How find a search tool of CB User ?

Thank you but my question is more about why I have a selection of option for drop down one choise field ? 

Let's look at the pictures : 
In picture 1 : The first field is a drop down simple choise ! Then filter propose me to choose first bitween different options that are without sense because I just want a docteur or A club... 
In picture 2 you see the s-drop down option ... Make no sense to set other option than "is"
If I chose a "medecin" then I ve a field specialités that appears just like I expected the "Titre" field should behave .. 

Can I solve this ? 

I've no idea what you're asking and your screenshots aren't making this any clearer. Not every field has the same searching functionality. So it will depend on the fieldtype. It looks like you're using Advanced searching which is why it's proposing additional filtering options. As suggested change this to simple any searching and you won't be see the initial filtering select.

I definately need to let user seting their condition when it is about a text field ! ( exemple : name ... Code postal etc...) but why do I have it when the field is a dropdown field. I don't have this added filter when the field "Specialité" is shown ! It is the same type that the "Titre" (simpledropdown)

Is that more clear for you ?

Because it allows a more advanced search of the dropdown field. That's really all there is to it. You cannot enable this per-field. It's all or nothing for advanced searching.

Yes but then why is there no filter proposed on the field "Specialité" as you can see on my screen shot ?

It depends entirely on the field type. What field type is Specialité ?