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   15530篇
  免费   582篇
  2020年   192篇
  2019年   284篇
  2018年   318篇
  2017年   379篇
  2016年   497篇
  2015年   327篇
  2014年   317篇
  2013年   4394篇
  2012年   413篇
  2011年   447篇
  2010年   465篇
  2009年   414篇
  2008年   373篇
  2007年   371篇
  2006年   349篇
  2005年   209篇
  2004年   207篇
  2003年   189篇
  2002年   200篇
  2001年   231篇
  2000年   212篇
  1999年   266篇
  1998年   180篇
  1997年   132篇
  1996年   158篇
  1995年   158篇
  1994年   154篇
  1993年   166篇
  1992年   156篇
  1991年   125篇
  1990年   117篇
  1989年   139篇
  1988年   138篇
  1987年   147篇
  1986年   138篇
  1985年   186篇
  1984年   183篇
  1983年   211篇
  1982年   168篇
  1981年   164篇
  1980年   169篇
  1979年   165篇
  1978年   154篇
  1977年   160篇
  1976年   148篇
  1975年   153篇
  1974年   129篇
  1973年   126篇
  1972年   113篇
  1970年   96篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
81.
"An empirical test of the effects of exogenous shocks upon a region's population size is conducted in the framework of an equilibrium locational model. The model emphasizes the separation of endogenous from exogenous factors, a point omitted in most empirical studies of aggregate migration. Exogenous changes are manifested in the local relative cost of living and the local relative unemployment rate. Hypotheses are tested using a national sample of youth, in addition to census, data [for the United States]. Surprisingly, a simple measure of the size of shock to a regional economy has the greatest explanatory power compared to more sophisticated measures based on prior business cycles."  相似文献   
82.
ABSTRACT The origins and development of the network equilibrium problem are traced and interrelated. Two principal formulations are considered the network equilibrium problem with variable travel demand, and the combined model of trip distribution and traffic assignment. The relation of these models to subsequent developments concerning mode choice, residential location, estimation of origin-destination tables from link flows and stochastic route choice are then reviewed.  相似文献   
83.
ABSTRACT This paper examines the role of the structure of transportation rates in the Weber-Moses triangle model. It shows that, in Zeigler's analysis, the appearance of the price elasticities of demand for inputs actually vanish by a simple application of the envelope theorem. Applying comparative statics analysis, we show when transportation rates are a function of quantity and distance, the assumptions that the production function is homogeneous of degree one and the transportation rates elasticities with respect to quantity and distance are constant are not sufficient to insure that the optimum location is independent of the level of output. This result is significantly different from that obtained by either Miller and Jensen or Zeigler.  相似文献   
84.
ABSTRACT. This paper introduces the household interactive variable input-output (HIVIO) model to measure the effect of cost variation on industrial outputs. The model produces a variety of cost elasticities that separate out impacts on industrial prices, imports, and outputs, with “own” and “cross” elasticity components. Like the conventional input-output multipliers, these cost elasticities can be useful parameters to evaluate the substituting behavior of firms and consumers. By using the 1980 Korean input-output transactions table, we find the wage and import price effects on industrial prices, outputs, and import demands.  相似文献   
85.
86.
Eastern North America in late Pleistocene times was characterized by two major environmental regions: a periglacial tundra or open spruce parkland and an extensive complex boreal/deciduous forest in the unglaciated, lower latitudes. These environments selected for different adaptive strategies on the part of human foraging groups—known archaeologically as Paleoindians. Those in the tundra and tundra-forest region were highly mobile, possibly specialized hunters, exploiting caribou; those in the forest were generalists, exploiting a variety of subsistence resources with a less mobile settlement system. There is little evidence in either area for hunting of Pleistocene megafauna. These differences in adaptive strategies are reflected in the record of sites and isolated fluted points scattered throughout the region, as well as aspects of tool technology, function, and patterns of stone use.  相似文献   
87.
88.
89.
90.
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