In recent years, Linked Data became a key technology for organizations in order to publish their data collections on the web and to connect it with other data sources on the web. With the ongoing change in the research infrastructure landscape where an integrated search for comprehensive research information gains importance, organizations are challenged to connect their historically unconnected databases with each other. In an online survey with 337 social science researchers in Germany, we found evidence that researchers are interested in links between information of different types and from different sources. However, in current scientific portals this is often not yet reflected. In this presentation, we present how Linked Open Data technologies can generally be used to build a backend infrastructure for scientific search portals. This backend infrastructure is set as an additional layer between unconnected non-RDF data collections and makes the links between datasets visible and usable for retrieval via a search index. To address occurring heterogeneity with vague links between datasets, a research data ontology is used in addition for representing different versions and aggregations of research datasets. The LOD backend infrastructure is in use at the search portal of GESIS. The in-use application of our approach has been evaluated in this scientific search portal for the social sciences by investigating the benefit of links between different data sources in a user study. The source code of this project is publicly available.