科学技术类搜索引擎及目录索引

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声学 Acoustics：

Acoustics and Vibrations WWW Virtual Library - Directory of acoustics links including bioacoustics (whales, bats, dolphins), machine diagnostics, audio, underwater acoustics, architectural acoustics, lutherie, universities, active noise cancellation, ultrasonic imaging, medical imaging, sonar, structural vibration, and more.