| 释义 |
periodicity|ˌpɪərɪəʊˈdɪsɪtɪ|
[ad. F. périodicité (1796 in Hatz.-Darm., Dict. Acad. 1835), f. L. periodic-us: see periodic and -ity.]
1. a. The quality or character of being periodic; the quality of regular recurrence; tendency to recur at (more or less) regular intervals. (Chiefly in scientific use.)
1833Herschel Astron. xii. 380 Wherever we can trace the law of periodicity—the regular recurrence of the same phænomena in the same times. 1868Lockyer Guillemin's Heavens (ed. 3) 27 We shall see..that the number of [sun] spots follow a certain periodicity. 1879[see periodic 2]. 1882Vines Sachs' Bot. 755 A similar periodicity exists in the growth of leaves when day and night alternate normally.
b. Chem. The complex periodic variation of the properties of the chemical elements with increasing atomic number.
1879Roscoe & Schorlemmer Treat. Chem. II. ii. 506 The law of periodicity was afterwards further developed by Meyer and Mendelejeff. 1907Westm. Gaz. 4 Feb. 6/3 Gallium, scandium, and germanium, all subsequently discovered, did fit into the scale of ‘periodicity’. 1969A. J. Ihde in J. W. Van Spronsen Periodic Syst. Chem. Elem. p. x, The periodic table reached its final forms before atomic structure revealed the basis for periodicity.
c. The frequency of a periodic phenomenon, esp. an alternating current.
1900Jrnl. Soc. Arts XLVIII. 848/2 The other carrying about 20 amperes with a periodicity of 60 cycles per second. 1913Chambers's Jrnl. Jan. 102/1 The electricity used for wireless telegraphy is..used under different conditions as to pressure and periodicity. 1938Times 13 Oct. 8/3 The periodicities of the front and back springs are arranged at a predetermined variance so that coincidence should not occur. 1943Gloss. Terms Electr. Engin. (B.S.I.) 11 Frequency (periodicity, deprecated), the number of cycles per second. The reciprocal of the period.
2. Physiol. Recurrence of the ‘monthly period’; menstruation: cf. period n. 3 b.
1848[see periodoscope]. 1875N. Amer. Rev. CXX. 187 In this harsh climate..in their case, periodicity, nervous system, intellect, and health require especial care. |