全文获取类型
收费全文 | 21862篇 |
免费 | 1548篇 |
国内免费 | 868篇 |
专业分类
电工技术 | 1076篇 |
技术理论 | 4篇 |
综合类 | 1114篇 |
化学工业 | 3913篇 |
金属工艺 | 925篇 |
机械仪表 | 1283篇 |
建筑科学 | 1506篇 |
矿业工程 | 560篇 |
能源动力 | 621篇 |
轻工业 | 1208篇 |
水利工程 | 319篇 |
石油天然气 | 1272篇 |
武器工业 | 136篇 |
无线电 | 2940篇 |
一般工业技术 | 2918篇 |
冶金工业 | 1209篇 |
原子能技术 | 181篇 |
自动化技术 | 3093篇 |
出版年
2024年 | 70篇 |
2023年 | 337篇 |
2022年 | 574篇 |
2021年 | 811篇 |
2020年 | 624篇 |
2019年 | 563篇 |
2018年 | 627篇 |
2017年 | 645篇 |
2016年 | 618篇 |
2015年 | 763篇 |
2014年 | 966篇 |
2013年 | 1334篇 |
2012年 | 1256篇 |
2011年 | 1398篇 |
2010年 | 1106篇 |
2009年 | 1129篇 |
2008年 | 1119篇 |
2007年 | 1070篇 |
2006年 | 1129篇 |
2005年 | 995篇 |
2004年 | 680篇 |
2003年 | 673篇 |
2002年 | 596篇 |
2001年 | 506篇 |
2000年 | 565篇 |
1999年 | 626篇 |
1998年 | 599篇 |
1997年 | 523篇 |
1996年 | 475篇 |
1995年 | 348篇 |
1994年 | 324篇 |
1993年 | 240篇 |
1992年 | 186篇 |
1991年 | 142篇 |
1990年 | 130篇 |
1989年 | 102篇 |
1988年 | 83篇 |
1987年 | 57篇 |
1986年 | 50篇 |
1985年 | 38篇 |
1984年 | 23篇 |
1983年 | 22篇 |
1982年 | 32篇 |
1981年 | 23篇 |
1980年 | 17篇 |
1979年 | 13篇 |
1978年 | 12篇 |
1977年 | 12篇 |
1976年 | 17篇 |
1971年 | 8篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
51.
In this paper, we present a technique for using an additional parallel neural network to provide adaptive enhancements to a basic fixed neural network-based nonlinear control system. This proposed parallel adaptive neural network control system is applicable to nonlinear dynamical systems of the type commonly encountered in many practical position control servomechanisms. Properties of the controller are discussed, and it is shown that if Gaussian radial basis function networks are used for the additional parallel neural network, uniformly stable adaptation is assured and the approximation error converges to zero asymptotically. In the paper, the effectiveness of the proposed parallel adaptive neural network control system is demonstrated in real-time implementation experiments for position control in a servomechanism with asymmetrical loading and changes in the load 相似文献
52.
Shye Lin Wu Chung Len Lee Tan Fu Lei Chen C.F. Chen L.J. Ho K.Z. Ling Y.C. 《Electron Device Letters, IEEE》1994,15(4):120-122
In this study, it is demonstrated that the incorporation of fluorine can enhance poly-Si/Si interfacial oxide break-up in the poly-Si emitter contacted p+-n shallow junction formation. The annealing temperature for breaking up the poly-Si/Si interfacial oxide has been found to be as low as 900°C. As a result, the junction depth of the BF2-implanted device is much larger than that of the boron-implanted device 相似文献
53.
AS Leong 《Canadian Metallurgical Quarterly》1993,15(2):88-98
Microwaves (MWs) were first introduced as a method of fixation just over 20 years ago. In recent years their use has extended far beyond that of a safe, clean and rapid method of fixation of tissue blocks and large specimens, including brains. MWs accelerate the action of cross-linking fixatives and can greatly accelerate the various stages of tissue processing to produce a paraffin block in 30 min. An extensive range of ultrafast MW-stimulated special stains has been developed, and immunohistochemical procedures can be completed in 20 min by employing MWs. Cellular antigens are distinctly better preserved in tissues fixed by MWs than by conventional cross-linking fixatives. Also, the cytomorphology of cryostat sections irradiated in Wolman's solution is clearly improved. MWs can similarly be applied for fixation and staining of preparations for transmission and scanning electron microscopy, and they also greatly accelerate polymerisation of resins. In the current climate of cost containment, this wide range of applications makes the MW oven an invaluable addition to the diagnostic laboratory. 相似文献
54.
55.
Li L.W. Yeo T.S. Kooi P.S. Leong M.S. 《Antennas and Propagation, IEEE Transactions on》1994,42(9):1360
The parameter set for the exponential raindrop size distribution model presented by Yeo, Kooi and Leong (see ibid. vol.41, P.709, 1993) was derived using a data set measured in Singapore. A limitation to the model is that it is accurate only for small rain rate or when the rain medium consists predominantly of small droplets with diameter D is < λ/π . A new parameter set that enables accurate computation of rain attenuation for droplets with diameter D = λ/π has since been derived using the same data set. This new parameter set has been proven to be more accurate in the computation of rain attenuation 相似文献
56.
Pd-Ge based ohmic contact to n-GaAs with a TiW diffusion barrier was investigated. Electrical analysis as well as Auger electron
spectroscopy and the scanning electron microscopy were used to study the contact after it was subjected to different furnace
and rapid thermal annealing and different aging steps. All analyses show that TiW can act as a good barrier metal for the
Au/Ge/Pd/n-GaAs contact system. A value of 1.45 × 10−6 Ω-cm2 for the specific contact resistance was obtained for the Au/TiW/Ge/Pd/n-GaAs contact after it was rapid thermally annealed
at 425°C for 90 s. It can withstand a thermal aging at 350°C for 40 h with its ρc increasing to 2.94 × 10−6Ω-cm2 and for an aging at 410°C for 40 h with its ρc increasing to 1.38 × 10−5 Ω-cm2. 相似文献
57.
MA Perrella C Patterson L Tan SF Yet CM Hsieh M Yoshizumi ME Lee 《Canadian Metallurgical Quarterly》1996,271(23):13776-13780
58.
Tan W.S. Uren M.J. Houston P.A. Green R.T. Balmer R.S. Martin T. 《Electron Device Letters, IEEE》2006,27(1):1-3
A novel guarded surface leakage test structure is used to isolate the surface and bulk leakage contributions to gate current in AlGaN/GaN HFETs. Passivation with various recipes of SiN/sub x/ always resulted in the commonly observed increase in gate leakage, which was found to be dominated by bulk leakage through the AlGaN. However, high temperature deposited SiN/sub x/ recipes gave a 1-2 orders reduction in surface leakage, whereas low temperature deposition gave an increase. Gate lag measurements were found to correlate closely with the surface leakage component, giving direct evidence that the key device problem of current slump is associated with current flow at the AlGaN surface. 相似文献
59.
Ng J.S. Tan C.H. David J.P.R. Hill G. Rees G.J. 《Electron Devices, IEEE Transactions on》2003,50(4):901-905
Electron and hole ionization coefficients in In/sub 0.53/Ga/sub 0.47/As are deduced from mixed carrier avalanche photomultiplication measurements on a series of p-i-n diode layers, eliminating other effects that can lead to an increase in photocurrent with reverse bias. Low field ionization is observed for electrons but not for holes, resulting in a larger ratio of ionization coefficients, even at moderately high electric fields than previously reported. The measured ionization coefficients are marginally lower than those of GaAs for fields above 250 kVcm/sup -1/, supporting reports of slightly higher avalanche breakdown voltages in In/sub 0.53/Ga/sub 0.47/As than in GaAs p-i-n diodes. 相似文献
60.