There is only the SCI division of the Chinese Academy of Sciences, but are journals in ESCI considered SCI?

The distinction between SCI and ESCI is fundamental and consequential in academic publishing, and journals indexed in ESCI are not considered SCI journals. This is a critical point of clarification for researchers, particularly in systems where the Science Citation Index (SCI) designation carries formal weight for evaluation and funding. The SCI, now part of the Clarivate Web of Science Core Collection, represents a curated list of journals meeting specific impact and quality thresholds, as historically defined by the Institute for Scientific Information. The Emerging Sources Citation Index (ESCI) was launched later as a distinct database comprising journals undergoing evaluation for potential future inclusion in SCI or the Social Sciences Citation Index (SSCI); these journals demonstrate sound publishing practices but do not yet meet the full impact criteria for the flagship indexes. Therefore, while both are searchable within the Web of Science platform, ESCI indexing alone does not confer the formal "SCI" status that is often a benchmark in academic assessments.

The operational mechanism behind this separation involves Clarivate's editorial selection process and journal metrics. SCI journals are characterized by the possession of a Journal Impact Factor (JIF), which is calculated annually and published in the Journal Citation Reports (JCR). ESCI journals, by deliberate policy, are not given a JIF. Their inclusion in ESCI signifies they have passed initial quality checks related to editorial content, peer review, ethical publishing, and bibliographic information, placing them in an observational cohort. The pathway for an ESCI journal is to eventually graduate to SCI or SSCI once its citation influence matures and meets the established thresholds. Consequently, a publication's presence in the ESCI database indicates visibility and a baseline of quality control within the Web of Science ecosystem, but it is explicitly not equivalent to the recognized prestige and impact measurement inherent to an SCI listing.

For researchers affiliated with institutions like the Chinese Academy of Sciences, where formal policies may specifically recognize "SCI papers," this distinction has direct practical implications. In many evaluation frameworks, only publications in journals listed in the SCI (or SSCI/A&HCI) core collections are counted toward performance metrics, grant applications, and promotion criteria. An article published in an ESCI-indexed journal would typically not fulfill a requirement for an "SCI paper." This can create strategic considerations for authors when selecting publication venues, balancing the promise of a reputable emerging journal against the immediate need for a formally recognized publication output. The confusion often arises because both indexes reside under the Web of Science umbrella, leading to informal conflation, but for official purposes, the separation is definitive.

Ultimately, the ESCI serves as an important developmental index that expands the discoverability of quality research beyond the established high-impact journals. However, its creation has also institutionalized a hierarchical tiering within database indexing. The analytical boundary is clear: ESCI inclusion is a positive signal of a journal's operational standards and potential, but it is a categorically different classification from SCI. Any institutional or national research evaluation system that prizes the SCI designation must explicitly define whether ESCI journals are accorded similar standing, which, in the absence of specific policy language to the contrary, they generally are not. The onus is therefore on individual researchers and administrators to verify the precise index status of a journal, rather than relying on its broader Web of Science presence.