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排序方式: 共有182条查询结果,搜索用时 15 毫秒
1.
Metallurgist - We consider domestic and foreign standards for rolled metals used in bridge building. Domestic standards contain elevated requirements to the reliability of rolled metals in terms of... 相似文献
2.
Nor?Azowa?IbrahimEmail author Faraj?Abu-Ilaiwi Mohamad?Zaki?Ab.?Rahman Mansor?B.?Ahmad Khairul?Zaman?M.?Dahlan Wan?Md?Zin?Wan?Yunus 《Journal of Polymer Research》2005,12(3):173-179
Grafting of acrylamide (AAm) onto oil palm empty fruits bunch fiber using hydrogen peroxide as initiator and methyl acrylate as comonomer was investigated. The amount of comonomer needed to make grafting of acrylamide possible was determined. The percentage of poly(acrylamide) and the comonomer in the final graft copolymer was estimated by elemental analysis. Results obtained indicated that methyl acrylate facilitated the incorporation of acrylamide monomer onto OPEFB. The reactivity ratios for both monomers were determined by using Fineman–Ross plot. The effects of reaction temperature and period as well as amount of the initiator, solvent, monomer and comonomer on the percentage of grafting at fixed amount of comonomer (11 mmol) were studied. Maximum percentage of grafting was achieved when the amount of initiator and solvent 3.98×10−3 mol and 50 mL respectively. The optimum reaction temperature was 50 ○C and the reaction period was 90 min. Highest percentage of grafting was 232% when 25.6 mmol of acrylamide was used under these optimum conditions. The presence of functional group in the grafted polymer is characterized by infrared spectroscopy and the surface morphology is observed by scanning electron microscopy. Thermoanalytic investigation on OPEFB and OPEFB-g-PAAM were carried out to evaluate the thermal stability and respective activation energy of the materials. 相似文献
3.
Inhibition of corrosion by a mixture of nonchromate pigments in organic coatings on galvanized steel 总被引:3,自引:0,他引:3
We consider several possible substitutes for toxic chromate pigments. Among the most promising compositions for the corrosion inhibition of galvanized steel with a protective organic coating, we should mention a mixture of phosphate- and calcium-containing pigments. As was shown earlier, such a mixture possesses a high efficiency under conditions of the corrosion of zinc and galvanized steel sheet; however, it is less efficient for the protection of carbon steels. This pigment mixture forms an adsorbed phosphate film on the metal and hinders the course of anodic and cathodic reactions. Zinc ions play an important role for obtaining a synergistic protective effect, increasing the coherence and decreasing the porosity of the deposited film. Traditional and local electrochemical methods (EIS and SVE) were used for studying the corrosion of galvanized steel with coatings in acid rain solution. The data obtained corroborated the high anticorrosive efficiency of a pigment mixture in an organic coating on galvanized steel. In addition, we established some specific features of its inhibiting action near defects in the coating.Translated from Fizyko-Khimichna Mekhanika Materialiv, Vol. 40, No. 3, pp. 74–80, May–June, 2004. 相似文献
4.
Reinforcement of graphene nanoplatelets on plasticized poly(lactic acid) nanocomposites: Mechanical,thermal, morphology,and antibacterial properties 下载免费PDF全文
Buong Woei Chieng Nor Azowa Ibrahim Wan Md Zin Wan Yunus Mohd Zobir Hussein Yoon Yee Then Yuet Ying Loo 《应用聚合物科学杂志》2015,132(11)
Plasticized poly(lactic acid) (PLA)‐based nanocomposites filled with graphene nanoplatelets (xGnP) and containing poly(ethylene glycol) (PEG) and epoxidized palm oil (EPO) with ratio 2 : 1 (2P : 1E) as hybrid plasticizer were prepared by melt blending method. The key objective is to take advantage of plasticization to increase the material ductility while preserving valuable stiffness, strength, and toughness via addition of xGnP. The tensile modulus of PLA/2P : 1E/0.1 wt % xGnP was substantially improved (30%) with strength and elasticity maintained, as compared to plasticized PLA. TGA analysis revealed that the xGnP was capable of acting as barrier to reduce thermal diffusion across the plasticized PLA matrix, and thus enhanced thermal stability of the plasticized PLA. Incorporation of xGnP also enhanced antimicrobial activity of nanocomposites toward Escherichia coli, Salmonella typhimurium, Staphylococcus aureus, and Listeria monocytogenes. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41652. 相似文献
5.
6.
Mechanisms of helium porosity formation in vanadium alloys as a function of the chemical composition
I. I. Chernov M. S. Staltsov B. A. Kalin O. S. Mezina Kyi Zin Oo V. M. Chernov 《Atomic Energy》2011,109(3):176-183
Transmission electron microscopy is used to study the effect of doping vanadium with titanium and iron on the formation of
helium porosity and gas swelling with ionic embedding of helium at 650°C. It is found that large facetted pores larger than
20 nm form in pure vanadium and vanadium exhibits the largest gas swelling. Doping with any amount of titanium (from 0.1 to
10%) and iron (from 1 to 10%) considerably decreases helium swelling. The titanium concentration has almost no effect on the
density of the bubbles. The effect of titanium doping of vanadium on the porosity parameters and swelling is of a nonmonotonic
character; in the case of iron doping of vanadium the bubble density increases and the bubble size increases monotonically
and swelling occurs with increasing iron concentration. The minimum sizes of the bubbles and swelling are observed in alloy
with the maximum titanium content V–10%Ti and the structural alloy V–4%Ti–Cr. 相似文献
7.
Summary
The synthesis and characterization of 4-[poly(propyleneoxy)propyloxy]-4'-bis[4-decyloxycarbonylbiphenyl-4'-biphenylcarboxylate]
with poly(propylene oxide) coil of seven (dimer-7), twelve (dimer-12), seventeen (dimer-17), twenty one (dimer-21) are described. Dimer-7 with short length of poly(propylene oxide) coil exhibits successively smectic C, smectic A and nematic mesophases, while
dimer-12 and dimer-17 with longer lengths of coils exhibit a bicontinuous cubic mesophase with Ia3d symmetry. Further increasing the length of coil, as in the case of dimer-21, suppresses liquid crystallinity.
Received: 22 February 2000/Revised version: 21 March 2000/Accepted: 29 March 2000 相似文献
8.
Study of morphology and gas separation properties of polysulfone/titanium dioxide mixed matrix membranes 下载免费PDF全文
Pourya Moradihamedani Nor Azowa Ibrahim Wan Md Zin Wan Yunus Nor Azah Yusof 《Polymer Engineering and Science》2015,55(2):367-374
Polysulfone (PSf)‐based mixed matrix membranes (MMMs) with the incorporation of titanium dioxide (TiO2) nanoparticles were prepared. Distribution and agglomeration of TiO2 in polymer matrix and also surface of membranes were observed by scanning electron microscopy, transmission electron microscopy, and energy dispersive X‐ray. Variation in surface roughness of MMMs with different TiO2 loadings was analyzed by atomic force microscopy. Physical properties of membranes before and after cross‐linking were identified through thermal gravimetric analysis. At low TiO2 loadings (≤3 wt%), both CO2 and CH4 permeabilities decreased and consequently gas selectivity improved and reached to 36.5 at 3 bar pressure. Interestingly, PSf/TiO2 3 wt% membrane did not allow to CH4 molecules to pass through the membrane and this sample just had CO2 permeability at 1 bar pressure. Gas permeability increased considerably at high filler contents (≥5 wt%) and CO2 permeance reached to 37.7 GPU for PSf/TiO2 7 wt% at 7 bar pressure. It was detected that, critical nanoparticle aggregation has occurred at higher filler loadings (≥5 wt%), which contributed to formation of macrovoids and defects in MMMs. Accordingly, MMMs with higher gas permeance and lower gas selectivity were prepared in higher TiO2 contents (≥5 wt%). POLYM. ENG. SCI., 55:367–374, 2015. © 2014 Society of Plastics Engineers 相似文献
9.
V. I. Pokhmurs’kyi V. I. Marukha I. M. Zin’ I. P. Hnyp L. M. Bilyi 《Materials Science》2011,46(5):573-582
For corrosion-electrochemical investigations, we have developed and manufactured original model concrete specimens-cells to
identify testing conditions for six reinforcement specimens. We have studied the polarization characteristics of model specimens
held in an environment of weak-acid rain, as well as the kinetics and frequency dependences of impedance characteristics.
It has been established that, for the rust protection of steel reinforcement, an inhibiting mixture containing equal quantities
of sodium molybdate and calcium nitrate is the most efficient. Its inhibiting efficiency is 10 to 12 times as high as the
efficiencies of its components separately, which demonstrates the synergetic effect. The mechanism of the synergetic protective
action of these inhibitors lies in passing two processes, which mutually strengthen each other, on the metal surface. The
addition of inhibitor to the polyurethane injection composition, applied for the repair of armored concrete structures, increases
the strength of adherence of reinforcement with concrete, subjected to the long-term action of a corrosive environment, as
compared with noninhibited. Using the synergetic effect in developing inorganic inhibiting mixtures, one can reduce significantly
the consumption of materials and improve substantially the manufacturability of injection polymeric compositions for the repair
of armored concrete structures of long-term operation. 相似文献
10.
Mobile ad hoc networks (MANETs) will play a vital role in civilian and military applications where users move around and share
information with each other. The movement of users varies depending on the environment, e.g. people may move randomly in different
directions (Random Waypoint and Gauss Markov mobility models); or walk, run and drive in two directions in the street (Manhattan
Mobility Model); or move as a group (Reference Point Group Mobility model). The interaction between mobility patterns and
routing protocols contributes significantly to vary the overall network performance. We build an analytical framework that
shows an analysis structure for the overall network performance test. In this framework, we first compare the properties of
the mobility models that are designated for MANETs. Second, we measure single path (proactive and reactive) and multipath
(proactive and reactive) routing protocols across the mobility models by tuning into TCP and CBR traffic individually. Finally,
we examine the performance of each routing protocol across mobility models and discuss the possibility of interaction between
them. Most of the previous findings only evaluate the impact of mobility models and single path routing protocols with CBR
traffic, whereas a significant finding of this study is that how the interaction between mobility models and single path and
multipath routing protocols varies depending on the usage of traffic (TCP and CBR). 相似文献