1 Corinthians 15:12 Now if Christ is preached as raised from the dead, how can some of you say that there is no resurrection of the dead? 13 But if there is no resurrection of the dead, then Christ has not been raised; 14 if Christ has not been raised, then our preaching is in vain and your faith is in vain. 15 We are even found to be misrepresenting God, because we testified of God that he raised Christ, whom he did not raise if it is true that the dead are not raised. 16 For if the dead are not raised, then Christ has not been raised. 17 If Christ has not been raised, your faith is futile and you are still in your sins. 18 Then those also who have fallen asleep in Christ have perished. 19 If for this life only we have hoped in Christ, we are of all men most to be pitied.
20 But in fact Christ has been raised from the dead, the first fruits of those who have fallen asleep. 21 For as by a man came death, by a man has come also the resurrection of the dead. 22 For as in Adam all die, so also in Christ shall all be made alive. 23 But each in his own order: Christ the first fruits, then at his coming those who belong to Christ. 24 Then comes the end, when he delivers the kingdom to God the Father after destroying every rule and every authority and power. 25 For he must reign until he has put all his enemies under his feet. 26 The last enemy to be destroyed is death. 27 “For God[a] has put all things in subjection under his feet.” But when it says, “All things are put in subjection under him,” it is plain that he is excepted who put all things under him. 28 When all things are subjected to him, then the Son himself will also be subjected to him who put all things under him, that God may be everything to every one.
29 Otherwise, what do people mean by being baptized on behalf of the dead? If the dead are not raised at all, why are people baptized on their behalf? 30 Why am I in peril every hour? 31 I protest, brethren, by my pride in you which I have in Christ Jesus our Lord, I die every day! 32 What do I gain if, humanly speaking, I fought with beasts at Ephesus? If the dead are not raised, “Let us eat and drink, for tomorrow we die.” 33 Do not be deceived: “Bad company ruins good morals.” 34 Come to your right mind, and sin no more. For some have no knowledge of God. I say this to your shame.
35 But some one will ask, “How are the dead raised? With what kind of body do they come?” 36 You foolish man! What you sow does not come to life unless it dies. 37 And what you sow is not the body which is to be, but a bare kernel, perhaps of wheat or of some other grain. 38 But God gives it a body as he has chosen, and to each kind of seed its own body. 39 For not all flesh is alike, but there is one kind for men, another for animals, another for birds, and another for fish. 40 There are celestial bodies and there are terrestrial bodies; but the glory of the celestial is one, and the glory of the terrestrial is another. 41 There is one glory of the sun, and another glory of the moon, and another glory of the stars; for star differs from star in glory.
42 So is it with the resurrection of the dead. What is sown is perishable, what is raised is imperishable. 43 It is sown in dishonor, it is raised in glory. It is sown in weakness, it is raised in power. 44 It is sown a physical body, it is raised a spiritual body. If there is a physical body, there is also a spiritual body. 45 Thus it is written, “The first man Adam became a living being”; the last Adam became a life-giving spirit. 46 But it is not the spiritual which is first but the physical, and then the spiritual. 47 The first man was from the earth, a man of dust; the second man is from heaven. 48 As was the man of dust, so are those who are of the dust; and as is the man of heaven, so are those who are of heaven. 49 Just as we have borne the image of the man of dust, we shall[b] also bear the image of the man of heaven. 50 I tell you this, brethren: flesh and blood cannot inherit the kingdom of God, nor does the perishable inherit the imperishable.
So Paul teaches that a physical/bodily resurrection is essential to Christianity but then teaches that it is a physical/bodily resurrection is not to a physical/natural body but to a spiritual body. This is NOT in conflict with science because science says NOTHING about spiritual bodies but only about physical/natural bodies.
Can you be a Christian if you disagree with Paul either about there being any kind of resurrection or that this is a resurrection to a physical/natural body rather than to a spiritual body? Well I think Christianity is defined most minimally according to the creed of Nicea 325 AD.
We believe in one God, the Father Almighty, Maker of all things visible and invisible. And in one Lord Jesus Christ, the Son of God, begotten of the Father [the only-begotten; that is, of the essence of the Father, God of God,] Light of Light, very God of very God, begotten, not made, consubstantial with the Father; By whom all things were made [both in heaven and on earth]; Who for us men, and for our salvation, came down and was incarnate and was made man; He suffered, and the third day he rose again, ascended into heaven; From thence he shall come to judge the quick and the dead. And in the Holy Ghost. [But those who say: ‘There was a time when he was not;’ and ‘He was not before he was made;’ and ‘He was made out of nothing,’ or ‘He is of another substance’ or ‘essence,’ or ‘The Son of God is created,’ or ‘changeable,’ or ‘alterable’— they are condemned by the holy catholic and apostolic Church.]
According to the very first ecumenical council, this is what Christians believed. Now after this the church divided and different groups added other things to their creed. But if you want to ask what first defined Christianity before all that, then here it is. And the resurrection is stated as a part of this: “and the third day he rose again, ascended into heaven.” It does not say what kind of resurrection you have to believe in but it does say that the resurrection is part of Christian belief.