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   9823篇
  免费   1839篇
  国内免费   1篇
电工技术   571篇
综合类   650篇
化学工业   6918篇
金属工艺   110篇
机械仪表   41篇
建筑科学   337篇
矿业工程   37篇
能源动力   24篇
轻工业   384篇
水利工程   19篇
石油天然气   4篇
武器工业   1篇
无线电   56篇
一般工业技术   1623篇
冶金工业   20篇
原子能技术   4篇
自动化技术   864篇
  2023年   538篇
  2022年   275篇
  2021年   553篇
  2020年   584篇
  2019年   458篇
  2018年   451篇
  2017年   313篇
  2016年   474篇
  2015年   576篇
  2014年   610篇
  2013年   776篇
  2012年   370篇
  2011年   260篇
  2010年   593篇
  2009年   674篇
  2008年   243篇
  2007年   203篇
  2006年   119篇
  2005年   140篇
  2004年   192篇
  2003年   145篇
  2002年   187篇
  2001年   81篇
  1999年   58篇
  1998年   58篇
  1996年   69篇
  1995年   90篇
  1994年   66篇
  1993年   125篇
  1992年   85篇
  1991年   75篇
  1990年   87篇
  1989年   92篇
  1988年   71篇
  1987年   92篇
  1986年   102篇
  1985年   86篇
  1984年   83篇
  1983年   106篇
  1982年   75篇
  1981年   105篇
  1980年   82篇
  1979年   66篇
  1977年   61篇
  1976年   49篇
  1975年   64篇
  1974年   67篇
  1973年   133篇
  1972年   76篇
  1971年   49篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
41.
Ohne Zusammenfassung This article is also available in English via http://www.springerlink.com and http://www.bise-journal.org: BISE – Call for Papers, Issue 3/2010, High-Impact Requirements Engineering. Bus Inf Syst Eng. doi: .  相似文献   
42.
Summary This paper presents a unique approach, named mathematical regularization, to remove the nearly-singular and singular integrals occurring in the boundary integral formulations for the solution of the boundary value problems with a pathologica integration boundary due to the very near or coinciding parts of the total boundary. Nonsingular boundary integral equations are derived for thin-walled structure problems. In the case of crack-like problems, we present two kinds of the nonsingular integral representations of the secondary fields and the derivative boundary integral equations.  相似文献   
43.
The present paper contains a stability concept for discretization methods of a certain, very general classM, which is optimal (in the sense of yielding the best general, two-sided error bounds) without being more restrictive than any of the classical stability definitions. The optimal stability functional Ψh related to it depends on the linear part of the discretization operator, and has the important property that Ψh [δ] may be of orderq+1, i.e. Ψh [δ] = O(h q+1), even if the local error δ only has orderq, δ = O(h q). This result may be used for the construction of methods with maximum order. Its application to linear cyclic methods, for example, furnishes a new approach to the theory of linearM-cyclick-step methods of maximum order.  相似文献   
44.
The purpose of this paper is to show that for continuous functions the related quadratic splines converge without any assumption on the spline grid. The points of the interpolatory grid can be chosen between the corresponding points of the spline grid with a division ratio from \(\frac{{\sqrt 2 }}{2}\) to \(1 - \frac{{\sqrt 2 }}{2}\) . In the case of continuously differentiable functions the division ratio can even be taken between 0 and 1; in addition, the order of convergence is increased. For twice differentiable functions the full order of convergence is obtained. Analogous results about the convergence of histo splines are proved.  相似文献   
45.
We give a simple method based on Cauchy's integral formula for estimating the errors of numerical approximation for periodic analytic functions. We then obtain error estimates for the quadrature formulas of Chawla and Ramakrishnan [1] for the numerical evaluation of the Cauchy principal value integral $$I\left( {f;a} \right) = \int\limits_0^{2\pi } {f(x)\cot \left( {\left( {x - a} \right)/2} \right)dx,} $$ and for the quadrature formula of Garrick [2] for the evaluation ofI (f;o), Based on these error estimates, we are led to conclude that for the evaluation ofI (f;o), Garrick's formula has a better error estimate than the formula of Chawla and Ramakrishnan with the same number of function evaluations. Finally, we extend Garrick's formula for the evaluation ofI (f;a) for arbitrarya∈[0,2π); the extended formula has, for alla, the same error estimate as Garrick's formula. While, for a=xj, the extended formula is identical with the quadrature formula of Wittich [3], forax j, the extended formula is much better in that it uses only half the number of function evaluations of Wittich's formula for the same accuracy.  相似文献   
46.
This paper discusses the prediction of the output of a stochastic sourceQ having positive transition function. If the sourceQ has two output alphabets,X andY, then there exists such a stochastic automaton \(\mathfrak{A}(V_{opt} )\) with input alphabetX, output alphabetY, and a countable set of states, that realizes the optimal predictionV opt fromX toY. Here it will be shown thatV opt can be approximated with any precision by a predictionV which is realized by a stochastic automaton with finite set of states.  相似文献   
47.
Summary A context-free grammar form G defines a family of context-free grammars {ie397-01}(G). In this paper {ie397-02}(G) is extended to give the family of terminal context grammars {ie397-03}(G), which were introduced by Book [4]. It is shown that the families of languages defined by {ie397-04}(G) and {ie397-05}(G) are equal when G is an -free context-free grammar form. This generalizes the result of Book [4] for context-free grammars and underlines the usefulness of the notion of grammar forms in formal language theory.The work of the second author was carried out partially under a National Research Council of Canada Grant. No. A-7700 and partially under the auspices of the University of Karlsruhe  相似文献   
48.
对恒速成长公司股票的投资价值进行了弹性分析。结果表明,恒速成长公司投资价值的利率与业绩弹性既敏感地依赖于公司的成长速度和利率水平等内外部因素,也是刻画股票某种投机价值的恰当指标。  相似文献   
49.
Definition of the problem: In Austria the legal discussion on initiating and withdrawing artificial nutrition in incompetent patients has just begun. Arguments and conclusion: Legal regulations are lacking, but there appears to be agreement on accepting advance directives under specific criteria. This would mean that a presumed will and documented refusal of treatment and nutrition has to be respected by physicians. However, there is no consensus with regard to the “supposed will” of an incompetent patient to refuse treatment and nutrition. At present, surrogate decision making with regard to refusing life-sustaining treatment or nutrition is only accepted according to a declared and documented directive of the patient himself. When the patient’s will has to be “surmised” the protection of life has priority. In Austria this concept is based on the national constitution and its duty to protect life.  相似文献   
50.
会计职业道德对提高会计信息质量的影响   总被引:1,自引:0,他引:1  
会计信息质量与环境、会计系统等诸多因素有关,同时会计职业道德也是一个非常重要的因素。它作为一种引导和制约会计行为的社会规范,与会计信息的质量息息相关。我国会计信息质量的现状不容乐观,重整我国会计职业道德,将对我国会计信息质量的提高起到积极的推动作用。文中分析了会计职业道德的特征和现状,提出了重整会计职业道德的几点思考.  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