全文获取类型
收费全文 | 36342篇 |
免费 | 4358篇 |
国内免费 | 1966篇 |
专业分类
电工技术 | 4047篇 |
技术理论 | 5篇 |
综合类 | 3984篇 |
化学工业 | 2244篇 |
金属工艺 | 1631篇 |
机械仪表 | 2998篇 |
建筑科学 | 1436篇 |
矿业工程 | 1070篇 |
能源动力 | 624篇 |
轻工业 | 623篇 |
水利工程 | 839篇 |
石油天然气 | 937篇 |
武器工业 | 1121篇 |
无线电 | 9166篇 |
一般工业技术 | 4123篇 |
冶金工业 | 992篇 |
原子能技术 | 340篇 |
自动化技术 | 6486篇 |
出版年
2024年 | 189篇 |
2023年 | 523篇 |
2022年 | 897篇 |
2021年 | 1031篇 |
2020年 | 1158篇 |
2019年 | 855篇 |
2018年 | 922篇 |
2017年 | 1282篇 |
2016年 | 1434篇 |
2015年 | 1660篇 |
2014年 | 2363篇 |
2013年 | 2406篇 |
2012年 | 2828篇 |
2011年 | 2972篇 |
2010年 | 2228篇 |
2009年 | 2053篇 |
2008年 | 2160篇 |
2007年 | 2666篇 |
2006年 | 2287篇 |
2005年 | 1965篇 |
2004年 | 1566篇 |
2003年 | 1254篇 |
2002年 | 1031篇 |
2001年 | 958篇 |
2000年 | 768篇 |
1999年 | 634篇 |
1998年 | 475篇 |
1997年 | 410篇 |
1996年 | 345篇 |
1995年 | 275篇 |
1994年 | 253篇 |
1993年 | 197篇 |
1992年 | 129篇 |
1991年 | 104篇 |
1990年 | 94篇 |
1989年 | 69篇 |
1988年 | 49篇 |
1987年 | 33篇 |
1986年 | 16篇 |
1985年 | 26篇 |
1984年 | 11篇 |
1983年 | 20篇 |
1982年 | 12篇 |
1981年 | 10篇 |
1980年 | 11篇 |
1979年 | 7篇 |
1977年 | 3篇 |
1975年 | 3篇 |
1963年 | 4篇 |
1959年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
2.
Javier Ramírez Antonio García Uwe Meyer-Bäse Fred Taylor Antonio Lloris 《The Journal of VLSI Signal Processing》2003,33(1-2):171-190
Currently there are design barriers inhibiting the implementation of high-precision digital signal processing (DSP) objects with field programmable logic (FPL) devices. This paper explores overcoming these barriers by fusing together the popular distributed arithmetic (DA) method with the residue number system (RNS) for use in FPL-centric designs. The new design paradigm is studied in the context of a high-performance filter bank and a discrete wavelet transform (DWT). The proposed design paradigm is facilitated by a new RNS accumulator structure based on a carry save adder (CSA). The reported methodology also introduces a polyphase filter structure that results in a reduced look-up table (LUT) budget. The 2C-DA and RNS-DA are compared, in the context of a FPL implementation strategy, using a discrete wavelet transform (DWT) filter bank as a common design theme. The results show that the RNS-DA, compared to a traditional 2C-DA design, enjoys a performance advantage that increases with precision (wordlength). 相似文献
3.
基于直升机目标旋转部件的调制模型,本文针对防空雷达提出了分析直升机信号特征的一种新方法——WVD法,并对直升机目标旋转部件调制回波信号在不同噪声情况下加以仿真分析,结果表明:用WVD分析雷达回波中直升机信号特征是一种非常有效的方法。 相似文献
4.
Ying Tan 《The Journal of VLSI Signal Processing》2002,32(1-2):45-54
In this paper, we propose a new approach for signal detection in wireless digital communications based on the neural network with transient chaos and time-varying gain (NNTCTG), and give a concrete model of the signal detector after appropriate transformations and mappings. It is well known that the problem of the maximum likelihood signal detection can be described as a complex optimization problem that has so many local optima that conventional Hopfield-type neural networks fail to solve. By refraining from the serious local optima problem of Hopfield-type neural networks, the NNTCTG makes use of the time-varying parameters of the recurrent neural network to control the evolving behavior of the network so that the network undergoes the transition from chaotic behavior to gradient convergence. It has richer and more flexible dynamics rather than conventional neural networks only with point attractors, so that it can be expected to have much ability to search for globally optimal or near-optimal solutions. After going through a transiently inverse-bifurcation process, the NNTCTG can approach the global optimum or the neighborhood of global optimum of our problem. Simulation experiments have been performed to show the effectiveness and validation of the proposed neural network based method for the signal detection in digital communications. 相似文献
5.
In this paper, the test results of liquid injection impact on the performance of new alternative refrigerant mixtures such as: R-410A, R-507, R-407C and R-404A are discussed, analysed and presented. The test results were obtained using an air-source heat pump set-up with enhanced surface tubing under various liquid injection ratios. Performance tests were conducted according to the ARI/ASHRAE standards. The performance data demonstrated that as liquid injection ratio increases, compressor head pressure and discharge temperature decrease. This has a positive effect in protecting the compressor. The effect of liquid injection on mixture behaviour varies from one mixture to another depending upon the mixture's composition. Furthermore, liquid injection appears to have a significant influence on R-410A behaviour compared to the other mixtures in question. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
6.
7.
论述了无线电引信多普勒信号增速器的实现原理及意义,介绍了采用TMS320C30作为CPU、多片大容量静态RAM芯片构成海量存储体的信号增速器硬件结构和软件设计,并提出了今后的研究方向。 相似文献
8.
张新华 《计算机应用与软件》1994,11(4):50-55
应用检相原理,可以提取有限长度调制信号和包络解调。通过改变A/D转换器的位数,提高检相分辨率,它与检测对象的速度无关。这为提高检相分辨率展示了新的途径。 相似文献
9.
Christina Dirk‐Faitakis D Grant Allen 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2005,80(7):737-745
This paper describes the development and simulation of an unsteady state biofilter model used to predict dynamic behaviour of cyclically‐operated biofilters and compares it with experimental results obtained from three, parallel, bench‐scale biofilters treating both periodically fluctuating concentrations and constant concentrations of an α‐pinene‐laden gas stream. The dynamic model, using kinetic parameters estimated from the constant concentration biofilter, was able to predict the performance of cyclic biofilters operating at short cycle periods (ie, in the order of minutes and hours). Steady state kinetic data from a constant concentration biofilter can be used to predict unsteady state biofilter operation. At a 24 h cycle period, the dynamic model compared well with experimental results. For long cycle periods (ie, hours and days), removal efficiency decreased after periods of non‐loading: the longer the period of non‐loading, the poorer the biofilter's performance at the re‐commencement of pollutant loading. At longer time scales the model did not effectively predict transient behaviour, as adsorption and changes in kinetic parameters were not accounted for. Modelling results showed that similar biofiltration performance for the cyclic and constant concentration biofiltration of α‐pinene is expected for biofilters operating solely in the first order kinetics regime. Poorer performance for cyclic biofilters following Monod kinetics spanning the entire kinetics range is expected as the cycle amplitude increases. The most important parameters affecting the performance of a cyclically‐operated biofilter with short cycle periods are: amplitude of cyclic fluctuations, Cg, max/Cg, relative value of the half‐saturation constant in the Monod expression, Ks, and effective diffusivity of α‐pinene in the biofilm, De. Copyright © 2005 Society of Chemical Industry 相似文献
10.
Results of metal testing in impact tension–compression and indentation are analyzed. As the analysis of these data demonstrates, the strength of metals increases greatly with strain rates and at moderate indentation rates. At high indentation rates, a decrease in the specific energy (per unit volume of a displaced material) necessary for the formation of a conical cavity was observed. The account of the effects of viscosity, temperature increase upon plastic deformation and its localization can be used to explain the above phenomena. 相似文献