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81.
The effect of conditioning dentin was investigated using ethyleneglycol bis(aminoethylether) tetraacetic acid (EGTA) and three proprietary agents containing ethylenediamine tetraacetic acid (EDTA), maleic acid and dipentaerythritol pentaacrylate phsophoric acid ester (PENTA). Ground dentin was treated with EGTA or one of the three proprietary agents. After adhering composite resin to treated surfaces, the shear bond strength (SBS) was determined with and without thermal stress. Scanning electron and atomic force microscopies were used to assess morphological effects of each of the agents, while low resolution X-ray photoelectron spectroscopy (XPS) was employed to evaluate elemental changes due to treatment. Mean bond strength was greatest for the PENTA-conditioned surfaces. EDTA and maleic acid demineralized the dentin surface while the agent containing PENTA produced an adherent surface film. The XPS survey showed a reduction in Ca and an increase in N for agents containing EGTA, EDTA and maleic acid, while a simultaneous reduction in both these species was observed for PENTA. EGTA did not improve adhesion for systems which were based on smear layer removal and substrate demineralization. For the PENTA-based system, which relied on the development of a molecular overlayer, EGTA degraded bond strength. 相似文献
82.
Thermophoresis is the movement of particles in a thermal gradient. It has the advantages of being simple to set up and to carry out. Here, it is used to prevent the recontamination of emitted particles smaller than 0.5 μm during the dry laser cleaning of particles not chemically bound to the substrate. Its use permits the efficiency of such dry laser cleaning to be greatly improved. A comparison between the thermophoretic and laminar flow techniques is carried out, showing that thermophoresis is more efficient. 相似文献
83.
A pulsed CO2 laser-based system, operating at a wavelength of 10.6 μm, was used as a cleaning tool to remove particles as small as 0.1 μm from hydrophilic, oxidized silicon surfaces. The laser beam served as a fast heating source to induce the explosive evaporation of a water film deposited on the particle-contaminated surface. The resulting explosive forces were high enough to expel particles from the surface efficiently. The contaminant particles used were 0.1 μm alumina, 0.1–0.2 μm silica, and 0.1 μm polystyrene latex. For each of these, the cleaning efficiency was monitored as a function of the laser fluence, the thickness of the deposited water film and the number of cleaning cycles. Whatever the nature of the particles, the cleaning efficiency was characterized by an upper limit of the energy density, determined to be 1.5 J/cm2, at which substrate damage occurred. At all lower laser fluences, the removal efficiency was particle-dependent. The thickness of the deposited water film was varied by changing the time of exposure of the surface to water vapor, the vapor flow being fixed at 4700 ml/min. An exposure time of 1.5 s was found to be the most effective. Increasing the number of cleaning cycles permitted the evaluation of the effect of the zeta potentials of the particles with respect to that of the surface. 相似文献
84.
Multilevel interconnect devices, made of alternating layers of a low permittivity polymer (e.g., Teflon AF1600TM) and a low resistivity metal (e.g., copper), are increasingly being used in microelectronics in order to decrease the RC signal transmission time delay. The mechanical stability of the multilevel interconnects is related to the adhesion developed at the metal-dielectric interface. Since Cu/Teflon AF1600 adhesion is moderate and may not satisfy the requirements of the microelectronics industry, new treatments of the fluoropolymer surface are needed to improve it. In this note, we present several surface modifications, such as the formation of reactive sites during intense X-ray exposure, and S- or N-grafting, activated by UV radiation in the presence of H2S and NH3; copper is well known to react with both thiols (R—SH) and amines (R—NH2) to form strong bonds. Both X-ray exposure and N-grafting lead to enhanced adhesion. 相似文献
85.
The usual procedure for shifting dynamic mechanical data, involving the construction of a master plot, was compared with a simpler, computer-implemented double shift procedure, which obviates the need for such a construction. Data reproducibility indicates that the double shift may successfully be shifted to frequencies greater than one decade to either side of the experimental range. 相似文献
86.
Phase and amplitude stability of an external cavity laser diodemodelocked by optoelectronic feedback
The authors have investigated the stability of an external cavity laser diode modelocked by optoelectronic feedback. The measured picosecond pulses at repetition frequencies of up to 1.2 GHz exhibit an amplitude and phase jitter of the order of a few percent, increasing with increasing repetition frequency 相似文献
87.
EL Murphy S Glynn K Watanabe J Fridey J Smith R Sacher D Wright G Schreiber N Luban 《Canadian Metallurgical Quarterly》1998,17(4):332-338
Toxoplasmosis is caused by the protozoan organism, Toxoplasma gondii. Infection with this organism primarily results from contact with infected cats and from ingestion of improperly cooked meat. Most adults with toxoplasmosis are asymptomatic. When symptoms are present, they typically resemble a mononucleosis or flulike illness. The diagnosis of toxoplasmosis in the pregnant adult is best made using serological techniques to detect IgM antibody and to document significant changes in the IgG antibody titer. Congenital toxoplasmosis usually occurs as a result of primary maternal infection. The most useful tests for confirmation of fetal infection are ultrasound examination, cordocentesis for detection of IgM-specific antibody, and amniocentesis for detection of toxoplasma DNA in amniotic fluid. Congenital toxoplasmosis can be treated with reasonable success by administration of antibiotics (spiramycin, sulfadiazine, and pyrimethamine) to the mother. In an effort to prevent acquisition of infection, pregnant women should be counseled to avoid contact with cat litter and improperly cooked beef, pork, or lamb. 相似文献
88.
Hofmann M. Baums D. Sacher J. Elsasser W. Schilling M. Idler W. Wunstel K. Zielinski E. Hildebrand O. 《Photonics Technology Letters, IEEE》1993,5(10):1135-1137
The first report on active modelocking of interferometric Y-lasers in an external cavity are reported. Pulse widths between 20 and 30 ps for 1.3-μm and 1.55-μm devices were achieved by modulation of the injection current synchronously to the external cavity roundtrip frequency. A time-bandwidth-product of 0.97 was determined for 1.55-μm devices 相似文献
89.
M. Di Renzo T. H. Ellis A. Domingue L. Bertrand E. Sacher I. Stangel 《The Journal of Adhesion》1994,47(1):115-121
The possible interaction between dentin and a proprietary dentin bonding agent (DBA), Gluma, was studied by Phase Photoacoustic FTIR. The determination of the existence and nature of a chemical bond between the DBA and the substrate can be of great importance in explaining the performance of these agents. Human dentin was treated by solutions of 2-hydroxyethyl methacrylate (HEMA), glutaraldehyde and a combination of both (Gluma Primer). Spectra of dentin samples treated with 35% and 100% HEMA as well as Gluma Primer show loss of both the hydroxyl (O-H stretch) and methylene (CH2 stretches) peaks from HEMA while other peaks are retained, even after thorough washing. This indicates a reaction between HEMA and the collagenous fraction of dentin. 相似文献
90.
Andreas Tiehm Natalie Schmidt Michael Stieber Frank Sacher Leif Wolf Heinz Hoetzl 《Water Resources Management》2011,25(4):1195-1203
In particular in arid regions the reuse of waste water and aquifer recharge is an important issue. Elimination of persistent emerging pollutants represents a key factor in integrated water resources management, and identifying suitable treatment processes to eliminate such compounds becomes inevitably necessary. It is the objective of this study (1) to assess the occurrence of emerging pollutants in the Jordan Valley and (2) to review and examine the biodegradability of selected key compounds. Among the most frequently detected compounds during a sampling campaign in 2007 were pharmaceutical residues such as carbamazepine, diclofenac, or naproxen, and X-ray contrast agents such as diatrizoic acid and iopromide, all typically found in Europe and the USA as well. To gain further insight into elimination processes, biodegradation studies were conducted with batch tests and flow-through soil columns under unsaturated, aerobic conditions. Results demonstrated biodegradation for pharmaceutical residues such as ibuprofen, diclofenac and bezafibrate. The degradation rate was faster in treated waste water as compared to raw waste water, most probably due to competing substrate consumption in raw waste water. The antiepileptic carbamazepine showed no degradation in the batch tests and only moderate removal during soil passage, probably due to sorption. The results of this study and previously published data emphasize the need for further studies under more defined conditions to elucidate the specific conditions under which biodegradation of emerging pollutants proceeds. 相似文献