At one time there were millions of these birds in North America, but now there are none.
曾经还有数以百万计的这些鸟类在北美，但现在没有。
There are many more examples, but none hold a candle to what's happening right now.
还有更多的例子，但是没有一个对眼下正在发生的事情有什么帮助。
While there are now regional warning centers in the Indian Ocean, there are none in the Mediterranean.
印度洋上已经设置了预警中心，但地中海地区还没有行动。
Schuchter says melanoma patients are celebrating this moment because there are now two good treatment options for patients, when there really were none before.
舒特很高兴，因为病患过去想治疗却无药，而现在有两种药可供治疗选择。
There are 31 items on the World Heritage List in China, but none of them is the heritage on ocean. Furthermore, the researching of the heritages on ocean is scarcity in home now.
中国目前已列入《世界遗产名录》的31项物质类世界遗产中，还没有一项海洋类遗产，国内对海洋遗产的专门研究也很少。
Now there are many methods of edge extraction to have been researched, but none of them is an effective method that is suitable to all kinds of image, especially to the noise image.
目前已研究出不少边缘提取的方法，但还没有一种普遍适用于各种图像的有效方法，尤其对于噪声图像。
Now there are many methods of edge extraction to have been researched, but none of them is an effective method that is suitable to all kinds of image, especially to the noise image.
目前已研究出不少边缘提取的方法，但还没有一种普遍适用于各种图像的有效方法，尤其对于噪声图像。
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