$("input[@type=radio][@checked]").val();

$("input[@type=radio]").attr("checked",'2');//設置value=2的項目為當前選中項

var item = $('input[@name=items][@checked]').val();

$('input[@name=items]').get(1).checked = true

var_name = $("input[@name='radio_name']:checked").val();

var_name = $("input[name='radio_name']:checked").val();

function getra(){

var_name = $("input[name='isspecialcnt']:checked").val();
//alert(var_name);
if(var_name=='1'){
$("#isspecialcntyes").show();
$("#isspecialcntno").hide();
}
if(var_name=='0'){
$("#isspecialcntyes").hide();
$("#isspecialcntno").show();
}
}

<form name="form1" method="post" action="">
<p>
<label>
<input type="radio" name="radiogroup1" value="單選" id="radiogroup1_0">
單選</label>
<br>
<label>
<input type="radio" name="radiogroup1" value="單選" id="radiogroup1_1">
單選</label>
<br>
<label>
<input type="radio" name="radiogroup1" value="單選" id="radiogroup1_2">
單選</label>
<br>
<label>
<input type="radio" name="radiogroup1" value="單選" id="radiogroup1_3">
單選</label>
<br>
<label>
<input type="radio" name="radiogroup1" value="單選" id="radiogroup1_4">
單選</label>
<br>
<label>
<input type="radio" name="radiogroup1" value="單選" id="radiogroup1_5">
單選</label>
<br>
</p>
</form>