全文获取类型
收费全文 | 17833篇 |
免费 | 140篇 |
国内免费 | 405篇 |
专业分类
电工技术 | 161篇 |
综合类 | 82篇 |
化学工业 | 1476篇 |
金属工艺 | 332篇 |
机械仪表 | 754篇 |
建筑科学 | 722篇 |
矿业工程 | 377篇 |
能源动力 | 61篇 |
轻工业 | 3380篇 |
水利工程 | 208篇 |
石油天然气 | 237篇 |
武器工业 | 33篇 |
无线电 | 4475篇 |
一般工业技术 | 4974篇 |
冶金工业 | 229篇 |
原子能技术 | 148篇 |
自动化技术 | 729篇 |
出版年
2015年 | 66篇 |
2014年 | 162篇 |
2013年 | 108篇 |
2012年 | 1690篇 |
2011年 | 1962篇 |
2010年 | 369篇 |
2009年 | 370篇 |
2008年 | 1450篇 |
2007年 | 1290篇 |
2006年 | 1116篇 |
2005年 | 970篇 |
2004年 | 772篇 |
2003年 | 648篇 |
2002年 | 546篇 |
2001年 | 452篇 |
2000年 | 449篇 |
1999年 | 273篇 |
1998年 | 167篇 |
1997年 | 139篇 |
1996年 | 149篇 |
1995年 | 116篇 |
1994年 | 101篇 |
1993年 | 89篇 |
1992年 | 120篇 |
1991年 | 113篇 |
1990年 | 91篇 |
1989年 | 120篇 |
1988年 | 125篇 |
1987年 | 136篇 |
1986年 | 128篇 |
1985年 | 154篇 |
1984年 | 119篇 |
1983年 | 136篇 |
1982年 | 117篇 |
1981年 | 98篇 |
1980年 | 125篇 |
1979年 | 98篇 |
1978年 | 80篇 |
1977年 | 234篇 |
1976年 | 229篇 |
1975年 | 269篇 |
1974年 | 271篇 |
1973年 | 174篇 |
1972年 | 264篇 |
1971年 | 267篇 |
1970年 | 256篇 |
1968年 | 191篇 |
1967年 | 345篇 |
1965年 | 266篇 |
1964年 | 118篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
An intensive computer keyboard training course, based on an information processing model of man, was tested on a variety of personnel in work. Over a one or two week period, 241 adult subjects were trained. Subjects achieved mean speeds of 7.1 words per minute (WPM) after the second and 13.7 WPM after the ninth lesson. Significant decreases in errors per minute (EPM) occurred from 2.67 to 1.78. Previous experience with a keyboard and being female were factors associated with enhanced keyboard operating performance. Compressing the ten lessons from two into one week reduced the effectiveness of the programme. 相似文献
22.
The physical metallurgy underlying the development of cast microstructures in abrasion resistant high chromium cast irons, and their structural modification by thermal treatments is relatively complex. Structural characterisation via electron microscopy therefore has a key role to play in furthering our understanding of the phase transformations that control the microstructures and hence the service performances of these irons as wear parts. This paper shows how both scanning and especially transmission electron microscopy can provide valuable information on the nature of eutectic and secondary carbides and on the matrix structures in these irons. Particular attention is given to current characterisation research on conventionally cast 30%Cr irons that are used for applications involving corrosive wear e.g. slurry pumps and on a semi-solid cast 27%Cr iron that has a potential for applications in industry. 相似文献
23.
E. Q. Xie W. W. Wang N. Jiang D. Y. He Department of Physics Lanzhou University Lanzhou China 《金属学报(英文版)》2002,15(2):221-226
1. IntroductionThe transition metal silicides have attraeted much attention because of their potentialapplicatiOIl in very large scale integration (VLSI) de.ice[1]. Near-noble metal silicides canbe used as Schottky al1d ohn1ic col1tacts in silicon-based d… 相似文献
24.
25.
以基斯罗古布斯卡亚(Kislogubskaya)潮汐电站为例,综述了俄罗斯潮汐电站的发展历程。从修建该电站所采用的建筑材料、建筑方法以及发电机组的选型等方面,对过去40多年的运行经验进行了总结。 相似文献
26.
Dowson N Bowden R 《IEEE transactions on pattern analysis and machine intelligence》2008,30(1):180-185
Mutual Information (MI) is popular for registration via function optimisation. This work proposes an inverse compositional formulation of MI for Levenberg-Marquardt optimisation. This yields a constant Hessian, which may be pre-computed. Speed improvements of 15% were obtained, with convergence accuracies similar to those of the standard formulation. 相似文献
27.
28.
29.
The introduction of laser scanners at supermarket checkout areas has resulted in previous ergonomics studies focusing specifically on the scanning process and associated cumulative trauma disorders in the hands and arms. Few studies have evaluated the increased musculoskeletal load and exertion of checkout staff when they are also expected to pack the products into bags for the customers. This paper describes an ergonomics evaluation of three different designs of checkout workstation, which require the operator to stand when they scan the products, pack them into plastic bags and transfer the packed bags to the customer. Musculoskeletal load and exertion associated with the different checkouts were measured using OWAS, heart rate recordings and ratings of perceived exertion. In addition, subjective rankings of the workstations were obtained and the productivity associated with each design examined as part of the evaluation. Some of the variables measured showed significant differences in postural load between the workstations. The results of the evaluation formed the basis of recommendations for an improved workstation design. Some of the suggestions made to reduce postural load and increase productivity include positioning the weigh scale to the side and the bag frame beneath the scanner. 相似文献
30.
This article analyzes the transmission line characteristics of plasmonic hybrid metal insulator metal (HMIM) waveguide, circular ring resonator (CRR) based dual-band band-pass filters with two transmission poles in both pass-bands in the optical regime using coupled line feed. The transmission line characteristics of an HMIM waveguide, such as characteristic impedance (ZPV), effective refractive index (neff) and propagation length (Lspp), have been obtained by using full wave simulation. Using basic HMIM slot waveguide, a CRR with periodic loading of double- and triple-ring CRR is numerically analyzed. Two input ports have been used for excitation, which are located at the separation of 180° positions along the CRR, and are coupled with the ring by parallel coupled lines, producing the dual pass-bands with the synchronous excitation of two transmission poles. The proposed double-ring dual-band band-pass filter (DR-DB-BPF) offers 35 dB extinction ratio (ER), 299.69 nm free spectral range (FSR) and narrow band full width half maximum (FWHM) of 78.057—112.43 nm. The triple-ring DB-BPF (TR-DB-BPF) has 22.5 dB ER, FSR of 292.18 nm and FWHM of 42.751—59.58 nm. The proposed filters are very useful in the development of dual-band filters for electronic photonic integrated circuits (EPICs), as the optical signals are filtered at two wavelengths simultaneously. 相似文献