Some kinds of batteries can be recharged by connecting them to a source of direct current.

有些型号的电池在接入直流电源时就能充电。

《柯林斯英汉双解大词典》

That can be worth it, but it's never a direct source of revenue.

虽然这可能是值得的，但是这却从来不是直接的收入来源。

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The second hypothesis is focusing on a possible direct source of poultry-to-human transmission.

第二种假定注重于家禽传播给人的可能直接来源。

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Police searched the suspect's home, "a short distance" from the temple, on Sunday evening, according to a law enforcement source with direct knowledge of the investigation.

CNN: Gunman, six others dead at Wisconsin Sikh temple

"Her lack of fundamental understanding of some key issues was dramatic, " said another McCain source with direct knowledge of the process to prepare Palin after she was picked.

CNN: Palin's off-script comments irk McCain aides

This is a well-known problem and one I wrote about in 2011, with specific reference to Twitter which was at the time a significant source of direct visits.

FORBES: Filling In The 'Direct Visits' Data Hole