美国国家标准与技术研究院数字数学函数库（DLMF）
The NIST Digital Library of Mathematical Functions (DLMF) serves as the authoritative, peer-reviewed successor to the Abramowitz and Stegun Handbook
计算
塑料成型和注塑价格计算器
Great for rapid estimations of the cost of your next plastic injected part. It has a nice database of plastic
GeoGebra 科学计算器
Basic but does it well, with history, fractions and all features you want from a scientific calculator: GeoGebra Scientific is
免费FEM可安装或在线使用
FEM software. Install is normally required (Mac, Windows, Linux) … but an online version is available (look at the right
Framacalc 在线协作电子表格
Not the most feature-rich spreadsheet, but ZERO install or registration: Framacalc is a collaborative, web-based spreadsheet service hosted by Framasoft
MH-Audio 声音和音频计算器（存档）
A very good resource for online Audio Calculators, classified into 6 categories: Loudspeaker Crossover Acoustic Electronic Turntable Various that really
在线整数序列百科全书（OEIS）
The largest online integer sequences database, searchable. It provides a searchable interface to identify sequences by numerical terms, keywords, or
在线单位转换器
Efficient and well organised (be sure to look at the “by Family” drop-down and not stay at the “Most Popular”
Wolfram Alpha 科学参考计算
Provides engineering information and problem solving techniques and maths, all powered by a powerful search engine: WolframAlpha functions as a
统计表
Provides all the statistical tables when MS Excel has no formula to compute it automatically. All these tables here are