching_ENFldsvRmtDBIndx.htm))
* 下列字段不可用： PDF，Any Field + PDF with Notes，PDF Notes
* 比较运算符只有 Contains


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# Agent Instructions: Querying This Documentation

If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter:

```
GET https://kb.howsci.com/online-databases/online-database-searching/ke-yong-jian-suo-xuan-xiang.md?ask=<question>
```

The question should be specific, self-contained, and written in natural language.
The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.