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   1118篇
  免费   4篇
  国内免费   10篇
系统科学   95篇
丛书文集   2篇
教育与普及   8篇
理论与方法论   22篇
现状及发展   168篇
研究方法   141篇
综合类   608篇
自然研究   88篇
  2021年   2篇
  2020年   5篇
  2019年   6篇
  2018年   5篇
  2017年   9篇
  2016年   8篇
  2015年   7篇
  2014年   7篇
  2013年   28篇
  2012年   78篇
  2011年   178篇
  2010年   31篇
  2009年   7篇
  2008年   78篇
  2007年   69篇
  2006年   73篇
  2005年   94篇
  2004年   89篇
  2003年   91篇
  2002年   73篇
  2001年   11篇
  2000年   12篇
  1999年   16篇
  1998年   13篇
  1997年   4篇
  1996年   5篇
  1995年   14篇
  1993年   5篇
  1992年   17篇
  1991年   5篇
  1990年   8篇
  1989年   4篇
  1988年   6篇
  1987年   2篇
  1986年   4篇
  1985年   9篇
  1984年   2篇
  1983年   4篇
  1982年   7篇
  1981年   2篇
  1979年   5篇
  1978年   2篇
  1977年   4篇
  1975年   2篇
  1974年   4篇
  1972年   3篇
  1967年   2篇
  1965年   2篇
  1957年   3篇
  1956年   2篇
排序方式: 共有1132条查询结果,搜索用时 0 毫秒
81.
This paper estimates a forecasting equation for the hourly peak electricity demand one day in the future. The models incorporate deterministic influences such as holidays, stochastic influences such as average loads by building bivariate models, and exogenous influences such as the weather which is given a careful non-linear formulation. Out-of-sample comparisons are made using an additional year of data.  相似文献   
82.
83.
General systems formalizations of expert knowledge play a foundational role in the process of knowledge engineering of intelligent systems. Canonical definitions of systems (knowledge structures) which have been arrived at by a crossdisciplinary inductive modeling process are shown to be the basis for the modeling of certain generic categories of expert reasoning processes which are of current interest in knowledge engineering. The methodology for transforming the representation of knowledge expressed in general systems formalizations to the representation of that knowledge in expert systems is also developed. In particular, transformations from general systems formalizations into frames are presented.  相似文献   
84.
85.
An intranasal immunization with a A/PR8/34-isolated NA, protected mice as well as the whole virus and A/Hong Kong/1/68 virus against a subsequent infection with mice-adaptated A/PR8/34 strain.  相似文献   
86.
87.
Clements and Hendry (1993) proposed the Generalized Forecast Error Second Moment (GFESM) as an improvement to the Mean Square Error in comparing forecasting performance across data series. They based their conclusion on the fact that rankings based on GFESM remain unaltered if the series are linearly transformed. In this paper, we argue that this evaluation ignores other important criteria. Also, their conclusions were illustrated by a simulation study whose relationship to real data was not obvious. Thirdly, prior empirical studies show that the mean square error is an inappropriate measure to serve as a basis for comparison. This undermines the claims made for the GFESM.  相似文献   
88.
Conclusion The brief summary of our present knowledge on the aging of intercellular matrix macromolecules shows the progress which has been made since the original important discovery of Verzár, but it also points out the very considerable gaps which still have to be filled by continued research efforts in this theoretically and practically important area. It is no secret to anyone that most of the disabling and killing diseases of advanced societies concern connective tissues: arteriosclerosis, diabetes, pulmonary obstructive lung diseases, osteoarticular diseases and cancer itself are all age-dependent, so-called aging diseases. The interaction between intercellular matrix and cancer cells plays an important role in the spreading of the tumors. For these other major diseases, the direct involvement of intercellular matrix is well documented. It is therefore hoped that a better grasp of the basic mechanisms involved in these diseases will help us to understand the difference between pathology and aging per se.  相似文献   
89.
90.
Biogenesis, maturation and aging of elastic tissue   总被引:1,自引:0,他引:1  
L Robert  M Moczar  M Robert 《Experientia》1974,30(2):211-212
  相似文献   
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