static linking only some libraries

gcc -lsome_dynamic_lib code.c some_static_lib.a

You could also use ld option -Bdynamic

gcc <objectfiles> -static -lstatic1 -lstatic2 -Wl,-Bdynamic -ldynamic1 -ldynamic2

All libraries after it (including system ones linked by gcc automatically) will be linked dynamically.

gcc objectfiles -o program -Wl,-Bstatic -ls1 -ls2 -Wl,-Bdynamic -ld1 -ld2

you can also use: -static-libgcc -static-libstdc++ flags for gcc libraries

keep in mind that if libs1.so and libs1.a both exists, the linker will pick libs1.so if it's before -Wl,-Bstatic or after -Wl,-Bdynamic. Don't forget to pass -L/libs1-library-location/ before calling -ls1.