如果需要响应式的让".navbar-nav"里的内容隐藏，必须在以下代码的第三行设置：
.navbar-expand{-sm|-md|-lg|-xl}
其对应的是在不同屏幕宽度时进行菜单项目的显示和隐藏。

<nav class="navbar navbar-expand-md navbar-light">
...
</nav>

<template>
  <div class="header">
    <nav class="navbar navbar-expand-md navbar-light">
      <a class="navbar-brand" href="#">
        <img src="../assets/images/logo_PB.png" width="150" alt="">
      </a>
      <button class="navbar-toggler" type="button" data-toggle="collapse" data-target="#navbarSupportedContent" aria-controls="navbarSupportedContent" aria-expanded="false" aria-label="Toggle navigation">
        <span class="navbar-toggler-icon"></span>
      </button>
      <div class="collapse navbar-collapse justify-content-end" id="navbarSupportedContent">
          <ul class="navbar-nav">
            <li class="nav-item">
              <a class="nav-link" href="#">Préstamos en vivo <span class="sr-only">(current)</span></a>
            </li>
            <li class="nav-item">
              <a class="nav-link" href="#">Invierte</a>
            </li>
            <li class="nav-item">
              <a class="nav-link" href="#">Pide tu préstamo</a>
            </li>
            <li class="nav-item">
              <a class="nav-link" href="#">Blog</a>
            </li>
            <li class="nav-item">
              <a class="nav-link" href="#"><span class="text-blue">Ingresar</span></a>
            </li>
          </ul>
      </div>
    </nav>
  </div>
</template>
<script>
export default {

  data() {
    return {

    }
  },
}
</script>
<style media="screen">
@media (min-width: 796px){
  .navbar-expand-lg {
      -ms-flex-flow: row nowrap;
      /* flex-flow: row nowrap; */
      -ms-flex-pack: start;
      /* justify-content: flex-start; */
  }
}


/*@media (min-width: 768px) and (max-width: 1000px) {
   .collapse {
       display: none !important;
   }
}*/
.header {
    box-shadow: none;
  transition: all 0.4s ease-in-out 0s;
  z-index: 900;
  background: rgba(255, 255, 255, 1);
  width: 100%;
  position: fixed;
  top:0;
  left:0;
    border-bottom: 1px solid #c6c6c5;
}
.header .container-fluid {
    width: 95%;
}
.navbar-nav > li > a{
    text-transform: uppercase;
    font-size: 12px;
    color: #7b7b7c;
    letter-spacing: .8px;
    font-weight: 900;
    font-family: 'Open Sans', sans-serif;
}
.text-blue{
  color:#0181c2;
}
</style>