全文获取类型
收费全文 | 9327篇 |
免费 | 410篇 |
出版年
2023年 | 56篇 |
2021年 | 65篇 |
2020年 | 185篇 |
2019年 | 196篇 |
2018年 | 252篇 |
2017年 | 239篇 |
2016年 | 295篇 |
2015年 | 234篇 |
2014年 | 214篇 |
2013年 | 2066篇 |
2012年 | 331篇 |
2011年 | 424篇 |
2010年 | 386篇 |
2009年 | 430篇 |
2008年 | 349篇 |
2007年 | 357篇 |
2006年 | 334篇 |
2005年 | 269篇 |
2004年 | 133篇 |
2003年 | 169篇 |
2002年 | 176篇 |
2001年 | 185篇 |
2000年 | 145篇 |
1999年 | 142篇 |
1998年 | 103篇 |
1997年 | 89篇 |
1996年 | 96篇 |
1995年 | 80篇 |
1994年 | 65篇 |
1993年 | 84篇 |
1992年 | 74篇 |
1991年 | 65篇 |
1990年 | 62篇 |
1989年 | 57篇 |
1988年 | 52篇 |
1987年 | 60篇 |
1986年 | 60篇 |
1985年 | 69篇 |
1984年 | 79篇 |
1983年 | 84篇 |
1982年 | 68篇 |
1981年 | 67篇 |
1980年 | 67篇 |
1979年 | 62篇 |
1978年 | 66篇 |
1977年 | 67篇 |
1976年 | 61篇 |
1975年 | 71篇 |
1974年 | 42篇 |
1972年 | 41篇 |
排序方式: 共有9737条查询结果,搜索用时 15 毫秒
131.
132.
A multidisciplinary programme of research on Islamic pottery has been focused on questions of the dating, provenance and technology of Islamic pottery. One particular question has been the development of stonepaste, a material made primarily of crushed quartz with added frit-glass and clay. The combination of the different approaches of this study has revealed early foundations for the technology in ninth-century AD Iraq, apparently originating in the clay ceramic rather than the ‘Egyptian faience’ tradition. Subsequent and final practice developed in tenth- and eleventh-century AD Egypt. This technology becomes the primary body for all fine Islamic ceramics. 相似文献
133.
This paper introduces a pattern recognizer, similar to weighting schemes used in combining time series forecasts, for use in spatial adaptive filtering applied to estimating multivariate cross-sectional models. The pattern recognizer enhances the ability to automatically detect and estimate parameters with discontinuous or sharp gradient changes over geographic contexts. Results from Monte Carlo studies suggest that the weighted spatial adaptive filter is at least as accurate as the unweighted filter for cases having smoothly changing parameters, but superior for cases having discontinuous, step-jump parameters. A case study on illicit drug-market activities using census tract-level data from Pittsburgh, Pennsylvania, further illustrates the advantages of the weighted filter. 相似文献
134.
135.
Fifty-three copper-based metal fragments, recovered from the Robitaille site in southcentral Ontario, were analysed by neutron activation to establish their chemical make-up and to sort them by their trace elemental chemistries. Three different European copper samples, one brassy copper and 48 brass samples with five different chemistries were found. As few as eight trading actions may account for all of the recovered European metal fragments. 相似文献
136.
137.
The possibility of lead isotope fractionation in ancient lead production is examined. Kinetic theory relating to isotopic fractionation in non-equilibrium evaporation is considered and the feasibility of the alteration of lead isotope abundance ratios in ore roasting and smelting is assessed. Previous experimental work is shown to have been inconclusive and conclusions are drawn on the need for further research to quantify the possible extent of fractionation in practice. 相似文献
138.
D. E. NELSON G. CHALOUPKA C. CHIPPINDALE M. S. ALDERSON J. R. SOUTHON 《Archaeometry》1995,37(1):151-156
Accelerator mass spectrometry radiocarbon ages have been taken for a test suite of small samples of material removed from some of the ‘beeswax’art figures found in rock shelters in northern Australia. The results indicate that we can reliably date this unique form of rock art with no noticeable damage. We had not expected to find figures of any great antiquity, and so we were surprised to find that the ages obtained spanned the time period from the recent past to about 4000 BP. 相似文献
139.
A Roman archaeological site in northern Spain (La Maja, province of La Rioja) includes pottery workshops, part of an important ceramic industry that developed from about the first century BC to the first century AD. A geophysical study was planned to determine the extent of the industrial complex in the vicinity of an excavated kiln. Magnetic observations were done on a grid of 30 × 36m, with a sampling interval of 1m. Two dipolar-shaped anomalies were found: one in the north-east and the other in the south-west of the area. Low-pass and band-pass filters were used in the Fourier domain to enhance the characteristics of the magnetic data and to remove noise and undesirable shallow features. Three-dimensional polygonal prisms were used to model the magnetic anomalies based on palaeomagnetic measurements performed over an uncovered kiln that helped to constrain the induced and remanent parameters of the magnetizing fields. 相似文献
140.
This paper examines interprovincial migration in the People's Republic of China (PRC) during 1982–87 when China was going through economic restructuring. Chinese migration patterns bear some resemblances as well as dissimilarities with those generally observed in Western societies. In China, the age-specific migration rate does not vary much until the preretirement stage. Return to places of origin is obviously the most plausible explanation of Chinese migration patterns. In addition, a clear-cut gender gap exists, higher than that imagined in Western societies. Chinese women appear far behind Chinese men in their propensity to migrate, and the determinants of migration are quite different for Chinese women and Chinese men. 相似文献