American Chemical Society
Teaching Chemical Information:
Tips and Techniques
— August 1998 —
Chemical Literature (Chem 184/284)
University of California at Santa Barbara
Lecture 6: Indexes and Abstracts
Indexes & Abstracts: Definitions
- Index — A tool which provides access to some body of information
by a “pointer” derived from the original.
- Examples of pointers: author names, subject terms, chemical formulas, cited references.
- Abstract — A brief summary of the content of a document.
Considerations in Selecting an Index for Searching
Scope
- What subject areas does the index cover?
- Broad scope is useful for comprehensive searches, and “interdisciplinary” topics. Example: Science Citation Index covers the whole of science, engineering and medicine.
- Narrow scope may be quicker and easier to use, cover less irrelevant material and/or have specialized indexes useful to your search. Example: Analytical Abstracts
Comprehensiveness
- What kinds of documents are covered?
- Most indexes are aimed at journal articles. Examples: Current Contents, Biological Abstracts.
- Others specialize in conference papers, technical reports or patents. Examples: NTIS for technical reports; BA/RRM for reports and conference papers; Dissertation Abstracts for dissertations.
- Some cover multiple document types. Example: Chemical Abstracts.
- How much of the world literature does it attempt to cover? Some are limited geographically.
- Example: Though both cover medical literature worldwide, Index Medicus (MEDLINE) favors US literature; Excerpta Medica (EMBASE) favors European literature.
- Dissertation Abstracts only covers North American and European dissertations.
- Everything or just “the best”?
- Chemical Abstracts attempts to cover all of the chemical literature.
- Science Citation Index goes by the rule “20% of the journals publish 80% of the literature” and only indexes the top journals in each field, as measured primarily by citation count.
Chronological factors
- What years does the source cover?
- Few sources do retrospective coverage, i.e. indexing the literature before the index began. But some do.
- Many electronic sources don’t go back as far as the corresponding printed tools.
- Sometimes you only need recent years. For example, in biotechnology or particle physics, information dates quickly. Not so in synthesis, taxonomy, geology, math.
- How often does the index come out? Online is usually faster than print, which may be faster than CD-ROM.
- How much time lag between publication of the original document and its appearance in the
index does the index have?
- Current Contents is very fast…since it doesn’t do detailed indexing.
- May vary depending on type of document and source of document. Chemical Abstracts does rapid indexing for a set of key chemistry journals, slower processing for others. Technical reports and dissertations are delayed further since CAS uses secondary sources for that information.
- Sometimes an index listing can appear before the issue arrives in the library.
- Compare the publication date of the most recently issued publication of the type you are interested in to the date of the index.
Access points
- Subject indexing
- Some use keywords from document titles and/or abstracts. Example: Biological Abstracts in print and Current Contents on MELVYL use title keywords only. Chemical Abstracts weekly issues use text keywords.
- Some use standard subject headings or classification codes, like the Chemical Abstracts volume indexes or Index Medicus. Such indexes may have a thesaurus—an alphabetical listing of headings with cross-references to broader, narrower and related terms.
- Many electronic files use a combination of keyword searching and assigned subject headings or classification codes.
- Keyword indexing responds more quickly to new concepts, may be easier for quick, limited searching.
- For some documents, indexers enhance the author's title and/or abstracts with additional keywords. Used often in patents.
- Subject headings and classification codes bring related concepts together regardless of jargon; are better for browsing and comprehensive searching.
- The combination of the two provides maximum power and flexibility; in electronic forms, it lets you use keyword searching as a first step to discover the assigned headings or codes which apply.
- Author Access
- Nearly all indexes have an author index but…
- Some don’t index all authors of a paper.
- Some use initials for first names (example: Science Citation Index), some use full names where available (example: Chemical Abstracts).
- Some try to bring different forms of an author’s name together; most don’t.
- Access points — Specialized indexing
- Corporate source
- Useful for locating the research of a given company.
- Can be combined with author searching to distinguish authors with similar names.
- Geographic indexing — common for biological, environmental, geological indexes.
- Genus/species indexing
- Chemical substance indexing
- A specialized form of subject indexing.
- Some index individual compounds; example: Chemical Abstracts
- Some index classes of compounds.
- Some index compounds and component elements.
- Indexing may be by name (sometimes multiple forms), chemical formula or structural feature.
- More sophisticated forms, such as structure, reaction or substructure indexing usually electronic tools only.
- Patent indexing
- Indexes by patent country and number, as well as inventor and patent assignee.
- Concordances relate “families” of patents from different countries.
- Citation Indexing
- Connects cited papers to citing papers.
- Can be effectively used for subject searching, based on the premise that an author only cites papers which are directly relevant to the current paper.
- Some electronic forms use co-citation techniques (e.g. Related Record searching.)
- Corporate source
- Combining access points
- By their nature, print indexes rarely allow combination of different access points, such as author and keyword.
- Electronic indexes can allow combinations of multiple access points (and usually have more access points to begin with…)
See Important Indexes and Abstracts in Sciences and Engineering for more details on some specific print indexes and abstracts.
This page created by Chuck Huber (huber@library.ucsb.edu).