本文介绍了一种高灵敏度中子监测器，它对天然中子本底的计数率约每分钟20次计数。

A high sensitive neutron monitor is described in this paper. It has an approximate counting rate of 20 CPM for natural background neutrons.

youdao

同位素是存在于元素的变体，天然存在，同位素与元素具有相同的化学性质，但由于所含的中子数不同而重量不同。

These are naturally occurring variants of elements,which share the same chemical properties but have different weights because their nuclei contain different numbers of neutrons.

youdao

对于天然铌的全套中子核数据评价是依据测量到1989年的实验数据。同时，理论计算采用了MUP2和AUJP程序。

An evaluation of a complete neutron nuclear data for natural niobium has been finished on the data measured by experiments up to 1989 and theoretical calculations with program MUP2 and AUJP.

youdao