Data for analysis in "A tipping point for open citation data"

Metadata used for the analysis in the article "A tipping point for open citation data" appearing in Quantitative Science Studies, 2021. Metadata were adapted from the NIH Open Citation Collection (NIH-OCC, https://doi.org/10.1371/journal.pbio.3000385) and the PubMed Knowledge Graph (PKG, https://doi.org/10.1038/s41597-020-0543-2).<br><br>The NIH-OCC, for which a more recent update is available than the PKG, was truncated at the max PubMed Identifier (PMID) found in the PKG, to ensure the comparison of the two covers the same range of articles.<br><br>nihocc_and_pkg.csv.gz: Gzipped citations from the NIH-OCC that were also found in the PKG (2 columns, citing PMID followed by referenced PMID)<br><br>nihocc_not_pkg.csv.gz: Gzipped citations from the NIH-OCC that were not found in the PKG (2 columns, citing PMID followed by referenced PMID)<br><br>pkg_not_nihocc.csv.gz: Gzipped citations from the PKG that were not found in the NIH-OCC (2 columns, citing PMID followed by referenced PMID)<br><br>The paper describing the PKG is provided under a CC-BY 4.0 license, and Creative Commons Public Domain Dedication applies to the metadata files associated with that article https://doi.org/10.1038/s41597-020-0543-2). The paper describing the NIH-OCC and the NIH-OCC itself are both public domain (https://icite.od.nih.gov).<br>

本数据集元数据用于发表于《定量科学研究》(Quantitative Science Studies)2021年的论文《开放引用数据的临界点》(A tipping point for open citation data)中的分析工作。本元数据改编自美国国立卫生研究院开放引用集(NIH Open Citation Collection, NIH-OCC，https://doi.org/10.1371/journal.pbio.3000385)与PubMed知识图谱(PubMed Knowledge Graph, PKG，https://doi.org/10.1038/s41597-020-0543-2)。

相较于PKG，NIH-OCC拥有更新版本，为确保二者覆盖的文献范围一致，我们将NIH-OCC截断至PKG中出现的最大PubMed标识符(PMID)。

nihocc_and_pkg.csv.gz：经gzip压缩的引用数据集，包含同时存在于NIH-OCC与PKG中的引用条目（共2列，依次为引用文献PMID与被引文献PMID）

nihocc_not_pkg.csv.gz：经gzip压缩的引用数据集，包含仅存在于NIH-OCC但未在PKG中出现的引用条目（共2列，依次为引用文献PMID与被引文献PMID）

pkg_not_nihocc.csv.gz：经gzip压缩的引用数据集，包含仅存在于PKG但未在NIH-OCC中出现的引用条目（共2列，依次为引用文献PMID与被引文献PMID）

描述PKG的论文采用CC BY 4.0许可协议发布，该论文关联的元数据文件适用知识共享公共领域授权（https://doi.org/10.1038/s41597-020-0543-2）。描述NIH-OCC的论文及NIH-OCC本身均属于公共领域（https://icite.od.nih.gov）。