I haven't been able to produce a link that will get you to the actual page. However, I have managed to figure out how to construct a URL that queries their MSQL interface for NCBI ID 1017:

http://www.freebase.com/api/service/mqlread?query={"query":{"/type/object/id":[],"/biology/gene/ncbi_id":"1017"}}

It correctly returns (in JSON format) that this corresponds to the Freebase concept /en/cyclin_dependent_kinase_2:

{
  "code": "/api/status/ok",
  "result": {
    "/biology/gene/ncbi_id": "1017",
    "/type/object/id": [
      "/en/cyclin_dependent_kinase_2"
    ]
  },
  "status": "200 OK",
  "transaction_id": "cache;cache02.p01.sjc1:8101;2010-08-18T18:36:48Z;0038"
}

I hope it is possible to make some clever little Javascript uses this JSON as input to direct you to the correct web page, but I fear that you may run into the dreaded cross-domain security problems.

At the moment, there is no direct way to link to a gene via its NCBI identifier.

However, it would be possible to modify the Freebase schema to make the NCBI identifier act as a "key" to the topic, rather than its current behaviour of being "just" a property. You'd then be able to access it as something like

http://www.freebase.com/view/biology/ncbi_gene/1017

(but that's not possible yet).

If this is something you're interested in doing, I'd suggest joining the freebase-discuss list and floating the idea there - it seems sensible to me.

Hope this helps.