Note 4 - Stockholders' Equity, Stock Options and Warrants - Schedule of Listing of Stock Options and Warrants (Details)	Dec. 31, 2021 $ / shares shares
Shares, options (in shares) | shares	1,062,871
Shares, warrants (in shares) | shares	31,699,885
Minimum [Member]
Price, options (in dollars per share)	$ 0.72
Warrants issued, exercise price (in dollars per share)	0.80
Maximum [Member]
Price, options (in dollars per share)	5,962.50
Warrants issued, exercise price (in dollars per share)	$ 22.50
Warrants 2017 [Member]
Shares, warrants (in shares) | shares	108,435
Warrants 2017 [Member] | Minimum [Member]
Warrants issued, exercise price (in dollars per share)	$ 10.71
Warrants 2017 [Member] | Maximum [Member]
Warrants issued, exercise price (in dollars per share)	$ 22.50
Warrants 2018 [Member]
Shares, warrants (in shares) | shares	196,946
Warrants 2018 [Member] | Minimum [Member]
Warrants issued, exercise price (in dollars per share)	$ 8.36
Warrants 2018 [Member] | Maximum [Member]
Warrants issued, exercise price (in dollars per share)	$ 13.125
Warrants 2019 [Member]
Shares, warrants (in shares) | shares	1,690,286
Warrants 2019 [Member] | Minimum [Member]
Warrants issued, exercise price (in dollars per share)	$ 0.845
Warrants 2019 [Member] | Maximum [Member]
Warrants issued, exercise price (in dollars per share)	$ 11.80
Warrants 2020 [Member]
Shares, warrants (in shares) | shares	2,010,144
Warrants 2020 [Member] | Minimum [Member]
Warrants issued, exercise price (in dollars per share)	$ 0.845
Warrants 2020 [Member] | Maximum [Member]
Warrants issued, exercise price (in dollars per share)	$ 2.992
Warrants 2021 [Member]
Shares, warrants (in shares) | shares	27,694,074
Warrants 2021 [Member] | Minimum [Member]
Warrants issued, exercise price (in dollars per share)	$ 0.80
Warrants 2021 [Member] | Maximum [Member]
Warrants issued, exercise price (in dollars per share)	$ 2.992
Stock Options 2012 [Member]
Shares, options (in shares) | shares	114
Stock Options 2012 [Member] | Minimum [Member]
Price, options (in dollars per share)	$ 1.54
Stock Options 2012 [Member] | Maximum [Member]
Price, options (in dollars per share)	$ 1,500.00
Stock Options 2013 [Member]
Shares, options (in shares) | shares	146
Stock Options 2013 [Member] | Minimum [Member]
Price, options (in dollars per share)	$ 1.54
Stock Options 2013 [Member] | Maximum [Member]
Price, options (in dollars per share)	$ 5,962.50
Stock Options 2014 [Member]
Shares, options (in shares) | shares	84
Stock Options 2014 [Member] | Minimum [Member]
Price, options (in dollars per share)	$ 1.54
Stock Options 2014 [Member] | Maximum [Member]
Price, options (in dollars per share)	$ 3,468.75
Stock Options 2015 [Member]
Shares, options (in shares) | shares	394
Stock Options 2015 [Member] | Minimum [Member]
Price, options (in dollars per share)	$ 1.54
Stock Options 2015 [Member] | Maximum [Member]
Price, options (in dollars per share)	$ 862.50
Stock Options 2016 [Member]
Shares, options (in shares) | shares	9,174
Stock Options 2016 [Member] | Minimum [Member]
Price, options (in dollars per share)	$ 1.54
Stock Options 2016 [Member] | Maximum [Member]
Price, options (in dollars per share)	$ 42.50
Stock Options 2017 [Member]
Shares, options (in shares) | shares	214,555
Stock Options 2017 [Member] | Minimum [Member]
Price, options (in dollars per share)	$ 1.54
Stock Options 2017 [Member] | Maximum [Member]
Price, options (in dollars per share)	$ 21.00
Stock Options 2018 [Member]
Shares, options (in shares) | shares	78,325
Stock Options 2018 [Member] | Minimum [Member]
Price, options (in dollars per share)	$ 1.54
Stock Options 2018 [Member] | Maximum [Member]
Price, options (in dollars per share)	$ 13.50
Stock Options 2019 [Member]
Shares, options (in shares) | shares	314,963
Stock Options 2019 [Member] | Minimum [Member]
Price, options (in dollars per share)	$ 1.54
Stock Options 2019 [Member] | Maximum [Member]
Price, options (in dollars per share)	$ 7.50
Stock Options 2020 [Member]
Shares, options (in shares) | shares	303,199
Stock Options 2020 [Member] | Minimum [Member]
Price, options (in dollars per share)	$ 0.73
Stock Options 2020 [Member] | Maximum [Member]
Price, options (in dollars per share)	$ 3.48
Stock Options 2021 [Member]
Shares, options (in shares) | shares	141,917
Stock Options 2021 [Member] | Minimum [Member]
Price, options (in dollars per share)	$ 0.72
Stock Options 2021 [Member] | Maximum [Member]
Price, options (in dollars per share)	$ 1.47