Custom Post Type Pagination

I create custom post type and display in front end successfully but I have a problem in “pagination”.
Below is my archive-dp_work.php code,

<?php
$temp = $wp_query;
$wp_query = null;
$wp_query = new WP_Query();
$wp_query->query('showposts=1&post_type=dp_work'.'&paged='.$paged);
if ($wp_query->have_posts()) : while ($wp_query->have_posts()) : $wp_query->the_post(); ?>
 <div class="dp-devblogc">
          <div class="col-md-6 work_list_left">
                                      <h2><a>"><?php the_title(); ?></a></h2>
                                      <div class="dp-blogtbg"> 

                                      </div>
                                      <?php the_excerpt(); ?>
                                      <a>" title="Read More"> Read More  <span></span><i class="fa fa-caret-right"></i></a>
                                      </div>
              <div class="col-md-6 work_list_right">
          <?php the_post_thumbnail('post-thumbnail', array( 'class' => "img-responsive")); ?>
              </div>
                                   </div>
<?php endwhile; ?>
<div class="navigation">
<div class="alignleft"><?php next_posts_link('? Older Entries') ?></div>
<div class="alignright"><?php previous_posts_link('Newer Entries ?') ?></div>
</div>
<?php $wp_query = null;
$wp_query = $temp;
?>
<?php else : ?>
<h2>Not Found</h2>
<p>Sorry, but you are looking for something that isn't here.</p>
<?php endif; ?>