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51.
52.
Mechanical Properties of Submicrometer‐Grained Transparent Yttria Ceramics by Hot Pressing with Hot‐Isostatic Pressing 下载免费PDF全文
Lin Gan Young‐Jo Park Haneul Kim Jin‐Myung Kim Jae‐Woong Ko Jae‐Wook Lee 《International Journal of Applied Ceramic Technology》2016,13(4):678-684
Here, we report the fabrication and mechanical properties of submicrometer‐grained (0.29–0.58 μm) transparent yttria ceramics by hot pressing combined with hot‐isostatic pressing. The effects of the grain size on the microhardness and the fracture toughness were studied. An unusual decrease of the fracture toughness with an increase in the grain size was revealed, which may be attributed to the different grain size dependence of the fracture behavior of the ZrO2‐doped yttria ceramics compared to that of other yttria ceramics. The microhardness and fracture toughness of the transparent yttria ceramics were found to be better than those of the large‐grained yttria ceramics. 相似文献
53.
We have solved both steady state and transient problems on the biofiltration of toluene vapor. The effect of inlet toluene
concentration and inlet gas-flow rate on the removal rate of toluene and the elimination capacity of a lab-scale biofilter
has been investigated. In this study, the effectiveness factor was a function of pollutant concentration. The dynamic solutions
show good agreement with experimental results. At an inlet toluene concentration of 100 ppm, the diffusion of toluene into
biofilm was obviously a rate determining step. Above 200 ppm, however, biofilm already showed full activity. The steady-state
simulation confirmed that the change of elimination capacity obtained by increasing only inlet toluene concentration was the
same as that obtained by increasing only flow rate of contaminated air. The maximum possible performance is about 20 g/m3h with no addition of nutrients. 相似文献
54.
Min Chan Kim David M. Phillips Myung S. Jhon Xiaoding 《Chemical Engineering Communications》2004,191(1):1-16
The surface diffusion characteristics of nonpolar perfluoropolyether (PFPE) Z on carbon surfaces are investigated in two regimes, submonolayer and multilayer, for nano-thin films. For the submonolayer regime, the two-dimensional, cubic van der Waals equation of state is applied to determine the dependence of the surface diffusion coefficient on the film thickness, as experimental surface diffusion coefficients increase with increasing film thickness. For the multilayer regime, a conventional fluid mechanics analysis with position dependent viscosity and a van der Waals disjoining pressure gradient is applied to investigate the surface diffusion characteristics. The present theoretical analysis qualitatively agrees with the experimental results. 相似文献
55.
The synergistic effects of boron nitride (BN) powder and die on the rheology and processability of metallocene‐catalyzed low density polyethylene (mLDPE) were investigated. The processability in the extrusion process is closely related to the interfacial properties between the polymer melts and the die wall. BN powder was added to mLDPE to reduce the friction coefficient and surface energy. Adding 0.5 wt% BN powder to mLDPE was very effective in improving the processability and the extrudate appearance. To study the effect of die surface property, three different dies were applied in capillary extrusion. One was conventional tungsten carbide (TC) die, and the others were hot‐pressed BN (hpBN) die and hot‐pressed BN composite (hpBNC) die. The applications of these BN dies were quite effective in delaying surface melt fracture (sharkskin) and postponing gross melt fracture to higher shear rate compared to the TC die. These improvements result from the fact that BN dies reduce the wall shear stress significantly and promote slip. The synergistic effect of processability could be obtained when both BN powder and hpBN die were used together. 相似文献
56.
Jin Woo Kook In Seop Gwak You Ra Gwak Myung Won Seo See Hoon Lee 《Korean Journal of Chemical Engineering》2017,34(12):3092-3101
Characteristics of Char-CO2 gasification were compared in the temperature range of 1,100–1,400 °C using a thermogravimetric analyzer (TGA) for petroleum coke, coal chars and mixed fuels (Petroleum coke/coal ratios: 0, 0.25, 0.5, 0.75, 1). The results showed that reaction time decreased with increasing gasification temperature, BET surface area and alkali index of coal. Mixed fuels composed of petroleum coke/coal exhibited reduced activation energies. Modified volumetric reaction model and shrinking core model might be suitably matched with experimental data depending on coal type and petroleum coke/coal ratio. Rate equations were suggested by selecting gas-solid reaction rate models for each sample that could simulate CO2 gasification behavior. 相似文献
57.
In this study, 1-(2,6-diisopropylphenyl)-2,5-di(2-thienyl)pyrrole-based metal-free organic dyes containing three different non planar electron donor groups such as methoxy or hexyloxy substituted triphenylamine and difluorenephenylamine were prepared in order to see the effect of electron donor groups on the opto-electrical properties and applied in dye-sensitized solar cells (DSSC). All three dyes showed broad absorption band in visible part of the solar spectrum (∼300 nm–600 nm). The dye (TPTDYE-3) containing sterically less hindered methoxy substituted triphenylamine was found to show relatively red shifted absorption compared to that of the dye (TPTDYE-4) containing hexyloxy substituted triphenylamine or the dye (TPTDYE-5) containing difluorenephenylamine. The optical band gaps of the three dyes were calculated to be 2.19 eV, 2.22 eV and 2.24 eV, respectively, and the highest occupied molecular orbital (HOMO) energy levels of the three dyes were found to be located at 0.65 V, 0.68 V and 0.75 V, respectively. The DSSC performance of each dye was investigated with and without coadsorbent. The maximum solar to electrical energy conversion efficiencies (η) of the DSSCs made from only sensitizer were 4.18%, 5.28% and 5.42% while those of the DSSCs made from sensitizer with coadsorbent were 5.47%, 5.58% and 5.63%, respectively. 相似文献
58.
Kim Sung-Hou; Kang Chui-Hee; Kim Rosalind; Cho Joong Myung; Lee Yong-Beom; Lee Tae-Kyu 《Protein engineering, design & selection : PEDS》1989,2(8):571-575
Monellin is one of two natural proteins from African berrieswith potent sweet taste. Monellin is the smaller of the two,and consists of two peptides. The protein loses sweetness whenheated above 50°C under acidic pH. Based on the crystalstructure of monellin we have fused the two chains into a singlechain using several different linkers copied and transplantedfrom the same molecule. One of the newly designed proteins isas potently sweet as the natural one, is more stable upon temperatureor pH changes, and renatures easily even after heating to 100°Cat low pH. 相似文献
59.
Hyung Ik Lee Seok Kim Jin Hoe Kim Myung Hee Yun Jei-Won Yeon Ji Man Kim 《Carbon》2009,47(4):1043-1293
A mesoporous carbon material, CMK-1 was successfully functionalized with carboxymethylated polyethyleneimine (CMPEI) by a simple adsorption method. The physicochemical properties of the polymer-carbon composite (denoted as CMPEI/CMK-1) were investigated by X-ray diffraction, N2 adsorption-desorption and X-ray photoelectron spectroscopy (XPS). The adsorption behaviors of Cu(II) ion on the CMK-1 and CMPEI/CMK-1 materials were examined under the batch-type experimental conditions. The CMPEI/CMK-1 material showed a typical Langmuir isotherm with a 10-fold increase in adsorption capacity, compared to that of CMK-1. In the case of 0.02 mM Cu(II) solution, the copper ions were completely removed by utilizing the CMPEI/CMK-1 material both at pH values of 3 and 5. The CMPEI/CMK-1 material also exhibited a remarkably high distribution coefficient value (Kd = 2.75 × 105). The results from XPS depth profiles before and after the copper-ion adsorption indicated that the CMPEI and the adsorbed Cu(II) ions were uniformly distributed within the CMK-1 particles. 相似文献
60.
Hee Jung Kim Ji Eun Park Myung Gil Choi Sangdoo Ahn Suk-Kyu Chang 《Dyes and Pigments》2010,84(1):54-58
A novel, Hg2+-selective chemosensor was prepared via Mannich reaction of dichlorofluorescein with piperazinyl-coumarin moiety. The dichlorofluorescein–coumarin derivative exhibited well-defined Hg2+-selective chromogenic behavior, indicated by a green to pink colour change in solution, as well as fluorogenic signalling. Significant changes in fluorescence of the dichlorofluorescein subunit were analyzed in reference to the rather constant coumarin emission as an internal standard yielding Hg2+ selectivity. The Hg2+ selectivity of the chemosensor was not appreciably affected by the presence of common coexisting alkali, alkaline earth, and transition metal ions. The detection limit of the dichlorofluorescein–coumarin conjugate for the determination of Hg2+ ions was 4.3 × 10−6 mol L−1 and the conjugate dye could be used as a chemosensor for the analysis of Hg2+ ions in aqueous environments. 相似文献