首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   11964篇
  免费   549篇
  2020年   177篇
  2019年   245篇
  2018年   332篇
  2017年   334篇
  2016年   394篇
  2015年   263篇
  2014年   228篇
  2013年   3308篇
  2012年   313篇
  2011年   346篇
  2010年   341篇
  2009年   342篇
  2008年   306篇
  2007年   291篇
  2006年   252篇
  2005年   177篇
  2004年   158篇
  2003年   163篇
  2002年   171篇
  2001年   193篇
  2000年   167篇
  1999年   192篇
  1998年   146篇
  1997年   127篇
  1996年   136篇
  1995年   125篇
  1994年   108篇
  1993年   125篇
  1992年   119篇
  1991年   90篇
  1990年   91篇
  1989年   106篇
  1988年   97篇
  1987年   110篇
  1986年   107篇
  1985年   139篇
  1984年   165篇
  1983年   166篇
  1982年   131篇
  1981年   129篇
  1980年   144篇
  1979年   130篇
  1978年   137篇
  1977年   122篇
  1976年   127篇
  1975年   141篇
  1974年   84篇
  1973年   77篇
  1972年   71篇
  1971年   66篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
121.
122.
A number of investigations have been undertaken by the New South Wales Water Resources Commission to determine the regional and compound effects of large scale extractive industries on the stability of the Hunter River, New South Wales. Sedimentologic studies of bed material suggest that the Hunter River upstream of Denman has an armoured gravel bed that is immobile during regulated releases from Glenbawn Dam but is disrupted by moderate but less than bankfull flows. Annual bedloadyields have been computed by the bedload rating-flow duration technique for five river gauging stations. Approximate sand and gravel budgets for selected reaches of the Hunter River demonstrate that the present annual extraction rate from temporary sediment storages within the channel greatly exceeds the transport rate upstream of Denman and is approximately equal to the transport rate downstream of Denman. River degradation is imminent if extractive industries continue operating in the channel of the Hunter River  相似文献   
123.
Nearshore water circulation and bar patterns at Coledale, New South Wales, were surveyed daily over thirty-six consecutive days, from 3 November to 8 December 1978, to identify sequences of changes that might occur in response to spring-to-spring tide cycles of fourteen days, changing barometric and wind conditions associated with the passage of anticyclonic weather systems across the coast, and day to day variation in the nearshore wave regime. During the survey the bar patterns tended to vary from transverse bars, through a composite arrangement incorporating longshore and transverse bars, to a longshore bar pattern as the tide changed from its spring to neap tide phase. However, this sequence was too brief to unequivocally establish variations in nearshore bar pattern that might be attributed to the fourteen day, spring-to-spring tide cycle. Nevertheless, morphologic changes occurring in response to wave regime fluctuation at Coledale were broadly in accord with studies from elsewhere by Dolan et al. (1979, 1982), and Clarke and Eliot (1982, 1983) in that bars and rips were systematically distributed along the beach. At Coledale, bars tended to relocate approximately 0.4 and 0.75 of the distance along the beach from its southern end. The preferred bar spacing closely matches hypothetical standing waves trapped between the headlands of the Coledale embayment. Temporally, the nearshore morphology is highly responsive to wave regime changes such that, as primary breaker heights decrease and remain below Hmax=1.0m, the bar pattern changes from longshore through mixed to transverse bar patterns within three to five days. On one occasion the bar pattern switched from a longshore to a transverse bar pattern within twenty-four hours.  相似文献   
124.
Streamline analyses of mean monthly resultant surface winds over Australia are presented. Mean confluences represent either cyclone trajectories, or modal fronts. These analyses suggest that Australia's annual airstream climate is of two regimes: that of September to March inclusive, and April to August inclusive. The winter half-year is exemplified by a continental airstream source in southern Australia which diverges over virtually the entire continent. It continues into September and October, although dominating only the southern third to half of Australia, and is absent from November to March. During the summer half-year a new pattern emerges, with three maritime air stream sources represented over the continent: first, air from the Southern Ocean penetrates the south coast reaching its furthest northward extension from December to March inclusive; a second source originating over the Pacific Ocean dominates eastern and northern Australia; and a monsoon source originating over the Indian Ocean which flows overland affecting northern Western Australia. Two modal confluences are noted, one over northwestern Australia from November-February separating monsoon flow from that emanating from the east, and another extending from the west central coast east-southeastward to the southeast coast from November-March separating Southern Ocean air from that originating over the Pacific Ocean.  相似文献   
125.
126.
Book reviews     
Derek McDougall, Harold D. Lasswell and the Study of International Relations. University Press of America, Lanham, USA, 1984, pp.370. $16.50.

John W. Burton, Global Conflict: The Domestic Sources of International Crisis. Wheatsheaf Books, UK, 1984, pp.194. $54.00.

K.J. Holsti, The Dividing Discipline: Hegemony and Diversity in International Theory. Allen and Unwin, Boston and Sydney, 1985. pp.165. $39.95.

Hedley Bull (ed.), Intervention in World Politics. Clarendon Press, Oxford, 1984, pp. viii + 198. $31.00.

Hedley Bull, Justice in International Relations. 1983–84 Hagey Lectures, University of Waterloo, 1984, pp. iii + 36. No price given. (Available from University Publications Distribution Service, Dana Porter Arts Library, University of Waterloo, Waterloo, Ontario N2L3G1, Canada.)

Benedict Anderson, Imagined Communities: Reflections on the Origin and Spread of Nationalism. Verso Editions and NLB, London, 1983, pp. 160. £15.00.

Chalmers Johnson, Revolutionary Change. Second edition. Longman, London, 1983, pp.xii + 217. $13.85.

Peter Calvert, Politics, Power and Revolution. An Introduction to Comparative Politics. Wheatsheaf Books, Brighton, 1983, pp.208. £5.95.

John Walton, Reluctant Rebels. Comparative Studies of Revolution and Underdevelopment. Columbia University Press, New York, 1984, pp.xii + 230 $US36.00 (cloth), $US10.00 (paper).

E. A. Tiryakian and R. Rogowski (eds), New Nationalisms of the Developed West. Toward Explanation. Allen and Unwin, Boston, 1985, pp.xii + 394. $69.00.

Peter H. Merkl and Ninian Smart (eds), Religion and Politics in the Modern World. New York University Press, New York, 1985, pp.276. No price given.

Richard Lowenthal, Social Change and Cultural Crisis. Columbia University Press, New York, 1984, pp.viii + 252. $US29.50.

Dietrich Fischer, Preventing War in the Nuclear Age. Rowman and Allanheld, Totowa, N.J./Croom Helm, London, 1984, pp. x + 236. $27.95.

F. Dyson, Weapons and Hope Harper and Row, New York, 1984, pp.340. $24.95.

John Langmore and David Peetz (eds), Wealth, Poverty and Survival. Australia in the World. George Allen and Unwin, Sydney, in association with the Australian Labor Party, 1983, pp. 225.  相似文献   

127.
128.
129.
Sutton and Lawless review a selection of the prolific literature on the Maghreb's human geography published from the late 1970s onward. The pedigree of the discipline in Maghreb was established by several notable geographers who lived, researched, and wrote there. Augustin Bernard's writings on rural settlement, his atlas, and study of Algeria are still cited. Jean Despois's regional study with Raynal and his work on Tunisia, together with the detailed rural research of Jean Poncet, provides a particularly rich coverage for that country. Jean Dresch's early work on Morocco exemplified an early critique of the contemporaneous uncritical colonial human geography. The Sahara's fascination also inspired pioneering studies by Robert Capot-Rey. The work of these notables and others provided a solid background of geographical literature on the Maghreb to be supplemented, criticized, and challenged by more recent researchers, sometimes pupils of the above individuals, and increasingly North African by birth. The tradition of general texts on the Maghreb has continued, though increasingly with systematic approaches replacing regional appraisals. The geography of the decolonization of the Maghreb by Isnard has been replaced by a study summarizing recent collaborative work by a team of French geographers. The Saharan extensions of the Maghreb states have often been linked in general works, sometimes being juxtaposed against the Maghreb as in the essays offered to Jean Despois. Lawless and Findlay's collaborative study juxtaposes geographical studies of each country's economic development with political scientists' evaluations of their sociopolitical development. This review limits itself largely to geographers and geographical journals, only occasionally including significant works from other subject areas, and to 1977-1978 publications, with a few notable exceptions. The spatial juxtaposition of contrasting approaches to economic development, liberal market economy approaches by Tunisia and Morocco arguably leading to dependency, and centrally-planned strategies by Algeria and Libya resulting in bureaucratic constraints serves to offer the Maghreb as a pertinent case-study region for the applied geographer of developing countries.  相似文献   
130.
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号