controlled study human Humans 1,360 article 1,314 priority journal 1,126 human cell 994 female 746 nonhuman 680 male 630 Female 622 Animals 578 adult 544 Male 512 unclassified drug 506 Article 462 protein expression 428 metabolism 422 animal cell 384 Adult 344 mouse 330 Mice 292 animal 290 signal transduction 272 cell proliferation 250 clinical article 250 genetics 246 animal experiment 240 Middle Aged 238 in vitro study 228 major clinical study 220