data = Table[{x, Exp[.2 + .3 x + .1 Sin[x] + RandomReal[{-.2, .2}]]},
             {x, RandomReal[5, 100]}]; 
nlm = NonlinearModelFit[data, Exp[a + b Sin[x] + c Cos[x]], {a, b, c}, x];
pt = nlm["ParameterTable"];

You can also use Part as follows to access the row labels, column labels and the content of pt:

rowlabels = Sequence[1, 1, 2 ;;, 1];
collabels = Sequence[1, 1, 1, 2 ;;];
content = Sequence[1, 1, 2 ;;, 2 ;;];

pt[[rowlabels]]
(* {a, b, c} *)

pt[[collabels]]
(* {"Estimate", "Standard Error", "t-Statistic", "P-Value"} *)

pt[[content]]
(* {{1.00159, 0.0252967, 39.5938, 1.10726*10^-61},
    {-0.375734, 0.0304626, -12.3343, 1.3907*10^-21},
    {-0.157534, 0.0357183, -4.41046, 0.0000267067}} *)

pt[[content]] == nlm["ParameterTableEntries"]
(* True *)

data = Table[{x, Exp[.2 + .3 x + .1 Sin[x] + RandomReal[{-.2, .2}]]},
             {x, RandomReal[5, 100]}]; 
nlm = NonlinearModelFit[data, Exp[a + b Sin[x] + c Cos[x]], {a, b, c}, x];
pt = nlm["ParameterTable"];

You can also use Part as follows to access the row labels, column labels and the content of pt:

rowlabels = Sequence[1, 1, 2 ;;, 1];
collabels = Sequence[1, 1, 1, 2 ;;];
content = Sequence[1, 1, 2 ;;, 2 ;;];

pt[[rowlabels]]
(* {a, b, c} *)

pt[[collabels]]
(* {"Estimate", "Standard Error", "t-Statistic", "P-Value"} *)

pt[[content]]
(* {{1.00159, 0.0252967, 39.5938, 1.10726*10^-61},
    {-0.375734, 0.0304626, -12.3343, 1.3907*10^-21},
    {-0.157534, 0.0357183, -4.41046, 0.0000267067}} *)

pt[[content]] == nlm["ParameterTableEntries"]
(* True *) 

Row[Labeled[#, #2, Top] & @@@ {{pt,"ParameterTable\n"},
    {MapAt[Style[2 #, Red, 20] &, pt, {{1, 1, 2, 4}}], 
     "ParameterTable\nwith part {1,1,2,4} modified"}}, Spacer[10]]