全文获取类型
收费全文 | 602篇 |
免费 | 19篇 |
国内免费 | 3篇 |
专业分类
电工技术 | 2篇 |
综合类 | 2篇 |
化学工业 | 147篇 |
金属工艺 | 40篇 |
机械仪表 | 19篇 |
建筑科学 | 19篇 |
能源动力 | 48篇 |
轻工业 | 33篇 |
水利工程 | 1篇 |
石油天然气 | 4篇 |
无线电 | 53篇 |
一般工业技术 | 122篇 |
冶金工业 | 22篇 |
原子能技术 | 4篇 |
自动化技术 | 108篇 |
出版年
2024年 | 4篇 |
2023年 | 9篇 |
2022年 | 23篇 |
2021年 | 20篇 |
2020年 | 22篇 |
2019年 | 21篇 |
2018年 | 28篇 |
2017年 | 15篇 |
2016年 | 16篇 |
2015年 | 12篇 |
2014年 | 18篇 |
2013年 | 46篇 |
2012年 | 44篇 |
2011年 | 41篇 |
2010年 | 38篇 |
2009年 | 38篇 |
2008年 | 36篇 |
2007年 | 21篇 |
2006年 | 22篇 |
2005年 | 7篇 |
2004年 | 10篇 |
2003年 | 8篇 |
2002年 | 8篇 |
2001年 | 5篇 |
2000年 | 9篇 |
1999年 | 7篇 |
1998年 | 5篇 |
1997年 | 4篇 |
1996年 | 9篇 |
1995年 | 4篇 |
1994年 | 5篇 |
1992年 | 7篇 |
1991年 | 2篇 |
1990年 | 2篇 |
1989年 | 6篇 |
1988年 | 4篇 |
1987年 | 5篇 |
1986年 | 7篇 |
1985年 | 4篇 |
1984年 | 5篇 |
1983年 | 2篇 |
1982年 | 2篇 |
1980年 | 3篇 |
1979年 | 5篇 |
1978年 | 3篇 |
1977年 | 2篇 |
1974年 | 2篇 |
1973年 | 3篇 |
1972年 | 2篇 |
1970年 | 1篇 |
排序方式: 共有624条查询结果,搜索用时 15 毫秒
91.
The sintering and graphitization behavior of mesocarbon microbeads (MCMB) at high temperatures (1900-2800 K) is investigated. It is shown that while the low temperature sintering performance of MCMB is unique, at high temperature it appears to be similar to that of conventional materials. In contrast, the obtained activation energy for MCMB high-temperature graphitization is ∼100 kcal/mol, which is smaller than that (∼240 kcal/mol) for typical carbon systems. It is concluded that the combination of such unique properties as excellent compressibility, low temperature sinterability, and rapid graphitization makes MCMB an attractive precursor for manufacturing carbon-based materials. 相似文献
92.
Arvind Bharti 《Bulletin of Materials Science》1988,11(2-3):191-212
A brief state-of-the-art review of laser welding has been presented. Results of our experimental studies on laser welding
of Ti-6Al-4V have been reported. Results of weld evaluation including microstructure, mechanical properties and microchemistry
have also been presented. 相似文献
93.
Arvind Mishra A. G. Gopalakrishna J. V. Prabhakar 《Journal of the American Oil Chemists' Society》1988,65(10):1605-1609
Components of rice bran oil have been assessed for their effect on refining losses. Rice bran oil used in the study had the following (percent) analysis: free fatty acids, 6.8; phosphatides, 1.25; wax, 2.85; monoglycerides, 1.67; diglycerides, 4.84, and oryzanol, 1.85; the rest (80.74) was mostly triglycerides. The phosphatides and mono- and diglycerides had no noticeable effect on refining losses at levels of up to 2% in the oil. Waxes and oryzanol increased the refining losses substantially. In model experiments where these were incorporated into peanut oil individually and in combination, the wax at as low a level as 1% increased the refining losses by about 80% more than control and the refining losses increased with concentration of wax. Oryzanol had a similar effect. When wax and oryzanol were present together in the oil, the effect was synergistic—the refining losses were higher than the sum of their individual effects. Phosphatides, mono- and diglycerides tended to reduce the adverse effect of wax and oryzanol. The main components responsible for higher than normal refining losses in rice bran oil have been identified as wax and oryzanol. 相似文献
94.
The possibility of shape normalization of catalyst pellets with non-uniform catalytic activity profiles is examined. A first order isothermal reaction occurring in slab or spherical catalyst pellets, with a variety of activity profiles, is considered. Analytic solutions for the effectiveness factor are reported in all cases. When the catalytic activity at the external surface of the pellet is non-zero, a physically significant normalization of the Thiele modulus is suggested which makes the asymptotic behavior of the effectiveness factor identical for all pellet shapes and all activity profiles. For an operational range intermediate between kinetic and diffusion control, however, the normalization can lead to significant errors. No such normalization exists when the surface catalytic activity is zero. 相似文献
95.
Autothermal reforming is an attractive method for on-site production of hydrogen for use in proton exchange membrane (PEM) fuel cells. The use of liquid hydrocarbons as feedstock, however, remains a challenge as these fuels cause severe coking of the currently available catalysts. In this work, cerium- and nickel-substituted LaFeO3 perovskites were investigated as potential low cost coking resistant catalysts for autothermal reforming of a JP-8 fuel surrogate. The high surface area complex oxides were prepared using aqueous (solution) combustion synthesis at fuel-rich conditions and characterized by BET and XRD techniques. The catalysts exhibited excellent stability during autothermal reforming at and 1 atm, with near-equilibrium hydrogen yield even at high GHSV values (). The addition of cerium significantly improved coking resistance, attributed to improved oxygen ion conductivity, resulting in carbon oxidation on the catalyst surface. 相似文献
96.
Das B.P. Amrutur B. Jamadagni H.S. Arvind N.V. Visvanathan V. 《Semiconductor Manufacturing, IEEE Transactions on》2009,22(2):256-267
We report the design and characterization of a circuit technique to measure the on-chip delay of an individual logic gate (both inverting and noninverting) in its unmodified form. The test circuit comprises of digitally reconfigurable ring oscillator (RO). The gate under test is embedded in each stage of the ring oscillator. A system of linear equations is then formed with different configuration settings of the RO, relating the individual gate delay to the measured period of the RO, whose solution gives the delay of the individual gates. Experimental results from a test chip in 65-nm process node show the feasibility of measuring the delay of an individual inverter to within 1 ps accuracy. Delay measurements of different nominally identical inverters in close physical proximity show variations of up to 28% indicating the large impact of local variations. As a demonstration of this technique, we have studied delay variation with poly-pitch, length of diffusion (LOD) and different orientations of layout in silicon. The proposed technique is quite suitable for early process characterization, monitoring mature process in manufacturing and correlating model-to-hardware. 相似文献
97.
Arvind Ananthanarayanan Satyandra K. Gupta Hugh A. Bruck 《Polymer Engineering and Science》2009,49(2):293-304
This article reports a mold design strategy and a detailed mechanics‐based modeling approach to characterize and control the plastic deformation of premolded components during in‐mold assembly of mesoscale revolute joints. The following new results are reported in this article. First, a mesoscale mold design with varying cavity shape is described to perform in‐mold assembly of the mesoscale revolute joint. Second, a transient computational fluid dynamics (CFD) modeling approach to determine the forces experienced by the mesoscale parts due to injection molding is described. Finally, a mechanics‐based model approach developed using a combination of experimental materials property data and the CFD results as input to a finite element simulation of the deformation response of the mesoscale part is presented for the determination of critical mold design parameters that are necessary for repeatable fabrication of articulating mesoscale revolute joints. Using the advances reported in this article a mesoscale revolute joint has been successfully molded. To the best of our knowledge, this is the first demonstration of in‐mold assembly process using a varying cavity shape mold tocreate an articulating mesoscale revolute joint. POLYM. ENG. SCI., 2009. © 2008 Society of Plastics Engineers 相似文献
98.
Lithium aluminum silicate glasses of composition (wt%) 12.6Li2O–71.7SiO2–5.1Al2O3–4.9K2O–3.2B2O3–2.5P2O5 were prepared by the melt quench technique. These glasses were converted to glass–ceramics based on DTA data. X-ray diffraction (XRD) and Fourier transform infra-red spectroscopy (FTIR) were used to discern the phases evolved in the glass–ceramics. Phase morphology was studied using scanning electron microscopy (SEM). Thermal expansion coefficient (TEC) and glass transition temperature (Tg) of all samples were measured using thermo-mechanical analyzer (TMA). It was found that 3 h dwell time at crystallization temperature yielded samples with good crystallinity with a TEC of 9.461 × 10−6 °C−1. Glass–ceramic-to-metal compressive seal with SS-304 was fabricated using LAS glass–ceramic. The presence of metal housing and compressive stresses at the glass–ceramic-to-metal interface reduced average grain size and changed the overall microstructure. 相似文献
99.
Rakesh Kumar Gupta Raghwesh Mishra Kingsuk Mukhopadhyay Rajesh Kumar Tiwari Ashok Ranjan Arvind Kumar Saxena 《SILICON》2009,1(2):125-129
Multiwalled carbon nanotubes (MWCNTs) have been coated with silicon carbide (SiC) using polycarbosilane as precursor in order
to improve their thermo oxidative stability. The polycarbosilane coated MWCNTs were heated to ~1300°C under an inert atmosphere
to generate the SiC coating. X-ray diffraction, energy dispersive X-ray analysis and scanning electron microscopy have confirmed
the formation of SiC on the MWCNTs. The retention of the tubular structure of the MWCNTs has been confirmed by transmission
electron microscopy. Thermogravimetric analysis has been performed to evaluate the thermo oxidative stabilities of coated
and virgin MWCNTs. Sonication studies have shown that the mechanical strength of the MWCNTs was increased after coating with
SiC. 相似文献
100.
Nonequilibrium Operation of Arsenic Diffused Long-Wavelength Infrared HgCdTe Photodiodes 总被引:1,自引:0,他引:1
Priyalal S. Wijewarnasuriya P.Y. Emelie Arvind D’Souza Gregory Brill Maryn G. Stapelbroek Silviu Velicu Yuanping Chen Chris Grein Sivalingam Sivananthan Nibir K. Dhar 《Journal of Electronic Materials》2008,37(9):1283-1290
We demonstrated a device with a unique planar architecture using a novel approach for obtaining low arsenic doping concentrations
in long-wavelength (LW) HgCdTe on CdZnTe substrates. HgCdTe materials were grown by molecular beam epitaxy (MBE). We fabricated
a p-on-n structure that we term P
+/π/N
+ where the symbol “π” is to indicate a drastically reduced extrinsic p-type carrier concentration (on the order of mid 1015 cm−3); P
+ and N
+ denote a higher doping density, as well as a higher energy gap, than the photosensitive base π-region. Fabricated devices
indicated that Auger suppression is seen in the P
+/π/N
+ architecture at temperatures above 130 K and we obtained a saturation current on the order of 3 mA on 250-μm-diameter devices at 300 K with Auger suppression. Data shows that about a 50% reduction in dark current is achieved at 300 K
due to Auger suppression. The onset of Auger suppression voltage is 450 mV at 300 K and 100 mV at 130 K. Results indicate
that a reduction of the series resistance could reduce this further. A principal challenge was to obtain low p-type doping levels in the π-region. This issue was overcome using a novel deep diffusion process, thereby demonstrating successfully
low-doped p-type HgCdTe in MBE-grown material. Near-classical spectral responses were obtained at 250 K and at 100 K with cut-off wavelengths
of 7.4 μm and 10.4 μm, respectively. At 100 K, the measured non-antireflection-coated quantum efficiency was 0.57 at 0.1 V under backside illumination.
Received November 7, 2007; accepted March 19, 2008 相似文献