Physics

Bradley's library uses the Library of Congress classification system.  All natural sciences are in the Q's.  
Astronomy is located at QB and Physics at QC
Related fields
QA - Mathematics
QC 172-173 - Constitution and properties of matter
QC 310-319 - Thermodynamics
​QC 450-467 – Spectroscopy
QC 762-763 - NMR, EPR
QD - Chemistry
QE - Earth Sciences, including Geochemistry
T 174.7 - Nanotechnology 
TA 455 - Materials (non-metallic)
TP - Chemical Technology (includes engineering)

You may also find the ebooks from the "Very Short Introduction" series helpful for learning about a topic. This series from Oxford University Press "offers concise and original introductions to a wide range of subjects...Each volume provides an authoritative and engaging assessment of a concept, field, or body of work, drawing out the central ideas, themes, and approaches. Our expert authors combine facts, analysis, new insights, and enthusiasm to make often challenging topics highly readable to develop your core knowledge...the series is an indispensable and accessible guide that will enrich your understanding." (from the publisher).

Physics Encyclopedias and Dictionaries

• CRC Handbook of Chemistry and Physics
• Dictionary of Pure and Applied Physics
• Encyclopedia of Physics
• Physicists Desk Reference

Astronomy Encyclopedias and Dictionaries

• The Astronomical Almanac for the Year
• Encyclopedia of Astronomy and Astrophysics
• Encyclopedia of Space and Astronomy

Study Help and Other Introductory Material

• Basic Concepts in Physics: From the Cosmos to Quarks
• Entropy Demystified: The Second Law Reduced to Plain Common Sense
• Fluid Mechanics Demystified
• Fundamentals of Physics: Mechanics, Relativity, and Thermodynamics
• Modern Introductory Physics
• Modern Particle Physics
• Quantum Mechanics for Pedestrians 1: Fundamentals
• Thermodynamics: For Physicists, Chemists and Materials Scientists