8. Sources of Research Articles

To gather literature, researchers must use various information formats. The most prominent tools today are categorized into physical/library types and academic search engines.

Primary vs. Secondary Sources

• Primary Journals: Publish results of original research. They carry the latest and highly specific accounts of current work, peer-reviewed for quality.
• Secondary Journals & Books: Publish review articles or teaching materials summarizing existing work. Books include textbooks, yearbooks, manuals, and directories. Books may lack the absolute latest findings due to long publishing times but provide excellent foundational knowledge.

Major Academic Search Engines & Databases

Rather than relying on basic web searches, specialist search engines are used to mine academic and scientific contents:

1. Google Scholar: Indexes full-text and metadata of academic literature across all disciplines. Features citation counting (h-index, i10-index) and a 'cited by' feature.
2. Entrez: A federated search engine for life sciences operated by the NCBI, allowing simultaneous searches of multiple biomedical databases.
3. PubAg / AGRICOLA: Maintained by the USDA for agricultural information. PubAg contains full-text peer-reviewed articles; AGRICOLA serves as the public catalogue for the National Agricultural Library.
4. Microsoft Academic: A massive multidisciplinary search engine that provides citation analysis and domain-specific filtering.
5. BASE (Bielefeld Academic Search Engine): One of the world's largest search engines for academic web resources, ensuring scientific relevance.
6. CiteSeerX: Concentrates on computer and information science with active document retrieval and citation indexing.
7. WorldWideScience.org & Science.gov: Global and US-federated search engines that access 'deep web' databases not searchable by commercial search engines.
8. ResearchGate: A deeply popular social networking site for academics where researchers upload papers, preprints, data, and collaborate directly. Accounts require institutional emails to verify researcher status.
9. Directory of Open Access Journals (DOAJ): An online directory indexing over 12,300 high-quality, fully open-access, peer-reviewed journals.

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