小缩略图在一个位置以稍大的形式展现，鼠标点击小缩略图，大图更换，鼠标精工大图某个部分，该部分以放大镜的形式放大显示

实现您所提到的这种效果，需要使用 JavaScript 和 CSS 技术。以下是一种实现方式：

1. HTML部分：

<div class="thumbnail">
  <img src="small.jpg" alt="Thumbnail">
  <div class="magnifier"></div>
</div>
<div class="large-image">
  <img src="large.jpg" alt="Large Image">
</div>

2. CSS部分：

.thumbnail {
  position: relative;
  width: 200px;
  height: 200px;
  overflow: hidden;
}
.thumbnail img {
  display: block;
  width: 100%;
  height: 100%;
}
.magnifier {
  position: absolute;
  top: 0;
  left: 0;
  width: 100px;
  height: 100px;
  border: 1px solid #ccc;
  display: none;
  cursor: move;
}
.large-image {
  position: relative;
  margin-top: 20px;
}
.large-image img {
  display: block;
  width: 100%;
}

3. JavaScript部分：

// 获取DOM元素
var thumbnail = document.querySelector('.thumbnail');
var magnifier = document.querySelector('.magnifier');
var largeImage = document.querySelector('.large-image img');

// 当鼠标悬停在小图上时，显示放大镜和大图
thumbnail.addEventListener('mouseenter', function(e) {
  magnifier.style.display = 'block';
  largeImage.src = 'large.jpg';
});

// 当鼠标移出小图时，隐藏放大镜和大图
thumbnail.addEventListener('mouseleave', function(e) {
  magnifier.style.display = 'none';
  largeImage.src = '';
});

// 当鼠标在小图上移动时，移动放大镜，同时更新大图的显示区域
thumbnail.addEventListener('mousemove', function(e) {
  var thumbnailRect = thumbnail.getBoundingClientRect();
  var magnifierRect = magnifier.getBoundingClientRect();
  var x = e.clientX - thumbnailRect.left - magnifierRect.width / 2;
  var y = e.clientY - thumbnailRect.top - magnifierRect.height / 2;
  x = Math.max(0, x);
  y = Math.max(0, y);
  x = Math.min(thumbnailRect.width - magnifierRect.width, x);
  y = Math.min(thumbnailRect.height - magnifierRect.height, y);
  magnifier.style.left = x + 'px';
  magnifier.style.top = y + 'px';
  largeImage.style.left = -x * 2 + 'px';
  largeImage.style.top = -y * 2 + 'px';
});

// 当鼠标按下放大镜时，禁用文本选择和拖拽
magnifier.addEventListener('mousedown', function(e) {
  e.preventDefault();
  magnifier.style.cursor = 'move';
  thumbnail.style.userSelect = 'none';
  thumbnail.style.MozUserSelect = 'none';
  thumbnail.style.webkitUserSelect = 'none';
  thumbnail.style.msUserSelect = 'none';
  document.addEventListener('mousemove', moveMagnifier);
  document.addEventListener('mouseup', releaseMagnifier);
});

// 移动放大镜
function moveMagnifier(e) {
  var thumbnailRect = thumbnail.getBoundingClientRect();
  var magnifierRect = magnifier.getBoundingClientRect();
  var x = e.clientX - thumbnailRect.left - magnifierRect.width / 2;
  var y = e.clientY - thumbnailRect.top - magnifierRect.height / 2;
  x = Math.max(0, x);
  y = Math.max(0, y);
  x = Math.min(thumbnailRect.width - magnifierRect.width, x);
  y = Math.min(thumbnailRect.height - magnifierRect.height, y);
  magnifier.style.left = x + 'px';
  magnifier.style.top = y + 'px';
  largeImage.style.left = -x * 2 + 'px';
  largeImage.style.top = -y * 2 + 'px';
}

// 释放放大镜
function releaseMagnifier(e) {
  magnifier.style.cursor = 'default';
  thumbnail.style.userSelect = 'auto';
  thumbnail.style.MozUserSelect = 'auto';
  thumbnail.style.webkitUserSelect = 'auto';
  thumbnail.style.msUserSelect = 'auto';
  document.removeEventListener('mousemove', moveMagnifier);
  document.removeEventListener('mouseup', releaseMagnifier);
}

以上代码实现了一个简单的图片放大镜效果，您可以根据需要进行修改和优化。