全文获取类型
收费全文 | 1672篇 |
免费 | 61篇 |
国内免费 | 10篇 |
专业分类
电工技术 | 22篇 |
综合类 | 2篇 |
化学工业 | 355篇 |
金属工艺 | 46篇 |
机械仪表 | 51篇 |
建筑科学 | 31篇 |
矿业工程 | 2篇 |
能源动力 | 99篇 |
轻工业 | 124篇 |
水利工程 | 11篇 |
石油天然气 | 4篇 |
无线电 | 232篇 |
一般工业技术 | 374篇 |
冶金工业 | 163篇 |
原子能技术 | 17篇 |
自动化技术 | 210篇 |
出版年
2023年 | 31篇 |
2022年 | 74篇 |
2021年 | 89篇 |
2020年 | 82篇 |
2019年 | 59篇 |
2018年 | 103篇 |
2017年 | 68篇 |
2016年 | 77篇 |
2015年 | 48篇 |
2014年 | 68篇 |
2013年 | 121篇 |
2012年 | 70篇 |
2011年 | 91篇 |
2010年 | 67篇 |
2009年 | 44篇 |
2008年 | 49篇 |
2007年 | 67篇 |
2006年 | 30篇 |
2005年 | 32篇 |
2004年 | 22篇 |
2003年 | 13篇 |
2002年 | 28篇 |
2001年 | 25篇 |
2000年 | 14篇 |
1999年 | 18篇 |
1998年 | 38篇 |
1997年 | 42篇 |
1996年 | 26篇 |
1995年 | 13篇 |
1994年 | 15篇 |
1993年 | 16篇 |
1992年 | 12篇 |
1991年 | 15篇 |
1990年 | 8篇 |
1989年 | 8篇 |
1988年 | 8篇 |
1987年 | 9篇 |
1986年 | 11篇 |
1985年 | 8篇 |
1984年 | 14篇 |
1983年 | 11篇 |
1982年 | 6篇 |
1981年 | 10篇 |
1980年 | 8篇 |
1979年 | 9篇 |
1978年 | 9篇 |
1977年 | 10篇 |
1976年 | 16篇 |
1974年 | 4篇 |
1973年 | 5篇 |
排序方式: 共有1743条查询结果,搜索用时 15 毫秒
71.
Separation of nickel from copper in ammoniacal/ammonium carbonate solution using ACORGA M5640 by selective stripping was carried out. The influence of equilibration time, equilibrium pH and extractant concentration on the extraction of both the metals was studied. It was found that the copper extraction equilibrium was reached in a shorter time than the nickel extraction equilibrium. Nickel extraction decreases above an equilibrium pH of 9.0, while the extraction of copper remains unaffected by the changes in the equilibrium pH range of 7–10. Co-extraction, ammonia scrubbing and the selective stripping of copper and nickel were performed for a solution containing 3 g/l each of copper and nickel and 60 g/l ammonium carbonate. The extraction and the percentage stripping of copper and nickel were almost quantitative. 相似文献
72.
A three-lobe journal bearing is analytically investigated to determine its dynamic performance when three main parameters, i.e. turbulence, load orientation, and rotor flexibility are varied. Reynolds numbers up to 12000, rotor dimensionless flexibilities up to 4, and load orientations up to 30 degrees on either side of the vertical load line are considered. Thus, almost all cases of practical interest are studied. The stability of a three-lobe bearing improves due to turbulence at high Sommerfeld numbers (more than 0.6) for a rigid rotor, while it is virtually the same for flexible rotors. Conversely, the load orientation has a pronounced effect on stability for both rigid and flexible rotors. 相似文献
73.
High-density SRAMs utilize aggressively small bit-cells, which are subject to extreme variability, degrading their read SNM and read-current. Additionally, array performance is also limited by sense-amplifier offset and strobe-timing uncertainty. This paper, presents a sense-amplifier that targets all of these performance degradations: specifically, simple offset compensation reduces sensitivity to variation while imposing minimal loading on high-speed nodes; stable internal voltage references serve as an internal means to self-trigger regeneration to avoid tracking mismatch in an external strobe-path; precise small-signal detection withstands small read-currents so that other bit-cell parameters can be optimized; and single-ended sensing provides compatibility to asymmetric bit-cells, which can have improved operating margins. The design is integrated with a 64-kb high-density array composed of 0.25 mum2 6T bit-cells. A prototype, in low-power 45 nm CMOS, compares its performance with a conventional sense-amplifier, demonstrating an improvement of 4X in access-time sigma and 34% in overall worst case access time. 相似文献
74.
Kumar Nikhil Verma A. K. Sardana Sahil Sarkar K. Singh T. N. 《Bulletin of Engineering Geology and the Environment》2018,77(2):595-608
Bulletin of Engineering Geology and the Environment - Landslides that occur due to the rapid motion of a rock-mass are a primary risk in mountainous terrains and are a danger to human life and... 相似文献
75.
76.
Preeti Mani Natthapon Nakpathomkun Heiner Linke 《Journal of Electronic Materials》2009,38(7):1163-1165
The Seebeck coefficient S is an important performance characteristic of thermoelectric materials. In this paper we establish the fact that quantum
dots and single-electron tunneling devices with narrow, well-spaced energy levels and sharp transmission resonances have a
Seebeck coefficient independent of material parameters. By employing a delta function for the transmission resonances we arrive
at an intrinsic expression for S in terms of the fundamental electronic charge e. We further confirm the validity of our result in the case of a transmission resonance with finite width. 相似文献
77.
Sachin Nalawade M. Sundararaman J. B. Singh Amit Verma R. Kishore 《Transactions of the Indian Institute of Metals》2010,63(1):35-41
Alloy 718 samples under two initial microstructural conditions, viz., solution annealed to form only γ phase (ST) and aged
to precipitate only δ particles (DELTA), were deformed in tension till fracture in the temperatures range from 200°C–700°C.
From the comparison of the evolved microstructure of deformed and undeformed specimens that have been subjected to similar
thermal history, deformation induced precipitation could be identified. Deformation in the range of 550°C to 650°C promoted
the precipitation of γ′ and γ″ phases in both structures. In case of DELTA alloy, the γ′ precipitation was found to precede
the γ′ phase precipitation while no such preference for precipitation could be identified in ST specimens. This difference
in the precipitation behaviour and the sequence of precipitation has been explained on the basis of the relative concentration
of solutes in the matrix of the starting microstructures of ST and DELTA specimens. 相似文献
78.
Hydrogen is the most environment friendly fuel and has the largest energy density but still much away from being a viable technology due to the cost associated with its production on-site on-demand. However, hydrogen production via water splitting could become potential commercial technology by designing new catalyst materials with low cost, desired surface structures and properties that govern hydrogen evolution reaction (HER) activity and stability. Here, we report the methanol assisted electrochemical water splitting using silver nanoparticles decorated hematite (Ag-hematite) dendrite nanostructures. Ag-hematite nano-dendrites prepared via two different methods viz. chemical co-precipitation and hydrothermal treatment are analysed and compared for their potential applications towards methanol assisted water splitting. It is found that Ag-hematite nano-dendrites prepared by chemical precipitation method shows much better activity as compared to both the parent materials (i.e. Ag NPs and hematite nano-dendrites) as well as Ag-hematite nano-dendrites synthesized by hydrothermal treatment. A baseline study showing the influence of methanol concentration, catalyst, catalyst support, and operating mode has been established. The analysis of the system was carried out as a function of onset potentials and kinetic parameters, including the Tafel slopes and exchange current densities. The effect of electrochemical promotion was investigated to see if it can increase the efficiency and performance of H2 production through electrochemical processes. The observed electro-catalytic enhancement could be attributed to the synergistic effect of hematite dendrites, larger surface area of dendrite structure leading to higher loading of Ag NPs on the surface of HDs. Moreover, the endurance study was performed to check the stability of the presented electrocatalyst in acidic medium under both dark and light illumination conditions which shows that the presented composite catalyst is stable for minimum 100 scans even under light illumination with no signs of photo-corrosion. 相似文献
79.
80.
E. G. Rini N. K. Gaur V. Shelke J. Galgale M. P. Verma R. K. Singh 《Journal of Superconductivity》2002,15(6):583-585
We have developed a shell model, which includes the long-range coulomb, van der Waals interaction, and the short-range Hafemeister–Flygare repulsive interaction operative up to second neighbor atom to study the cohesive and thermal properties of LaMnO3 + . The results on cohesive energy obtained by us are in good agreement with that of calculated value by DeSouza et. al. (R. A. DeSouza, M. S. Islam, and E. I. Tiffee, J. Mater. Chem.
9, 1621 (1999)). In addition, we have also calculated molecular force constant (f), compressibility (), restrahlen frequency (o), Debye temperature (D), and the low temperature specific heat at 50 K T 160 K. Our results on Debye temperature and specific heat for the temperature range 50 K T 160 K are closer to the recently measured data with an automated quasi-adiabatic pulse technique. 相似文献