there were always restriction for china to invest in key industries in Russia, but this is a good opportunity for China to extend their reach in Russia, but still if I'm not mistaking Russia will not open the gate just yet, which any smart person should do, key industries such as oil and Gas (exploitation and investment in gazprom and stuff), rare metals, military, pharmaceutic and banking system will be open for Chinese,
There is a lot of Chinese investment in the agricultural and manufacturing sectors of Russia. But their involvement in the oil and gas, and mineral sector is limited. And they are not just limited to the Chinese. In general, all foreigners are limited from investing in these sectors Almost all the oil deposits and mines are fully owned by the Russian government or the individual Russian citizens, although there are some exceptions, such as the Exxon Neftegas / Sakhalin-I (30% owned by Exxon Mobil, 20% owned by ONGC) and Sakhalin Energy / Sakhalin-II (Shell - 27.5%, Mitsui - 12.5%, and Mitsubishi - 10%).