全文获取类型
收费全文 | 1094篇 |
免费 | 76篇 |
国内免费 | 15篇 |
专业分类
电工技术 | 25篇 |
综合类 | 4篇 |
化学工业 | 252篇 |
金属工艺 | 28篇 |
机械仪表 | 38篇 |
建筑科学 | 29篇 |
能源动力 | 82篇 |
轻工业 | 101篇 |
水利工程 | 3篇 |
石油天然气 | 4篇 |
武器工业 | 1篇 |
无线电 | 114篇 |
一般工业技术 | 281篇 |
冶金工业 | 63篇 |
原子能技术 | 22篇 |
自动化技术 | 138篇 |
出版年
2023年 | 27篇 |
2022年 | 75篇 |
2021年 | 86篇 |
2020年 | 66篇 |
2019年 | 62篇 |
2018年 | 79篇 |
2017年 | 53篇 |
2016年 | 69篇 |
2015年 | 41篇 |
2014年 | 56篇 |
2013年 | 88篇 |
2012年 | 50篇 |
2011年 | 65篇 |
2010年 | 32篇 |
2009年 | 43篇 |
2008年 | 31篇 |
2007年 | 36篇 |
2006年 | 21篇 |
2005年 | 27篇 |
2004年 | 11篇 |
2003年 | 8篇 |
2002年 | 5篇 |
2001年 | 7篇 |
2000年 | 6篇 |
1999年 | 6篇 |
1998年 | 18篇 |
1997年 | 12篇 |
1996年 | 8篇 |
1995年 | 6篇 |
1994年 | 12篇 |
1993年 | 7篇 |
1992年 | 3篇 |
1991年 | 7篇 |
1990年 | 5篇 |
1989年 | 6篇 |
1988年 | 3篇 |
1987年 | 4篇 |
1986年 | 2篇 |
1985年 | 3篇 |
1984年 | 3篇 |
1983年 | 4篇 |
1982年 | 2篇 |
1981年 | 2篇 |
1980年 | 4篇 |
1979年 | 5篇 |
1978年 | 8篇 |
1977年 | 3篇 |
1976年 | 3篇 |
1969年 | 1篇 |
1966年 | 1篇 |
排序方式: 共有1185条查询结果,搜索用时 15 毫秒
81.
Raz Muhammad Yaseen Iqbal Carlos R. Rambo 《Journal of Materials Science: Materials in Electronics》2014,25(4):1652-1656
Ba4.5Re9Ti18O54 (Re = La, Nd) ceramics were prepared via a solid state mixed oxide route. X-ray diffraction (XRD) analysis revealed the formation of the major Ba4.5Re9Ti18O54 phase along with rutile (TiO2) as a secondary phase. Rietveld structure refinement of the recorded XRD data confirmed that the crystal structure of Ba4.5Nd9Ti18O54 (BNT) was orthorhombic (Pnma) with unit cell parameters a = 22.3412 Å, b = 7.6824 Å and c = 12.1952 Å. Ba4.5La9Ti18O54 (BLT) exhibited high relative permittivity (95.6), low quality factor (2,102 GHz) and a high temperature coefficient of resonance frequency (+352 ppm/°C). The substitution of Nd for La caused a decrease in both the relatively permittivity and temperature coefficient of resonance frequency to 84.2 and 167 ppm/°C respectively and an increase in quality factor to 8,007 GHz. Raman spectroscopic analysis revealed that lattice defects may be responsible for the observed decrease in quality factor of BLT ceramics in comparison to BNT. The Raman shifts at 533.5 and 613.6 cm?1, related to Ti–O bond stretching, decreased for BNT ceramics, which may be a possible reason for the observed decrease in relative permittivity. 相似文献
82.
Ahmed Iqbal I. Ani Rizwan Rajput 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2012,87(2):177-188
BACKGROUND: Generally the fabrication of polymeric membranes is a complicated and expensive process since it involves several steps. The preliminary preparation steps involve polymer drying and dissolution and is very time consuming and expensive. Currently, conventional electrothermal heating (CEH) is used to dissolve polyethersulfone in an aprotic solvent for membrane fabrication. Usually CEH requires 6 to 8 h at temperatures of 80 to 95 °C. This paper reports the fabrication and characterization of polyethersulfone (PES) asymmetric ultrafiltration membrane made from microwave (MW) synthesis casting solution consisting of various compositions of double solvents and lithium bromide (LiBr) additive. RESULTS: Homogeneous dual solvent dope solutions prepared via microware irradiation took only 1 h instead of the 7 h when prepared using CEH. The results also revealed that the membrane permeation and rejection rates, pore size and porosity were dependent on the ratio of LiBr to acetone. Membranes with LiBr kept at 2 and 3 wt% exhibited both high rejection and permeation rates with minimum pore sizes of 1.067 and 1.214 nm respectively. The presence of LiBr and the occurrence of chain scission were elucidated using Fourier transform infrared (FTIR) spectroscopy while its hydrophilic property was confirmed by water absorption and contact angle measurements. CONCLUSIONS: It was concluded that the microwave technique is capable of producing 1 L membrane solutions in less than 1 h. The membranes prepared from the microwave solutions show good rejection and permeation rates. Copyright © 2011 Society of Chemical Industry 相似文献
83.
K. Park H.Y. Hong G.W. Jung D.H. Kim D.A. Hakeem A. Iqbal 《Ceramics International》2018,44(13):15024-15034
Fe2-xAgxO3 (0?≤?x?≤?0.04) nanopowders with various Ag contents were synthesized at different hydrothermal reaction temperatures (150?°C and 180?°C). Their structural properties were fully investigated through an X-ray diffraction, a Fourier transform infrared spectroscopy, and an X-ray photoelectron spectroscopy. The hydrothermal reaction temperature, time, and Ag content remarkably affected the morphological characteristics and crystal structure of the synthesized powders. The Fe2-xAgxO3 (0?≤?x?≤?0.04) powders synthesized at 150?°C for 6?h and the Fe2-xAgxO3 (0.02?≤?x?≤?0.04) powders synthesized at 180?°C for 12?h formed the orthorhombic α-FeOOH phase with a rod-like morphology, whereas the Fe2-xAgxO3 (0?≤?x?≤?0.01) powders synthesized at 180?°C for 12?h formed the rhombohedral α-Fe2O3 phase with a spherical-like morphology. The Fe1.98Ag0.02O3 fabricated by utilizing Fe1.98Ag0.02O3 powders synthesized at 180?°C showed the largest power factor (0.64?×10?5 Wm?1 K?2) and dimensionless figure-of-merit (0.0036) at 800?°C. 相似文献
84.
A novel current-mode active-only universal filter based on and employing three DO-CCCIIs and two OAs is introduced. The circuit is fully integrable and programmable, and implements all the five generic filtering functions. The three basic filtering responses LP, BP and HP are implemented simultaneously by the circuit, while AP and notch signals can be realized simply by connecting appropriate node currents. The currents are available at high output impedances, so the synthesized filter can be cascaded without additional buffers to realize higher order filters. The filter performance factors ω 0 and Q are electronically tunable in an orthogonal manner through separate bias currents of the CCCII. The PSPICE simulation was carried out to realize the proposed circuit. 相似文献
85.
Abdul Ghafar Shah Tahir Mahmood Muhammad N. Naeem Zafar Iqbal Shahid H. Arshad 《Acta Mechanica》2010,211(3-4):293-307
In this paper, a study on the vibrations of functionally graded cylindrical shells based on the Winkler and Pasternak foundations is presented. The shell equations are amended by inducting the moduli of the Winkler and Pasternak foundations. The wave propagation method is employed to solve the shell dynamical equations. The method is based on the approximate eigenvalues of characteristic beam functions. The validity and accuracy of the present approach are verified by a number of comparisons. 相似文献
86.
Controlled-release naproxen using micronized ethyl cellulose by wet-granulation and solid-dispersion method 总被引:3,自引:0,他引:3
This study has been undertaken to develop a controlled-release tablet dosage form of naproxen using ethocel (ethyl cellulose) as the rate-controlling polymer. The formulations were made by employing the conventional wet-granulation method and the solid-dispersion method. Tablets made by both methods were compared for their controlled-release dissolution profiles. Both methods were useful in developing the controlled-release formulations of naproxen with desirable properties. However, the amount of polymer required to make a formulation with the desired release profile was 33% less via solid dispersion than via wet granulation. A cumulative 88% of naproxen was released from the solid-dispersion formulation, compared with 84% from the wet-granulation formulation. 相似文献
87.
R. Iqbal S. C. Moratti A. B. Holmes G. yahioglu L. R. Milgrom F. cacialli J. Morgado R. H. friend 《Journal of Materials Science: Materials in Electronics》2000,11(2):97-103
A new series of soluble porphyrin-containing copolymers have been synthesized via the Gilch methodology [1], for use in light-emitting devices (LEDs). These materials consist of random copolymers of 2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylene vinylene (MEH-PPV) and a porphyrin-substituted phenylene vinylene. Low concentrations of porphyrin monomers were used in order to improve solubility, and help prevent aggregation (and consequent fluorescence quenching) of the porphyrin units. Emission is red-shifted from that expected in dialkoxy-PPVs such as MEH-PPV owing to an efficient exciton transfer to the fluorescent porphyrin unit. 相似文献
88.
The biosorption process for the removal of nickel(II) by loofa sponge-immobilized biomass of Chlorella sorokiniana (LIBCS), a newly developed immobilized biosorbent, was characterized. Effects of environmental factors on metal uptake capacity of LIBCS were studied and compared with free biomass of C. sorokiniana (FBCS). Nickel(II) removal by LIBCS was found to be influenced by pH of the solution, initial metal concentration, and biomass concentration. The biosorption of nickel(II) ions by both LIBCS and FBCS increased as the initial concentration of nickel(II) ions increased in the medium. No loss to biosorption capacity of LIBCS for nickel(II) was found due to the presence of loofa sponge, indeed as compared to FBCS an increase of 25.3% was noted in the biosorption capacity of LIBCS. Maximum biosorption capacities for FBCS and LIBCS were found as 48.08 and 60.38 mg nickel(II)/g, respectively, whereas the amount of nickel(II) ions adsorbed on the plain loofa sponge was 6.1mg/g. During these biosorption studies, LIBCS exhibited excellent physical and chemical stability without any significant release/loss of microalgal biomass from loofa sponge matrix. The kinetics of nickel(II) removal was extremely fast reaching at equilibrium in about 15 min for LIBCS and 20 min for FBCS. The biosorption equilibrium was well described by the Langmuir and Freundlich adsorption isotherms. The biosorption capacities were found to be solution pH dependent and the maximum adsorption was found at a solution pH 4-5. The LIBCS could be regenerated using 75 mM HCl, with up to 98% recovery. The LIBCS were shown to be robust and stable with little decrease in the nickel(II) uptake capacity when used in consecutive seven biosorption-desorption cycles. Continuous removal of nickel(II) from electroplating effluent by LIBCS packed in fixed bed column bioreactor confirm the possibility of developing a biological treatment process for the removal of toxic metals from authentic wastewater. 相似文献
89.
Tungsten inert gas (TIG) welded joints between Zircaloy-4 and stainless steel 304L have been studied by scanning electron
microscope (SEM) having energy dispersive system (EDS) as an attachment. Intermetallic compound Zr(Cr, Fe)2 and Zr2Fe–Zr2Ni eutectic phase have been observed in the molten zone. The surface area occupied by intermetallic compound Zr(Cr, Fe)2 is about twice compared to Zr2Fe–Zr2Ni eutectic phase. The shape of the intermetallic compound is rod like. The phases were also identified by using X-ray diffraction
(XRD) technique. EDS and XRD results are quite in agreement. 相似文献
90.
Novel polystyrene microsphere (PSMS)-based PSMS/Si and polystyrene/silica nanoparticle/multi-walled carbon nanotube (PS/Si/MWCNT) nanocomposite has been prepared using in situ sol-gel and chemical amalgamation methods. Aniline monomer was introduced by in situ route to form PSMS/PANI, PSMS/PANI/Si and PSMS/PANI/Si/MWCNT nanocomposite. FESEM of nanocomposite indicated core-shell spherical and tubular morphology. Glass transition temperature (Tg) and maximum decomposition temperature (Tmax) of PSMS/PANI/Si/MWCNT nanocomposite were found as 295°C and 524°C, respectively, which were higher than the PSMS/PANI (Tg = 245°C; Tmax = 387°C) and PSMS/PANI/Si (Tg = 257°C; Tmax = 388°C) nanocomposite. For nanocomposite dispersion, tetrahydrofuran was studied as fine solvent. XRD depicted amorphous nature of PSMS/Si and PSMS/PANI/Si; however MWCNT reduced amorphous character of PSMS/PANI/Si/MWCNT. Electromagnetic interference (EMI) shielding effectiveness improved from 0.1 dB (PSMS) to 12.3 dB (PSMS/PANI/Si) to 24.5 dB (PSMS/PANI/Si/MWCNT). The increase in EMI shielding effectiveness was also observed with variation in log of conductivity from ?14 mho m?1 (PSMA) to 1.17 mho m?1 (PSMS/PANI/Si/MWCNT). 相似文献