A fertile, plowed field is rapidly invaded by a large variety of weeds, whereas a neighboring construction si... [查看全文]
Whatever the source of the original tamed herds might have been, it seems entirely likely that much the same... [查看全文]
These include conducting vessels that transport water and minerals upward from the roots and that move the ph... [查看全文]
The frequency with which certain simple motifs appear in these oldest sites has led rock-art researchers to a... [查看全文]
Dinosaurs rapidly became extinct about 65 million years ago as part of a mass extinction known as the K-T e... [查看全文]
The principal elements in behavioral thermoregulation are basking (heliothermy),heat exchange with substrates such... [查看全文]
The Peisistratids, as the succession of tyrants were called (after the founder of the dynasty, Peisistratos), ... [查看全文]
Anaximander,observing the motions of the heavens around the polestar, was probably the first of the Greek phil... [查看全文]
Many prehistorians believe that farming may have emerged dependently in several different areas of the world w... [查看全文]
托福阅读长难句100句:动物群统治地位 However, no group or species can maintain its dominance indefinitely, and whe... [查看全文]