v3.26.1
Income taxes - Reconciliation between the income taxes expense (benefit) and provision for income taxes (Details)
12 Months Ended
Dec. 31, 2025
CNY (¥)
Dec. 31, 2025
USD ($)
Dec. 31, 2024
CNY (¥)
Dec. 31, 2023
CNY (¥)
Amount        
Expected income tax at Chinese Mainland income tax rate ¥ 437,497,699 $ 62,561,339 ¥ 473,582,524 ¥ 367,144,498
Share based compensation expense not deductible for income tax purposes     10,044,452 10,649,553
Other expenses not deductible for income tax purposes     1,671,017 916,343
Effect of preferential tax rate (211,556,757) (30,252,214) (207,311,932) (134,240,494)
Expiration of operating tax loss carryforwards 40,711,795 5,821,709    
Effect of different tax rate of subsidiary operation in other jurisdictions     2,299,728 (214,788)
Research and development tax deduction     (21,231,000) (20,676,415)
Change in valuation allowance     81,585,304 11,432,693
Gain on deregistration of an entity 93,831,476 13,417,723    
Other 8,894,916 1,271,956    
Income tax on subsidiary earnings 45,500,000 6,506,413 57,750,000 24,459,727
Others     7,311,621 1,659,386
Total income tax expense ¥ 291,649,324 $ 41,705,298 ¥ 405,701,714 ¥ 261,130,503
Tax Jurisdiction of Domicile [Extensible Enumeration] Chinese Mainland Chinese Mainland    
Percentage        
Expected income tax at Chinese Mainland income tax rate 25.00% 25.00%    
Gain on deregisteration of an entity 5.40% 5.40%    
Others 0.50% 0.50%    
Effect of preferential tax rate (12.10%) (12.10%)    
Expiration of operating tax loss carryforwards 2.30% 2.30%    
Income tax on subsidiary earnings 2.60% 2.60%    
Total 16.70% 16.70%    
Chinese Mainland        
Amount        
Change in valuation allowance ¥ (121,328,441) $ (17,349,736)    
Others ¥ (6,410,608) $ (916,704)    
Percentage        
Changes in valuation allowances (6.90%) (6.90%)    
Others (0.40%) (0.40%)    
Cayman Islands        
Amount        
Effect of different tax rate of subsidiary operation in other jurisdictions ¥ 1,886,056 $ 269,702    
Percentage        
Statutory tax rate difference between Chinese Mainland and other jurisdictions 0.10% 0.10%    
Hong Kong        
Amount        
Effect of different tax rate of subsidiary operation in other jurisdictions ¥ 920,370 $ 131,611    
Change in valuation allowance 916,330 131,033    
Others ¥ 786,488 $ 112,466    
Percentage        
Statutory tax rate difference between Chinese Mainland and other jurisdictions 0.10% 0.10%    
Others 0.00% 0.00%    
Changes in valuation allowances 0.10% 0.10%