Has not been difficult, then does not have attains.

没有艰辛，便无所得。

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It is also true that it is difficult to think of a single such system that has not, for better or worse, been substantially modified by human culture.

同样，很难想象一个这样的系统：不管是好是坏，都没有经过人类文化的实质性修改。

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In handwritten notes below a typed section of the letter, Dennis Milner wrote: "Arranging this so that it does not fail has been very difficult and traumatic for us."

在打印信中有一段手写段落，丹尼斯·米尔纳写道：“这样的成功安排是非常困难的，也让我们感到痛苦。”

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The performance of LIBs has not been sufficient either, thereby difficult to apply to flexible consumer electronics including rollable displays.

ENGADGET: Korean scientists solve flexible battery riddle (video)

Perhaps recruiting traditional head teachers has been difficult, not because the job is too large, but because it is too small.

ECONOMIST: Using scarce head teachers more wisely

The healing process has been difficult but not impossible.

CNN: To Amanda, Gina and Michelle, from a survivor