全文获取类型
收费全文 | 46176篇 |
免费 | 5789篇 |
国内免费 | 3584篇 |
专业分类
电工技术 | 6495篇 |
技术理论 | 6篇 |
综合类 | 5754篇 |
化学工业 | 2892篇 |
金属工艺 | 3155篇 |
机械仪表 | 3405篇 |
建筑科学 | 4767篇 |
矿业工程 | 1669篇 |
能源动力 | 1233篇 |
轻工业 | 915篇 |
水利工程 | 1222篇 |
石油天然气 | 1244篇 |
武器工业 | 604篇 |
无线电 | 6342篇 |
一般工业技术 | 4569篇 |
冶金工业 | 1732篇 |
原子能技术 | 378篇 |
自动化技术 | 9167篇 |
出版年
2024年 | 112篇 |
2023年 | 717篇 |
2022年 | 1322篇 |
2021年 | 1593篇 |
2020年 | 1838篇 |
2019年 | 1501篇 |
2018年 | 1219篇 |
2017年 | 1622篇 |
2016年 | 1784篇 |
2015年 | 2015篇 |
2014年 | 3433篇 |
2013年 | 2902篇 |
2012年 | 3722篇 |
2011年 | 3992篇 |
2010年 | 2919篇 |
2009年 | 2959篇 |
2008年 | 2696篇 |
2007年 | 3256篇 |
2006年 | 2751篇 |
2005年 | 2345篇 |
2004年 | 1885篇 |
2003年 | 1595篇 |
2002年 | 1309篇 |
2001年 | 1112篇 |
2000年 | 910篇 |
1999年 | 718篇 |
1998年 | 563篇 |
1997年 | 518篇 |
1996年 | 415篇 |
1995年 | 371篇 |
1994年 | 326篇 |
1993年 | 208篇 |
1992年 | 203篇 |
1991年 | 166篇 |
1990年 | 149篇 |
1989年 | 145篇 |
1988年 | 95篇 |
1987年 | 31篇 |
1986年 | 13篇 |
1985年 | 23篇 |
1984年 | 19篇 |
1983年 | 12篇 |
1982年 | 13篇 |
1981年 | 14篇 |
1980年 | 12篇 |
1979年 | 12篇 |
1978年 | 2篇 |
1976年 | 2篇 |
1959年 | 1篇 |
1951年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
991.
Özgür Sevgi Canarslan Levent Koroglu Erhan Ayas Necip Suat Canarslan Alpagut Kara Paolo Veronesi 《Ceramics International》2021,47(1):828-835
In the present study, 17 wt % TiN reinforced α-β SiAlON composites were sintered at low temperature by susceptor-assisted microwave heating. The effect of TiN addition on dielectrical properties of starting powders, as well as the influence of sintering temperature on phase evolution, microstructure development and mechanical properties of α/β-SiAlON-TiN composites were investigated. The obtained results showed that TiN addition increased the microwave absorbing properties which is reflected in the peak sintering temperature. Thus, the α:β ratio decreased and mechanical properties were improved, especially the fracture toughness of the composites. Furthermore, an estimate of energy consumption during microwave assisted sintering at the laboratory scale is presented. As a result, the highest values for relative density (97.1%), Vickers hardness (13.35 ± 0.47 GPa), and fracture toughness (7.52 ± 0.54 MPa m1/2) were obtained by microwave sintering for 30 min at 1300 °C. 相似文献
992.
Jinshuang Wang Luyao Chen Mengdi Chen Yuyang Wu Yinghui Wang Yongsheng Yu Junbin Sun Bing Liu Qiangshan Jing 《Ceramics International》2021,47(16):22965-22975
In this study, the destabilization resistance of Sc2O3 and CeO2 co-stabilized ZrO2 (SCZ) ceramics was tested in Na2SO4 + V2O5 molten salts at 750°C–1100 °C. The phase structure and microstructure evolution of the samples during the hot corrosion testing were analyzed with X-ray diffraction (XRD), Raman spectra, scanning electron microscopy (SEM), energy dispersive X-ray spectrum (EDS), and X-ray photoelectron spectroscopy (XPS). Results showed that the destabilization of SCZ ceramics at 750 °C was the result of the chemical reaction with V2O5 to produce m-ZrO2 and CeVO4, and little ScVO4 was detected in the Sc2O3-rich SCZ ceramics. The primary corrosion products at 900 °C and 1100 °C were CeO2 and m-ZrO2 due to the mineralization effect. The Sc2O3-rich SCZ ceramics exhibited excellent degradation resistance and phase stability owing to the enhanced bond strength and the decreased size misfit between Zr4+ and Sc3+. The destabilization mechanism of SCZ ceramic under hot corrosion was also discussed. 相似文献
993.
《Ceramics International》2021,47(23):32490-32504
The shortcomings of high-temperature solid oxide fuel cells necessitate research on SOFCs designs that are capable of operation at intermediate temperatures (600–800 °C), the so-called intermediate-temperature SOFCs. One of the limitations for the efficient operation of these fuel cells lies in insufficient ionic conductivity of the electrolyte material. This review briefly covers the types of ceramic electrolytes used in intermediate-temperature SOFCs and focuses on scandia-stabilized zirconia (ScSZ) electrolytes. It explores possibilities of control of phase stability and ionic conductivity of ScSZ by co-doping by various oxides, such as ceria, bismuth oxide, yttria, ytterbia, and several other co-dopants. It also covers a range of novel techniques applied to preparation of ScSZ electrolytes, which can be used to influence microstructure and phase composition of the electrolytes. The recommendations on the optimal ScSZ co-doping scheme are developed in the course of the present work. 相似文献
994.
We investigate nonlinear phase dynamics of an ideal kink mode, induced by E × B flow. Here the phase is the cross phase(θ_c) between perturbed stream function of velocity■ and magnetic field ■, i.e. θ_c= θ_φ-θ_ψ. A dimensionless parameter, analogous to the Richardson number,■(γ_(kink): the normalized growth rate of the pure kink mode; ■: normalized E × B shearing rate) is defined to measure the competition between phase pinning by the current density and phase detuning by the flow shear. When R_i 1, θ_c is locked to a fixed value,corresponding to the conventional eigenmode solution. When R_i≤1, θ_c enters a phase slipping or oscillating state, corresponding to a nonmodal solution. The nonlinear phase dynamics method provides a more intuitive explanation of the complex dynamical behavior of the kink mode in the presence of E × B shear flow. 相似文献
995.
煤炭资源型城市为我国经济发展提供了重要的资源和能源支持,研究资源型城市转型的经验模式对调整区域经济结构、确保社会稳定和改善生态环境具有重要的实践意义。本文采用文献综述法和实证分析法,研究我国东部煤炭资源枯竭型城市转型所面临的共性难题,并以徐州贾汪区转型探索经历为例,总结城市转型的"徐州贾汪区模式",主要包括放大正向外部效应、长期坚持矿地融合、大力建设矿区社会生态系统恢复力三条路径。研究结果表明,煤炭城市转型发展的共性问题相互联系、相互影响,是一个系统性难题,必须引入系统性思维。我国东部矿区普遍人口密集,农业发达、沉陷积水是最主要的共性特征,煤炭开采产生的社会问题、经济问题、生态问题、环境问题基本相同,转型发展模式值得互鉴。 相似文献
996.
The CREATE labs, a hybrid laboratory experience suitable for remote learning was developed at Imperial College in response to the COVID-19 pandemic. To facilitate the transformation from traditional to remote labs, a systematic review of offered projects was carried out to identify where learning objectives could be met using remote-friendly options such as simulations. Essential physical experiments were performed through the use of various technologies including online collaboration software and first-person point of view cameras to enable a high level of student involvement. Student surveys and interviews confirmed a positive experience comparable to previous years with an improvement in feedback provision. 相似文献
997.
An improved tracking technique of the reference current waveform in a shunt type active power filter is proposed in this paper using sliding mode control and feedback linearization. Feedback linearization approach helps to reduce the complexity of the controller. Excellent tracking is achieved in both for steady state and dynamic performance. A three-phase four-wire system is considered. The proposed algorithm is simulated first in MATLAB/SIMULINK. An experimental prototype using a dspace1104 based controller is also produced in the laboratory. Results from simulation match well with the corresponding results from experimental prototype confirming the usefulness of the proposed technique. 相似文献
998.
《Intermetallics》2016
The phase evolution of an Al0.5CrFeCoNiCu High Entropy Alloy has been characterised following isothermal exposures between 0.1 and 1000 h at temperatures of 700, 800 and 900 °C. The NiAl based B2 phase formed extremely quickly, within 0.1 h at the higher exposure temperatures, whilst the Cr-rich σ phase formed more slowly. The solvus temperatures of these two phases were found to be ∼975 and ∼875 °C respectively. Compilation of the data presented here with results previously reported in the literature enabled the production of a time-temperature-transformation diagram, which clearly indicates that the diffusion kinetics of this material cannot be considered sluggish. 相似文献
999.
《Intermetallics》2016
The influence of the different crystal structures and the variation of the lattice parameter on the evolution of the magnetism in the order-disorder transition produced by crushing and mechanical milling in the intermetallic Fe75Al25-xSix alloys (x = 7.5, 12.5, 17.5, 25) has been systematically studied by means of XRD measurements, Mössbauer spectroscopy and magnetic measurements. The results indicate that with the addition of Si to binary Fe75Al25 alloy the mechanical deformation needed to disorder the alloys increases. At the same time the variation of the lattice parameter due to the disorder is reduced as Si is added. The magnetic measurements indicate that there is a complex behaviour in ternary alloys with an opposite influence of Si and Al during the order-disorder transition. However, when the transition is fulfilled there is a linear relationship between structural and magnetic parameters. 相似文献
1000.
This paper proposes a new method to design suboptimal sliding manifolds for a class of nonlinear uncertain systems with state and input delays. A switching control law is obtained based on the designed suboptimal sliding manifold. It is proved that the proposed method is able to guarantee the stability of the closed-loop system in the presence of uncertainty. Three numerical simulations are given to illustrate the effectiveness of the proposed method. 相似文献