After observing seven tests, U.S. intelligence sources believe the Soviet Union has run into difficulty in developing its new long-range, submarine-launched Typhoon missile.

Nonetheless, sources said last week, the large, solid-fueled Russian missile is still far ahead of the comparably sized American missile, the Trident II, which won't be ready for testing for several years.

The Typhoon missile is only one of several Soviet strategic programs in development, but in the past year it has been the most active, according to intelligence and defense experts familiar with Russian military research programs.

While the Soviets have been testing the sub-launched Typhoon, they have not yet fired their newly designed, land-based ICBMs, several of which have been ready for testing for more than a year.

Several of these sources, interviewed in the past few weeks, said the Soviet emphasis on the sea-based Typhoon may represent a change in direction by Moscow in its strategic weapons development programs, putting a new emphasis on forces that could survive a nuclear attack, rather than simply more and bigger missiles.

"The emphasis of its major programs," one source said last week, "is on survivability, much like the direction we are taking."

To support that view, he and others noted that the Soviets are putting more emphasis on hardening land-based command and control facilities and missile silos. In addition, the Soviets have a major program under way to modernize their old Galosh antiballistic missile system around Moscow.

Such steps, these sources say, are primarily defensive and indicate a desire by Moscow to move away from adding to its first-strike capability and toward a force that could survive an American first strike.

They say that when the Soviets finally test a new land-based ICBM, it should be a solid-fueled mobile missile, smaller than the large, liquid-fueled, silo-based ones to be replaced, and less threatening as a first-strike weapon.

Other sources interpret differently the changes in the Soviet strategic development program. They say the Russians are ahead in land-based ICBM systems and now seek to gain a similar advantage at sea.

They say the additional efforts at hardening silos can also be interpreted as a Soviet desire to be able to strike first with their larger SS18 land-based ICBMs and then be able to ride out any American response.

Almost all sources agree that the Soviets appear to be adhering to the SALT I limits on the number of allowable launchers (they have decommissioned two nuclear missile-launching submarines in the past year to stay within their limits).

They also are believed to have followed most of the terms of the signed, but unratified, SALT II treaty. In fact, sources believe part of the delay in testing a new ICBM may be because SALT II limits each side to one new type of ICBM.

Analysts also have been looking at Soviet weapons development for some sign that the tremendous costs of these programs, which are forcing delays and some cutbacks in American strategic systems, may also be influencing the even larger Russian effort.

The only area where a Soviet pause seems evident is in land-based ICBMs, and that may stem less from a money shortage than from a desire to see what happens to the American ICBM program.

On the other hand, at least one U.S. weapons decision was justified in part by its financial effects on the Soviets.

One reason for building both the B1 and a radar-evading "stealth" bomber was to force the Soviets to invest billions of dollars in a new air defense system.

"For the Soviets to detect even the B1 . . . and proceeding with the stealth , their investment in their defense system will be fantastic," Dr. Richard D. DeLauer, undersecretary of defense for research and engineering, told a House Appropriations subcommittee last July. With these new bombers, DeLauer said, "We are dictating their investment strategy."

Concern over American B52 bombers and cruise missiles already has forced the Soviets to invest tens of billions of dollars in air defense radars, fighter interceptors and surface-to-air missiles--programs for which the United States has no counterpart, because Soviet bombers have not been considered a threat to the continental United States for more than 10 years.

Despite disagreements over what the Soviet development programs may mean, most sources agree on what appears to be under way:

* Land-based ICBMs: The fourth generation of Soviet missiles appears to be just about in place. There are 308 of the giant SS18s, some with a 15-megaton warhead (equivalent to 15 million tons of TNT, compared to the Hiroshima bomb's 12,500 tons), others with up to 10 smaller 600-kiloton warheads. There are 360 slightly smaller SS19s, with six warheads that are the most accurate in the Soviet force. Finally, there are 150 of the SS17, each with four warheads.

The fifth generation of land-based ICBMs, none of which has been tested, reportedly consists of a large, liquid-fueled missile, much like the SS17 and SS19 it is supposed to replace; a medium-sized, silo-based, solid-fueled missile and a mobile, solid-fueled missile; and finally a smaller, mobile, solid-fueled missile, thought to be a follow-up to the SS20 intermediate-range missile now aimed at targets in Western Europe and China.

* Sub-based ICBMs: The Soviets have begun deploying their Delta III submarines, a long-range ICBM and their first with more than one warhead. This one carries seven on each missile. Meanwhile they continue testing, with varying results, the Typhoon missile. Two of the tests have been observable failures. One didn't get off the launch pad and another appeared to have been destroyed in flight, sources said, emphasizing that the Russians have had relatively little experience with solid-fueled, sub-launched missiles, because all models up to now have been liquid-fueled.

The Soviet data transmissions on the Typhoon missile tests have been in code more than is usual, so information available to American analysts is less detailed than in the past. For example, according to one source, there is still no conclusive data on how many warheads the missile could carry.

Sources said the Soviets also seem to be having difficulties with the giant Typhoon submarine. Its keel was laid in 1975, but it took until September, 1980, before the sub itself was launched U.S. Navy experts do not expect it to be operational for at least three years.

* Bombers: The Soviets, who have not built a true intercontinental bomber (the Backfire is considered primarily a medium-range aircraft) are testing a long-range, B1-type penetrating bomber. They are also at work on long-range, air-launched cruise missiles.

* ABMs: The Soviets have begun an extensive upgrading of the old Galosh system around Moscow. They are modernizing 32 of the 64 antimissile launchers around the city with a new launcher and missile, designed to intercept a warhead after it comes into the atmosphere. It is much like the Sprint that was part of the proposed American ABM system, some sources said.

Some analysts are noting that the new missiles and their launcher components appear to be in a production line that normally turns out much larger numbers than would be required to modernize the Moscow ABM system--the only one permitted under the SALT I treaty. This, according to one source, could mean the Russians have put themselves in a position to go quickly to a larger system.

Other sources, however, point out that the upgraded system still would not provide a firm defense against a serious ICBM attack, even if it were rapidly installed around the country.

* Command and Control: The Soviets are adding cement hardening to the major facilities that control their military forces and others that would direct the firing of their strategic missiles. In addition, they have continued programs to harden the silos of some of their missiles, using a cement-and-steel protective shell that some analysts believe is stronger than the most modern of the American Minuteman III missiles.