网络上可免费访问的教科书（不完整列表，欢迎补充）

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Abstract Algebra

Elementary Abstract Algebra: Examples and Applications
Abstract Algebra: Theory and Applications

Calculus

Multivariable Calculus, Don Shimamoto, Swarthmore College
Gilbert Strang, MIT
whitman
Mathematical Analysis I
Mathematics for Biomedical Physics
Yet Another Calculus Text
A Primer of Real Analysis
Vector Calculus, by Michael Corral

Combinatorics

Applied Combinatorics
A Cool Brisk Walk Through Discrete Mathematics
Introduction to Game Theory: a Discovery Approach
Algorithms and Data Structures With Applications to Graphics and Geometry
Applied Finite Mathematics
Combinatorics Through Guided Discovery
Applied Discrete Structures

Differential Equations

Ordinary Differential Equations
Notes on Diffy Qs: Differential Equations for Engineers
MATHEMATICA / Mathics TUTORIAL for the First Course in Applied Differential Equations
Elementary Differential Equations with Boundary Value Problems

Geometry

Geometry with an Introduction to Cosmic Topology
Euclidean plane and its relatives

Linear Algebra

Tea Time Linear Algebra Explorations in Mathematics - 2nd Edition
Linear Algebra, Theory And Applications
Linear Algebra by Jim Hefferon
A First Course in Linear Algebra
Introduction to GNU Octave: A brief tutorial for linear algebra and calculus students

Logic

Open Logic Project
forallX: an Introduction to Formal Logic
A Friendly Introduction to Mathematical Logic

Number Theory

An Introduction to the Theory of Numbers
Yet Another Introductory Number Theory Textbook (Cryptology Emphasis Version)
The Joy of Cryptography
A Computational Introduction to Number Theory and Algebra

Numerical Analysis

First Semester in Numerical Analysis with Julia
First Semester in Numerical Analysis with Python
The Art of Polynomial Interpolation
Tea Time Numerical Analysis

Real Analysis

Math 105: A second course to real analysis (2022 Spring)
KSU
Bath - Advanced Real Analysis
Introduction To Real Analysis
Harvard - Real Analysis
Basic Analysis: Introduction to Real Analysis
Basic Analysis I & II
Measure, Integration & Real Analysis
How We Got From There To Here: A Story of Real Analysis
Real Analysis
Introduction to Mathematical Analysis I - Second Edition
Introduction to Real Analysis

Statistics, probability

Mostly Harmless Statistics
Optimal, Integral, Likely Optimization, Integral Calculus, and Probability for Students of Commerce and the Social Sciences
Statistical Thinking for the 21st Century
Lies, Damned Lies, or Statistics: How to Tell the Truth with Statistics
Learning Statistics with R: A tutorial for psychology students and other beginners
Introductory Statistics with Randomization and Simulation - First Edition
Online Statistics Education: An Interactive Multimedia Course of Study
Statistical Inference For Everyone
Linear Regression Using R: An Introduction to Data Modeling
Applied Probability
Introduction to the Modeling and Analysis of Complex Systems
Introductory Statistics
OpenIntro Statistics
Introduction to Probability