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   6613篇
  免费   256篇
  2020年   94篇
  2019年   112篇
  2018年   163篇
  2017年   165篇
  2016年   174篇
  2015年   139篇
  2014年   142篇
  2013年   1890篇
  2012年   186篇
  2011年   192篇
  2010年   157篇
  2009年   193篇
  2008年   205篇
  2007年   161篇
  2006年   118篇
  2005年   75篇
  2004年   85篇
  2003年   75篇
  2002年   75篇
  2001年   115篇
  2000年   99篇
  1999年   92篇
  1998年   64篇
  1997年   54篇
  1996年   75篇
  1995年   68篇
  1994年   52篇
  1993年   61篇
  1992年   46篇
  1991年   60篇
  1990年   47篇
  1989年   66篇
  1988年   60篇
  1987年   68篇
  1986年   66篇
  1985年   78篇
  1984年   74篇
  1983年   90篇
  1982年   68篇
  1981年   76篇
  1980年   76篇
  1979年   69篇
  1978年   82篇
  1977年   67篇
  1976年   81篇
  1975年   49篇
  1974年   46篇
  1973年   52篇
  1972年   49篇
  1969年   45篇
排序方式: 共有6869条查询结果,搜索用时 0 毫秒
101.
Isolation effects on the distributions of plant species in fragmented forests appear to be weak over tens to hundreds of years and strong over geological eras. The 250 km wide, 6.5 millennia old Bass Strait, and other millennium-scale disjunctions in the range of Eucalyptus regnans forests, were used to determine the effects of intermediate periods of isolation on plant species occurrence and composition. Three of six floristic communities were found on both sides of Bass Strait. The residuals from multiple regression models using climatic variables on the latitude vector were not explained by latitude, indicating negligible isolation effects from Bass Strait. However, there was a lesser compositional effect of disjunctions within land masses than between land masses, suggesting some effect of the larger barrier. No species that commonly occurred with E. regnans and were largely confined to wet forest exhibited absences from any region where the climate and soils were within their range. If areas isolated from each other for millennia can maintain their vascular plant biota, the expenditure of conservation funds on creating corridors to connect large areas separated by anthropogenic landscape modification might require more justification than it is currently afforded.  相似文献   
102.
103.
104.
Book reviews     
In Search of Khayyam. By Ali Dashti (translated by L. P. Elwell‐Sutton). New York: Columbia University Press, 1972. 276pp. $11.00.

The Emergence of Modern Afghanistan: Politics of Reform and Modernization, 1880–1946. By Vartan Gregorian. Stanford: Stanford University Press, 1969. 398pp. $17.50.  相似文献   

105.
106.
107.
108.
Review articles     
Hugh Stretton: The Political Sciences, Routledge & Kegan Paul, London, 1969, pp. xii + 453, $8.15.  相似文献   
109.
Reviews     
DYNAMICS OF WORLD POLITICS: STUDIES IN THE RESOLUTION OF INTERNATIONAL CONFLICT. Linda B. Miller (ed.). Prentice‐Hall, 1968. Pp. viii + 294. $5.40.

THE UNITED NATIONS AND UNITED STATES SECURITY POLICY. Ruth B. Russell. The Brookings Institution, Washington, D.C., 1968. Pp. ix + 510. $10.00 (U.S.).

THE POLITICS OF PEACE‐KEEPING. Alan James. Studies in International Security: 12. Chatto & Windus, London, for The Institute for Strategic Studies, 1969. Pp. 452. £.3.3.0.

INTERNATIONAL INFORMATION CENTER ON PEACE‐KEEPING OPERATIONS MONOGRAPHS NOS. 6–8. Paris, 1968. $1.00 each.

No. 6 CHARACTERISTICS AND SOME ASPECTS OF LAUNCHING U.N. PEACE‐KEEPING FORCES. Lieut.‐General P. S. Gyani. Pp. 13.

No. 7 PEACE‐KEEPING AND SELF‐DEFENCE. Dr Kjell Goldmann. Pp. 60.

No. 8 THE AUTHORIZATION OF PEACE‐KEEPING OPERATIONS IN TERMS OF THE NATURE OF THE CONFLICT. Albert Legault. Pp. 62

CANADA AND THREE CRISES. Robert W. Reford. Toronto, Canadian Institute of International Affairs, 1968. Pp. xii + 246. $5.00 (Canadian).

SYSTEMS, STATES, DIPLOMACY AND RULES. J. W. Burton. Cambridge University Press, 1968. Pp. xii + 251. $7 (U.S.).

GERMAN FOREIGN POLICY IN TRANSITION. BONN BETWEEN EAST AND WEST. Karl Kaiser. Issued under the joint auspices of the Harvard University Center for International Affairs, the Twentieth Century Fund's ‘Tocqueville Series’ and the Royal Institute of International Affairs. London, Oxford University Press, Oxford Paperbacks No. 159, 1968. Pp. x + 153. $2.00.

PEOPLE'S WAR. THE CONDITIONS AND THE CONSEQUENCES IN CHINA AND IN SOUTH‐EAST ASIA. J. L. S. Girling. London, Allen and Unwin, 1969. Pp. 244. $6.65.

ASIAN CONTRACT LAW. David Allan (General Editor). Melbourne University Press, 1969. Pp. xiii + 237. $9.60.

MODERN FEDERALISM. G. F. Sawer. The New Thinker's Library, No. 29. London, C. A. Watts & Co., 1969. Pp. 204. 15/‐ (U.K.).  相似文献   

110.
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