全文获取类型
收费全文 | 5870篇 |
免费 | 173篇 |
国内免费 | 206篇 |
专业分类
电工技术 | 137篇 |
综合类 | 39篇 |
化学工业 | 717篇 |
金属工艺 | 288篇 |
机械仪表 | 86篇 |
建筑科学 | 141篇 |
矿业工程 | 17篇 |
能源动力 | 93篇 |
轻工业 | 310篇 |
水利工程 | 14篇 |
石油天然气 | 331篇 |
武器工业 | 13篇 |
无线电 | 351篇 |
一般工业技术 | 616篇 |
冶金工业 | 2497篇 |
原子能技术 | 42篇 |
自动化技术 | 557篇 |
出版年
2021年 | 84篇 |
2020年 | 44篇 |
2019年 | 59篇 |
2018年 | 86篇 |
2017年 | 83篇 |
2016年 | 86篇 |
2015年 | 91篇 |
2014年 | 118篇 |
2013年 | 178篇 |
2012年 | 180篇 |
2011年 | 290篇 |
2010年 | 245篇 |
2009年 | 245篇 |
2008年 | 253篇 |
2007年 | 226篇 |
2006年 | 272篇 |
2005年 | 230篇 |
2004年 | 238篇 |
2003年 | 189篇 |
2002年 | 235篇 |
2001年 | 195篇 |
2000年 | 155篇 |
1999年 | 179篇 |
1998年 | 181篇 |
1997年 | 172篇 |
1996年 | 115篇 |
1995年 | 130篇 |
1994年 | 136篇 |
1993年 | 143篇 |
1992年 | 97篇 |
1991年 | 52篇 |
1990年 | 98篇 |
1989年 | 100篇 |
1988年 | 72篇 |
1987年 | 60篇 |
1986年 | 66篇 |
1985年 | 54篇 |
1984年 | 51篇 |
1983年 | 45篇 |
1981年 | 56篇 |
1979年 | 40篇 |
1978年 | 35篇 |
1977年 | 37篇 |
1976年 | 32篇 |
1975年 | 41篇 |
1974年 | 34篇 |
1973年 | 29篇 |
1971年 | 79篇 |
1970年 | 41篇 |
1968年 | 35篇 |
排序方式: 共有6249条查询结果,搜索用时 31 毫秒
991.
992.
Ali Hojeij Laurent Jossic Philippe Séchet Cyrille Bonamy Albert Magnin Stéphane Hattou 《American Institute of Chemical Engineers》2022,68(2):e17442
Mixing by gas injection is an operation used in industrial processes such as wastewater treatment, metallurgy, or methanization in which pressurized gas is injected into a fluid in order to reduce concentrations and temperatures gradients. This study demonstrates how the CFD toolbox OpenFOAM can be used to simulate such flows. Experimental measurements and observations have been performed on a pilot-scale reactor where pressurized air is injected in a yield stress fluid. The volume of fluid method and an adaptive mesh with refinement at the interface have been used to track the gas inclusions. The numerical model accuracy has been assessed by comparing experimental and numerical results related to the bubble's frequency, dimensions, and rising velocities as well as the fluid recirculation, yielded, and unyielded regions in the tank. The influence of injection parameters such as the injection flow rate and the fluid rheological parameters has been quantified. 相似文献
993.
Valentin Segouin Mathieu Domenjoud Yves Bernard Laurent Daniel 《Journal of the European Ceramic Society》2019,39(6):2091-2102
The strain response of a polarised PZT was characterised using Digital Image Correlation (DIC). The DIC algorithm is based on a global approach and regularises the displacement field using the balance equations of solid mechanics. The measurement error is reduced by correcting the displacements that are mechanically not admissible. A ferroelectric test showed that the standard deviations of strain fields remain mostly under 1.2 × 10?4 for an element size of 64 px. The standard deviation on the average value is 3 × 10?6. The strain field is homogeneous and its average value is consistent with the strain obtained from a CCD laser measurement device. The longitudinal strain, transverse strain and polarisation response of the PZT were measured for bipolar and unipolar loadings ranging from 50 to 5000 V/mm. Material properties were extracted from these measurements. This work shows the advantages of a novel 2D-DIC algorithm for piezoelectric strain characterisation. 相似文献
994.
Pauline Glatz Monique Comte Lionel Montagne Bertrand Doumert Fabrice Cousin Laurent Cormier 《Journal of the American Ceramic Society》2020,103(9):4969-4982
Li2O-Al2O3-SiO2 (LAS) glass-ceramics have important industrial applications and bulk nucleation is usually achieved by using nucleating agents. In particular, P2O5 is an efficient agent in glasses containing a low level of Al2O3 but its role in the first stages of nucleation is not well established. In this study, we combine structural investigations from local to mesoscales to describe the structural evolution during crystallization of LAS glass-ceramics. Local environment is probed using 29Si and 31P MAS-NMR, indicating organization of P in poorly crystallized Li3PO4 species prior to any crystallization. To better understand the detailed nanoscale changes of the glass structure, 31P-31P DQ-DRENAR homonuclear correlation experiments have been carried out, revealing the gradual segregation of P atoms associated with the formation of disordered Li3PO4. Small-angle neutron scattering data also show the apparition of nanoscale heterogeneities associated with Li3PO4 species upon heating treatments and allow the determination of their average sizes. These new structural information enhance our understanding of the role of P in nucleation mechanisms. Nucleation is initiated by gradual change in P environment implying P segregation upon heating treatments, forming disordered Li3PO4 heterogeneities. The segregation of P atoms enables the precipitation of meta- and disilicate phases. 相似文献
995.
Nicolas Jeannin Laurent Castanet Isabelle Dahman Vivien Pourret Batrice Pouponneau 《International Journal of Satellite Communications and Networking》2019,37(1):43-55
The use Q/V band spectrum for the feeder links of high throughput satellites and the need to cope with the significant propagation impairments at those frequencies motivate the development of smart diversity techniques. Those techniques aim at improving the availability level of the overall feeder link with a limited level of redundancy. The combinatorial gain of availability provided by those techniques can be obtained only if efficient switching methodologies are developed, performing the best trade‐off between system flexibility and channel prediction accuracy. This paper proposes various propagation forecast mechanisms for the control of switching between gateways in smart diversity, corresponding to various system assumptions in terms of required anticipation time for the triggering of the switches. The performances of those algorithms are then assessed against measured attenuation and meteorological data. It enables to evaluate the performance degradation regarding an idealized case. 相似文献
996.
997.
998.
A robust and precise viscometer using the forces exerted by a laminar flow inside a small duct is presented: the force is measured on a long cylindrical sensor dipped into the flow. Two devices of respective volumes 1.4 and 0.031?ml have been realized, demonstrating that the technique is usable with small fluid volumes. Several Newtonian and non-Newtonian fluids have been tested at shear rates ranging from 0.3 to 10?s(-1) for the first device and from 85 to 2550?s(-1) for the second one. For Newtonian fluids, of viscosities ranging from 10(-3) to 0.1?Pa?s, the linear response of the device has been verified and a 90% agreement with the values provided by commercial rheometers is obtained. For non-Newtonian polymer solutions, the variation of the force with the flow velocity allows one to determine the dependence of the viscosity on the shear rate. Two shear thinning polymer solutions with a power law behavior at intermediate shear rates have been investigated and their rheological parameters have been determined. 相似文献
999.
本文根据大型矿用机械式挖掘机动态测试方案的要求,开发研制出一种新型的推压力传感器,解决了大型挖掘机国产化研究中动态测量这一关键性技术难题。传感器结构新颖独特,性能良好在矿山机械和工程机械中具有广泛地应用价值。 相似文献
1000.