Sources:
Marie Curie - Pioneer of radioactivity research and the first person to win two Nobel Prizes (Physics in 1903, & Chemistry in 1911).
Hertha Ayrton - Studied electric arcs and sand ripples, wrote a textbook "The Electric Arc" in 1902, and was the first woman to read a paper before the Institution of Electrical Engineers in 1904.
Florence Bascom - One of the first female geologists in the US and, in 1896, became the first woman hired by the US Geological Survey and later became the second woman elected to the Geological Society of America in 1894.
Nettie Stevens - An American geneticist who, ironically enough, discovered that sex is determined by chromosomes (that bigot!).