Below is the link for official website of Jee Advanced 2018.

JEE Advanced Official Website

Thank You...

JEE advanced examination 2018 shall be conducted only via computer mode, to check the entire sylabus please refer below official link:

https://www.jeeadv.ac.in/Syllabus.html

You can get analysis of 2017 paper to know more about syallabus and weightage each chapter has been given in last years paper:

https://engineering.careers360.com/articles/jee-advanced-exam-analysis

Moreover, You can refert to books mentioned below for reference which covers the entire syllabus and has coverage to all difficult problems.

Physics:- 

Concepts of Physics Vol I and II by H.C. Verma

New Pattern JEE Problems: Physics by DC Pandey.

Chmeistry:-

Organic Chemistry by O.P. Tandon

Numerical Chemistry by P.Bahadur

Mathematics:-

Maths XI & XII by R.D. Sharma

Below is the official site to check the JEE Advanced updates including syllabus

Click on the below link

JEE Advanced Official Website

You can also check the syllabus from the given below link

JEE Advanced Syllabus

Good Luck!!