To pick more than one parameter from the list, you may need to hold down the Shift key, or the Control key, if the parameters are no consecutively listed.
The operators AND and OR are provided to assist users in developing a query that includes or excludes the parameters of interest. OR is most useful for searching with similar terms and synonyms. AND is more useful for finding data that will typically contain a set of specific parameters.
For example, you may wish to find all data objects containing Oxygen. Note that there are quite a few parameters that begin with the recommended "o2". However, there are some datasets that use "oxy" for this element. If you conduct a search using "o2" as well as its variants and "oxy" and combine these terms with OR, all data objects found with either name will be included in the result.