全文获取类型
收费全文 | 531篇 |
免费 | 26篇 |
国内免费 | 3篇 |
专业分类
电工技术 | 10篇 |
化学工业 | 135篇 |
金属工艺 | 15篇 |
机械仪表 | 10篇 |
建筑科学 | 3篇 |
能源动力 | 32篇 |
轻工业 | 40篇 |
水利工程 | 5篇 |
石油天然气 | 1篇 |
无线电 | 77篇 |
一般工业技术 | 103篇 |
冶金工业 | 12篇 |
原子能技术 | 13篇 |
自动化技术 | 104篇 |
出版年
2024年 | 3篇 |
2023年 | 7篇 |
2022年 | 24篇 |
2021年 | 31篇 |
2020年 | 23篇 |
2019年 | 26篇 |
2018年 | 32篇 |
2017年 | 33篇 |
2016年 | 23篇 |
2015年 | 17篇 |
2014年 | 22篇 |
2013年 | 33篇 |
2012年 | 39篇 |
2011年 | 51篇 |
2010年 | 21篇 |
2009年 | 24篇 |
2008年 | 22篇 |
2007年 | 24篇 |
2006年 | 11篇 |
2005年 | 16篇 |
2004年 | 7篇 |
2003年 | 7篇 |
2002年 | 11篇 |
2001年 | 5篇 |
2000年 | 3篇 |
1999年 | 7篇 |
1998年 | 3篇 |
1997年 | 4篇 |
1996年 | 4篇 |
1995年 | 7篇 |
1994年 | 6篇 |
1993年 | 4篇 |
1992年 | 3篇 |
1991年 | 3篇 |
1989年 | 2篇 |
1986年 | 1篇 |
1983年 | 1篇 |
排序方式: 共有560条查询结果,搜索用时 15 毫秒
91.
Kuttan Prabhakaran Anand Melkeri Mohd Oveas Beigh Nitin Madhusudan Gokhale Suresh Chandra Sharma 《Journal of the American Ceramic Society》2007,90(2):622-625
A porous NiO–YSZ substrate for anode-supported solid oxide fuel cells has been prepared by gelcasting of NiO–YSZ powders using urea–formaldehyde monomers, followed by humidity-controlled drying, binder removal, and sintering of the gelled bodies. The gelled bodies had sufficient strength to remove even 2-mm-thick samples from the mold immediately after gelation. A gelcast NiO–YSZ sample sintered at 1450°C for 2 h showed an open porosity of ∼53 vol%, and the porosity increased to ∼58% upon reduction with hydrogen. Pore sizes measured on the scanning electron microscopy photomicrograph of NiO–YSZ and Ni–YSZ cermet substrates are in the range of 2–5 μm. Urea–formaldehyde polymer, present in a high amount (∼13 wt%) in the gelcast body, acts as a template for pores. 相似文献
92.
In Situ Processing of Silicon Carbide Layer Structures 总被引:1,自引:0,他引:1
Nitin P. Padture David C. Pender Sataporn Wuttiphan† Brian R. Lawn 《Journal of the American Ceramic Society》1995,78(11):3160-3162
A novel route to low-cost processing of silicon carbide (SiC) layer structures is desribed. The processing involves pressureless liquid-phase cosintering of compacted power layers of SiC, containing alumina (Al2 O3 ) and yttria (Y2 O3 sintering additives to yield and yttrium aluminum garnet (YAG) second phase. By adjusting the β:α SiC phase ratios in the individual starting powders, alternate layers with distinctively different microstructures are produced: (i) "homogeneous" microstructures, with fine equiaxed SiC grains, designed for high strength; and (ii) "heterogeneous: microstructures with coarse and elongate SiC grains, designed for high toughness. By virtue of the common SiC and YAG phases, the interlayer interfaces are chemically compatible and strongly bonded. Exploratory Hertzian indetation tests across a bilayer interface confirm the capacity of the tough heterogeneous layer to inhibit potentially dangerous cracks propagating through the homogeneous layer. The potential for application of this novel processing approach to other layer architectures and other ceramic systems is considered. 相似文献
93.
A comparative study of cyclic fatigue damage from Hertzian contacts in silicon carbide ceramics with homogeneous microstructure (fine, equiaxed grains, strong grain boundaries) and heterogeneous microstructure (coarse, contiguous elongate grains, weak interphase boundaries) is presented. Observations of the surface and subsurface damage patterns using optical microscopy reveal fundamentally different cyclic fatigue mechanisns: in the homogeneous material, by slow growth of a well-developed cone crack outside the contact area; in the heterogeneous material, by progressive mechanical degradation within a distributed damage zone below the contact area. Scanning electron micrographs of the latter material show copious fine debris in the damage zone, consistent with a degradation mechanism by frictional attrition by forward-reverse sliding at the weak interphase boundaries. Acoustic emission is recorded during both load and unload half-cycles, confirming hysteresis in the sliding process. Flexure tests indicate initially slight strength losses from the cyclic contact damage in both microstructures, followed by accelerated losses at higher numbers of cycles. The underlying basis for establishing an analytical model of damage accumulation in the heterogeneous microstructure in terms of shear-fault sliding, and for designing micro-structures for optimal properties in fatigue and wear applications, is foreshadowed. 相似文献
94.
Effect of Microstructure on Material-Removal Mechanisms and Damage Tolerance in Abrasive Machining of Silicon Carbide 总被引:3,自引:0,他引:3
Hockin H. K. Xu Nitin P. Padture Said Jahanmir 《Journal of the American Ceramic Society》1995,78(9):2443-2448
Effects of microstructural heterogeneity on material-removal mechanisms and damage-formation processes in the abrasive machining of silicon carbide are investigated. It is shown that the process of material removal in a conventional silicon carbide material with equiaxed-grain micro-structure and strong grain boundaries consists of the formation and propagation of transgranular cracks which results in macroscopic chipping. However, in a silicon carbide material, containing 20 vol% yttrium aluminum garnet (YAG) second phase, with elongated-grain micro-structure and weak grain boundaries, intergranular micro-cracks are formed at the interphase boundaries, leading to dislodgment of individual grains. These different mechanisms of material-removal affect the nature of machining-induced damage. While in the conventional silicon carbide material the machining damage consists of transgranular median/radial cracks, in the heterogeneous silicon carbide material, abrasive machining produces interfacial micro-cracks distributed within a thin surface layer. These two distinct types of machining damage result in a different strength response in the two forms of silicon carbide materials. In the case of the conventional silicon carbide, grinding damage results in a dramatic decrease in strength relative to the as-polished specimens. In contrast, the ground heterogeneous silicon carbide specimens show no strength loss at all. 相似文献
95.
G. Sundararajan Nitin P. Wasekar N. Ravi 《Transactions of the Indian Institute of Metals》2010,63(2-3):203-208
The primary objective of this study is to evaluate the influence of coating technique on the high cycle fatigue of an Al6061 alloy. Towards this purpose, Al6061 alloy fatigue samples have been coated with Al2O3 utilising the detonation spray, air plasma spray, micro arc oxidation and hard anodizing techniques. The high cycle fatigue life of these coated samples has been evaluated over a range of alternating stress values and compared with the fatigue life of the uncoated Al6061 alloy. It is observed that the detonation spray coated sample exhibits a higher fatigue life than the uncoated sample. In contrast, the samples coated using the other techniques exhibit poorer fatigue life compared to the uncoated sample especially at lower alternating stress values. These results have been explained on the basis of the nature of the coating-substrate interface which is strongly determined by the coating technique used to deposit the Al2O3 coatings. 相似文献
96.
The 1∕f noise of silicon nanowire biochemical field effect transistors is fully characterized from weak to strong inversion in the temperature range 100-300 K. At 300 K, our devices follow the correlated Δn-Δμ model. As the temperature is lowered, the correlated mobility fluctuations become insignificant and the low frequency noise is best modeled by the Δn-model. For some devices, evidence of random telegraph signals is observed at low temperatures, indicating that fewer traps are active and that the 1∕f noise due to number fluctuations is further resolved to fewer fluctuators, resulting in a Lorentzian spectrum. 相似文献
97.
Microstructure and Property Evolution for Hot-Rolled and Cold-Rolled Austenitic Stainless Steel 316L
Nitin Kumar Sharma Shashank Shekhar 《Transactions of the Indian Institute of Metals》2017,70(5):1277-1284
Grain boundary character distribution plays an important role in determining the functional and mechanical properties of polycrystalline materials. The aim of this work was to achieve improved coincident site lattice (CSL) fraction without increasing low angle grain boundary (LAGB) proportion. We utilized single-step thermo-mechanical processing route involving rolling followed by short heat treatment and compared the effect of rolling temperature. Our results indicated that rolling at elevated temperature led to significant increase in the fraction of special boundaries while keeping the fraction of LAGB very low, as desired. We conducted thermal stability of our sample-conditions at elevated temperatures for various lengths of time and found the microstructure of the samples to be stable up to 1000 °C. This study showed that even commercially suitable process (single step processing with short heat treatment duration) could lead to microstructure with considerable increase in CSL boundaries fraction, improved hardness values and good thermal stability. 相似文献
98.
Nitin Jain Anant Raj M. S. Kalra Prabhat Munshi V. R. Ravindran 《Research in Nondestructive Evaluation》2013,24(3):147-168
The present work is concerned with the evaluation of the performance and the efficient implementation of multiplicative algebraic reconstruction technique (MART) to reconstruct three-dimensional (3D) objects for two different source/detector trajectories. Three types of MART algorithms are tested on a numerical phantom (Defrise), and they are implemented on a 3D X-ray system of Vikram Sarabhai Space Centre (VSSC). Circular and helical cone-beam trajectories are used. The results are compared with convolution backprojection (CBP) algorithm for each trajectory. It is found that iterative algorithms perform better than their counterpart, the transform-based CBP algorithm, whenever tomography systems are ill-conditioned due to limited views and/or noisy projection data. 相似文献
99.
Ghosh D Sarkar D Girigoswami A Chattopadhyay N 《Journal of nanoscience and nanotechnology》2011,11(2):1141-1146
The citrate reduction method of synthesis of gold nanoparticles (AuNPs) as introduced by Frens has been standardized to enable one to prepare AuNPs of desired dimension by controlling the composition of the reactants. The standardization has been made through characterization of the nanoparticles by UV-vis spectroscopy and from the transmission electron microscopic (TEM) measurements. Linearity of the plot of the plasmon absorption maximum (lambda(max)) of the synthesized AuNPs against their diameter as measured from TEM, as well as the plot of lambda(max) with the fractional concentration of citrate in the reaction mixture provides a convenient and easy route to dictate the size of the synthesized AuNPs from a control on the composition of the reactants. The standardization reveals that a calculated composition of citrate (in terms of fractional concentration) in the reaction mixture produces AuNPs of a desired dimension within the range of 15-60 nm. The diameter of the synthesized gold nanoparticles can be confirmed simply from the UV-vis spectrophotometric technique. This essentially makes the use of costly TEM unnecessary, at least for the primary purposes. 相似文献
100.
C. S. P. Ojha Rao Y. Surampalli Pramod Kumar Sharma Nitin Joshi 《Canadian Metallurgical Quarterly》2011,137(8):731-739
In this paper, an advective dispersive virus transport equation, including first-order adsorption and an inactivation constant, is used for simulating the movement of viruses in fractured porous media. The implicit finite-difference numerical technique is used to solve the governing equations for viruses in the fractured porous media. In this work, the focus is (1)?to investigate the transport processes of the movement of viruses in both fractured rock and porous rock without fracture and (2)?to simulate the experimental data of biocolloids through a fractured aquifer model. It is seen that movement of the contaminant is faster in the fractured rock than in the porous rock formation. Higher values of diffusion coefficient, matrix porosity, mass transfer constant, and inactivation rate reduce both temporal and spatial virus concentrations in the fracture. Also, experimental data of biocolloids in the fractured aquifer model with constant and time-dependent inactivation rates were simulated successfully. 相似文献