全文获取类型
收费全文 | 3711篇 |
免费 | 90篇 |
出版年
2020年 | 39篇 |
2019年 | 52篇 |
2018年 | 46篇 |
2017年 | 70篇 |
2016年 | 68篇 |
2015年 | 53篇 |
2014年 | 59篇 |
2013年 | 1260篇 |
2012年 | 61篇 |
2011年 | 81篇 |
2010年 | 66篇 |
2009年 | 61篇 |
2008年 | 59篇 |
2007年 | 57篇 |
2006年 | 47篇 |
2005年 | 41篇 |
2004年 | 45篇 |
2003年 | 44篇 |
2002年 | 33篇 |
2001年 | 44篇 |
2000年 | 52篇 |
1999年 | 84篇 |
1998年 | 56篇 |
1997年 | 42篇 |
1996年 | 41篇 |
1995年 | 31篇 |
1994年 | 38篇 |
1993年 | 36篇 |
1992年 | 31篇 |
1990年 | 37篇 |
1989年 | 36篇 |
1988年 | 29篇 |
1987年 | 43篇 |
1986年 | 34篇 |
1985年 | 43篇 |
1984年 | 48篇 |
1983年 | 57篇 |
1982年 | 49篇 |
1981年 | 35篇 |
1980年 | 61篇 |
1979年 | 44篇 |
1978年 | 45篇 |
1977年 | 52篇 |
1976年 | 41篇 |
1975年 | 49篇 |
1974年 | 39篇 |
1973年 | 26篇 |
1970年 | 35篇 |
1969年 | 27篇 |
1967年 | 27篇 |
排序方式: 共有3801条查询结果,搜索用时 15 毫秒
941.
X‐L. Chen Y‐M. Fang Y‐W. Hu Y‐F. Hou P. Lü J. Yuan G‐D. Song B. T. Fuller M. P. Richards 《International Journal of Osteoarchaeology》2016,26(5):808-817
During the late Longshan period (ca. 4200–3900 BP) settlements on the Central Plains of China underwent a diversification in food production technologies, which set the stage for rapid economic and social development. The introduction of novel domesticates such as rice, wheat, cattle, and sheep not only provided more food choices, but also changed ideas concerning land use, farming techniques, and the use and mobilization of large scale labor forces. To better understand the contribution that these new dietary items and practices made to shaping the late Longshan period societies, a stable isotope ratio study of humans (n = 12) and animals (n = 42) was conducted at the late Longshan period site of Wadian. The human δ13C and δ15N values are clustered into two distinct groups. One group of nine individuals (δ13C = −9.9 ± 0.7‰; δ15N = 7.5 ± 0.5‰) had a predominately C4 diet based on millet grains with little protein input from the domestic animals. The other group of three individuals (δ13C = −14.3 ± 0.8‰; δ15N = 10.2 ± 0.3‰) had a mixed C3/C4 diet of millets and rice and were consuming sheep and cattle. The animals also displayed dietary diversity with the pigs (δ13C = −11.3 ± 2.5‰; δ15N = 6.9 ± 1.0‰, n = 10) and dogs (δ13C = −10.1 ± 1.0‰; δ15N = 7.2 ± 1.1‰, n = 7) having mostly a C4 plant based diet (millets). In contrast, the cattle (δ13C = −12.8 ± 2.1‰; δ15N = 7.6 ± 0.7‰, n = 9), sheep (δ13C = −16.7 ± 0.9‰; δ15N = 7.6 ± 0.1‰, n = 2), and cervids (δ13C = −20.8 ± 0.9‰; δ15N = 5.0 ± 1.2‰, n = 10) had diets with a greater contribution from C3 sources such as rice and wild plants. The discovery that humans and animals had different subsistence patterns indicates dietary complexity at Wadian and that rice agriculture, and cattle and sheep husbandry practices were already an important part of the local economy by the late Longshan period in the southern region of the Central Plains of China. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
942.
L. L. Dai Z. P. Li C. Q. Zhao J. Yuan L. L. Hou C. S. Wang B. T. Fuller Y. W. Hu 《International Journal of Osteoarchaeology》2016,26(5):885-896
Located in the Central Plains of China, the early Xia Dynasty site of Xinzhai (2050 BC–1750 BC) with large archaeological features and exquisite artifacts of jade and copper is pivotal for probing the origin and formation of Chinese civilisation. Here, stable isotope ratios analysis, supplemented by zooarchaeological results, was used to investigate the exploitation and management of animals utilised by humans. It was demonstrated that a diverse pattern of animal raising and exploitation was present at the Xinzhai site. The domestic pigs were fed with substantial amounts of millets or their byproducts to guarantee a food source for the dietary demands of the humans. Dogs were also found to have consumed large amounts of C4 protein sources, likely in the form of human food scraps or leftovers. The domestic herbivores, sheep and cattle, showed different dietary characteristics in that the former mainly grazed in the natural environment, while the latter species were fed with large amounts of C4 products. This intra‐species variation was somewhat related to their physiological characteristics but seems to have been more determined by their different status in social and ritual activities. Thus, this research at Xinzhai provides a glimpse of the organisation of animal resources during the initial formation of Chinese civilisation. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
943.
Measurements on cranial and pectoral girdle bones of 56 museum specimens of modern sturgeon (Acipenser sturio and A. oxyrinchus) were used for the establishment of regression equations allowing back‐calculation of size from isolated sturgeon remains. Different curve fittings (power, linear, logarithmic and exponential fit) were modeled to retain the most accurate regression. These were then applied to archaeological sturgeon remains (A. sturio/A. oxyrinchus) from Vlaardingen, a Dutch late Neolithic settlement. The back‐calculated lengths obtained on the archaeological remains all stayed within the known size ranges of the two species and allowed making inferences on the possible place of capture of the fish. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
944.
X.‐L. Chen S.‐M. Hu Y.‐W. Hu W.‐L. Wang Y.‐Y. Ma P. Lü C.‐S. Wang 《International Journal of Osteoarchaeology》2016,26(1):42-52
Although a patchwork of projects shows a process of agriculture intensification in North China during the Neolithic, the impact of cereal farming on animal husbandry and their mutual interaction remain cloudy. This study reports bone collagen δ13C and δ15N of humans and animals from Wayaogou (ca 6.5–6.0 kyrs bp ) and Dongying (ca 5.9–5.6 kyrs bp , 4.6–4.0 kyrs bp ) to explore temporal trend of livestock raising and particularly the importance of millet fodder to stock raising practices in the Wei River valley, North China. The isotopic evidence overall shows that millet products increased in human and domestic animal diets during the mentioned chronological span. δ13C values of pigs and dogs at Dongying are higher than those at Wayaogou, implying that the importance of millet nutrients increased to animal husbandry diachronically. Interestingly, δ13C results of domestic cattle of Dongying late phase (−14.1 ± 1.1‰, N = 5) are more enriched than Wayaogou wild Bos (−17.8 ± 0.3‰, N = 3), indicating that millet fodder had taken a significant place in early cattle husbandry. Besides, differences between Bos species of the two periods also imply that δ13C values of bone collagen constitute a potential indicator for tracing the origin of cattle husbandry in North China. In addition, domestic sheep at Dongying produced similar isotope data to wild ovicaprid at Wayaogou, suggesting that they possibly had grazed for the most in grassland and therefore experienced a different lifestyle from cattle. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
945.
Peter W. Abrahams Jane A. Entwistle Robert A. Dodgshon 《Journal of Archaeological Method and Theory》2010,17(3):231-248
X-ray fluorescence spectrometry (XRFS) was used in the analysis of A horizon soil samples collected from a former farming
settlement and its associated area of infield (i.e. arable) located in the Central Highlands of Scotland. To date, XRFS has not been extensively used in geoarchaeological research,
but in our study the simultaneous multi-element capabilities of this instrumental technique allowed the total concentrations
of 25 major, minor, and trace elements to be fully quantified with acceptable levels of accuracy and precision. Included within
this group of chemical elements are a number (e.g. Ba, Ca, P, Pb, Sr and Zn) that have proved to be of value to archaeological interpretation in earlier investigations undertaken
in Scotland. In our preliminary work documented here, significant differences were found between the A horizon soils of former
settlement and infield areas for 18 chemical elements. Subjecting the XRFS data—and three other measured variables: soil organic
carbon (SOC), pH and A horizon depth—to discriminant analysis indicates that soils of former settlement and arable farming
can be effectively classified according to their pH, SOC content and Ca, Cu, Mg, Rb, and Zn concentrations. The inference
is that areas of former infield and settlement elsewhere at this study location in the Central Highlands may be able to be
identified according to their soil chemical composition and use of discriminant function, even though the surface remains
of pre-eighteenth century settlement sites are not readily evident today because they were constructed of perishable materials. 相似文献
946.
947.
948.
The rate of reaction of a natural hornblende garnet granulite with water under a range of mid- to lower crustal conditions has been investigated experimentally. In runs of between 7 and 84 days small but measurable amounts of water were consumed, and sheet silicates (300°C, 300 MPa and 400°C, 400 MPa) and/or secondary actinolite (400°C, 400 MPa and 500°C, 500 MPa) were observed to have grown. When normalized to the surface area of the starting materials, hydration rates were in the range of 2–5 × 10−8 g m−2 sec−1 . These reaction rates imply that a film of water that infiltrated a planar crack with a half width of 100 μm would be completely consumed within c. 100 years. These results imply that where water infiltrates the crust along faults or underlying shear zones in response to a deformation, it will remain as a free phase for only a finite period of time, which in some cases will be less than the repeat time for major earthquakes in the fault system. Thus, the rheology of fault zones and shear zones is likely to be cyclical, with the zone becoming stronger with time as water is consumed, and then weakened by infiltration of water after each rupture. 相似文献
949.
The adsorption onto other minerals of charged gold nanoparticles, carried by gas ascending from the Earth’s interior, is an important component of their transport and deposition in surficial cover such as alluvial, aeolian, and glacial sediments. To simulate the adsorption of these particles, an experiment was conducted in which a flow of air that contained gold nanoparticles was passed upward through a sample of alluvium from the middle–lower reaches of the Yangtze River. These experiments showed that gold nanoparticles are adsorbed on kaolinite, halloysite, goethite, and hematite in the alluvial cover. Both the gold nanoparticles and minerals (i.e., kaolinite, halloysite, goethite, and hematite) carry surface charges that provide them with excellent adsorption properties. This study showed that the specific mineral composition of surficial alluvial cover affects the concentration of gold nanoparticles in the ascending gas. This phenomenon may plausibly be used in exploration for concealed gold, copper–gold, and silver–gold deposits in areas of thick alluvial cover. Geofluids (2010) 10 , 438–446 相似文献
950.