Keywords are put forward to meet the needs of computer retrieval, which are located after the abstract. As early as 1963, American Chemical Abstracts began to use computers to compile keyword indexes, which provided a method to quickly retrieve the topics of literature materials. With the rapid development of scientific and technological information, hundreds of thousands of scientific and technological papers are published every day all over the world. Academic circles have long agreed to use subject concept words to retrieve the latest published papers. If the author's published papers are not marked with keywords or descriptors, such articles will not be included in the literature database, and readers will not be able to retrieve them. Whether the keyword selection is appropriate or not is related to the retrieval of articles and the utilization rate of results.
1 keyword classification
Keywords include narrative words and free words.
1) Description refers to a standardized word or phrase that can be used to index the Chinese thesaurus and the concept of document theme in MeSH.
2) Free words-new nouns and terms that reflect new technologies and disciplines in the theme of this paper are not included in the thesaurus or words that cannot be found in the thesaurus.
2 keyword index
In order to meet the needs of computer automatic retrieval, GB/T 3 179-92 stipulates that all modern sci-tech journals should give 3-8 keywords (or descriptors) at the back of the abstracts of academic papers. The key words should be selected according to the principles and methods of GB/T 3860- 1995 "Rules for Indexing Document Description" and referring to various thesaurus and reference books. Important terms in new disciplines and technologies that are not included in the glossary, as well as the names and places of articles can also be marked as keywords (free words).
The so-called indexing refers to the process of subject analysis of documents and some features with retrieval significance, such as research objects, processing methods and experimental equipment, and the identification of subject retrieval by using thesaurus. The purpose of document theme analysis is to find out the basic elements that constitute the document theme through analysis, so as to accurately index the required descriptors. Indexing is the premise of retrieval. Without correct indexing, there can be no correct retrieval. Scientific papers should index keywords according to the indexing method of descriptors.
3 Key words indexing should follow the basic principles
3. 1 specificity principle
A word can only express one thematic concept as specificity. As long as the corresponding specific descriptor is found in the thesaurus, it is not allowed to use the superordinate word (item S) or the hyponym (item F) in the thesaurus. If you can't find a thesaurus directly corresponding to the theme concept, you can choose. For example, the corresponding special word "special plane fire prevention" can be found in the thesaurus, so it must be given priority. You can't use its superordinate word "fire prevention" as an index, nor can you use the two subject words "airplane" and "fire prevention" as an index.
3.2 Assembly principle
Descriptive phrase collocation should be conceptual collocation. Conceptual collocation includes two types:
Cross-matching refers to the combination of two or more narratives with cross-conceptual relationship, and the result expresses a specific concept. For example, the two general concept words "jet plane" and "vertical take-off and landing plane" can be used to accurately express specific concepts that are not in the thesaurus; Kidney calculi can use two words to express a specific concept: kidney disease and calculus.
Aspect combination refers to the combination of a narrative representing a thing and another narrative representing a certain attribute or aspect of a thing, and the result expresses a specific concept. For example, "signal simulator stability" can be combined with "signal simulator" and "stability", that is, the specific concept is expressed by things and their properties; "Color picture tube phosphor screen coating" can be matched with three phrases: color picture tube, phosphor screen (electron beam tube) and coating, that is, a specific concept can be expressed by describing things, their states and technological processes.
In combination indexing, cross combination is given priority, and then aspect combination is considered; The words involved in collocation must be the words most closely related to the theme concept of the document to avoid leapfrog collocation; The matching results require clear and accurate concepts, and can only express a single concept; If the theme concept cannot be expressed by collocation, it can be indexed by the most direct superordinate word or related descriptor.
3.3 Free Word Index
Free word indexing of keywords is allowed under the following circumstances.
A. Subject concept words obviously omitted from the subject glossary.
B express new concepts such as new disciplines, new theories, new technologies and new materials.
C names of regions, people, products and important data not included in the glossary.
D. When some concepts are collocated and the results are ambiguous, the indexed concepts can also be indexed with free words. Free words should be selected from other words or authoritative tools as far as possible, and the selected free words must be concise in form, clear in concept and practical. After using free words for indexing, records should be made and reported to thesaurus management department in time.
4 keyword indexing steps?
Firstly, the theme of the literature is analyzed to find out the theme concept and central content of this paper; Try to extract words and phrases consistent with the theme concept from the title, abstract, hierarchical title and important paragraphs of the text; Sort the selected words to find out which words can be directly used as descriptors, which words can be transformed into descriptors through standardization, and which descriptors can be combined into phrases that refer to the theme concept. There are still quite a few words that can't be standardized as descriptive words. As long as they are necessary to express the theme concept, they can be indexed as free words and included in keywords.
In keyword indexing, we should make good use of China Thesaurus and other thesaurus, and look it up in the indexing process; Avoid the mistakes of theme concept analysis and word combination; The number of free word indexes should be controlled.
Papers with English abstracts should record English keywords corresponding to Chinese keywords under the English abstracts.