In the secondary structure of roots, xylem rays and phloem rays belong to ( ). A: Secondary rays B: Vascular rays C: Pith rays
In the secondary structure of roots, xylem rays and phloem rays belong to ( ). A: Secondary rays B: Vascular rays C: Pith rays
The ________________ has prepared the X-rays. A: adiologist B: pharmacist
The ________________ has prepared the X-rays. A: adiologist B: pharmacist
以下属于直接电离辐射的是（） A: X-rays B: γ-rays C: β-rays D: neutrons
以下属于直接电离辐射的是（） A: X-rays B: γ-rays C: β-rays D: neutrons
ItwasDr.Rontgenwho（）X-rays. A: discovered B: invented C: madeup
ItwasDr.Rontgenwho（）X-rays. A: discovered B: invented C: madeup
If we have a tungsten anode (work function f=4.63 eV) and electron acceleration voltage of 35 kV, what is the minimum wavelength of the x rays? ( )
If we have a tungsten anode (work function f=4.63 eV) and electron acceleration voltage of 35 kV, what is the minimum wavelength of the x rays? ( )
The ( )prepared the X-rays. A: radiologist B: pharmacist C: nurse D: obstetrician
The ( )prepared the X-rays. A: radiologist B: pharmacist C: nurse D: obstetrician
It was Dr. Rontgen who （） X-rays. A: Adiscovered B: Binvented C: Cmade up
It was Dr. Rontgen who （） X-rays. A: Adiscovered B: Binvented C: Cmade up
It was Dr. Rontgen who （） X-rays. A: discovered B: invented C: made u
It was Dr. Rontgen who （） X-rays. A: discovered B: invented C: made u
The anti-UV mutation of microorganisms must be induced by ultraviolet rays
The anti-UV mutation of microorganisms must be induced by ultraviolet rays
Ultraviolet rays from the Sun can cause which of the following?
Ultraviolet rays from the Sun can cause which of the following?