全文获取类型
收费全文 | 1544篇 |
免费 | 191篇 |
国内免费 | 108篇 |
专业分类
电工技术 | 313篇 |
综合类 | 47篇 |
化学工业 | 172篇 |
金属工艺 | 114篇 |
机械仪表 | 102篇 |
建筑科学 | 21篇 |
矿业工程 | 37篇 |
能源动力 | 122篇 |
轻工业 | 6篇 |
水利工程 | 3篇 |
石油天然气 | 3篇 |
武器工业 | 11篇 |
无线电 | 255篇 |
一般工业技术 | 96篇 |
冶金工业 | 22篇 |
原子能技术 | 6篇 |
自动化技术 | 513篇 |
出版年
2024年 | 13篇 |
2023年 | 101篇 |
2022年 | 71篇 |
2021年 | 83篇 |
2020年 | 122篇 |
2019年 | 85篇 |
2018年 | 63篇 |
2017年 | 146篇 |
2016年 | 123篇 |
2015年 | 133篇 |
2014年 | 118篇 |
2013年 | 79篇 |
2012年 | 106篇 |
2011年 | 117篇 |
2010年 | 77篇 |
2009年 | 82篇 |
2008年 | 42篇 |
2007年 | 70篇 |
2006年 | 61篇 |
2005年 | 33篇 |
2004年 | 14篇 |
2003年 | 10篇 |
2002年 | 19篇 |
2001年 | 12篇 |
2000年 | 10篇 |
1999年 | 7篇 |
1998年 | 4篇 |
1997年 | 6篇 |
1996年 | 5篇 |
1995年 | 7篇 |
1994年 | 5篇 |
1993年 | 3篇 |
1992年 | 2篇 |
1991年 | 4篇 |
1990年 | 1篇 |
1989年 | 1篇 |
1988年 | 8篇 |
排序方式: 共有1843条查询结果,搜索用时 31 毫秒
71.
《Electric Power Systems Research》2006,76(8):663-670
Arcing faults are the most common faults that occur in the 220 kV transmission line national grid of Egypt, in the vicinity of ‘Alexandria’ city. This part of the network also feeds a large industrial load in the form of steel works, which injects a large amount of harmonics into the network. In this paper, the performance of this 220 kV TL network during arcing faults is studied with the aid of the PSCAD/EMTDC program together with a specially designed arcing fault custom model incorporated in the program. Several arcing faults are simulated, and the effect of harmonics on the fault current and secondary arc duration time is demonstrated. Based upon the simulation results, recommendations regarding single-pole autoreclosing and arc suppression methods are suggested. 相似文献
72.
73.
《Engineering Analysis with Boundary Elements》2005,29(2):126-135
The Laplace Transform Dual Reciprocity Boundary Element Method (LTDRM or LT-DRBEM) provides with an alternative numerical technique to finite difference (FDM) or finite element methods (FEM) for solving transient diffusion problems. With this method, solutions are calculated directly at any specific time thus avoiding the use of time-stepping schemes. Besides, domain integrals are removed from the problem formulation.In this work we study the applicability of the LT-DRBEM method for laser heat treatment modelling purposes. A simple model was developed based on a two dimensional transient heat conduction equation, in which the laser beam is included as a heat flux boundary condition of gaussian shape. Results corresponding to a stationary and a moving beam are presented and discussed. Non-linear formulations of the problem as those given by temperature dependent material properties are also considered. Good accuracy results were obtained for the stationary beam approach, whereas severe limitations were found for the moving beam case. 相似文献
74.
遗传算法和神经网络融合的滑模控制系统及其在印刷机中的应用 总被引:7,自引:1,他引:7
针对一类非线性系统, 提出了一种综合集成滑模控制器设计方法. 首先, 采用遗传算法进行参数调节, 从而构造出一个最佳切换函数, 使得系统既具有良好的动态性能, 又扩大了鲁棒区域. 然后, 采用神经网络在线调整控制器参数, 从而克服了由不确定性引起的系统轨迹偏离切换函数, 并且通过变学习率学习算法来加快神经网络的收敛性. 最后, 研究了所提出方法在凹版印刷机张力调节中的应用. 仿真结果表明该控制器具有较好的动态性能及鲁棒性, 并有效减少了抖动. 相似文献
75.
76.
Texture classification using the support vector machines 总被引:12,自引:0,他引:12
In recent years, support vector machines (SVMs) have demonstrated excellent performance in a variety of pattern recognition problems. In this paper, we apply SVMs for texture classification, using translation-invariant features generated from the discrete wavelet frame transform. To alleviate the problem of selecting the right kernel parameter in the SVM, we use a fusion scheme based on multiple SVMs, each with a different setting of the kernel parameter. Compared to the traditional Bayes classifier and the learning vector quantization algorithm, SVMs, and, in particular, the fused output from multiple SVMs, produce more accurate classification results on the Brodatz texture album. 相似文献
77.
This work proposes a systematic approach for the adaptive identification and implementation of efficient power management strategies (PMS) in the course of operation of hybrid renewable energy microgrids. The approach is based on the temporal evolution of the system power grand composite curve (PGCC), which is adaptively shaped on-line and within short-term time intervals to form a sequence of decisions indicating the instant and duration of activation of different subsystems. It builds on from previous work where the potential for system performance enhancement could not be exploited through pre-specified PMS identified off-line. More specifically, it involves a stored energy targeting step that exploits the PGCC to identify the desired operational profile of an accumulator during a prediction horizon in order to satisfy the system operating goals. The identified energy targets are subsequently enforced through a sequence of control actions that enable the exact matching of the PGCC hence resulting in a new PMS. The method is elaborated graphically for multiple potential operating goals and is supported by a formal mathematical model that captures system structural and temporal characteristics. It is implemented on an actual hybrid microgrid considering multiple RES-based energy generation and storage options for expected and unexpected weather conditions. 相似文献
78.
The efficient utilization of lignocellulosic biomass and the reduction of production cost are mandatory to attain a cost-effective lignocellulose-to-ethanol process. The selection of suitable pretreatment that allows an effective fractionation of biomass and the use of pretreated material at high-solid loadings on saccharification and fermentation (SSF) processes are considered promising strategies for that purpose. Eucalyptus globulus wood was fractionated by organosolv process at 200 °C for 69 min using 56% of glycerol-water. A 99% of cellulose remained in pretreated biomass and 65% of lignin was solubilized. Precipitated lignin was characterized for chemical composition and thermal behavior, showing similar features to commercial lignin. In order to produce lignocellulosic ethanol at high-gravity, a full factory design was carried to assess the liquid to solid ratio (3–9 g/g) and enzyme to solid ratio (8–16 FPU/g) on SSF of delignified Eucalyptus. High ethanol concentration (94 g/L) corresponding to 77% of conversion at 16FPU/g and LSR = 3 g/g using an industrial and thermotolerant Saccharomyces cerevisiae strain was successfully produced from pretreated biomass. Process integration of a suitable pretreatment, which allows for whole biomass valorization, with intensified saccharification-fermentation stages was shown to be feasible strategy for the co-production of high ethanol titers, oligosaccharides and lignin paving the way for cost-effective Eucalyptus biorefinery. 相似文献
79.
《Carbon》2014
Relevant carbon-based materials, home-made carbon–silica hybrids, commercial activated carbon, and nanostructured multi-walled carbon nanotubes (MWCNT) were tested in the oxidative dehydrogenation of ethylbenzene (EB). Special attention was given to the reaction conditions, using a relatively concentrated EB feed (10 vol.% EB), and limited excess of O2 (O2:EB = 0.6) in order to work at full oxygen conversion and consequently avoid O2 in the downstream processing and recycle streams. The temperature was varied between 425 and 475 °C, that is about 150–200 °C lower than that of the commercial steam dehydrogenation process. The stability was evaluated from runs of 60 h time on stream. Under the applied reactions conditions, all the carbon-based materials are apparently stable in the first 15 h time on stream. The effect of the gasification/burning was significantly visible only after this period where most of them fully decomposes. The carbon of the hybrids decomposes completely rendering the silica matrix and the activated carbon bed is fully consumed. Nano structured MWCNT is the most stable; the structure resists the demanding reaction conditions showing an EB conversion of ∼30% (but deactivating) with a steady selectivity of ∼80%. The catalyst stability under the ODH reaction conditions is predicted from the combustion apparent activation energies. 相似文献
80.
Inkjet-printed electronics are showing promising potential in practical applications, but methods for real-time, non-contact monitoring of printing quality are lacking. This work explores Terahertz (THz) sensing as an approach for such monitoring. It is demonstrated that alterations in the localised dielectric characteristics of inkjet-printed electronics can be qualitatively distinguished using quasi-optically-based, sub-THz reflection spectroscopy. Decreased reflection coefficients caused by the sintering process are observed and quantified. Using THz near-field scanning imaging, it is shown that sintering produces a more uniform spatial distribution of permittivity in the printed carbon patterns. Images generated using THz-TDS based imaging are presented, demonstrating the combination of high resolution imaging with quantification of complex permittivities. This work, for the first time, demonstrates the feasibility of quality control in printed electronic-ink with THz sensing, and is of practical significance to the development of in-situ and non-contact commercial-quality characterisation methods for inkjet-printed electronics. 相似文献