Perhaps you should try some spelling variations:
"beiras en investigacion" » "beiras e investigacion", "beiras la investigacion", "letras en investigacion", "negras en investigacion"
"detras de investigacion" » "detras la investigacion"
"temas ciencia investigacion" » "temas ciencias investigacion", "textos ciencia investigacion", "alma ciencia investigacion"

Try widening your search to All Fields.

You may be able to get more results by adjusting your search query.

• Performing a fuzzy search may retrieve terms with similar spellings: (("temas ciencia investigacion") or ((("detras de investigacion") or ("beiras en investigacion"))))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (("temas ciencia investigacion") OR ((("detras de investigacion") OR ("beiras en investigacion")))).
• Removing quotes may allow a broader search: (( temas ciencia investigacion ) or ((( detras de investigacion ) or ( beiras en investigacion )))).
• Adding a wildcard symbol may retrieve word variants: (("temas ciencia investigacion") or ((("detras de investigacion") or ("beiras en investigacion"))))*.