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23 小時前 · Bibliography. External links. Silicon is a chemical element; it has symbol Si and atomic number 14. It is a hard, brittle crystalline solid with a blue-grey metallic luster, and is a tetravalent metalloid and semiconductor. It is a member of group 14 in the periodic table: carbon is above it; and germanium, tin, lead, and flerovium are below it.
5 天前 · Infobox references. Silicon dioxide, also known as silica, is an oxide of silicon with the chemical formula SiO2, commonly found in nature as quartz. [5] [6] In many parts of the world, silica is the major constituent of sand. Silica is abundant as it comprises several minerals and synthetic products.
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2 天前 · Science is a rigorous, systematic endeavor that builds and organizes knowledge in the form of testable explanations and predictions about the world. Modern science is typically divided into three major branches: the natural sciences (e.g., physics, chemistry, and biology), which study the physical world; the social sciences (e.g., economics, psychology, and sociology), which study individuals ...
3 天前 · The number π (/paɪ/; spelled out as "pi") is a mathematical constant that is the ratio of a circle's circumference to its diameter, approximately equal to 3.14159. The number π appears in many formulae across mathematics and physics. It is an irrational number, meaning that it cannot be expressed exactly as a ratio of two integers, although ...
1 天前 · Definitions. Identities. Properties relating to the quadrants. Fixed points. Arc length. Laws. Special values. Relationship to complex numbers. History. Software implementations. See also. Citations. References. External links. Sine and cosine. In mathematics, sine and cosine are trigonometric functions of an angle.
1 天前 · Asia ( / ˈeɪʒə / ⓘ AY-zhə, UK also / ˈeɪʃə / AY-shə) is the largest continent [note 1] [10] [11] in the world by both land area and population. [11] It covers an area of more than 44 million square kilometers, [note 2] about 30% of Earth 's total land area and 8% of Earth's total surface area.
3 天前 · Viscosity is defined scientifically as a force multiplied by a time divided by an area. Thus its SI units are newton-seconds per square meter, or pascal-seconds. Viscosity quantifies the internal frictional force between adjacent layers of fluid that are in relative
