全文获取类型
收费全文 | 499篇 |
免费 | 18篇 |
国内免费 | 4篇 |
专业分类
电工技术 | 4篇 |
综合类 | 2篇 |
化学工业 | 117篇 |
金属工艺 | 19篇 |
机械仪表 | 10篇 |
建筑科学 | 10篇 |
矿业工程 | 1篇 |
能源动力 | 13篇 |
轻工业 | 41篇 |
水利工程 | 3篇 |
石油天然气 | 3篇 |
无线电 | 84篇 |
一般工业技术 | 134篇 |
冶金工业 | 20篇 |
原子能技术 | 1篇 |
自动化技术 | 59篇 |
出版年
2023年 | 4篇 |
2022年 | 14篇 |
2021年 | 25篇 |
2020年 | 13篇 |
2019年 | 15篇 |
2018年 | 18篇 |
2017年 | 12篇 |
2016年 | 26篇 |
2015年 | 13篇 |
2014年 | 20篇 |
2013年 | 40篇 |
2012年 | 20篇 |
2011年 | 35篇 |
2010年 | 22篇 |
2009年 | 29篇 |
2008年 | 24篇 |
2007年 | 14篇 |
2006年 | 12篇 |
2005年 | 8篇 |
2004年 | 6篇 |
2003年 | 10篇 |
2002年 | 8篇 |
2001年 | 5篇 |
2000年 | 3篇 |
1999年 | 2篇 |
1998年 | 5篇 |
1997年 | 7篇 |
1996年 | 11篇 |
1995年 | 6篇 |
1994年 | 6篇 |
1993年 | 7篇 |
1992年 | 8篇 |
1991年 | 4篇 |
1990年 | 2篇 |
1989年 | 7篇 |
1988年 | 7篇 |
1987年 | 8篇 |
1986年 | 4篇 |
1985年 | 6篇 |
1984年 | 2篇 |
1983年 | 4篇 |
1982年 | 6篇 |
1981年 | 7篇 |
1980年 | 4篇 |
1978年 | 2篇 |
1976年 | 2篇 |
1971年 | 1篇 |
1969年 | 1篇 |
1968年 | 1篇 |
1966年 | 1篇 |
排序方式: 共有521条查询结果,搜索用时 31 毫秒
91.
Ranjith Arimboor VV Venugopalan K Sarinkumar C Arumughan Ramesh Chand Sawhney 《Journal of the science of food and agriculture》2006,86(14):2345-2353
An efficient pilot‐scale process was developed to produce nutraceutical products from fresh sea buckthorn (Hippophae rhamnoides) berries. Fresh berries were subjected to high‐pressure dewatering using a continuous screw press. The separated liquid phase containing 80–90% of pulp oil was clarified at 80 °C and centrifuged to obtain pulp oil, clear juice and sludge. The pulp oil yield was 2.7–2.8% of fresh berry weight with 66–70% extraction efficiency. The pulp oil was remarkably rich in carotenoids (2450–2810 mg kg?1), tocopherols (1409–1599 mg kg?1) and sterols (4096–4403 mg kg?1), with a characteristic fresh berry flavour and 16:1 as the major fatty acid (45.6–49.1%). The clear juice obtained was free from oil and contained high amounts of vitamin C (1683–1840 mg kg?1) and phytochemicals such as polyphenols (2392–2821 mg kg?1) and flavonoids (340–401 mg kg?1). Isorhamnetin (251–310 mg kg?1) was the major flavonoid in the juice, along with quercetin (77–81 mg kg?1) and kaempherol (12–16 mg kg?1). The juice was very acidic (pH 3), with high concentrations of organic acids (30.8–36.0 g kg?1). High‐performance liquid chromatography profiling of organic acids revealed quinic acid (18.1–19.9 g kg?1) as the major acid in the juice. The seeds in the pressed cake were separated and extracted for oil using supercritical CO2. Copyright © 2006 Society of Chemical Industry 相似文献
92.
Pawan Kumar S. K. Sharma M. Knobel Jagdish Chand M. Singh 《Journal of Electroceramics》2011,27(2):51-55
The magnetic properties of nano-crystallite cobalt lanthanum ferrite (CoLaxFe2-x O4) with varied quantities of lanthanum (x = 0, 0.1, 0.15, 0.2, 0.25, 0.3) prepared by co-precipitation method have been studied by vibrating sample magnetometer (VSM)
and LCR meter. X-ray diffraction (XRD) and transmission electron microscopy (TEM) confirmed the size, structure, and morphology
of the ferrite samples. The average crystallite size varied from 17.83 nm to 49.99 nm. All the samples, although, in nano
range, show significant hysteresis. The saturation magnetization (Ms) values decreased from 60.57 emu/g to 30.15 emu/g. The remanence (MR) fell from 10.85 emu/g to 6.39 emu/g. Doping with lanthanum La3+ ions modulates significantly the magnetic properties of cobalt spinel ferrites without sacrificing the ferromagnetic character. 相似文献
93.
Jagdish Chand Gagan KumarPawan Kumar S.K. SharmaM. Knobel M. Singh 《Journal of Alloys and Compounds》2011,509(40):9638-9644
MgGdxFe2−xO4 (x = 0.0, 0.05, 0.1 and 0.15) ferrites, with improved dc resistivity, initial permeability, saturation magnetization, and extremely low relative loss factor, have been synthesized by solid state reaction technique. The microstructures, electric, dielectric and magnetic properties have been investigated by means of X-ray diffraction, Keithley 2611 system, impedance analyzer and VSM respectively. The addition of Gadolinium in Mg ferrite has been shown to play a crucial role in enhancing the electric, dielectric and magnetic properties. The dc resistivity is increased by two orders of magnitude as compared to Mg ferrite. Saturation magnetization has been increased by two times and remnant magnetization has been increased by more than three times due to the doping of Gd3+ ions in Mg ferrite. The relative loss factor was found to have very low values and is of the order of 10−4-10−5 in the frequency range 0.1-30 MHz. The variations of electric, dielectric and magnetic properties of the samples have been studied as a function of frequency and Gd3+ ions concentration measured at room temperature. High resistivity and improved magnetic properties can be correlated with better compositional stoichiometry and the replacement of Fe3+ ions by Gd3+ ions. The mechanisms responsible to these results have been discussed in this paper. 相似文献
94.
Ternary ZnCdO alloy semiconductor nanostructures were grown using electrochemical deposition. Crystalline nanostructures/nanorods with cadmium concentration ranging from 4 to 16 at% in the initial solution were electrodeposited on tin doped indium oxide (ITO) conducting glass substrates at a constant cathodic potential −0.9 V and subsequently annealed in air at 300 °C. X-ray diffraction measurements showed that the nanostructures were of wurtzite structure and possessed a compressive stress along the c-axis direction. The elemental composition of nanostructures was confirmed by energy dispersive spectroscopy (EDS). ZnO nanostructures were found to be highly transparent and had an average transmittance of 85% in the visible range of the spectrum. After the incorporation of Cd content into ZnO the average transmittance decreased and the bandgap tuning was also achieved. 相似文献
95.
This paper presents a brief summary of the results of the role of water in air-jet texturing from a number of authors. The explanations of the results put forward by the authors have been reviewed and some have been analysed. 相似文献
96.
Nanostructured (Pb1 − xSrx)TiO3 (PST) (x = 0.1, 0.2 and 0.3) thin films have been prepared by chemical solution deposition process using spin coating technique. The solution as such was deposited on Pt/Ti/SiO2/Si substrates and annealed at 650 °C/3h. Nanograins dependent dielectric properties of PST films show dielectric constant up to the higher frequency region, low losses, large tunability and phase transition at small temperature. The impedance data has been fitted by Cole-Cole model to study the effect of grain boundaries on the dielectric properties. The current-voltage characteristics have been measured to study leakage current in PST films and described by Poole-Frenkel emission model. It is suggested that the key carrier transport process in PST films is emission of electrons from a trap state near the metal-film interface into a continuum of states associated with each conductive dislocation. The activation energy value for carrier transport in PST films is obtained from temperature-dependent current-voltage characteristics. 相似文献
97.
Chand R Narimura K Kawakita H Ohto K Watari T Inoue K 《Journal of hazardous materials》2009,163(1):245-250
Grape waste generated in wine production is a cellulosic material rich in polyphenolic compounds which exhibits a high affinity for heavy metal ions. An adsorption gel was prepared from grape waste by cross-linking with concentrated sulfuric acid. It was characterized and utilized for the removal of Cr(VI) from synthetic aqueous solution. Adsorption tests were conducted in batch mode to study the effects of pH, contact time and adsorption isotherm of Cr(VI), which followed the Langmuir type adsorption and exhibited a maximum loading capacity of 1.91 mol/kg at pH 4. The adsorption of different metal ions like Cr(VI), Cr(III), Fe(III), Zn(II), Cd(II) and Pb(II) from aqueous solution at different pH values 1-5 has also been investigated. The cross-linked grape waste gel was found to selectively adsorb Cr(VI) over other metal ions tested. The results suggest that cross-linked grape waste gel has high possibility to be used as effective adsorbent for Cr(VI) removal. 相似文献
98.
Arsenic removal using hydrous nanostructure iron(III)-titanium(IV) binary mixed oxide from aqueous solution 总被引:1,自引:0,他引:1
The synthetic bimetal iron(III)–titanium(IV) oxide (NHITO) used was characterized as hydrous and nanostructured mixed oxide, respectively, by the Föurier transform infra red (FTIR), X-ray diffraction (XRD) pattern and the transmission electron microscopic (TEM) image analyses. Removal of As(III) and As(V) using the NHITO was studied at pH 7.0 (±0.1) with variation of contact time, solute concentration and temperature. The kinetic sorption data, in general, for As(III) described the pseudo-first order while that for As(V) described the pseudo-second order equation. The Langmuir isotherm described the equilibrium data (303 (±1.6) K) of fit was well with the Langmuir model. The Langmuir capacity (qm, mg g?1) value of the material is 85.0 (±4.0) and 14.0 (±0.5), respectively, for the reduced and oxidized species. The sorption reactions on NHITO were found to be endothermic and spontaneous, and took place with increasing entropy. The energy (kJ mol?1) of sorption for As(III) and As(V) estimated, respectively, is 9.09 (±0.01) and 13.51 (±0.04). The sorption percentage reduction of As(V) was significant while that of As(III) was insignificant in presence of phosphate and sulfate. The fixed bed NHITO column (5.1 cm × 1.0 cm) sorption tests gave 3.0, 0.7 and 4.5 L treated water (As content ≤ 0.01 mg L?1) from separate As(III) and As(V) spiked (0.35 ± 0.02 mg L?1) natural water samples and from high arsenic (0.11 ± 0.01 mg L?1) ground water, respectively when inflow rate was (0.06 L h?1). 相似文献
99.
In this study, polypropylene and polyethylene terephthalate blend were modified by incorporating different percentages of ultrahigh molecular weight polyethylene (UHMWPE) ranging from 1 to 5 phr. Modified blends were prepared by melt mixing the PP/PET blend and UHMWPE. Ultimate tensile strength of UHMWPE filled blend was determined at 10, 20, 50, and 100 mm/min cross head speeds of testing. It was found that increase of cross head speed from 10 to 100 mm/min increases the tensile strength of PP/PET/UHMWPE blends. Maximum ultimate tensile strength is exhibited by the blend containing 2 phr UHMWPE. Breaking strain of the UHMWPE modified and unmodified PP/PET blend increased with the increase of cross head speed due to the highly entangled chain structure of UHMWPE. Shore A hardness of the filled blends also increased from 341 to 356, which is highest for 2 phr UHMWPE. High stress abrasive wear of UHMWPE modified blend was determined by using Suga abrasion tester, model NUS‐1 Japan. Wear rate of the PP/PET(90/10) blends having 1, 2, and 5 phr of UHMWPE was determined at different loads such as 1, 3, 5, and 7 N and sliding distances from 6.4 m to 25.6 m. Wear rate values show that UHMWPE has prominent effect on abrasive wear of PP/PET blends. Addition of 2 and 5 phr UHMWPE improved the wear resistance of PP/PET blends at different loads, which has been explained on the basis of improved bonding as compared with pure PP/PET blend and increased hardness. Maximum abrasive wear rate reduction was achieved by adding 2 phr UHMWPE in PP/PET(90/10) blend. POLYM. COMPOS. 28:267–272, 2007. © 2007 Society of Plastics Engineers 相似文献
100.
Zhenxing Han Manoj Kumar Ram Rajeev Kamal Turki Alamro D. Yogi Goswami Chand Jotshi 《国际能源研究杂志》2019,43(8):3732-3745
This paper aims to study the effect on the characteristics of molten salt because of the dispersion of different size nanoparticles of Al2O3. The eutectic mixture of 54 wt% KNO3 and 46 wt% NaNO3 was selected as the base salt. Five different size nanoparticles of Al2O3, 80, 135, 200, 300, and 1000 nm, were dispersed into the base salt at a mass concentration of 1% to make the nanomaterials by a two‐step method, respectively. Thermal properties of the base salt and the samples with Al2O3 nanoparticles, including the melting point temperature, fusion heat, specific heat capacity, and thermal diffusivity, were measured with differential scanning calorimeter (DSC) and Xenon Flash Apparatus (XFA). On the basis of the measured specific heat capacities and thermal diffusivities, their thermal conductivities in the solid state were calculated at discrete specified temperatures. The results showed that the dispersions of 200‐ and 135‐nm Al2O3 nanoparticles could enhance the average solid and liquid specific heat capacities by up to 17.2% and 19.7%, respectively. The research on thermal diffusivity and thermal conductivity also verified that the influences of different size nanoparticles were different. Although no new strong intensity peaks or peak position variations were found in the diffraction patterns of the two samples with 80‐ and 1000‐nm nanoparticles of Al2O3, the larger deviations in the lower wavenumber region still meant possible crystalline structure variation because of the dispersion of Al2O3 nanoparticles. Scanning electronic microscope (SEM) images showed the inhomogeneity and the agglomeration of dispersed nanoparticles in the base salt, and the formation of a nanolayer around the nanoparticles could be a possible explanation to the thermal‐physical property variation. 相似文献