全文获取类型
收费全文 | 6454篇 |
免费 | 262篇 |
专业分类
6716篇 |
出版年
2023年 | 40篇 |
2020年 | 118篇 |
2019年 | 118篇 |
2018年 | 445篇 |
2017年 | 383篇 |
2016年 | 421篇 |
2015年 | 159篇 |
2014年 | 148篇 |
2013年 | 1449篇 |
2012年 | 191篇 |
2011年 | 323篇 |
2010年 | 316篇 |
2009年 | 174篇 |
2008年 | 211篇 |
2007年 | 176篇 |
2006年 | 106篇 |
2005年 | 104篇 |
2004年 | 61篇 |
2003年 | 70篇 |
2002年 | 64篇 |
2001年 | 87篇 |
2000年 | 63篇 |
1999年 | 67篇 |
1998年 | 67篇 |
1997年 | 43篇 |
1996年 | 46篇 |
1995年 | 57篇 |
1994年 | 51篇 |
1993年 | 48篇 |
1992年 | 50篇 |
1991年 | 43篇 |
1990年 | 45篇 |
1989年 | 37篇 |
1988年 | 46篇 |
1987年 | 52篇 |
1986年 | 49篇 |
1985年 | 51篇 |
1984年 | 48篇 |
1983年 | 50篇 |
1982年 | 56篇 |
1981年 | 50篇 |
1980年 | 39篇 |
1979年 | 34篇 |
1978年 | 37篇 |
1977年 | 42篇 |
1976年 | 32篇 |
1974年 | 37篇 |
1971年 | 22篇 |
1970年 | 24篇 |
1969年 | 22篇 |
排序方式: 共有6716条查询结果,搜索用时 15 毫秒
91.
Ceramic vessels from Later Stone Age sites in the Seacow river valley, South Africa, were heavily tempered with C4 grasses. However, most δ13C values of the temper fall between the known δ13C ranges for C4 and C3 grasses. Among possible C3 additives that could skew the signal, ground bone, animal dung, alpine grass, Karoo scrub ash, and humic acid contamination are eliminated. The sherd surfaces yield fatty chars with C3-like values. Although these are not enough to account for all the skewing, they represent only the final cooking event. They were preceded by many such events in which fat was absorbed into the C4 grass then charred to soot by later periods in the fire. Thus organic carbon with the isotope composition of the fat built up while the vessel remained in use. 相似文献
92.
Some 630 Roman silver coins excavated at Augusta Raurica (Switzerland) have been analysed by non-destructive X-ray fluorescence and X-ray diffraction. Furthermore, the density and the weight have been determined. The measured average density of plated and massive depletion-silvered coins is lower than the density calculated from the chemical composition, whereas massive coins display equal values for both of the densities. Based on experimental X-ray investigations of modern silver (tempering, acid treatment, production of corrosion layers), the nature of corrosion products on silver, their impact on surface analysis, and aspects of wearing-off by circulation are briefly discussed. 相似文献
93.
The present paper surveys the discussions conducted by official statisticians regarding the ideal structure according to which a national data collection system should have been designed if it was to meet the challenges put up by the various transformation Western countries have undergone since the beginning of the 19th century. Arguments in favour of coordination, centralization, or decentralization have emerged for the first time in 1832 Britain, when the Statistical Bureau of the Board of Trade was created. Up to 1945, this debate went on, the industrial take-off, the economic crises, and the world wars all being occasions for its protagonists to put forward their preferred view. The perspective we take here is original in two respects: on the one hand, instead of confining ourselves to the major statistical systems (those of France, Britain, and the USA), we intend to evoke a large number of cases and, from this comparative standpoint, propose a general account of the drive towards centralization; on the other hand, instead of restraining our-selves to the 19th century, we cover the entire time-frame extending from 1800 to 1945. 相似文献
94.
Jean-Marc Drouin Patrick Gautier Dalché Fabien Chareix Charles Lenay Monique Cottret Bernard Vandewalle François Laplanche Françoise Waquet Agnès Spiquel Ariane Poulantzas Olivier Martin Sophie Roux Ilana Löwy Françoise Waquet Isabelle Brian Michel Cassan Jean-Marc Rohrbasser Jean-Michel Vienne Marc Renneville Bernard Lahire Mikhaäl Xifaras Bertrand Binoche Stéphane Haber Jean-François Pradeau Noël Bonneuil Marie Jaisson 《Revue de synthèse / Centre international de synthèse》1997,118(4):551-613
95.
96.
Latham MC 《Africa today》1993,40(3):39-53
Issues surrounding the spread of acquired immunodeficiency syndrome (AIDS) in Africa are summarized. Subjects considered include the disease's origins, proportion of the population infected with the human immunodeficiency virus (HIV) and AIDS, the problems in caring for children orphaned by the disease, innovations in drug treatments discovered by African scientists, the spread among women, and the difficulties inherent in incorporating Western-based policy and aid provisions into the African context. 相似文献
97.
C. ORTON 《Archaeometry》1993,35(2):169-184
This paper reviews the ways in which assemblages of pottery have been quantified throughout the twentieth century, and the use to which such data have been put. The values of various ways of quantifying pottery are compared, and a theoretical basis for the comparison of assemblages is described. Finally, the practical steps that need to be taken to make best use of the theory are set out. 相似文献
98.
99.
100.