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   10805篇
  免费   740篇
  国内免费   277篇
系统科学   1324篇
丛书文集   195篇
教育与普及   168篇
理论与方法论   290篇
现状及发展   899篇
研究方法   12篇
综合类   8933篇
自然研究   1篇
  2024年   17篇
  2023年   52篇
  2022年   106篇
  2021年   124篇
  2020年   75篇
  2019年   31篇
  2018年   792篇
  2017年   809篇
  2016年   531篇
  2015年   206篇
  2014年   263篇
  2013年   262篇
  2012年   521篇
  2011年   1293篇
  2010年   1095篇
  2009年   793篇
  2008年   822篇
  2007年   1056篇
  2006年   220篇
  2005年   233篇
  2004年   264篇
  2003年   336篇
  2002年   345篇
  2001年   247篇
  2000年   190篇
  1999年   200篇
  1998年   131篇
  1997年   133篇
  1996年   117篇
  1995年   97篇
  1994年   106篇
  1993年   86篇
  1992年   50篇
  1991年   52篇
  1990年   50篇
  1989年   41篇
  1988年   41篇
  1987年   20篇
  1986年   8篇
  1985年   2篇
  1984年   2篇
  1980年   1篇
  1967年   1篇
  1955年   1篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
971.
给出了基于矩依赖推导算法,并可推导出的关系上能够保持的函数依赖集。  相似文献   
972.
抗日战争时期,尤其是太平洋战争爆发后,日本的中国通长野朗经常以私人身份参与社会活动。长野朗的活动主要有三个内容:一是向日本政府呼吁调整对华政策,二是希望政府解决农民贫困问题,三是密切关注政界和军队的动向。长野朗的目的并非单纯地为了实现和平,而是出于日本国家前途和利益的考虑。  相似文献   
973.
在现代社会,文化已经成为构成一个国家综合国力的重要组成部分.跨文化是对全球化时代在文化方面的积极回应.这种回应也正是在经济的全球化,即资本的全球化的基础上建立起来的,或者也可以说跨文化就是人类在全球化发展背景下对文化选择的结果.  相似文献   
974.
975.
Different from traditional tax audit, supervision with self-audit is a combination of audit by the taxpayer himself and audit by the tax authority. This paper mainly studies a taxpayer's optimal policy of tax evasion under supervision with self-audit and its related properties, in order to deduce some effective suggestions and theoretical bases to restrain tax evasion. Assuming that only a certain proportion of evaded tax can be discovered when the audit is executed, the authors first formulate a static model with self-audit. This model is divided into two stages. At the first stage, taxpayers declare their taxes, then the tax authority chooses audit objects, based on a known probability, and announces the result; if the taxpayer is chosen, he will enter the second stage, during which he has a chance to pay the evaded tax and the corresponding late fees and then is audited by the tax authority. The authors show the existence and uniqueness of the optimal amount of tax evasion at the first stage and the optimal proportion to self-expose at the second stage. The authors also discuss the related properties of the interior solution, and do elasticity analyses on some parameters. Besides, the authors extend the static model into the corresponding two-period model, and study the existence and uniqueness of the solution of the extended model. Finally, under the assumption that tax evasion can only be discovered with a certain probability when the audit is executed, the authors formulate another static model with self-audit and investigate its properties.  相似文献   
976.
本文介绍了湿热交变试验箱计算机控制系统的软、硬件实现。  相似文献   
977.
Outcrossing rate in a natural population of Caldesia grandis was estimated by the dominant random amplified polymorphism DNA (RAPD) marker using 10 open-pollinated progeny arrays of 24 individuals. The multilocus outcrossing rate estimated based on all 25 RAPD loci was 0.872 ±0.033 and the single-locus outcrossing rate was 0.795 ±0.032. Multilocus estimates did not differ significantly from the single-locus estimates. The fixation index, F, in the progeny estimated from RAPD data was -0.142 ±0.000. The estimates of multilocus outcrossing rates (t_m) and single-locus outcrossing rates (t_s) obtained from MLDT clearly indicate that outcrossing is predominant in the open-pollinated C. grandis population. An empirical analysis suggests that 15 should be the minimum number of dominant marker loci necessary to achieve robust estimates of t_m.  相似文献   
978.
979.
Most cipher systems designed thus far are binary-valued or integer-valued cipher systems. Their security relies on the assumption that one-way functions exist. Though the existence of one-way functions has not been proved yet, most cryptographic researchers believe that one-way functions exist. In addition, many candidates for one-way functions have been proposed. Therefore, the key step for developing real-valued cipher systems is to define real one-way functions and to propose candidates for them. In this paper, based on computational complexity theory over the real field, we give two definitions of real one-way functions; one is for digital one-way functions and the other is for general one-way functions. Candidates for these two classes of one-way functions are also proposed. Moreover, we present two examples to demonstrate that the candidates for both digital one-way functions and general one-way functions can be applied to construct secure real-valued cipher systems.  相似文献   
980.
开发了新型。资管理信息系统,从总体设计到各模块的功能、特声、等进行了详细介绍和理论探讨.  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