Ocultar y mostrar un Select a Partir de un Radio

<script>
  function  mostrar_select1(){
   
    document.getElementsByName('select2')[0].style.display = 'none';
    document.getElementsByName('select1')[0].style.display = 'block';
  }
    function  mostrar_select2(){
    document.getElementsByName('select1')[0].style.display = 'none';
    document.getElementsByName('select2')[0].style.display = 'block';
  }
</script>

<table width="44%" border="1">

<tr>
<td width="40%" class="parrafo"><div align="left"><strong>Posee SubNivel:</strong></div></td>
<td width="60%" class="parrafo">&nbsp;&nbsp;Si
<input type="radio" name="radio" id="radio" value="radio"  onClick="mostrar_select1()"> 
&nbsp;&nbsp;No
<input type="radio" name="radio" id="radio2" value="radio" onClick="mostrar_select2()"></td>
</tr>
<tr id="link1">
<td class="parrafo">&nbsp;</td>
<td class="parrafo">
  <select name="select1" id="select1" style="display:none;">
<option>dato1</option>
<option>datos1</option>
</select>
  
  <select name="select2" id="select2" style="display:none;">
<option>otras opciones 1</option>
<option>otras opciones 2</option>
</select>
</td>
</tr>

</table>