!       ===============================================================
!       |iswth 調用功能開關
!       |      ＝＝ 1   讀入材料參數并獲取材料參數
!       |      ＝＝ 2   計算切線模量
!       |      ＝＝ 3   由應變增量計算應力增量
!       |      ＝＝ 4
!       |      ＝＝ 5
!       |      ＝＝ 6
!       |      ＝＝ 7
!       |      ＝＝ 8   計算歷史量
!       ===============================================================

        SUBROUTINE MatLib( dmatx, strsg, strng, dstrs, dstrn, ietyp,           &
                           imtyp, imats, iposp, iposh, iswth, nstrg )
        USE CtrlData
        USE MeshData
        USE GlobData
        IMPLICIT DOUBLE PRECISION( a-h, o-z )
        DIMENSION strsg( nstrg ), dstrs( nstrg )
        DIMENSION strng( nstrg ), dstrn( nstrg ), dmatx( nstrg, nstrg )

        DO istrg = 1, nstrg
          DO jstrg = 1, nstrg
            dmatx( istrg, jstrg ) = 0.0D0
          END DO
        END DO

        SELECT CASE( imtyp )
        CASE( 1 )
          CALL Mat001( dmatx, strsg, strng, dstrs, dstrn, ietyp,           &
                       imats, iposh, iposp, iswth )
        CASE( 301 )
          CALL Mat301( dmatx, strsg, strng, dstrs, dstrn, ietyp,           &
                       imats, iposh, iposp, iswth, nstrg )
        END SELECT
        END