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991.
Ted Goebel Heather L. Smith Lyndsay DiPietro Michael R. Waters Bryan Hockett Kelly E. Graf Robert Gal Sergei B. Slobodin Robert J. Speakman Steven G. Driese David Rhode 《Journal of archaeological science》2013
The dispersal of Homo sapiens across the New World is one of the greatest chapters in the history of our species; however, major questions about this late Pleistocene diaspora remain unanswered. Two contentious issues are the timing of colonization of the Bering Land Bridge and origin of Clovis, which at 13,000 calendar years ago is the earliest unequivocal complex of archaeological sites in temperate North America, known by its specialized fluted spear points. One hypothesis is that fluting technology emerged in Beringia and from there was carried southbound, with fluted points becoming the diagnostic “calling card” of early Paleoindians spreading across the Western Hemisphere. Fluted points have long been known from Alaska, yet until now they have never been found in a datable geologic context, making their relationship to Clovis a mystery. Here we show that a new archaeological site at Serpentine Hot Springs, Bering Land Bridge National Preserve, Alaska, contains fluted points in a stratified geologic deposit dating to no earlier than 12,400 calendar years ago. Our results suggest that Alaska's fluted-point complex is too young to be ancestral to Clovis, and that it instead represents either a south-to-north dispersal of early Americans or transmission of fluting technology from temperate North America. These results suggest that the peopling of the Americas and development of Paleoindian technology were much more complex than traditional models predict. 相似文献
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993.
Robert G. Beattie Steven Avery 《Alcheringa: An Australasian Journal of Paleontology》2013,37(4):453-468
BEATTIE, R.G. & AVERY, S., December 2012. Palaeoecology and palaeoenvironment of the Jurassic Talbragar Fossil Fish Bed, Gulgong, New South Wales, Australia. Alcheringa 36, 451–465. ISSN 0311-5518. The Talbragar Fossil Fish Bed has produced a significant number and variety of insect fossils, including the orders Hemiptera, Coleoptera, Orthoptera, Plecoptera, Odonata, Neuroptera, Diptera, Hymenoptera and Mecoptera. Hemiptera are the most common insects. Coleoptera are both common and diverse. Both orders include terrestrial and aquatic species. The other insect orders represented are less common. Many of the insect fossils discovered were previously unknown in the Australian region during the Jurassic, and the new records extend their palaeogeographic range into southeastern Gondwana. A recent collection of insects, fish, coprolites, gastropods, bivalves, bark, leaves, fruiting bodies, burrows and other ichnofossils supports a model of a shallow-water-lake palaeoenvironment at the northern end of the deposit, grading to a shoreline palaeoenvironment towards the southern end of the deposit. The existence of a productive lake supporting a large population of fish and a diverse, aquatic/shoreline and terrestrial woodland fringe palaeoecosystem, dominated by insects and woody plants, is demonstrated. There is no evidence of tetrapods. The Talbragar Fossil Fish Bed has similarities to Type A and B Mesozoic lake deposits reported from Transbaikalia. Culicimorph pupae are numerous and may have filled a significant niche near the base of the aquatic palaeoecosystem. Other immature aquatic insects are rare. The generally articulated nature of the fossil insects is interpreted to have resulted from a sudden but low-energy burial event. 相似文献
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In the early eighteenth century a slave-owning landed gentry emerged in the Cape Colony. Although wealth was unevenly distributed in 1682 and 1705 economic conditions, which included cheap land and labour, favoured small farmers, who earned higher returns on their capital than those with some-what larger investments in farming. These conditions changed between 1705 and 1731. While prices for crops and livestock remained steady or fell slightly, costs of production rose steeply. Slaves cost more and were more widely used. Land cost more and greater efforts were needed to maintain its fertility. Large estates swallowed up unsuccessful small farms and a few were enlarged by dynastic marriages. Large-scale production yielded low returns on capital, but small farms often ceased to make profits. Those with insufficient capital to compete with established gentry in the south-west Cape might take up stock farming in frontier regions, which had long been used by wealthy freehold farmers as additional pasture for their livestock. 相似文献
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