核酸热力学是指温度影响双链DNA（dsDNA）的核酸结构。DNA变性（DNA denaturation）又称DNA融化（DNA melting）是DNA双螺旋解开成为两条单股长链的过程。在过程中，使两股长链上的碱基相连的氢键会断裂。 DNA的变性可以是温度升高而产生的作用，也可能是其他化学物质如尿素的诱导。使DNA解开的融化温度（T_m）是依DNA链的长度，以及特定核苷酸串行的组成形式而定。

Nucleic acid thermodynamics is the study of how temperature affects the nucleic acid structure of double-stranded DNA (dsDNA). The melting temperature (T_m) is defined as the temperature at which half of the DNA strands are in the random coil or single-stranded (ssDNA) state. T_m depends on the length of the DNA molecule and its specific nucleotide sequence. DNA, when in a state where its two strands are dissociated (i.e., the dsDNA molecule exists as two independent strands), is referred to as having been denatured by the high temperature.