全文获取类型
收费全文 | 2302篇 |
免费 | 162篇 |
国内免费 | 7篇 |
专业分类
电工技术 | 41篇 |
化学工业 | 573篇 |
金属工艺 | 61篇 |
机械仪表 | 89篇 |
建筑科学 | 72篇 |
矿业工程 | 4篇 |
能源动力 | 86篇 |
轻工业 | 396篇 |
水利工程 | 22篇 |
石油天然气 | 9篇 |
无线电 | 185篇 |
一般工业技术 | 396篇 |
冶金工业 | 221篇 |
原子能技术 | 19篇 |
自动化技术 | 297篇 |
出版年
2024年 | 5篇 |
2023年 | 22篇 |
2022年 | 38篇 |
2021年 | 125篇 |
2020年 | 75篇 |
2019年 | 75篇 |
2018年 | 102篇 |
2017年 | 110篇 |
2016年 | 112篇 |
2015年 | 74篇 |
2014年 | 119篇 |
2013年 | 175篇 |
2012年 | 175篇 |
2011年 | 153篇 |
2010年 | 106篇 |
2009年 | 117篇 |
2008年 | 110篇 |
2007年 | 81篇 |
2006年 | 103篇 |
2005年 | 60篇 |
2004年 | 54篇 |
2003年 | 38篇 |
2002年 | 40篇 |
2001年 | 32篇 |
2000年 | 19篇 |
1999年 | 27篇 |
1998年 | 59篇 |
1997年 | 47篇 |
1996年 | 40篇 |
1995年 | 21篇 |
1994年 | 19篇 |
1993年 | 10篇 |
1992年 | 9篇 |
1991年 | 16篇 |
1990年 | 16篇 |
1989年 | 7篇 |
1988年 | 5篇 |
1987年 | 5篇 |
1986年 | 6篇 |
1985年 | 6篇 |
1984年 | 7篇 |
1983年 | 4篇 |
1982年 | 5篇 |
1981年 | 3篇 |
1980年 | 5篇 |
1979年 | 3篇 |
1978年 | 4篇 |
1977年 | 5篇 |
1976年 | 5篇 |
1969年 | 3篇 |
排序方式: 共有2471条查询结果,搜索用时 15 毫秒
71.
Compact yet efficient hardware implementation of artificial neural networks with customized topology
Nadia Nedjah Rodrigo Martins da Silva Luiza de Macedo Mourelle 《Expert systems with applications》2012,39(10):9191-9206
There are several neural network implementations using either software, hardware-based or a hardware/software co-design. This work proposes a hardware architecture to implement an artificial neural network (ANN), whose topology is the multilayer perceptron (MLP). In this paper, we explore the parallelism of neural networks and allow on-the-fly changes of the number of inputs, number of layers and number of neurons per layer of the net. This reconfigurability characteristic permits that any application of ANNs may be implemented using the proposed hardware. In order to reduce the processing time that is spent in arithmetic computation, a real number is represented using a fraction of integers. In this way, the arithmetic is limited to integer operations, performed by fast combinational circuits. A simple state machine is required to control sums and products of fractions. Sigmoid is used as the activation function in the proposed implementation. It is approximated by polynomials, whose underlying computation requires only sums and products. A theorem is introduced and proven so as to cover the arithmetic strategy of the computation of the activation function. Thus, the arithmetic circuitry used to implement the neuron weighted sum is reused for computing the sigmoid. This resource sharing decreased drastically the total area of the system. After modeling and simulation for functionality validation, the proposed architecture synthesized using reconfigurable hardware. The results are promising. 相似文献
72.
Agustin Gajate Rodolfo Haber Raul del Toro Pastora Vega Andres Bustillo 《Journal of Intelligent Manufacturing》2012,23(3):869-882
Tool wear detection is a key issue for tool condition monitoring. The maximization of useful tool life is frequently related with the optimization of machining processes. This paper presents two model-based approaches for tool wear monitoring on the basis of neuro-fuzzy techniques. The use of a neuro-fuzzy hybridization to design a tool wear monitoring system is aiming at exploiting the synergy of neural networks and fuzzy logic, by combining human reasoning with learning and connectionist structure. The turning process that is a well-known machining process is selected for this case study. A four-input (i.e., time, cutting forces, vibrations and acoustic emissions signals) single-output (tool wear rate) model is designed and implemented on the basis of three neuro-fuzzy approaches (inductive, transductive and evolving neuro-fuzzy systems). The tool wear model is then used for monitoring the turning process. The comparative study demonstrates that the transductive neuro-fuzzy model provides better error-based performance indices for detecting tool wear than the inductive neuro-fuzzy model and than the evolving neuro-fuzzy model. 相似文献
73.
I.F. Pinto Correia P.G. Martins C.M. Mota Soares C.A. Mota Soares J. Herskovits 《Composite Structures》2006,75(1-4):49-59
In this paper two shell finite element models are presented for the structural analysis of composite laminated piezoelectric shells. One is an axisymmetric conical frustum with two nodal rings and the other is a conic shell panel with eight nodes. Both models are based in a mixed laminated theory that combines a higher order shear deformation theory for the mechanical displacement field with a layerwise representation with linear functions for the electric potential through each piezoelectric layer. In order to obtain the optimal design sensitivities analysis and optimization techniques based in the nonlinear mathematical programming are used. The design objectives can be the minimization of the deformed structure or the maximization of the natural fundamental frequency and the design variables are the electric potential difference applied to the actuators or the ply thicknesses among others. 相似文献
74.
A New Distribution System Reconfiguration Approach Using Optimum Power Flow and Sensitivity Analysis for Loss Reduction 总被引:2,自引:0,他引:2
Gomes F.V. Carneiro S. Jr. Pereira J.L.R. Vinagre M.P. Garcia P.A.N. De Araujo L.R. 《Power Systems, IEEE Transactions on》2006,21(4):1616-1623
This paper presents a new approach for distribution system reconfiguration (DSR) based on optimum power flow (OPF) in which the branch statuses (open/close) are represented by continuous functions. In the proposed approach, all branches are initially considered closed, and from the OPF results, a heuristic technique is used to determine the next loop to be broken by opening one switch. Then the list of switches that are candidates to be opened is updated, and the above process is repeated until all loops are broken, making the distribution system radial. This paper includes results and comparisons on test systems utilized in three classical papers published in the technical literature, as well as in a previous paper by the authors. Results obtained on a real large-scale distribution system are also presented 相似文献
75.
Martins Silvia S.; Mazzotti Guido; Chilcoat Howard D. 《Canadian Metallurgical Quarterly》2005,13(3):244
This study aims to estimate changes in the prevalence of ecstasy use over time, analyze the overlap of ecstasy use and other drug use, and compare other drug use in ecstasy versus marijuana users. The authors hypothesized that ecstasy users early in the "epidemic" would be polydrug users and that associations between ecstasy and other drug use would diminish as the prevalence of ecstasy use increased. Data were drawn from public use data files from the 1995, 1997, 1999, and 2001 National Household Survey on Drug Abuse. Ecstasy use increased in the U.S. population and the prevalence was greater in younger age groups. Ecstasy users were likely to use a variety of other drugs; however, association of ecstasy use with other drug use was strongest early in the "epidemic," diminishing as the number of new users increased. Later, more drug-naive adolescents and young adults began experimenting with ecstasy. These results can orient prevention strategies that target ecstasy users. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
76.
In most molten metal processing operations, the acts of melting, transporting and alloying the metal in preparation for casting into desired shapes introduces undesirable non‐metallic inclusions to the melt. Molten metals are highly reactive and tend to interact with gases and refractories during processing steps; undesirable phases are absorbed either as liquid or solid. Such examples of inclusion introduction are molten aluminum reacting with oxygen in air to form solid aluminum oxide, or molten cast iron reacting with oxygen in air to form liquid slag phases. 相似文献
77.
针对火电厂非线性、多变量和多控制目标的特点,设计了一个火电厂多代理控制系统(PPMACS).在PP MACS中,前馈控制代理(FFCAs)采用神经模糊系统进行决策,反馈控制代理(FBCAs)采用基于遗传算法的模糊系统进行决策.优化任务分解代理(OTDAs)通过一个优化代理和一个分解代理来进行多目标优化分解PPMACS的任务.协调代理根据运行条件协调PPMACS的各个代理.仿真结果显示了火电厂多代理控制系统能够实现火电单元机组的多目标运行和大范围负荷跟踪.神经网络、模糊逻辑和遗传算法是PPMACS中的智能代理进行决策的有效工具. 相似文献
78.
Freitas SP Gonçalves TC Serrão JE Santos-Mallet JR 《Microscopy research and technique》2007,70(4):355-360
Male of Triatoma rubrofasciata has four elongated sac-like reproductive mesodermic accessory glands, lined by an inner single layer of secretory cells, with basal plasma membrane infolds and short apical microvilli, and externally enveloped by a thin visceral muscle layer. The secretory cells have a well-developed rough endoplasmic reticulum, Golgi complex, mitochondria, and secretory granules. In one day old adult the gland cells are poorly developed, presenting small, electron-transparent secretory granules scattered among the rough endoplasmatic reticulum, whereas in three days old adult these cells have the cisternae of the rough endoplasmatic reticulum varing size degree, filled with granular electrondense content. In five days old males the secretory granules increase in diameter, being released to the gland lumen. Therefore, there is an increase of the secretory activity according to male maturation. 相似文献
79.
Auxetic materials are endowed with a behavior that contradicts common sense, when subjected to an axial tensile load they increase their transverse dimension. In case of a compression load, they reduce their transverse dimension. Consequently, these materials have a negative Poisson’s ratio in such direction. This paper reviews research related to these materials. It presents the theories that explain their deformation behavior and reveals the important role represented by the internal structure. Their mechanical properties are explored and some potential applications for these materials are shown. 相似文献
80.
Front Cover: Photoactivatable Mussel‐Based Underwater Adhesive Proteins by an Expanded Genetic Code (ChemBioChem 18/2017) 下载免费PDF全文
Dr. Matthias Hauf Dr. Florian Richter Tobias Schneider Thomas Faidt Dr. Berta M. Martins Dr. Tobias Baumann Dr. Patrick Durkin Prof. Dr. Holger Dobbek Prof. Dr. Karin Jacobs Prof. Dr. Andreas Möglich Prof. Dr. Nediljko Budisa 《Chembiochem : a European journal of chemical biology》2017,18(18):1771-1771