blink a led 10ms every 1 second
Figure 1. 555 timer with adjustable duty cycle.

To adjust the duty cycle you create alternate charge and discharge paths for the timing capacitor using diodes. This example uses a potentiometer to adjust. You can leave it and R3 out if you calculate the required values.

See LearnAbout-Electronics.



As @DanielTork suggests you can do the same thing by adjusting the charge (R1) and discharge (R2) resistors. 



Figure 2. A CMOS 555 will consume much less power.
Source: All About Circuits.