Two physicists won the Nobel Prize yesterday for their roles in discovering three subatomic particles. The discovery was regarded as a crucial step toward a central goal of 20th century physics: developing a single theory to account for all natural forces.

The prize winners were Dr. Carlo Rubbia, an Italian on the faculty of Harvard University, and Dr. Simon van der Meer of the Netherlands.

In experiments conducted at CERN, the European research center near Geneva, their work culminated in the detection of two W particles, one electrically positive and one negative, and of the neutral Z particle.

'The Most Prized Trophies'

In an article they published before the discovery in collaboration with Dr. David B. Cline of the University of Wisconsin, the researchers described the particles as ''the most prized trophies in all physics,'' and noted that discovering them would culminate a search that began 40 years ago.

It took that long partly because extremely high-energy collisions generated in massive machines deeply buried underground were necessary to produce the particles in a way that would allow them to be detected.

The particles were sought, at great cost in resources and manpower, because their discovery would confirm predictions based on a theory that unifies two of the basic forces of nature: the electromagnetic force and the weak force.

What Weak Force Does

Electromagnetism is the well-known force that drives electric moters, generates magnetism and illuminates electric light bulbs. The weak force is less obvious and operates only at extremely short ranges. It controls many atomic-scale reactions including those involved in radioactivity and in generating the sun's energy. Gravity and the strong force that binds together particles of the atomic nucleus are the other two fundamental forces.

The electromagnetic force is transmitted by photons, such as light waves and radio waves. Theorists had recently postulated that the weak force should be communicated by a form of ''heavy light,'' namely by the still-hypothetical W and Z particles.

By the late 1970's theorists had concluded that those particles would be extremely massive and short-lived. Their mass, expressed in units of equivalent energy, would be in tens of billions of electron volts. To create them, even briefly, would require atomic collisions far more violent than any achieved up to that time.

This, it appeared, could only be achieved by head-on collisions between nuclear particles each carrying 270 billion electron volts of energy. It was thought that this would require a giant, prohibitively costly new machine.

In 1976, however, Dr. Rubbia, Dr. Cline and Peter M. McIntyre pointed out that CERN's existing Super Proton Synchrotron in a circular, four-mile tunnel, could be modified for this purpose. The existing atom-smasher accelerated protons to very high energy for impact on stationary targets.

The proposal was to include in the same circular ring a beam of antiprotons circling in the opposite direction. Like all forms of matter, protons have antimatter twins, antiprotons, that are identical except being of opposite electric charge. High-Energy Collisions

Collisions between particles in the two beams would produce extremely energetic fireballs that would materialize into a variety of particles including, it was hoped, those being sought.

Dr. Rubbia, 50 years old, successfully campaigned for the conversion and led a team of about 100 physicists from 11 laboratories in designing a 1.200-ton detector to be installed in one of two cavernous experimental areas, placed deep underground to prevent escape of radiation.

Last November the discoveries that followed were exuberantly described by CERN's own publication, the CERN Courier, as ''among the greatest achievements in the history of science.'' They were, the Courier said, ''the culmination of deep theoretical inspiration, technological excellence, dedicated experimentation, and teamwork on a scale never before seen in the realm of pure science.''

Experimental collisions began late in 1982 and on Jan. 21, 1983, a collaboration of 126 physicists from 11 institutions reported evidence for W particles with positive and negative electric charge and roughly the predicted mass of about 80 billion electron volts. The finding was quickly confirmed by another group in a second experimental area. Evidence for the somewhat more massive Z particle was found the following June. Keeping the Particles on Line

Dr. van der Meer's essential role was in devising a way to ''cool'' the bunches of protons and antiprotons during early stages of their acceleration. Because it was expected that production of the W and Z particles would occur extremely rarely, an enormous number of collisions was called for. Only ten of the sought-for particles were expected for every billion collisions.

To prevent the particles from hitting the sides of the evacuated tube in which they were being accelerated it was necessary to compress each bundle of accelerating particles into a tight bunch and keep it flying down the centerline of the tube.