conda search搜索不带，但install却能安装是这么回事？

 conda search magma-cuda90

使用上的命令搜索不到：

Fetching package metadata .........................

PackageNotFoundError: Packages missing in current channels:
            
  - magma-cuda90

We have searched for the packages in the following channels:
            
  - https://mirrors.ustc.edu.cn/anaconda/cloud/menpo/linux-64
……………………

但使用install却能成果安装：

conda install -c pytorch magma-cuda90
Fetching package metadata ...........................
Solving package specifications: .

Package plan for installation in environment /home/king/anaconda3/envs/caffe2:

The following NEW packages will be INSTALLED:

    magma-cuda90: 2.4.0-1                                pytorch                      

这个是为什么呢？
使用下面命令试试是吧。conda搜索不到的替代方案：

$ anaconda search -t conda magma-cuda90
Using Anaconda API: https://api.anaconda.org
Packages:
     Name                      |  Version | Package Types   | Platforms       | Builds    
     ------------------------- |   ------ | --------------- | --------------- | ----------
     etcshadow/magma-cuda90    |    2.1.0 | conda           | linux-64        | h865527f_5
     pytorch/magma-cuda90      |    2.4.0 | conda           | linux-64        | 1, hae16b58_1
     soumith/magma-cuda90      |    2.3.0 | conda           | linux-64        | 1, hae16b58_1
Found 3 packages

Run 'anaconda show ' to get installation details

明显是使用了其他的源。