全文获取类型
收费全文 | 890篇 |
免费 | 46篇 |
国内免费 | 41篇 |
专业分类
电工技术 | 23篇 |
综合类 | 59篇 |
化学工业 | 79篇 |
金属工艺 | 18篇 |
机械仪表 | 99篇 |
建筑科学 | 35篇 |
矿业工程 | 8篇 |
能源动力 | 43篇 |
轻工业 | 48篇 |
水利工程 | 12篇 |
石油天然气 | 14篇 |
武器工业 | 2篇 |
无线电 | 132篇 |
一般工业技术 | 50篇 |
冶金工业 | 12篇 |
原子能技术 | 13篇 |
自动化技术 | 330篇 |
出版年
2024年 | 4篇 |
2023年 | 10篇 |
2022年 | 16篇 |
2021年 | 18篇 |
2020年 | 32篇 |
2019年 | 10篇 |
2018年 | 14篇 |
2017年 | 20篇 |
2016年 | 15篇 |
2015年 | 24篇 |
2014年 | 33篇 |
2013年 | 67篇 |
2012年 | 56篇 |
2011年 | 69篇 |
2010年 | 57篇 |
2009年 | 30篇 |
2008年 | 40篇 |
2007年 | 54篇 |
2006年 | 54篇 |
2005年 | 47篇 |
2004年 | 50篇 |
2003年 | 34篇 |
2002年 | 35篇 |
2001年 | 18篇 |
2000年 | 23篇 |
1999年 | 18篇 |
1998年 | 12篇 |
1997年 | 18篇 |
1996年 | 15篇 |
1995年 | 21篇 |
1994年 | 10篇 |
1993年 | 8篇 |
1992年 | 7篇 |
1991年 | 5篇 |
1990年 | 2篇 |
1989年 | 6篇 |
1988年 | 3篇 |
1987年 | 1篇 |
1986年 | 2篇 |
1985年 | 3篇 |
1984年 | 3篇 |
1982年 | 4篇 |
1981年 | 3篇 |
1980年 | 1篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1976年 | 1篇 |
1974年 | 1篇 |
1955年 | 1篇 |
排序方式: 共有977条查询结果,搜索用时 15 毫秒
91.
Approximate dynamic programming (ADP) commonly employs value function approximation to numerically solve complex dynamic programming problems. A statistical perspective of value function approximation employs a design and analysis of computer experiments (DACE) approach, where the “computer experiment” yields points on the value function curve. The DACE approach has been used to numerically solve high-dimensional, continuous-state stochastic dynamic programming, and performs two tasks primarily: (1) design of experiments and (2) statistical modeling. The use of design of experiments enables more efficient discretization. However, identifying the appropriate sample size is not straightforward. Furthermore, identifying the appropriate model structure is a well-known problem in the field of statistics. In this paper, we present a sequential method that can adaptively determine both sample size and model structure. Number-theoretic methods (NTM) are used to sequentially grow the experimental design because of their ability to fill the design space. Feed-forward neural networks (NNs) are used for statistical modeling because of their adjustability in structure-complexity . This adaptive value function approximation (AVFA) method must be automated to enable efficient implementation within ADP. An AVFA algorithm is introduced, that increments the size of the state space training data in each sequential step, and for each sample size a successive model search process is performed to find an optimal NN model. The new algorithm is tested on a nine-dimensional inventory forecasting problem. 相似文献
92.
93.
本文从超导电性起源于电声子机制出发,讨论了N(O)与原子核外电子层分布及电子层上的电子数的分布之间的关联问题,并用电负性均衡原理讨论了超导材料之中由于元素之间有化学键的形成,元素之间电子发生转移对N(O)的分布影响。 相似文献
94.
《Information Security Journal: A Global Perspective》2013,22(1):36-50
ABSTRACT Business enterprises are increasingly realizing the importance of business continuity management (BCM). Availability BS 25999 Standard has facilitated a consistent methodology that organizations can follow in designing their BCM System. This paper intends to provide a conceptual understanding of BCM right from BCM Policy to BCM maturity by describing the steps involved in the implementation of BCM Standard – BS 25999 – to ensure business continuity in the event of an outage. The key BCM tasks have been categorized into three phases of business continuity – Pre-event Preparation, Event Management, and Post-event Continuity. This paper also highlights some of the challenges experienced by the author in carrying out Risk Assessment and Business Impact Analysis. The Business Continuity Maturity Model® of Virtual Corporation is provided (with their permission) as a tool to strengthen business continuity maturity or organizations. 相似文献
95.
This paper considers a permutation flowshop problem with secondary resources with the objective of minimizing the number of tardy jobs. The number of secondary resources assigned to the machines (workcenters), as well as the allocation of resources among the various machines, will play a significant role in the time required to process each job by its specified due date. This problem finds application in a large number of environments including manufacturing, maintenance, warehousing operations, as well as in healthcare. The research presents a lower bound for the permutation flowshop problem and evaluates its performance against the optimal solution for small, medium, and large instances. Several heuristics, including neighborhood search and simulated annealing, are presented to generate the secondary resource assignment and the allocation of jobs to the schedule. The computational complexity of the lower bound and computational examples for the heuristics are discussed. 相似文献
96.
Yasutaka Hayamizu Kyoji Yamamoto Shinichiro Yanase Toru Hyakutake Toru Shinohara Shinichi Morita 《热科学学报(英文版)》2008,17(3):193-198
An objective of the present paper is to experimentally clarify the torsion effect on the flow in helical circular pipes. We have made six helical circular pipes having different pitches and common non-dimensional curvature δ of about 0.1. The torsion parameter β0, which is defined by β0 = τ/(2δ)1/2 with non-dimensional torsion r, are taken to be 0.02, 0.45, 0.69, 1.01, 1.38 and 1.89 covering from small to very large pitch. The velocity distributions and the turbulence of the flow are measured using an X-type hot-wire anemometer in the range of the Reynolds number from 200 to 20000. The results obtained are summarized as follows: The mean secondary flow pattern in a cross section of the pipe changes from an ordinary twin-vortex type as is seen in a curved pipe without torsion (toroidal pipe) to a single vortex type after one of the twin-vortex gradually disappears as β0 increases. The circulation direction of the single vortex is the same as the direction of torsion of the pipe. The mean velocity distribution of the axial flow is similar to that of the toroidal pipe at small β0, but changes its shape as β0 increases, and attains the shape similar to that in a straight circular pipe when ,β0 = 1.89. It is also found that the critical Reynolds number, at which the flow shows a marginal behavior to turbulence, decreases as ,β0 increases for small ,β0, and then increases after taking a minimum at ,β0 ≈ 1.4 as ,β0 increases. The minimum of the critical Reynolds number experimentally obtained is about 400 at ,β0 ≈ 1.4. 相似文献
97.
喷气纺纱喷嘴安装位置对成纱强力的影响 总被引:4,自引:0,他引:4
研究了喷气纺纱喷嘴安装位置有关参数及解捻管槽数对成纱强力的影响规律。试验结果表明:一级喷嘴与前钳口间距存在临界值,当间距为11mm时成纱强力最高;当两级喷嘴间距为4mm时,成纱强力较高且波最小;异纱钩与二级喷嘴的最佳 间距为88mm,该距离过大过小成纱强力均有降低;随着解捻管槽数的增加,成纱强力提高,实际生是中可选 用四槽。 相似文献
98.
Behavioral, neuropsychological, and brain imaging research points to a dedicated system for processing number that is shared across development and across species. This foundational Approximate Number System (ANS) operates over multiple modalities, forming representations of the number of objects, sounds, or events in a scene. This system is imprecise and hence differs from exact counting. Evidence suggests that the resolution of the ANS, as specified by a Weber fraction, increases with age such that adults can discriminate numerosities that infants cannot. However, the Weber fraction has yet to be determined for participants of any age between 9 months and adulthood, leaving its developmental trajectory unclear. Here we identify the Weber fraction of the ANS in 3-, 4-, 5-, and 6-year-old children and in adults. We show that the resolution of this system continues to increase throughout childhood, with adultlike levels of acuity attained surprisingly late in development. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
99.
In this paper we introduce new algorithm implementations of a new parametric image processing framework that will accurately process images and speed up computation for addition, subtraction, and multiplication. Its potential applications include computer graphics, digital signal processing and other multimedia applications. This Parameterized Digital Electronic Arithmetic (PDEA) model replaces linear operations with non-linear ones. The implementation of a parameterized model is presented. We also present the design of arithmetic circuits including parallel counters, adders and multipliers based in two high performance threshold logic gate implementations that we have developed. We will also explore new microprocessor architectures to take advantage of arithmetic. The experiments executed have shown that the algorithm provides faster and better enhancements from those described in the literature. The FPGA chips used is Spartan 3E from Xilinix. The critical length in the circuit implemented on the FPGA had the minimum period for the proposed subsystem is 10.209 ns (maximum frequency 97.957 MHz). Maximum power consumed is 2.4 mW using 32 nm process and we used parallelism and reuse of the Hardware components to accomplish and speed up the process. 相似文献
100.