1. Technical barriers: Technical barriers refer to some advanced countries or enterprises that keep their technology in the leading position to a certain extent by mastering high and new technologies and strengthening intellectual property protection. These technical barriers may restrict other countries or enterprises from obtaining high-end technology, thus hindering the international flow of R&D elements.
2. Insufficient protection of intellectual property rights: Insufficient protection of intellectual property rights means that the risk of infringement of intellectual property rights is increased, which may easily lead to a large amount of investment in technological innovation being illegally occupied by infringers, thus limiting the further development and application of new technologies.
3. Strategic restrictions: For security or other strategic reasons, some countries or enterprises may restrict the export of key technologies and patents to prevent the disclosure of technologies or intellectual property rights. This strategic restriction may reduce the international mobility of R&D elements and affect the process of technological innovation. These are all factors that hinder the flow of R&D molecules.