<header>
  <nav class="navbar navbar-expand-md">
    <div class="container">
      <a class="navbar-brand" href="/" aria-label="PDIS">
      網站名稱
      </a>
      <button class="navbar-toggler collapsed" type="button" data-bs-toggle="collapse" data-bs-target="#Navbar" aria-controls="Navbar" aria-expanded="true" aria-label="Toggle navigation">
        <span class="navbar-toggler-icon"></span>
      </button>
      <div class="navbar-collapse collapse" id="Navbar">
        <ul class="navbar-nav">
          <li class="nav-item dropdown order-2 order-md-1">
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            <ul class="dropdown-menu" aria-labelledby="DropdownMenu1">
              <li><a class="dropdown-item" href="#">下拉選單第一層標題文字</a></li>
              <li><a class="dropdown-item" href="#">下拉選單第一層標題文字</a></li>
              <li><a class="dropdown-item" href="#">下拉選單第一層標題文字</a></li>
              <li><a class="dropdown-item" href="#">下拉選單第一層標題文字</a></li>
              <li><a class="dropdown-item" href="#">下拉選單第一層標題文字</a></li>
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              <li><a class="dropdown-item" href="#">下拉選單第一層標題文字</a></li>
              <li><a class="dropdown-item" href="#">下拉選單第一層標題文字</a></li>
              <li><a class="dropdown-item" href="#">下拉選單第一層標題文字</a></li>
              <li><a class="dropdown-item" href="#">下拉選單第一層標題文字</a></li>
              <li><a class="dropdown-item" href="#">下拉選單第一層標題文字</a></li>
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          </li>
          <li class="nav-item dropdown order-2 order-md-1">
            <a class="nav-link" href="/">最新消息</a>
          </li>
          <li class="nav-item dropdown order-2 order-md-1">
            <a class="nav-link" href="/">聯絡我們</a>
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          <li class="nav-item dropdown order-1 order-md-2">
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              <i class="bi bi-search"></i>
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            <div class="dropdown-menu search-menu" aria-labelledby="DropdownSearch">
              <span class="dropdown-menu-title d-none d-md-block">使用關鍵字搜尋網站</span>
              <div class="input-group">
                <input type="text" class="form-control" id="Input1" placeholder="請輸入關鍵字">
                <div class="input-group-append">
                  <button class="btn btn-secondary" type="button"><i class="bi bi-search"></i></button>
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              <div class="dropdown-divider d-none d-md-block"></div>
              <div class="hot-searching">
                <span class="d-inline d-md-block">熱門關鍵字</span>
                <a href="#">國家科學技術發展計畫</a>
                <a href="#">申辦流程</a>
                <a href="#">啟動法規鬆綁</a>
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          <li class="nav-item dropdown ms-md-auto order-3">
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              <i class="bi bi-gear"></i><span>網站設定 / Setting</span>
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            <ul class="dropdown-menu setting-menu" aria-labelledby="DropdownSetting">
              <li><a class="dropdown-item dropdown-item-header">網站設定 Setting</a></li>
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                <select class="form-select" id="LanguageSelect" aria-label="LanguageSelect">
                  <option selected>請選擇一個選項</option>
                  <option value="zh-tw">繁體中文</option>
                  <option value="en-us">English (US</option>
                  <option value="en-uk">English (UK)</option>
                  <option value="jp">Japanese</option>
                  <option value="th">Thai</option>
                </select>
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              <li><a class="dropdown-item dropdown-item-title">文字大小</a></li>
              <li>
                <div class="btn-group" role="group" aria-label="Font size">
                  <button type="button" class="btn btn-secondary">小</button>
                  <button type="button" class="btn btn-secondary">預設</button>
                  <button type="button" class="btn btn-secondary">大</button>
                </div>
              </li>
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      </div>
    </div>
  </nav>
</header>