TECHNOLOGY FOCUS - ELECTRICAL POWER AND ENERGY - Preferred Parameters: Diameter of the through hole is 0.01-0.5 micron, the porosity is 30-60% by volume, and the thickness of the diaphragm is 12-30.    TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Components: Pore-forming substance is inorganic whisker. Inorganic whisker is calcium sulfate whisker, potassium titanate whisker, aluminum borate whisker, magnesium borate whisker, magnesium subsulfate whisker, magnesium hydrate whisker, cupric hydroxide whisker, monox whisker, alumina whisker, magnesia whisker, or zinc oxide whisker. Preferred Process: Pore-forming substance is removed by adding solvent    TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Components: Polynary organic carboxylic acid or ramification is quadribasic organic carboxylic acid, quadribasic organic acyl chloride, quadribasic organic acid ester, or dualistic organic estolide. Solvent is N-2-methyl ketopyrrolidine, N,N-dimethyl acetamide, N,N-dimethyl formamide, dimethyl sulfoxide, m-cresol, tetrahydrofuran, or methanol. Solvent for removing pore-forming substance is water and acid solution of organic solvent, or water and alkaline solution of organic solvent.    TECHNOLOGY FOCUS - POLYMERS - Preferred Composition: Content of polyimide is 50-96 wt.%, and polyolefine is 5-50 wt.%. Mass ratio of the polyimide to the pore-forming substance is 100:20-60, polyimide to the solvent is 8-15:100, and polyimide to the polyolefine is 100:5-50. Mass ratio of the polynary organic carboxylic acid or ramification and the total mass of the organic diamine to the pore-forming substance is 100:20-6. Mass ratio of the solvent and the polynary organic carboxylic acid or ramification and organic diamine polyimide is 100: 8-15. Moore ratio of the polynary organic carboxylic acid or ramification and the organic diamine is 0.99-1.05:1. Preferred Process: Polyporous film is coated with polyolefine solution to be dried in vacuum. Polynary organic carboxylic acid or ramification, organic diamine, pore-forming substance are mixed and contacted with the solvent to obtain an equal solution to film, and the pore-forming substance is removed. The process further comprises heating the film to remove the solvent for approximately 1~5 hours at 270-350 degrees C before removing the pore-forming substance. Preferred Conditions: Heating is done at 120-180 degrees C for 4-12 hours. Vitrification temperature of polyolefine is 100-300 degrees C. Mixing and contacting of the polynary organic carboxylic acid or ramification, organic diamine, pore-forming substance with the solvent is done at 0-90 degrees C, the contact time is 4-24 hours. Preferred Parameters: Melting point of polyimide is 400-700 degrees C. Preferred Components: Polyimide is polyimide of constitutional Formula I:R1,R2=fatty group or aromatic alkyl; andn=5-10000.Polyimide is polyimide of constitutional Formula II:R1, R2=fatty group or aromatic alkyl; andn=50-10000.