Open Access Guide

A skill for understanding open access publishing models, locating free full-text articles legally, and navigating self-archiving policies. Essential for researchers at institutions with limited journal subscriptions.

Open Access Models

Types of Open Access

Type	Description	Cost to Author	Reader Access
Gold OA	Published OA by journal (APC paid)	$1,000-$11,000	Immediate, permanent
Green OA	Self-archived preprint/postprint	Free	After embargo (0-24 months)
Diamond/Platinum OA	Journal charges no APC	Free	Immediate, permanent
Bronze OA	Free to read on publisher site	Free	No reuse license, may be temporary
Hybrid OA	OA article in subscription journal	$2,000-$5,000	Immediate for that article

Checking OA Status

import requests

def check_oa_status(doi: str) -> dict:
    """
    Check open access availability using the Unpaywall API.

    Args:
        doi: DOI of the paper (e.g., '10.1038/s41586-021-03819-2')
    Returns:
        OA status and best available link
    """
    email = "researcher@university.edu"  # Required by Unpaywall API
    url = f"https://api.unpaywall.org/v2/{doi}?email={email}"

    response = requests.get(url)
    if response.status_code != 200:
        return {'error': f'API returned status {response.status_code}'}

    data = response.json()

    # Find best OA location
    best_location = data.get('best_oa_location', {})

    return {
        'doi': doi,
        'title': data.get('title', ''),
        'is_oa': data.get('is_oa', False),
        'oa_status': data.get('oa_status', 'closed'),
        'journal_is_oa': data.get('journal_is_oa', False),
        'best_oa_url': best_location.get('url', None) if best_location else None,
        'version': best_location.get('version', None) if best_location else None,
        'license': best_location.get('license', None) if best_location else None,
        'all_locations': len(data.get('oa_locations', []))
    }

# Example
result = check_oa_status('10.1038/s41586-021-03819-2')
if result['is_oa']:
    print(f"OA available: {result['best_oa_url']}")
else:
    print("Not openly available -- check Green OA options below")

Legal Full-Text Sources

Repositories and Aggregators

Source	Type	Coverage	URL
PubMed Central (PMC)	Repository	Biomedical + life sciences	ncbi.nlm.nih.gov/pmc
arXiv	Preprint server	Physics, CS, Math, Stats	arxiv.org
bioRxiv/medRxiv	Preprint server	Biology, medicine	biorxiv.org / medrxiv.org
SSRN	Preprint server	Social sciences, law, economics	ssrn.com
Zenodo	Repository	All disciplines	zenodo.org
CORE	Aggregator	300M+ papers from repositories	core.ac.uk
OpenAlex	Search + OA links	Cross-disciplinary	openalex.org
BASE (Bielefeld)	Aggregator	400M+ documents	base-search.net

Batch OA Lookup

def batch_oa_lookup(dois: list[str]) -> list[dict]:
    """
    Check OA status for a batch of DOIs.
    Unpaywall supports up to 100,000 DOIs per day.
    """
    results = []
    for doi in dois:
        status = check_oa_status(doi)
        results.append(status)

    # Summary statistics
    total = len(results)
    oa_count = sum(1 for r in results if r.get('is_oa', False))
    print(f"OA availability: {oa_count}/{total} ({oa_count/total*100:.1f}%)")

    # Group by OA status
    by_status = {}
    for r in results:
        status = r.get('oa_status', 'unknown')
        by_status.setdefault(status, []).append(r)

    for status, papers in by_status.items():
        print(f"  {status}: {len(papers)} papers")

    return results

Self-Archiving and Green OA

Checking Publisher Policies

Use SHERPA/RoMEO to determine what you can self-archive:

def check_sherpa_romeo(issn: str, api_key: str) -> dict:
    """
    Check journal self-archiving policy via SHERPA/RoMEO.

    Args:
        issn: Journal ISSN
        api_key: SHERPA/RoMEO API key
    """
    url = f"https://v2.sherpa.ac.uk/cgi/retrieve/by_id?item-type=publication&format=Json&api-key={api_key}&filter=[[%22issn%22,%22equals%22,%22{issn}%22]]"

    response = requests.get(url)
    data = response.json()

    if not data.get('items'):
        return {'error': 'Journal not found'}

    journal = data['items'][0]
    policies = journal.get('publisher_policy', [])

    results = {
        'journal': journal.get('title', [{}])[0].get('title', ''),
        'publisher': journal.get('publishers', [{}])[0].get('publisher', {}).get('name', ''),
        'policies': []
    }

    for policy in policies:
        for permitted in policy.get('permitted_oa', []):
            results['policies'].append({
                'version': permitted.get('article_version', ''),
                'location': permitted.get('location', {}).get('location', []),
                'conditions': permitted.get('conditions', []),
                'embargo': permitted.get('embargo', {}).get('amount', 0),
                'license': permitted.get('license', [])
            })

    return results

Version Terminology

• Preprint (submitted manuscript): Author's version before peer review
• Postprint (accepted manuscript): Author's version after peer review, before typesetting
• Published version (Version of Record): Final published PDF with journal formatting

Most funders (NIH, UKRI, ERC) require deposit of at least the postprint in a repository. Always check your specific funder mandate and journal policy before self-archiving.

Institutional Repository Deposit

When depositing in your institutional repository:

1. Identify the correct version (usually postprint for Green OA)
2. Check the embargo period from SHERPA/RoMEO
3. Add complete metadata: title, authors, DOI, journal, abstract, keywords
4. Apply the correct license (often CC BY for funder mandates)
5. Link to the publisher's Version of Record via DOI

This maximizes discoverability while respecting publisher agreements.