The selection and determination of subject words, sub-subject words and keywords is extremely important for selecting the correct search term team and the accuracy of search results. Whether it is keywords, keywords or sub-keywords, in addition to the principles and basic skills of word selection, it mainly depends on the mastery of personal professional knowledge. The basic principles of choosing words are as follows. 1. Subject words (1) directly select corresponding and specific nouns (such as subject category name, drug name, disease term, inspection and experiment name, place name, person name, institution name, product name, etc. ) as a search term. (2) When there are no directly corresponding and specific words to choose from, there are two ways to choose words: one is to directly choose the words with the upper concept; Secondly, consider selecting two or more adjacent concept words for cross-matching, and the concepts expressed by the matching results should be clear and accurate, and only one theme concept can be expressed. (3) Pay attention to standard words. If the search result with self-selected keywords is zero, it is necessary to consider that the selected words may not be standardized and use standardized words instead. 2. Keywords keywords belong to the subject language category, mostly natural languages, and do not need standardization. There is no keyword list, but there are forbidden words. Any noun that can express the central content of the search topic can be used as a keyword. The key words to express the theme concept must independently quote the scope and essence of things and problems (such as "patent documents"); Can accurately express the essential attributes of things (such as "medical library"); The word form is monosyllabic, that is, a keyword expresses the concept of a thing, that is, a word has a meaning. 3. Basic procedures for selecting words, whether it is selecting subject words or keywords, the basic procedures for selecting words are as follows: First, select entity words that can accurately express the original intention of the search theme; When there are no entity words that can accurately express the original intention of the search topic, choose words that can be combined; When there are no words that can be combined, consider words with superordinate concepts; When you don't choose a word with a conceptual position, finally, consider choosing a word with similar meaning or similar meaning. 4. No matter which keyword or key word is selected, adverbs, adjectives, prepositions, conjunctions, pronouns, exclamations, certain verbs (conjunctions, modal verbs and auxiliary verbs) and articles, chemical structural formulas, reactive expressions and teaching methods can not explain the lack of nouns (such as theories, reports, experiments, learning, methods, problems and countermeasures) in the professional concepts of this discipline. 5. Sub-keywords Sub-keywords restrict keywords to improve the despotism of retrieval. Each sub-keyword in the grid table has a specific meaning and scope of use, and matches different topic phrases respectively. How many subtitle words are suitable for retrieval depends on the different keywords. Sub-subject words further advance and divide the concept of subject words, making the combination of subject words/sub-subject words a more specific concept. When searching, you can select one or more or even all sub-subject words to avoid missing detection, or you can search without selecting sub-subject words (search the general theory and general literature of subject words). For example, if you search for information related to breast cancer treatment, you can select multiple sub-topics:/dietotherapy,/drug therapy,/prevention &; Control (prevention), rehabilitation (rehabilitation),/radiotherapy (radiotherapy),/surgery (surgery),/therapy (treatment), in addition/Chinese medicine therapy,/Chinese medicine therapy,/Qigong,/integrated Chinese and Western medicine therapy, etc. 6. Word selection analysis Distance matters needing attention Theme analysis is the basis of word selection. By searching the characteristics of the central content consulted by the theme and the central content of other theme factors, the theme concept can be refined and selected accurately. Generally speaking, the title of a search topic can reflect the central content of the question. It is a shortcut to analyze and refine keywords according to the title of the search topic, but the title of the search topic cannot be used as the only basis for selecting search words, because there are often some deep-seated theme concepts or hidden theme concepts that are easily overlooked. This often happens because the professional knowledge and frontier development of retrieval topics are not fully mastered, or because some logical relationships between concepts are not clear or well understood. Therefore, it is necessary to analyze the theme content and decompose and recombine the compound concepts through theme analysis. (1) Selection of topic concept reorganization: Search for the topic "Low-dose aspirin for ischemic cerebrovascular disease", including "ischemic cerebrovascular disease" and "drug therapy", thus selecting the first group of search words of this search topic: ischemic cerebrovascular disease/drug therapy. As for "therapeutic application of aspirin" and "drug dosage", they are simpler and more specific concepts in this discipline, so the second group of keywords: aspirin/therapeutic effect. "Ischemic cerebrovascular disease" should be listed under several special terms such as "cerebral ischemia", "cerebral infarction" and "cerebral thrombosis" in thesaurus, so the third-party keywords are: cerebral ischemia/drug therapy; Cerebral infarction and cerebral thrombosis/drug therapy. If machine examination and hand examination coexist, the fourth group of keywords should be marked: cerebrovascular disease+aspirin treatment+research. This is a comprehensive analysis of this retrieval question. (2) Selection of words of recessive theme concepts: The retrieval theme "Clinical application of interferon" has dominant theme concepts "Interferon" and "Clinical application", and the important recessive theme concept "side effects" is often overlooked in retrieval. (3) Accurately express the concept of word selection: Search the topic "Bioethics Puzzlement in 2 1 century", and its leading theme concepts are "life" and "ethics", which obviously can't accurately express the meaning of the topic, and the detected results are naturally not ideal, so we should choose a more accurate word "medical ethics". (4) Comprehensive expression of concept selection: To retrieve the topic of "glucose metabolism in elderly diabetic patients", we must consider every concept, namely glucose, diabetes, metabolism and the elderly. Should choose: diabetes/metabolism; Liver/metabolism; Glucose/metabolism; Old people (characteristic words); People (characteristic words). In this way, relevant documents can be retrieved from different angles. (5) Word selection by location: search for the theme "upper gastrointestinal bleeding" and select the word "gastrointestinal bleeding" by location; Search for the topic "Study on Red Blood Cell Survival" and select the word "Red Blood Cell Aging" by location; Search the topic "Preventing common foods from being polluted by ginger and liquor" and choose words for several concepts: food pollution/prevention and control. (6) Analyze the subtitle: Search for the theme "Treatment of blindness caused by eye tuberculosis", and select the corresponding keywords and subtitle according to the causal relationship between tuberculosis and blindness: eye tuberculosis/complications, eye tuberculosis/diet therapy,/drug therapy,/prevention,/surgery,/treatment,/traditional Chinese medicine therapy,/integrated traditional Chinese and western medicine therapy, blindness. Chinese herbal medicines, choose the theme of "drug control"; Deficiency syndrome and cold syndrome in traditional Chinese medicine use the subject word "disease"; For the components of Chinese herbal medicine, you can choose related keywords such as family name and genus name; To search the literature of integrated traditional Chinese and western medicine, we can select multiple western medicine keywords, and then use keywords such as "traditional Chinese medicine" or "Chinese herbal medicine" for logical or "or" combination search. (8) Chinese medicine sub-keywords, such as "Chinese medicine therapy" and "integrated traditional Chinese and western medicine therapy" are often used in Chinese databases, but these sub-keywords are not available in foreign databases, and only "drug therapy" and "therapeutic application" can be used. (9) With the development of science and technology, some new words or new concept vocabularies that are constantly produced and have not been added to the list of subject words should be mainly free words, supplemented by subject words. Moreover, when choosing a theme, we should give full consideration to different categories of words, which level of words, transformed words, restored words and so on. (10) When searching for research methods, diagnosis and treatment techniques and experimental means, it is generally limited to subject fields, but it is best to search with subject words and free words "logical OR". Because such words can be mentioned in the title, abstract or text of the article, or they can not be mentioned. Only keywords are used for retrieval, and its missed detection rate is very high. However, "case report" and "comparative study" are mostly used as characteristic words in Chinese and foreign databases. (1 1) Place names should be based on thesaurus, and keywords with large concepts are often used in place name retrieval. For example, design related papers in Zhuhai, Guangdong Province, and use "China" on MEDLINE and "Guangdong Province" on CBM. (12) When selecting words for age retrieval, free words and limited characteristic words should be used for logical OR and OR retrieval. (13) When selecting keywords for experimental animals or animal experiments, experimental animals in foreign databases (such as MEDLINE) directly use relevant animal names as keywords, while in Chinese databases (such as CBM), only animal names can be used as keywords or "feature words" fields can be used for retrieval.
The full text is selected from Modern Medical Information Retrieval.