Попробуйте что-то вроде:
titles = tree.xpath('//span[@class="js-article-title"]')
for title in titles:
print(title.text)
Вывод:
Editorial Board
Transfer learning in computer vision tasks: Remember where you come from
FALF ConvNets: Fatuous auxiliary loss based filter-pruning for efficient deep CNNs
Out-of-region keypoint localization for 6D pose estimation
Region-based Fitting of Overlapping Ellipses and its application to cells segmentation
et c.