全文获取类型
收费全文 | 3910篇 |
免费 | 124篇 |
专业分类
4034篇 |
出版年
2020年 | 46篇 |
2019年 | 53篇 |
2018年 | 84篇 |
2017年 | 86篇 |
2016年 | 112篇 |
2015年 | 77篇 |
2014年 | 70篇 |
2013年 | 1116篇 |
2012年 | 103篇 |
2011年 | 131篇 |
2010年 | 115篇 |
2009年 | 88篇 |
2008年 | 94篇 |
2007年 | 67篇 |
2006年 | 64篇 |
2005年 | 66篇 |
2004年 | 55篇 |
2003年 | 32篇 |
2002年 | 42篇 |
2001年 | 61篇 |
2000年 | 49篇 |
1999年 | 58篇 |
1998年 | 40篇 |
1997年 | 45篇 |
1996年 | 38篇 |
1995年 | 30篇 |
1994年 | 38篇 |
1993年 | 42篇 |
1992年 | 44篇 |
1991年 | 36篇 |
1990年 | 31篇 |
1989年 | 37篇 |
1988年 | 34篇 |
1987年 | 45篇 |
1986年 | 30篇 |
1985年 | 49篇 |
1984年 | 39篇 |
1983年 | 65篇 |
1982年 | 48篇 |
1981年 | 55篇 |
1980年 | 54篇 |
1979年 | 39篇 |
1978年 | 40篇 |
1977年 | 58篇 |
1976年 | 42篇 |
1975年 | 45篇 |
1974年 | 32篇 |
1973年 | 29篇 |
1971年 | 33篇 |
1969年 | 26篇 |
排序方式: 共有4034条查询结果,搜索用时 15 毫秒
991.
992.
993.
B. FABBRI S. GUALTIERI C. MINGAZZINI P. SPADEA P. CASADIO R. COSTANTINI G. MALISANI 《Archaeometry》2000,42(2):317-324
Most of the Renaissance sgraffito tiles excavated in Udine (Italy) constitute a homogeous group, the tile body having a CaO/MgO molar ratio ?= 3:2. They were produced using a dolomite‐ and calcite‐containing clay fired at 900–950°C. A small group of samples, with a lower firing temperature and a CaO/MgO ratio ?= 2:3, was probably produced in a different factory. Slip and transparent glaze, characterized by optical microscopy and inductively coupled plasma atomic emission spectrometry, are an illite‐rich clay and a lead silicate, respectively. 相似文献
994.
995.
Reginald G. Golledge 《Geographical analysis》1999,31(4):318-323
996.
997.
998.
Tupholme Abbey, founded by c. 1166, was constructed of limestone masonry, some of which was reoriented at several times through its history. The limestone progressively acquired a ‘soft’, time-dependent magnetization in the earth's magnetic field—viscous remanent mag-netization (VRM)—that acts like a clock. Although VRM is normally disregarded by geologists because of its ephemeral nature, this remanence is acquired and persists over time-scales that are useful to archaeologists. Successive VRMs were initiated, at different ages of stabilization of the masonry, thus yielding a chronometric curve that allows us to determine, at least relatively, when masonry was installed. 相似文献
999.
Naturally occurring strontium and lead isotopes were used to study the impact of anthropogenic pollution on a c. 4500-year-old rock carving in Oslo, Norway. Strontium analyses have shown that road-salt from de-icing of a nearby road has accumulated in the soil surrounding the carving. Upon rainfall this salt is redissolved and drains over the rock carving. Analyses of the lead isotopic system have confirmed the impact of traffic from the nearby road on the rock carving site, but also indicate other sources of lead in the Oslo area and pollution in general. The rock carvings at Ekeberg are at high risk as, apart from natural weathering, they are exposed to the deposition of road salt, emissions from nearby traffic, local and long distance atmospheric pollution and meteorological inversion effects during the winter. 相似文献
1000.
G. Turner‐Walker C. M. Nielsen‐Marsh U. Syversen H. Kars M. J. Collins 《International Journal of Osteoarchaeology》2002,12(6):407-414
Total pore volume and pore size distribution are indicators of the degree of post‐mortem modification of bone. Direct measurements of pore size distribution in archaeological bones using mercury intrusion porosimetry (HgIP) and back scattered scanning electron microscopy (BSE‐SEM) reveal a common pattern in the changes seen in degraded bone as compared to modern samples. The estimates of pore size distribution from HgIP and direct measurement from the BSE‐SEM images show remarkable correspondence. The coupling of these two independent approaches has allowed the diagenetic porosity changes in human archaeological bone in the >0.01 µm range to be directly imaged, and their relationship to pre‐existing physiological pores to be explored. The increase in porosity in the archaeological bones is restricted to two discrete pore ranges. The smaller of these two ranges (0.007–0.1 µm) lies in the range of the collagen fibril (0.1 µm diameter) and is presumably formed by the loss of collagen, whereas the larger pore size distribution is evidence of direct microbial alteration of the bone. HgIP has great potential for the characterization of microbial and chemical alteration of bone. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献