We intend to visit China for 6/7days, as tourist. What type of visa is required ?

Yes, you can apply in your respective cities, your applications should be submitted to CVASC in New Delhi and Consulate General of China in Kolkata.
Documents are passport, application form for China visa, proof of sufficient finances to cover all expenditures in China (optional but better if any), confirmed return tickets and hotel reservation, covering letter from your company or office (if any).
A single entry China visa is valid for 3 months after issuance, so, apply one or two months before your departure.