全文获取类型
收费全文 | 714篇 |
免费 | 34篇 |
国内免费 | 6篇 |
专业分类
电工技术 | 17篇 |
化学工业 | 72篇 |
金属工艺 | 15篇 |
机械仪表 | 24篇 |
建筑科学 | 18篇 |
矿业工程 | 1篇 |
能源动力 | 23篇 |
轻工业 | 82篇 |
水利工程 | 5篇 |
石油天然气 | 3篇 |
无线电 | 88篇 |
一般工业技术 | 175篇 |
冶金工业 | 94篇 |
原子能技术 | 2篇 |
自动化技术 | 135篇 |
出版年
2023年 | 12篇 |
2022年 | 17篇 |
2021年 | 18篇 |
2020年 | 20篇 |
2019年 | 19篇 |
2018年 | 32篇 |
2017年 | 24篇 |
2016年 | 16篇 |
2015年 | 14篇 |
2014年 | 19篇 |
2013年 | 34篇 |
2012年 | 26篇 |
2011年 | 33篇 |
2010年 | 31篇 |
2009年 | 30篇 |
2008年 | 11篇 |
2007年 | 20篇 |
2006年 | 21篇 |
2005年 | 15篇 |
2004年 | 18篇 |
2003年 | 6篇 |
2002年 | 8篇 |
2001年 | 14篇 |
2000年 | 10篇 |
1999年 | 8篇 |
1998年 | 26篇 |
1997年 | 22篇 |
1996年 | 11篇 |
1995年 | 12篇 |
1994年 | 16篇 |
1993年 | 19篇 |
1992年 | 11篇 |
1991年 | 17篇 |
1990年 | 5篇 |
1989年 | 6篇 |
1988年 | 7篇 |
1987年 | 13篇 |
1986年 | 6篇 |
1985年 | 10篇 |
1984年 | 7篇 |
1983年 | 8篇 |
1982年 | 10篇 |
1981年 | 10篇 |
1980年 | 12篇 |
1979年 | 6篇 |
1978年 | 6篇 |
1977年 | 11篇 |
1976年 | 12篇 |
1975年 | 4篇 |
1972年 | 3篇 |
排序方式: 共有754条查询结果,搜索用时 334 毫秒
91.
This paper describes three procedures for calculating design derivatives of the non-linear critical load. Constraints on the critical load arise naturally in optimal design of structures having non-linear behavior. The incremental procedures used for non-linear analysis can fail before reaching the final load level due to buckling or collapse of the structure. Therefore, load carrying capability of the structure must be improved before optimal design process can proceed further. This requires design derivatives of the critical load factor. A very simple and effective procedure among the three derived, is selected. It uses most of the information already calculated during analysis and sensitivity analysis of other constraints. Design sensitivity analysis is verified using two known examples. Several other structures are optimized to show effectiveness of the procedure. The sensitivity analysis can be combined with another constraints to optimize structures with more general requirements.This research was initiated under a project sponsored by the National Science Foundations, USA, Grant No. CEE82-13851 相似文献
92.
93.
94.
Polymers of o-, m-, and p-nitrophenols with formaldehyde were used as fuel binders in composite propellants based on NH4ClO4 and KClO4 oxidizers. A study of the burning rate in nitrogen has revealed the occurrence of a breakpoint at about 3–5 atm in the burning rate-pressure curves of all six types of composite propellants that contained nitro-substituted phenolic resins as fuel binders. 相似文献
95.
96.
The problem of finding a minimum makespan permutation schedule in a deterministic flow-shop without intermediate queues is equivalent to the shortest distance routing traveling salesman problem. If the task system is semi-ordered, the associated distance matrix of the corresponding traveling salesman problem is found to exhibit some peculiar characteristics. Consequently, we are able to derive some important results which help us to eliminate permutations in the search of the minimum makespan permutation schedule. The most important result is that the optimal permutation schedule is pyramidal. An algorithm, having quadratic worst-case complexity in terms of the number of partial schedules explicitly enumerated, has been presented. Some particular cases of the semi-ordered flow-shop are also discussed. 相似文献
97.
The origin of the main electron trap (0.83 eV) in GaAs is investigated by creating conditions to favour the formation of Ga-vacancy-oxygen complex in the material. Two specific schemes have been used, (1) Liquid phase epitaxial (LPE) growth of the material at high temperatures (≈1000°C) with oxygen doping and (2) Electron bombardment of LPE material and subsequent annealing. The traps have been characterised by transient capacitance technique. The results show that the main electron trap cannot be produced by either of the schemes thereby implying that a complex involving Ga-vacancy and oxygen may not be responsible for the trap. 相似文献
98.
J. S. Arora E. J. Haug 《International journal for numerical methods in engineering》1976,10(4):747-766
The purpose of this paper is to present refinements in a steepest descent algorithm for optimal design of structures and numerical experience that demonstrates its numerical efficiency. The algorithm is based on a state space optimization technique that was initially developed and applied to optimal control problems. Design constraints are divided into four distinct subsets, the special characteristics of which are exploited to improve computational efficiency of the algorithm. Some further improvements in structural analysis, design sensitivity analysis, and constrained steepest descent programming calculations are presented. Optimum designs for three test problems are obtained and convergence rates are compared with results presented in the literature. 相似文献
99.
In this paper, an implementation scheme involving decoders and residue adders has been suggested to convert input data in fixed radix representation to residue representation. A method dealing with the reverse process is also demonstrated. A comparison has been made with the methods known hitherto. 相似文献
100.
Ashok D. Belegundu Jasbir S. Arora 《International journal for numerical methods in engineering》1984,20(5):803-816
Recursive quadratic programming methods have become popular in the field of mathematical programming owing to their excellent convergence characteristics. There are two recursive quadratic programming methods that have been published in the literature. One is by Han and the other is by Pshenichny, published in 1977 and 1970, respectively. The algorithm of Pshenichny had been undiscovered until now, and is examined here for the first time. It is found that the proof of global convergence by Han requires computing sensitivity coefficients (derivatives) of all constraint functions of the problem at every iteration. This is prohibitively expensive for large-scale applications in optimal design. In contrast, Pshenichny has proved global convergence of his algorithm using only an active-set strategy. This is clearly preferable for large-scale applications. The method of Pshenichny has been coded into a FORTRAN program. Applications of this method to four example problems are presented. The method is found to be very reliable. However, the method is found to be very sensitive to local minima, i.e. it converges to a local minimum nearest to the starting design. Thus, for optimal design problems (which usually possess multiple local minima) it is suggested that Pshenichny's method be used as part of a hybrid method. 相似文献