全文获取类型
收费全文 | 3974篇 |
免费 | 119篇 |
出版年
2020年 | 34篇 |
2019年 | 41篇 |
2018年 | 356篇 |
2017年 | 264篇 |
2016年 | 301篇 |
2015年 | 49篇 |
2014年 | 55篇 |
2013年 | 922篇 |
2012年 | 93篇 |
2011年 | 225篇 |
2010年 | 236篇 |
2009年 | 96篇 |
2008年 | 127篇 |
2007年 | 174篇 |
2006年 | 46篇 |
2005年 | 58篇 |
2004年 | 51篇 |
2003年 | 44篇 |
2002年 | 25篇 |
2001年 | 27篇 |
2000年 | 21篇 |
1999年 | 24篇 |
1998年 | 18篇 |
1997年 | 21篇 |
1995年 | 22篇 |
1994年 | 24篇 |
1993年 | 18篇 |
1992年 | 22篇 |
1990年 | 17篇 |
1989年 | 21篇 |
1988年 | 18篇 |
1987年 | 19篇 |
1986年 | 21篇 |
1985年 | 23篇 |
1984年 | 29篇 |
1983年 | 32篇 |
1982年 | 23篇 |
1981年 | 23篇 |
1980年 | 26篇 |
1979年 | 30篇 |
1978年 | 28篇 |
1977年 | 28篇 |
1976年 | 23篇 |
1975年 | 24篇 |
1974年 | 18篇 |
1973年 | 25篇 |
1972年 | 18篇 |
1971年 | 22篇 |
1970年 | 17篇 |
1969年 | 23篇 |
排序方式: 共有4093条查询结果,搜索用时 15 毫秒
51.
52.
Morphological Impacts and Implications of a Trial Release on the Wingecarribee River,New South Wales
A trial, monitored release on the Wingecarribee River over 27 days had a peak discharge below the Wingecarribee Dam of 1090 ML/d, which had a flow duration of 0.95 per cent. Morphological impacts on 29 km of channel below the dam included bank erosion, concentrated neck overflow, bed degradation and channel widening at recent cutoffs, sedimentation in weir pools and overbank flow, particularly at discharges greater than 800 ML/d. Prolonged operational releases at bankfull discharge (400–800 ML/d) will have the greatest morphologic impacts and should be avoided. Pulses which dissipate stream power over a broad, well-vegetated floodplain should be incorporated in the operational release policy, provided such pulses are phased to facilitate channel and vegetation recovery. 相似文献
53.
54.
C. F. W. Higham 《International Journal of Historical Archaeology》1998,2(3):235-260
The Early Historic Period in the Mun Valley occupies a critical three centuries, from A.D. 500 to A.D. 800, a period often known as that of Zhenla, a name derived from early Chinese accounts. This article first describes early findings of fieldwork designed to illuminate the prehistory of the upper Mun Valley, a period which covers approximately two millennia, with initial settlement now dated between 1500 and 1000 B.C. It then considers the nature of the transition to the complex polities of Zhenla. This involves a combination of archaeological and documentary evidence. Sources for the latter are rare for the Mun Valley, but by broadening the area considered, it is possible to integrate archaeological and historical sources in order to portray the intensifying social changes which characterize the Early Historic Period. It is suggested that most of the Mun Valley was occupied by Khmer speakers during the Iron Age, people responsible for the transition to increasingly centralized polities of the Early Historic Period. In the upper reaches of the Mun catchment, and in the Chi Valley to the north, the late prehistoric inhabitants spoke Mon. They had close affinities with the Dvaravati polities of Central Thailand. If confirmed, this hypothesis would indicate a series of local trends towards increasing social complexity which we can recognize in the early epigraphic record. 相似文献
55.
Cultural resource management (CRM) work accounts for most of the archaeology conducted in the United States. A diverse and
somewhat fragmented field, CRM has nonetheless achieved a degree of institutional and organizational maturity. CRM archaeology
has produced important contributions to archaeological methodology and has established and refined knowledge of regional cultural-historical
sequences and settlement and subsistence patterns. The current florescence of historical archaeology is attributable to CRM.
Yet the maintenance of high quality in CRM is a pervasive and enduring problem. Academic institutions need to reestablish
alliances with the CRM community. The future viability of CRM archaeology depends on factors both internal and external to
the discipline: regulatory and statutory “reform,” agency funding levels, looting and other destructive forces, and Native
American and other public involvement. 相似文献
56.
57.
Freemon FR 《Journal of the history of the neurosciences》1996,5(3):282-287
Neurology in its modern sense was first studied in the well-known neurological institutions of France and England. In America, however, this new field of medicine was developed by a physician in a private practice, Dr. William Alexander Hammond. This article addresses the question how Hammond was able to limit his practice to neurology. It is argued that Hammond was a famous military physician before becoming the first practitioner of clinical neurology in America. This fame translated into a large referral base. 相似文献
58.
ROBIN F. WARNER 《Geographical Research》1996,34(1):3-17
This address is concerned with the lack of detailed understanding we have of rivers. It is argued that to manage river systems for environ- mental and ecological sustainability, there must be understanding of riverine biophysical processes. These are explored through a consideration of: (1) channel airspace and water; (2) the perimeter conditions of the channel as the boundary between erosional channel and depositional floodplain, both of which occupy the valley-floor trough; (3) ecological components of channels and (4) the human components where human interactions with catchment environments have such impacts on the biophysical systems. Finally, the implications of these four components for understanding the systems for more sustainable management are discussed. 相似文献
59.
60.
Ancient mortars from northern Italy, dating from the fifth to the seventeenth century AD, were examined in order to formulate an hypothesis regarding the origin of the white lumps often observed in these mortars and in other samples of the same geographical provenance. Various characterization techniques were employed, including scanning electron microscopy, X-ray powder diffraction and Fourier transform infrared (FTIR) and micro-FTIR spectroscopy. 相似文献