The Senate gave President Reagan the entire defense spending increase he asked for and more yesterday, approving a $208.6 billion appropriations bill that is up $37.3 billion, or about 22 percent, from last year's level.

In sending the bill to conference with the House, the Senate also approved all the funds the president requested for the new land-based MX missiles and B1 bombers he says are needed to strengthen U.S. strategic striking power.

The vote, 84 to 5, was one more sign of congressional willingness to go along with the president in increasing military spending this year while cutting back on domestic programs.

The Senate bill provides $12 billion more than the version the House passed last month, but Sen. Ted Stevens (R-Alaska), floor manager of the bill, said yesterday the differences were more in accounting than policy. He predicted few difficulties in conference committee.

The B1 and MX proposals Reagan made in October initially seemed controversial. But both rather easily survived their first tests on the Senate floor in this bill, leading Senate Majority Leader Howard H. Baker Jr. (R-Tenn.) to hail the vote as one that will strengthen U.S. defense "for decades to come."

The bill did contain one gentle rebuff to the administration in the form of an amendment to block research funds from being spent on a Reagan proposal to place MX intercontinental missiles in existing, hardened silos on an interim basis. The Senate wants the military to continue research on other basing options, including a deceptive basing technique President Carter proposed.

Although the final vote on the bill was lopsided, the surface show of consensus belied 40 hours of debate and 26 roll calls in a week that Minority Whip Alan Cranston (D-Calif.) described as a descent into "rancorous partisanship."

The only senators voting no were Republican Mark O. Hatfield (Ore.) and Democrats Carl Levin (Mich.), Paul E. Tsongas (Mass.), William Proxmire (Wis.) and Claiborne Pell (R.I.).

The week-long debate was carried on mainly by Democrats, who sought to use consideration of the bill as a forum to establish their party as the one of conventional-force readiness and the Republicans as the party of big-ticket, budget-busting, exotic new military weaponry.

Of the 26 roll calls, roughly half came on proposals by Democrats to add money to conventional forces in such areas as ammunition, troop levels and ship fuel.

Levin, one of the Democrats who fashioned the strategy, said it was designed to "give senators a way to vote against the big systems without being perceived as antidefense."

The parade of Democratic amendments placed Republicans, who voted a party line, in the unhappy position of opposing readiness expenditures that Reagan had proposed in March but that did not survive the administration's fall budget cuts.

The whole gambit clearly discomfited the majority, and there were occasional outbursts on the floor throughout the week. However, Republicans insisted at week's end that the Democrats would reap no political bounty from their efforts.

Sen. Arlen Specter (R-Pa.) accused the Democrats of "posturing," and Sen. Alfonse D'Amato (R-N.Y.) said the Democratic strategy would not succeed "because everyone knows it is not a sincere effort."

During the week of debate, Democrats had a field day describing the sorry state of American readiness. Sen. Dale Bumpers (D-Ark.) paused in the middle of a lengthy lament about ill-equipped soliders to quote the Duke of Wellington. When the general was asked if his rag-tag soliders would frighten the enemy, Bumpers noted, the duke replied: "I don't know, but they sure scare the hell out of me." Sen. James Exon (D-Neb.) sounded the same theme, imploring his colleagues not to "fall into the trap of being preoccupied with exotic weapons at the expense of our ability to sustain our ground forces . . . the men who have to go eyeball-to-eyeball against the enemy."

But if those sentiments are intended as the rough outline of a Democratic policy posture on defense for the 1982 campaign, they lack unanamity within the party. Many Democratic senators spoke in support of the B1 and the MX, and nearly all appeared to support continued funding for the Stealth bomber, the the military's most technologically advanced project.