全文获取类型
收费全文 | 8052篇 |
免费 | 214篇 |
国内免费 | 363篇 |
专业分类
电工技术 | 114篇 |
综合类 | 249篇 |
化学工业 | 771篇 |
金属工艺 | 1109篇 |
机械仪表 | 1078篇 |
建筑科学 | 88篇 |
矿业工程 | 47篇 |
能源动力 | 313篇 |
轻工业 | 51篇 |
水利工程 | 23篇 |
石油天然气 | 27篇 |
武器工业 | 85篇 |
无线电 | 2023篇 |
一般工业技术 | 1844篇 |
冶金工业 | 132篇 |
原子能技术 | 168篇 |
自动化技术 | 507篇 |
出版年
2024年 | 10篇 |
2023年 | 99篇 |
2022年 | 141篇 |
2021年 | 184篇 |
2020年 | 175篇 |
2019年 | 125篇 |
2018年 | 140篇 |
2017年 | 168篇 |
2016年 | 175篇 |
2015年 | 191篇 |
2014年 | 390篇 |
2013年 | 359篇 |
2012年 | 334篇 |
2011年 | 535篇 |
2010年 | 344篇 |
2009年 | 400篇 |
2008年 | 405篇 |
2007年 | 435篇 |
2006年 | 447篇 |
2005年 | 372篇 |
2004年 | 330篇 |
2003年 | 295篇 |
2002年 | 328篇 |
2001年 | 209篇 |
2000年 | 224篇 |
1999年 | 232篇 |
1998年 | 274篇 |
1997年 | 260篇 |
1996年 | 236篇 |
1995年 | 152篇 |
1994年 | 126篇 |
1993年 | 116篇 |
1992年 | 88篇 |
1991年 | 75篇 |
1990年 | 86篇 |
1989年 | 48篇 |
1988年 | 66篇 |
1987年 | 20篇 |
1986年 | 9篇 |
1985年 | 7篇 |
1984年 | 4篇 |
1983年 | 5篇 |
1982年 | 1篇 |
1981年 | 4篇 |
1980年 | 1篇 |
1976年 | 1篇 |
1975年 | 1篇 |
1974年 | 1篇 |
1973年 | 1篇 |
排序方式: 共有8629条查询结果,搜索用时 15 毫秒
61.
胡才雄 《有色金属材料与工程》1994,15(1):31-36
本文介绍了硅片背面的三种主要损伤吸除技术:机械损伤、激光辐照和离子注入技术。对这三种吸除技术的机理、工艺条件、应用情况和近来进展,作了详细的评述。 相似文献
62.
由于面临越来越严重的激光制导武器的威胁 ,对来袭威胁进行早期预警日趋重要。概要介绍了微弱激光辐射探测技术国外研究现状及发展趋势。对微弱激光辐射探测关键技术进行了研究探讨。 相似文献
63.
H. Azuma A. Takeuchi T. Ito H. Fukushima T. Motohiro M. Yamaguchi 《Solar Energy Materials & Solar Cells》2002,74(1-4)
The pulsed KrF excimer laser annealing of silicon films for solar cell with EBEP-CVD and LP-CVD was studied theoretically and experimentally. Three-dimensional thermal diffusion equation for microcrystalline and amorphous silicon was solved by using the finite difference methods. The results of our heat-flow simulation of laser re-crystallization in a laser irradiation with 50 ns pulse duration almost agree with the experimental results in re-crystallization depth of 0.7 μm for microcrystalline silicon (EBEP-CVD) and 0.4 μm for amorphous silicon (LP-CVD) in a single pulse excimer laser annealing. 相似文献
64.
Agnieszka J Klemm Piotr Klemm Kazimierz Rozniakowski Tomasz W Wojtatowicz 《Building and Environment》2002,37(12):1221-1232
This paper present the results of the investigation into a potential application of laser radiation for the detection of phase transition processes occurring on the surface layers of porous materials. An attempt was made to discuss in the approximation equations, the relationships between coefficients of the reflected light, the temperature and humidity of the surrounding environment. Laser light reflected from the porous surface carries information about the roughness of the structure. The presence of water microdrop on the surface of the porous material, as a result of condensation and thus a phase transition, leads to the phase displacement of individual rays, which is represented by different images. Therefore, a comprehensive analysis of the reflected light parameters allows a dynamic study of the phase transition phenomena without mechanical intervention. 相似文献
65.
激光远距作用的机制与效应 总被引:1,自引:0,他引:1
本文定量分析激光远距作用的机理并对它们在治癌中的作用作简要的论述。 相似文献
66.
F. Nava G. Wagner C. Lanzieri P. Vanni E. Vittone 《Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment》2003,510(3):273-280
The development of SiC minimum ionising particle (MIP) detectors imposes severe constrains in the electronic quality and the thickness of the material due to the relatively high value of the energy required to produce an electron–hole pair in this material by MIP against the value for Si. In this work, particle detectors were made using semiconductor epitaxial undoped n-type 4H-SiC as the detection medium. The thickness of the epilayer is on the order of 40 μm and the detectors are realised by the formation of a nickel silicide on the silicon surface of the epitaxial layer (Schottky contact) and of the ohmic contact on the back side of 4H-SiC substrate. The low doping concentration (6×1013 cm−3) of the epilayer allows the detector to be totally depleted at relatively low reverse voltages (100 V). We present experimental data on the charge collection properties by using 5.486 MeV -particles impinging on the Schottky contact. A 100% charge collection efficiency (CCE) is demonstrated for reverse voltages higher than the one needed to have a depletion region equal to the -particle extrapolated range in SiC. The diffusion contribution of the minority change carriers to CCE is pointed out. By comparing measured CCE values to the outcomes of drift–diffusion simulation, values are inferred for the hole lifetime within the neutral region of the charge carrier generation layer. 相似文献
67.
An ab initio study using the local spin density approximation of the electronic and optical properties of materials where Cr transition metal substitutes for N in the GaN host semiconductor with an atomic concentration of 1.56% is presented. This material, characterized by an isolated and partially filled intermediate band, is a candidate for high-efficiency solar cells. The atomic and orbital composition of this band has been analyzed showing that is mainly made up of a t-group orbital of the transition metal. The absorption coefficient theoretical results show a sub-gap absorption with respect to the host semiconductor which could lead to an increase in solar conversion efficiency. 相似文献
68.
Th. Pretorius G. Habedank J. Woitschig F. Vollertsen 《Materialwissenschaft und Werkstofftechnik》2006,37(1):85-91
Thermal treatments of steel components with the goal of hardening often result in distortion by releasing the residual stresses which were brought into the specimen during the preceding processing steps. The goal of the presented work is the minimization of this distortion. By generating definite residual stress fields and investigating the resulting distortion, the distortion mechanism can be observed in detail. A flexible and reproducible way to generate such residual stress fields inside a specimen is by means of local thermal treatment with a laser beam. Computer simulations as well as experiments were carried out using an idealized tooth of a gearwheel (finger sample) as a model system. The deformation of the samples due to the laser heat treatment and the stress fields generated inside the samples were determined with respect to different process parameters. 相似文献
69.
70.