Get post only from ‘standard’ post format

I use the following codes to get posts only from ‘image‘ post format and it works.

<?php if( has_post_format('image')){ ?>
   <?php the_post_thumbnail(); ?>
<?php } ?>

I also need to get posts only from ‘standard‘ post format with the following codes, but it get post from all post formats.

 <?php if( has_post_format('standard')){ ?>
     <a href="https://wordpress.stackexchange.com/questions/103119/<?php the_permalink(); ?>" rel="bookmark"><?php the_title(); ?></a>
 <?php } ?>

Any solutions?

Do,

<?php if( false == get_post_format() ){ ?>
    <a href="https://wordpress.stackexchange.com/questions/103119/<?php the_permalink(); ?>" rel="bookmark"><?php the_title(); ?></a>
<?php } ?>

The standard post format isn’t actually a post format, so if you conditionally check whether a post contains a post format (other than the default standard), it will return false, because it’s set to… standard.