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   41535篇
  免费   1642篇
  2020年   525篇
  2019年   825篇
  2018年   927篇
  2017年   1135篇
  2016年   1234篇
  2015年   936篇
  2014年   912篇
  2013年   14070篇
  2012年   1052篇
  2011年   1080篇
  2010年   1080篇
  2009年   1069篇
  2008年   1017篇
  2007年   923篇
  2006年   839篇
  2005年   573篇
  2004年   575篇
  2003年   527篇
  2002年   506篇
  2001年   493篇
  2000年   448篇
  1999年   499篇
  1998年   453篇
  1997年   422篇
  1996年   399篇
  1995年   412篇
  1994年   356篇
  1993年   403篇
  1992年   385篇
  1991年   295篇
  1990年   289篇
  1989年   299篇
  1988年   305篇
  1987年   320篇
  1986年   303篇
  1985年   418篇
  1984年   445篇
  1983年   445篇
  1982年   384篇
  1981年   381篇
  1980年   419篇
  1979年   413篇
  1978年   398篇
  1977年   422篇
  1976年   381篇
  1975年   379篇
  1974年   290篇
  1973年   267篇
  1972年   245篇
  1970年   219篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
141.
ABSTRACT. This paper examines the RAS, Mc Menamin and Haring, and Lagrange-multiplier update methods in the context of the dual accounting system of the rectangular input-output model. The motivation was to determine if the additional information contained in the dual system is exploitable, while maintaining the integrity of the rectangular structure with all its advantages. Tests were conducted on the performance of the various algorithms for a derivative Leontief model relative to their performance on the rectangular structure. The results obtained for rectangular tables were generally better than those obtained for the more conventional Leontief ones.  相似文献   
142.
143.
Reviews     
Babi and Baha'i Religions: From Messianic Shi'ism to a World Religion, by Peter Smith, Cambridge University Press, London, New York, New Rochelle, Melbourne, Sydney 1987, pp.xiv, 243.

Panj Vaqf‐namah, by Mahmud Afshar Yazdi, (Five Endowment Deeds), Tehran Foundation for Mahmud Afshar Yazdi's Endowments, 1363/1984. Iraj Afshar and Karim Isfahaniyan, eds., Namvarah‐yi Doktor Mahmūd Afshar Yazdi (Mahmud Afshar Yazdi's Festschrift), 4 vols., Tehran: Foundation for Mahmud Afshar Yazdi's Endowments, 1364/1985–1367/1988.

Bulles et Sceaux sassanides de diverses collections, by Philippe Gignoux and Rika Gysclen, Paris: Sludia Iranica, Cahier 4, Association Pour l'avancemeni des études iraniennes, 1987, 306 pp, 23 plates.

Iran and Iraq at War , by Shahram Chubin and Charles Tripp, Boulder, Colorado: Westview Press, 1988.

The Tragedy of Sohrab and Rostam, from the Persian National Epic, the Shahnameh of Abol‐Qascm Ferdowsi, translated by Jerome W. Clinton, Seattle: The University of Washington Press, 1988, xxv + 190 pages, $25.00 cloth $12.50 paper.

Persian Carpets , by Michael Craig Hillmann, Austin: University of Texas Press, 1984, 98 pp. index to p. 112.

Resurrection and Renewal: The Making of the Babi Movement in Iran, 1844–1850, Abbas Amanat, Ithaca & London: Cornell University Press, 1989, pp. xv.+ 461, no price indicated.

Iran min al‐Dakhil, (Iran From Within), by Fahmi Huwaydi, Cairo: Markaz al‐Ahram li al‐tarjuma wa al‐nashr, 1987, 405 pp.

Woven From the Soul, Spun from the Heart: Textile Arts of Safavid and Qajar Iran, 16lh‐19lh Centuries , edited by Carol Bier, Washington, DC: The Textile Museum, 1987.

Summon Up Remembrance, by Marzich Gail, Oxford: George Ronald Books, 1987, 295 pp., appendix, bibliography, $14.95.

Iran and The United States, A Cold War Case Study, by Richard W. Cottam, Pittsburgh: University of Pittsburgh Press, 1988. $12.95 pb.  相似文献   

144.
145.
This paper has two main objectives. First, we review and evaluate four different computational methods for measuring the “fractality” of cartographic lines: these are known as the structured walk, the equipaced polygon, the hybrid walk, and the cell count methods. Second, because previous research has restricted the focus of fractal measurement exercises to isolated physical entities, the subject of our empirical study concerns the urban area of Swindon, United Kingdom, that comprises a mosaic of contiguous land-use parcels. In technical terms, the results pinpoint some of the comparative strengths and weaknesses of the four methods, whilst our substantive conclusion is that fractal dimension appears to be a function of both scale and land-use type in our geographical study.  相似文献   
146.
147.
148.
An axiomatic approach to distance is developed which focuses on those behavioral concepts of distance related to movement in space. In particular, spatial movement by behaving units is postulated to involve a choice from among some set of abstract trips in space, and implicitly, to involve the minimization of some relevant notion of trip costs. In this context, the relevant behavioral notion of distance in space is taken to be the minimum-cost distance generated by this choice process. These trip-cost concepts extend the classical notions of paths, path lengths, and shortest paths in metric spaces. Hence many of the analytical results of the paper involve extensions of classical shortest-path distance properties to minimum-cost distances. In addition to these extensions, a characterization theorem is given which specifies the possible functional relationships between trip costs and their associated path lengths. These relationships include most functional forms which are commonly employed in the literature.  相似文献   
149.
150.
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