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   37篇
  免费   0篇
化学   19篇
数学   9篇
物理学   9篇
  2023年   1篇
  2016年   1篇
  2013年   2篇
  2012年   1篇
  2011年   2篇
  2008年   1篇
  2005年   1篇
  2003年   1篇
  2001年   1篇
  2000年   1篇
  1999年   2篇
  1996年   2篇
  1994年   4篇
  1993年   4篇
  1970年   2篇
  1966年   2篇
  1963年   1篇
  1961年   1篇
  1960年   1篇
  1959年   1篇
  1935年   2篇
  1900年   2篇
  1891年   1篇
排序方式: 共有37条查询结果,搜索用时 15 毫秒
1.
This paper estimates a non-parametric production frontier for a population of 117 corn/livestock farms in the Corn Belt region in 1987, employing a hyperbolic graph efficiency approach. There are 7 outputs, 39 variable inputs, 4 fixed inputs, and one bad input (residual nitrogen). Three graph efficiency models are estimated. A profit maximization model is specified to estimate a production frontier constrained only by the fixed factors. Two other models involving tax constraints are also estimated. One involves a tax directly on nitrogen and the other involves a tax directly on residual nitrogen, making the disposal of residual nitrogen costly. The nitrogen tax constraint is more effective in reducing residual nitrogen loadings and causes a larger reduction in income than the residual tax constraint.  相似文献   
2.
3.
4.
5.
6.
Δ2-Oxazolines and 4H-5,6-dihydrooxazines are readily obtainable from carboxylic acids and 2- or 3-amino alcohols by gas-phase dehydration, and 4H-dihydrooxazines can also be obtained by condensation of N-(hydroxymethyl) carboxamides with olefins. These cyclic imidic esters undergo reactions in which the ring is cleaved; these reactions include a new type of polymerization. The behavior of alkyl groups in position 2 and the cyclodditions in the 2,3-position also have been studied. Reactions in side chains on position 2 and addition experiments on the sulfur analogues of the cyclic imidic esters are also reported. A table shows the principal infrared bands of substituted Δ2-oxazolines.  相似文献   
7.
For point processes we establish a link between integration‐by‐parts‐ and splitting‐formulas which can also be considered as integration‐by‐parts‐formulas of a new type. First we characterize finite Papangelou processes in terms of their splitting kernels. The main part then consists in extending these results to the case of infinitely extended Papangelou and, in particular, Pólya and Gibbs processes.  相似文献   
8.
9.
The logic of common belief does not always reflect that of individual beliefs. In particular, even when the individual belief operators satisfy the KD45 logic, the common belief operator may fail to satisfy axiom 5. That is, it can happen that neither is A commonly believed nor is it common belief that A is not commonly believed. We identify the intersubjective restrictions on individual beliefs that are incorporated in axiom 5 for common belief.  相似文献   
10.
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