全文获取类型
收费全文 | 3303篇 |
免费 | 41篇 |
专业分类
3344篇 |
出版年
2020年 | 62篇 |
2019年 | 55篇 |
2018年 | 101篇 |
2017年 | 102篇 |
2016年 | 95篇 |
2015年 | 64篇 |
2014年 | 85篇 |
2013年 | 1061篇 |
2012年 | 87篇 |
2011年 | 86篇 |
2010年 | 79篇 |
2009年 | 70篇 |
2008年 | 75篇 |
2007年 | 64篇 |
2006年 | 52篇 |
2005年 | 35篇 |
2004年 | 50篇 |
2003年 | 41篇 |
2002年 | 34篇 |
2001年 | 30篇 |
2000年 | 24篇 |
1999年 | 31篇 |
1998年 | 32篇 |
1997年 | 24篇 |
1995年 | 23篇 |
1994年 | 27篇 |
1992年 | 24篇 |
1991年 | 22篇 |
1990年 | 21篇 |
1989年 | 25篇 |
1988年 | 23篇 |
1987年 | 20篇 |
1986年 | 25篇 |
1985年 | 24篇 |
1984年 | 32篇 |
1983年 | 33篇 |
1982年 | 24篇 |
1981年 | 26篇 |
1980年 | 29篇 |
1979年 | 32篇 |
1978年 | 32篇 |
1977年 | 28篇 |
1976年 | 26篇 |
1975年 | 29篇 |
1974年 | 24篇 |
1973年 | 30篇 |
1972年 | 20篇 |
1971年 | 28篇 |
1970年 | 22篇 |
1969年 | 25篇 |
排序方式: 共有3344条查询结果,搜索用时 15 毫秒
931.
932.
933.
Stephen F. Poropat Sarah K. Martin Anne-Marie P. Tosolini Barbara E. Wagstaff Lynne B. Bean Benjamin P. Kear 《Alcheringa: An Australasian Journal of Paleontology》2018,42(2):157-229
Poropat, S.F., Martin, S.K., Tosolini, A.-M.P., Wagstaff, B.E, Bean, L.B., Kear, B.P., Vickers-Rich, P. &; Rich, T.H., May 2018. Early Cretaceous polar biotas of Victoria, southeastern Australia—an overview of research to date. Alcheringa 42, 158–230. ISSN 0311-5518.Although Cretaceous fossils (coal excluded) from Victoria, Australia, were first reported in the 1850s, it was not until the 1950s that detailed studies of these fossils were undertaken. Numerous fossil localities have been identified in Victoria since the 1960s, including the Koonwarra Fossil Bed (Strzelecki Group) near Leongatha, the Dinosaur Cove and Eric the Red West sites (Otway Group) at Cape Otway, and the Flat Rocks site (Strzelecki Group) near Cape Paterson. Systematic exploration over the past five decades has resulted in the collection of thousands of fossils representing various plants, invertebrates and vertebrates. Some of the best-preserved and most diverse Hauterivian–Barremian floral assemblages in Australia derive from outcrops of the lower Strzelecki Group in the Gippsland Basin. The slightly younger Koonwarra Fossil Bed (Aptian) is a Konservat-Lagerstätte that also preserves abundant plants, including one of the oldest known flowers. In addition, insects, crustaceans (including the only syncaridans known from Australia between the Triassic and the present), arachnids (including Australia’s only known opilione), the stratigraphically youngest xiphosurans from Australia, bryozoans, unionoid molluscs and a rich assemblage of actinopterygian fish are known from the Koonwarra Fossil Bed. The oldest known—and only Mesozoic—fossil feathers from the Australian continent constitute the only evidence for tetrapods at Koonwarra. By contrast, the Barremian–Aptian-aged deposits at the Flat Rocks site, and the Aptian–Albian-aged strata at the Dinosaur Cove and Eric the Red West sites, are all dominated by tetrapod fossils, with actinopterygians and dipnoans relatively rare. Small ornithopod (=basal neornithischian) dinosaurs are numerically common, known from four partial skeletons and a multitude of isolated bones. Aquatic meiolaniform turtles constitute another prominent faunal element, represented by numerous isolated bones and articulated carapaces and plastrons. More than 50 specimens—mostly lower jaws—evince a high diversity of mammals, including monotremes, a multituberculate and several enigmatic ausktribosphenids. Relatively minor components of these fossil assemblages are diverse theropods (including birds), rare ankylosaurs and ceratopsians, pterosaurs, non-marine plesiosaurs and a lepidosaur. In the older strata of the upper Strzelecki Group, temnospondyl amphibians—the youngest known worldwide—are a conspicuous component of the fauna, whereas crocodylomorphs appear to be present only in up-sequence deposits of the Otway Group. Invertebrates are uncommon, although decapod crustaceans and unionoid bivalves have been described. Collectively, the Early Cretaceous biota of Victoria provides insights into a unique Mesozoic high-latitude palaeoenvironment and elucidates both palaeoclimatic and palaeobiogeographic changes throughout more than 25 million years of geological time.Stephen F. Poropat*? [sporopat@swin. edu. au; stephenfporopat@gmail. com], Faculty of Science, Engineering and Technology, Swinburne University of Technology, John St, Hawthorn, Victoria 3122, Australia; Sarah K. Martin*? [sarah. martin@dmirs. wa. gov. au; martin. sarahk@gmail. com] Geological Survey of Western Australia, 100 Plain St, East Perth, Western Australia 6004, Australia; Anne-Marie P. Tosolini [a. tosolini@unimelb. edu. au] and Barbara E. Wagstaff [wagstaff@unimelb. edu. au] School of Earth Sciences, The University of Melbourne, Melbourne, Victoria 3010, Australia; Lynne B. Bean [lynne. bean@anu. edu. au] Research School of Earth Sciences, Australian National University, Acton, Canberra, Australian Capital Territory 2001, Australia; Benjamin P. Kear [benjamin. kear@em. uu. se] Museum of Evolution, Uppsala University, Norbyvägen 16, Uppsala SE-752 36, Sweden; Patricia Vickers-Rich§ [prich@swin. edu. au; pat. rich@monash. edu] Faculty of Science, Engineering and Technology, Swinburne University of Technology, John St, Hawthorn, Victoria 3122, Australia; Thomas H. Rich [trich@museum. vic. gov. au] Museum Victoria, PO Box 666, Melbourne, Victoria 3001, Australia. *These authors contributed equally to this work. ?Also affiliated with: Australian Age of Dinosaurs Museum of Natural History, Lot 1 Dinosaur Drive, PO Box 408, Winton, Queensland 4735, Australia. ?Also affiliated with: Earth and Planetary Sciences, Western Australian Museum, Welshpool, Western Australia 6101, Australia. §Also affiliated with: School of Earth, Atmosphere and Environment, Monash University, Melbourne, Victoria 3800, Australia. 相似文献
934.
935.
936.
In river deltas, human interference with regional and global socio-ecological systems has led to a plethora of gradual and more abrupt environmental changes that result in inundation, coastal and river bank erosion, land loss and, ultimately, displaced people. Often apolitically framed as protective, state-led transfer of people to new housing grounds, resettlement has become a common response to such displacements. In its process, existing arrangements of land tenure and occupancy and, at times more covertly, related arrangements of capital, labor and the social fabric become dislocated and reassembled. In line with emerging critical geographies of resettlement, this paper conceptualizes resettlement in river deltas against the background of environmental change as a highly political process with far-reaching environmental, economic, social and cultural implications. For this article is based on an in-depth review of both resettlement and political ecology literature, we first elucidate the concept of resettlement before providing a structured overview of categories and recent trends in resettlement literature. We then focus on river deltas that due to multi-scale environmental change are about to become hotspots of future resettlement. Building on identified gaps in resettlement literature, the article concludes with opening up three analytical strands of political ecology as entry points to resettlement studies, understood as critical geographic research into localized manifestations of environmental change in river deltas. Overall, our paper aims to initialize conceptual debate, grounded in a thorough review of recent case study literature on resettlement that is informed by political ecology. The review challenges positivist reductions of resettlement processes as technocratic-managerial tasks that so far have dominated scientific literature in this field and opens up new perspectives for critical research on resettlements in river deltas for human geographers. 相似文献
937.
Anna F. Graham 《Southeastern Archaeology》2020,39(3):166-182
ABSTRACT European colonization brought innumerable changes and choices to Native groups across the Southeast. Scholars continue to examine the various ways communities navigated these disruptions. Studying the remains of daily practice offers a window into how communities negotiated continuity and change. Wood charcoal, representing the remains of daily fires, provides an important, but underutilized, method for examining people’s daily routines and interactions with their surrounding landscapes. This paper examines wood charcoal assemblages from several sites in the North Carolina Piedmont that span the precontact to early colonial periods (AD 1400–1705). Fuelwood collection models are used to consider the environments, practices, and preferences that influenced the composition of wood charcoal assemblages. Comparison of these datasets shows a consistent significant pattern of high-quality fuelwood selection with additional patterns potentially related to long-term use of the same environment and factors related to colonialism. Altogether, these patterns suggest continuity of some daily practices despite disruptions to other aspects of life. 相似文献
938.
This study presents the results of compositional and lead isotopic analysis of coinage issued by the Greek colonies of Syracuse, Metapontum, Taras and Thurium in the fifth to third centuries bce . The data suggest that each colony in Magna Graecia, regardless of its motherland roots and despite ongoing conflicts between the cities, had access to the same silver, and that this supply was stable overall throughout their period of minting and issuing coinage. The paper retraces the silver sources of the colonies and points out a potential supply route for the metal. It includes a method development for a multi-standard quantification approach for laser ablation-inductively coupled-mass spectrometry (LA-ICP-MS) analysis of silver. 相似文献
939.
Laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) analysis was undertaken on 37 blue glass beads excavated from a tomb in the southern Faiyum region of northern Egypt. The tomb was undisturbed, contained the remains of seven females and two children, and dated between the reigns of Amenhotep I (1525–1504 bce ) and Tuthmosis III (1479–1425 bce ). The glass beads were coloured by copper and the trace element concentrations were compositionally consistent with glasses from Mesopotamia rather than from Egypt. Therefore, these glass beads represent a rare example of Mesopotamian glass to be discovered in Egypt, in addition to being some of the earliest glass found. Gurob is known to have been the site of a ‘harem palace' established in the reign of Tuthmosis III, the implication being that these beads represent luxury items transported to Egypt by high-ranking foreign women, possibly in connection with the harem palace. 相似文献
940.
E. Petersone-Gordina J. Montgomery A. R. Millard C. Roberts D. R. Gröcke G. Gerhards 《Archaeometry》2020,62(Z1):3-18
Carbon and nitrogen isotope profiles were obtained from incremental dentine analysis of 19 non-adults from a cemetery in Riga, Latvia. The research compared the life histories and diet between people buried in two mass graves and the general cemetery. The δ13C profiles of several children from the mass graves were similar but did not resemble the patterns seen in children from the general cemetery, suggesting that they probably represented a different population group. The rise in δ15N values towards the end of the life of four individuals from one mass grave suggests they were victims of an historically documented famine. 相似文献