He supposed that some minimum amount of energy is required in order to pull an electron away from a metal surface . 他假设，某个最小的能量是为把一个电子拉出某种金属表面所必需的。
The oxygenator, which gives the blood the oxygen with the body needs, is also part of the heart-lung machine . 心肺机中含有一部分叫供氧器，是往血液里送氧的，而氧是血液里所必需的。
For he did not have the qualities necessary for survival in the midst of a swamp of intrigues and struggles for power . 因为他没有具备在阴谋和权力斗争的渊薮中生存下来所必需的本领。
However, since the dose rate is steadily decreasing during the exposure, appropriate allowance for this must be made . 可是，由于在辐照过程中剂量率逐步下降，所以必需进行适当的修正。
Only young magma intrusions contain the amount of heat necessary for the heat supply of an economical geothermal field . 只有年青的岩浆侵入体才能拥有一个经济性地热田热补给所必需的热能。
It is apparent from inspection of the table that poultry meat and eggs are relatively high in many of the essential amino acids . 如表所示，显然在禽肉和蛋类里许多必需氨基酸含量相对较高。
This ignorance precludes the full theoretical calculation of wave forms necessary to compare with relevant observations . 这种未知使我们无法作出所必需的理论计算，以与有关观测结果相比较。
The hydrogen bonding that takes place between water molecules accounts for some of the remarkable and vital properties of water . 水分子之间的氢键解释了水的某些特具的和维持生命所必需的性质。
This was a massive task requiring the carriage of many thousand tons of stores and could be effected only by degrees . 这是一项庞大的任务，需要运输成千上万吨的必需物资，而且也只能逐步地完成。
Truly scientific economics can merely help to reveal the driving forces of economic development through different historical periods . 真正的科学经济学必需有助于揭示不同历史时期的经济发展动力。
