全文获取类型
收费全文 | 28378篇 |
免费 | 2030篇 |
国内免费 | 1009篇 |
专业分类
电工技术 | 1645篇 |
综合类 | 919篇 |
化学工业 | 6991篇 |
金属工艺 | 972篇 |
机械仪表 | 1187篇 |
建筑科学 | 371篇 |
矿业工程 | 217篇 |
能源动力 | 8010篇 |
轻工业 | 2895篇 |
水利工程 | 56篇 |
石油天然气 | 118篇 |
武器工业 | 55篇 |
无线电 | 2862篇 |
一般工业技术 | 2901篇 |
冶金工业 | 719篇 |
原子能技术 | 335篇 |
自动化技术 | 1164篇 |
出版年
2024年 | 77篇 |
2023年 | 637篇 |
2022年 | 1710篇 |
2021年 | 1972篇 |
2020年 | 1169篇 |
2019年 | 1109篇 |
2018年 | 877篇 |
2017年 | 1067篇 |
2016年 | 953篇 |
2015年 | 895篇 |
2014年 | 1557篇 |
2013年 | 1736篇 |
2012年 | 1726篇 |
2011年 | 2532篇 |
2010年 | 1844篇 |
2009年 | 1580篇 |
2008年 | 1617篇 |
2007年 | 1503篇 |
2006年 | 1248篇 |
2005年 | 1004篇 |
2004年 | 806篇 |
2003年 | 609篇 |
2002年 | 580篇 |
2001年 | 458篇 |
2000年 | 368篇 |
1999年 | 292篇 |
1998年 | 267篇 |
1997年 | 214篇 |
1996年 | 172篇 |
1995年 | 154篇 |
1994年 | 128篇 |
1993年 | 112篇 |
1992年 | 83篇 |
1991年 | 64篇 |
1990年 | 49篇 |
1989年 | 47篇 |
1988年 | 36篇 |
1987年 | 23篇 |
1986年 | 23篇 |
1985年 | 29篇 |
1984年 | 16篇 |
1983年 | 12篇 |
1982年 | 13篇 |
1981年 | 9篇 |
1980年 | 16篇 |
1979年 | 7篇 |
1978年 | 3篇 |
1976年 | 3篇 |
1975年 | 3篇 |
1951年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
以镁法海绵钛生产工艺中大型无隔板镁电解槽的实际节能情况为例,探讨了在镁电解生产中的非生产耗电、生产耗电、漏电等因素造成的能量浪费,阐述了生产中粗镁直流电耗、电流效率、工作电压3者之间的关系,指出了影响电解槽工作电压的有关因素及降低电解槽工作电压的途径。 相似文献
32.
In order to study water-gas transport processes in the gas-diffusion-layer (GDL) of a proton exchange membrane (PEM) fuel cell system, a multiphase, multiple-relaxation-time lattice Boltzmann model is presented in this work. The model is based on the mean-field diffuse interface theory and can handle the multiphase flows with large density ratios and various viscosities. By using the standard bounce back boundary condition and an approximate average scheme for the non-slip and wetting boundary walls, respectively, detailed liquid-gas transportation in the GDL, in which exact boundary condition is difficult to be implemented, can be simulated. Unlike most of lattice Boltzmann methods based on the Bhatnagar–Gross–Krook collision operator, the present model shows a viscosity-independent velocity field, which is very important in simulating multiphase flows where various viscosities coexist. We validate our model by simulating a static droplet on a wetting wall and compare with theoretical predictions. Then, we simulate a water-gas flow in the GDL of a PEM fuel cell and investigate the saturation-dependent transport properties under different conditions. The results are shown to be qualitatively consistent with the previous numerical and theoretical works. 相似文献
33.
铝电解槽磁流体稳定性有限元分析 总被引:2,自引:0,他引:2
本文采用有限元法求解分层磁流体小扰动方程系统特征值,研究铝电解槽稳定性。研究结果表明,在没有电磁力时,铝液表面波动(内波)是稳定的。存在电磁力时,它会激发铝液表面波动的某些低频长波分量不稳定性,高频短波不受影响。被激发的不稳定波动频率和扰动增长率与电流密度,磁感应强度垂直分量,铝电解槽长宽比,电解质和铝液的密度差,厚度等因素密切相关。减少电流密度,磁感应强度,增加电极距离和铝液厚度可以提高铝电解槽的稳定性。这对铝电解槽优化设计和在线控制有重要意义。 相似文献
34.
35.
Properties and Performance of Cation-Doped Ceria Electrolyte Materials in Solid Oxide Fuel Cell Applications 总被引:1,自引:0,他引:1
Christopher Milliken Sivaraman Guruswamy Ashok Khandkar 《Journal of the American Ceramic Society》2002,85(10):2479-2486
Cation-doped CeO2 electrolyte has been evaluated in single-cell and short-stack tests in solid oxide fuel cell environments and applications. These results, along with conductivity measurements, indicate that an ionic transference number of ∼0.75 can be expected at 800°C. Single cells have shown a power density >350 mW/cm2 . Multicell stacks have demonstrated a peak performance of >100 mW/cm2 at 700°C using metallic separators. 相似文献
36.
This paper focuses on the microscopic damage and progressive failure of a composite reinforced by plain-weave glass cloth under tensile fatigue loading. The fatigue process was divided into three stages like that of multi-directional laminates. It was found that the internal damage at each stage (matrix cracks, debonds in the weft, successive debonds in the warp and ‘metadelaminations’ between warps and wefts) occurred near the cross-over point of the fabric. The modulus decay mechanism was explained by considering the progression of this internal damage. From the end of the first stage to the beginning of the middle stage, a characteristic damage state (CDS) (called a ‘meta-CDS’) was observed. It was found that woven composites have a unit area of damage accumulation (called a ‘unit cell’) and the damage of each unit cell and its distribution control the total fatigue damage of the material. 相似文献
37.
A. Benati M.A. Butturi C. Capperdoni M.C. Carotta G. Martinelli M. Merli L. Passari G. Sartori R. Van Steenwinkel G.M. Youssef 《Solar Energy Materials & Solar Cells》1996,43(2):183
The newly developed ingot growing techniques, as the three-grain and the columnar multigrain ingot processes, are now offering the possibility of slicing thinner wafers (≤ 100 μm). In this paper we present the results obtained on p type large area (≥ 100 cm2) and 100 μm thick wafers by using both conventional and reverse cell manufacturing technologies.The conventional cells are provided with aluminium or boron BSF plus screen-printed silver mirror or a silver-aluminium net; the reverse cells have a FSF and the deep back junction completely covered by a screen-printed or CVD silver layer.The constructing parameters have been chosen on the base of one and two dimensions modeling and both raw material and devices have been completely characterized.This work shows that very thin wafers do not introduce serious problems for the conventional manufacturing of solar cells. The efficiencies of the normal and of the reverse cells are found to be comparable and are of the same order than those of thicker cells, however at a significant lower cost. The main obtained result has to be related to the demonstration of a cell manufacturing feasibility starting from very thin wafers. 相似文献
38.
本文从无线电通信基本要素出发 ,阐述上行信号和下行信号的无线传播 ,得出上下行信号平衡链路方程 ,并以我国普遍使用的TACS系统和GSM系统为例 ,着重讨论了信号平衡与蜂窝小区设计之间的关系。 相似文献
39.
本文在Knockout交换结构的基础上,探讨一种新的ATM交换结构,使其本身带有优先权控制功能,以适应不同业务对信元丢失率及时延的不同要求。这种结构既能最大限度地有效利用系统资源,又能满足不同用户对业务质量的不同要求,并能降低交换结构复杂度。 相似文献
40.