全文获取类型
收费全文 | 4672篇 |
免费 | 186篇 |
专业分类
4858篇 |
出版年
2023年 | 34篇 |
2020年 | 100篇 |
2019年 | 88篇 |
2018年 | 171篇 |
2017年 | 171篇 |
2016年 | 193篇 |
2015年 | 121篇 |
2014年 | 106篇 |
2013年 | 1376篇 |
2012年 | 134篇 |
2011年 | 148篇 |
2010年 | 106篇 |
2009年 | 101篇 |
2008年 | 104篇 |
2007年 | 69篇 |
2006年 | 82篇 |
2005年 | 114篇 |
2004年 | 67篇 |
2003年 | 48篇 |
2002年 | 63篇 |
2001年 | 64篇 |
2000年 | 40篇 |
1999年 | 50篇 |
1998年 | 37篇 |
1997年 | 40篇 |
1996年 | 35篇 |
1995年 | 30篇 |
1994年 | 47篇 |
1993年 | 45篇 |
1992年 | 41篇 |
1991年 | 29篇 |
1990年 | 42篇 |
1989年 | 34篇 |
1988年 | 38篇 |
1987年 | 38篇 |
1986年 | 44篇 |
1985年 | 36篇 |
1984年 | 52篇 |
1983年 | 54篇 |
1982年 | 52篇 |
1981年 | 41篇 |
1980年 | 35篇 |
1979年 | 42篇 |
1978年 | 42篇 |
1977年 | 31篇 |
1976年 | 32篇 |
1975年 | 35篇 |
1973年 | 28篇 |
1972年 | 31篇 |
1970年 | 32篇 |
排序方式: 共有4858条查询结果,搜索用时 0 毫秒
61.
By 1980, the Brasilian steel industry had grown to be the eighth largest among the market economies. It is a largely state-owned industry, much of the expansion of which has been funded by international capital. The pattern of development has not been externally imposed, however, but rather reflects the changing balance of class forces within Brasil as policies oscillate between nationalist, populist limits on foreign investment and open, pro-development strategies that rely on foreign investment. Both policies develop their own contradictions, that are reflected in frequent military interventions. 相似文献
62.
63.
64.
Johnson JH 《Transactions (Institute of British Geographers : 1965)》1990,15(3):259-276
"A classic case where out-migration interacted with many other geographical phenomena is provided by rural Ireland in the nineteenth century. The apparent turning point was the Great Famine of the 1840s, but the areas with the greatest suffering from starvation did not necessarily show the greatest population decline, suggesting that other forces were active. Considerable economic and social changes were already taking place before the Famine: fertility was being reduced, later marriage was becoming established and considerable emigration was already taking place. Immediately after the Famine those areas which had been hardest hit often reverted to pre-Famine conditions and did not show strong population decline until the 1870s. The Famine was a most serious event, but the modernization of Irish rural life, which linked emigration with changes in family structure, agriculture and population numbers, was more important in bringing about geographical change." 相似文献
65.
66.
F. Albarde J. Blichert‐Toft F. de Callataÿ G. Davis P. Debernardi L. Gentelli H. Gitler F. Kemmers S. Klein C. Malod‐Dognin J. Milot P. Tlouk M. Vaxevanopoulos K. Westner 《Archaeometry》2021,63(1):142-155
The reasons why the Western Mediterranean, especially Carthage and Rome, resisted monetization relative to the Eastern Mediterranean are still unclear. We address this question by combining lead (Pb) and silver (Ag) isotope abundances in silver coinage from the Aegean, Magna Graecia, Carthage and Roman Republic. The clear relationships observed between 109Ag/107Ag and 208Pb/206Pb reflect the mixing of silver ores or silver objects with Pb metal used for cupellation. The combined analysis of Ag and Pb isotopes reveals important information about the technology of smelting. The Greek world extracted Ag and Pb from associated ores, whereas, on the Iberian Peninsula, Carthaginians and Republican‐era Romans applied Phoenician cupellation techniques and added exotic Pb to Pb‐poor Ag ores. Massive Ag recupellation is observed in Rome during the Second Punic War. After defeating the Carthaginians and the Macedonians in the late second century bce , the Romans brought together the efficient, millennium‐old techniques of silver extraction of the Phoenicians, who considered this metal a simple commodity, with the monetization of the economy introduced by the Greeks. 相似文献
67.
68.
Lorena Grana Sonia Lanzelotti Victoria Arévalo Alvaro Yamil Tesio Nora Irene Maidana 《Archaeometry》2023,65(2):391-408
In the Andes, there are several pre-Hispanic irrigation networks with structures destined for water storage. However, it has not been widely discussed in archaeological research. This is probably due to their being difficult to identify. The aim of this study is to explore the use of diatom assemblage analysis as a methodological tool suitable to help in the identification and characterization of these ancient hydraulic structures. We analyzed two archaeological structures interpreted as water reservoirs from north-western Argentina (EH1 in Antofagasta de la Sierra and U-88R1 in Yocavil) and compared them to current reservoirs. The diatom species composition and the changes in the dominant ecological groups in the studied structures highlight different periods of hydraulic behavior. EH1 contained and stored water, but there were periods of time in which there was a lack of use or abandonment of the structure. However, the U88-R1 structure does not have diatom evidence of containing standing water for a prolonged time but presence of wet soils. Thus, the structure could have been used for other water management strategies. The results show that diatom analysis is a methodological tool with a high potential to study ancestral hydrotechnologies. 相似文献
69.
70.