全文获取类型
收费全文 | 63703篇 |
免费 | 5583篇 |
国内免费 | 2875篇 |
专业分类
电工技术 | 3569篇 |
技术理论 | 2篇 |
综合类 | 4108篇 |
化学工业 | 10695篇 |
金属工艺 | 3715篇 |
机械仪表 | 4063篇 |
建筑科学 | 4691篇 |
矿业工程 | 2137篇 |
能源动力 | 1693篇 |
轻工业 | 3992篇 |
水利工程 | 1070篇 |
石油天然气 | 3919篇 |
武器工业 | 524篇 |
无线电 | 7689篇 |
一般工业技术 | 7753篇 |
冶金工业 | 3065篇 |
原子能技术 | 634篇 |
自动化技术 | 8842篇 |
出版年
2024年 | 353篇 |
2023年 | 1131篇 |
2022年 | 1830篇 |
2021年 | 2588篇 |
2020年 | 1975篇 |
2019年 | 1766篇 |
2018年 | 1921篇 |
2017年 | 2115篇 |
2016年 | 1917篇 |
2015年 | 2476篇 |
2014年 | 3019篇 |
2013年 | 3620篇 |
2012年 | 4050篇 |
2011年 | 4448篇 |
2010年 | 3673篇 |
2009年 | 3514篇 |
2008年 | 3388篇 |
2007年 | 3290篇 |
2006年 | 3656篇 |
2005年 | 3030篇 |
2004年 | 2119篇 |
2003年 | 1796篇 |
2002年 | 1590篇 |
2001年 | 1443篇 |
2000年 | 1556篇 |
1999年 | 1708篇 |
1998年 | 1511篇 |
1997年 | 1266篇 |
1996年 | 1145篇 |
1995年 | 953篇 |
1994年 | 834篇 |
1993年 | 570篇 |
1992年 | 427篇 |
1991年 | 366篇 |
1990年 | 261篇 |
1989年 | 212篇 |
1988年 | 184篇 |
1987年 | 121篇 |
1986年 | 97篇 |
1985年 | 59篇 |
1984年 | 30篇 |
1983年 | 20篇 |
1982年 | 28篇 |
1981年 | 16篇 |
1980年 | 21篇 |
1979年 | 10篇 |
1978年 | 7篇 |
1977年 | 5篇 |
1976年 | 14篇 |
1975年 | 9篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
21.
Ma Z.J. Chen J.C. Liu Z.H. Krick J.T. Cheng Y.C. Hu C. Ko P.K. 《Electron Device Letters, IEEE》1994,15(3):109-111
It has been reported that high-temperature (~1100°C) N2 O-annealed oxide can block boron penetration from poly-Si gates to the silicon substrate. However, this high-temperature step may be inappropriate for the low thermal budgets required of deep-submicron ULSI MOSFETs. Low-temperature (900~950°C) N2O-annealed gate oxide is also a good barrier to boron penetration. For the first time, the change in channel doping profile due to compensation of arsenic and boron ionized impurities was resolved using MOS C-V measurement techniques. It was found that the higher the nitrogen concentration incorporated at Si/SiO2 interface, the more effective is the suppression of boron penetration. The experimental results also suggest that, for 60~110 Å gate oxides, a certain amount of nitrogen (~2.2%) incorporated near the Si/SiO2 interface is essential to effectively prevent boron diffusing into the underlying silicon substrate 相似文献
22.
简要介绍了蒸汽发生器水位控制系统的运行方式和试验方法。试验项目包括旁通阀控制试验、主给水阀控制试验和旁通阀与主给水阀的切换试验。文中给出了试验结果,即在液位扰动和核动率扰动时,蒸汽发生器液位的变化过程。经过两个月的运行和瞬态试验,证明蒸汽发生器水位控制系统满足设计要求。 相似文献
23.
Shaofeng Wang Yuan Hu Zhihua Lin Zhou Gui Zhengzhou Wang Zuyao Chen Weicheng Fan 《Polymer International》2003,52(6):1045-1049
Acrylonitrile–butadiene–styrene (ABS)/montmorillonite nanocomposites have been prepared using a direct melt intercalation technique by blending ABS and organophilic clay of two different particle sizes: OMTa (5 µm) and OMTb (38 µm). Their structure and flammability properties were characterized by X‐ray diffraction, high resolution electronic microscopy (HREM), thermogravimetric analysis (TGA) and cone calorimeter experiments. The results of HREM showed that ABS/5 wt% OMTa nanocomposite was a kind of intercalated–delaminated structure, while ABS/5 wt% OMTb nanocomposite was mainly an intercalated structure. The nanocomposites showed a lower heat release rate peak and higher thermal stability than the original ABS by TGA and cone calorimeter experiments. Also, the intercalated nanocomposite was more effective than an exfoliated–intercalated nanocomposite in fire retardancy. Copyright © 2003 Society of Chemical Industry 相似文献
24.
25.
26.
Function plotting using conic splines 总被引:1,自引:0,他引:1
27.
Seoijin Park R. Leavitt R. Enck V. Luciani Y. Hu P.J.S. Heim D. Bowler M. Dagenais 《Photonics Technology Letters, IEEE》2005,17(5):980-982
A semiconductor optical amplifier was developed for coarse wavelength-division-multiplexing (CWDM) operating over 1540-1620 nm (C-L band). A unique quantum-well structure was designed to meet the requirements for the CWDM operation such as wide bandwidth, low polarization-dependent gain, and high-saturation power at the short wavelength end of the band (1540 nm). Over the band, 24-dB maximum chip gain was obtained with less than 4.3-dB gain flatness and more than 14.6-dBm saturation power. 相似文献
28.
钢纤维聚合物混凝土抗压本构关系 总被引:2,自引:0,他引:2
钢纤维聚合物混凝土是由聚合物混凝土基体和钢纤维共同组成的纤维增强复合材料,它的力学行为不仅依赖于聚合物混凝土基体的行为,而且与钢纤维的掺量、分散特征以及钢纤维的几何尺寸有关,本文将基于损伤力学原理研究在不同纤维掺量下的钢纤维聚合物混凝土的全程压力-应变曲线及其本构模型。 相似文献
29.
SL Nyberg HJ Mann MY Hu WD Payne WS Hu FB Cerra RP Remmel 《Canadian Metallurgical Quarterly》1996,24(6):643-648
OBJECTIVE: The initially well-fixed implants of total hip replacement (THR) are in the long-term subject to aseptic loosening. Many cytokines can contribute to osteolysis due to osteoclast recruitment and/or activation. However, in this respect tumor necrosis factor-alpha (TNF-alpha) plays a pivotal role, because it upregulates interleukin-1 and 6 and granulocyte-macrophage colony stimulating factor. The aim of this study was to assess the eventual presence, cellular localization and extent of expression of TNF-alpha in the synovial-like membrane at the implant or at the cement to bone interface compared to control synovial membrane. METHODS: Twenty samples from the synovial-like membrane of the periprosthetic tissues were compared to control samples. TNF-alpha containing cells were visualized using an avidin-biotin-peroxidase complex (ABC) method and analyzed by light microscopy, double labelling and image analysis. RESULTS: TNF-alpha was found in the periprosthetic tissues in fibroblasts and vascular endothelial cells, but mainly in the macrophages was it found to coincide with areas containing implant-derived debris. TNF-alpha containing cells were more numerous in the synovial-like membrane in the interface tissue from the proximal stem area (2816 +/- 318 cells) than in the control synovial membrane (565 +/- 93 cells, p < 0.01). Interestingly, similarly high TNF-alpha expression (3452 +/- 582 cells) was also seen in the synovial-like membrane of the pseudocapsule. CONCLUSION: These findings suggest that the foreign body-type host reaction caused by THR is characterized by the high expression of TNF-alpha. Because such expression occurred in the interface tissue between the implant and surrounding bone, TNF-alpha, due to its pivotal direct and indirect role in the activation and recruitment of osteoclasts, may contribute to periprosthetic osteolysis and to the loosening of THR. 相似文献
30.
Xiaolin Hu Jun Wang 《IEEE transactions on systems, man, and cybernetics. Part B, Cybernetics》2007,37(3):528-539
This paper presents a recurrent neural-network model for solving a special class of general variational inequalities (GVIs), which includes classical VIs as special cases. It is proved that the proposed neural network (NN) for solving this class of GVIs can be globally convergent, globally asymptotically stable, and globally exponentially stable under different conditions. The proposed NN can be viewed as a modified version of the general projection NN existing in the literature. Several numerical examples are provided to demonstrate the effectiveness and performance of the proposed NN. 相似文献