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31.
The chemical polymerization of aniline in anhydrous medium was investigated using periodic acid, H5IO6 as an oxidant. This is the first time that H5IO6 has been used as an oxidant in the chemical synthesis of conductive polymers. The product was characterized by FTIR, UV–vis spectroscopies, scanning electron microscope (SEM), energy dispersive X-ray (EDX) spectroscopy, thermogravimetric (TG) analysis, and electrical conductivity measurements. EDX and thermogravimetric analysis showed that Pani includes ClO4− and iodine or iodide ion as dopants. Electrical conductivity of polyaniline with H5IO6 was measured as 100 S cm−1. H5IO6 oxidant produces first IO3− and then I2. Therefore, it could ensure both oxidation of aniline by IO3− and then doping polyaniline with I2, without any residual oxidant contamination. I2, which is a well known extrinsic dopant, was produced intrinsically in this study. Thus, H5IO6 was found to be an effective oxidant material for the chemical polymerization of aniline. 相似文献
32.
Evaluation of surface topography changes in three NiTi file systems using rotary and reciprocal motion: An atomic force microscopy study 下载免费PDF全文
Aim: To evaluate the surface topography changes in three nickel‐titanium (NiTi) file systems using either rotary or reciprocal motion using atomic force microscopy (AFM), and to determine the effect of scanning area on the AFM results in this study. Methodology: Five points on a F2 Protaper file, R25 Reciproc file, and a Primary file from WaveOne systems were scanned preoperatively in 1 × 1 and 5 × 5 µm2 with an AFM device that can scan an intact (not sectioned) file. One standardized resin block was used for each instrument, according to the manufacturer's recommendations. Points were re‐scanned postoperatively using the same AFM and settings. Root‐mean‐square (RMS) and roughness average (Ra) values were obtained. The preoperative and postoperative surface topographies were compared separately in terms of RMS and Ra values. The surface topography change scores were analyzed using Kruskal–Wallis and Mann–Whitney U tests using a 0.10 significance level. Results: There were no significant differences preoperatively among the NiTi file systems in 1 × 1 or 5 × 5 µm2 areas. Postoperatively, the WaveOne Primary had more surface irregularities (significant for 5 × 5 µm2 scan in Ra evaluation). Conclusions: Three‐dimensional AFM images of instrument surfaces showed topographic irregularities preoperatively and postoperatively. AFM results differ depending on the scanning area and file used. Microsc. Res. Tech. 77:177–182, 2014. © 2013 Wiley Periodicals, Inc. 相似文献
33.
Nihan Kaya Ferhat Arslan Zeynep Yildiz Uzun 《Fullerenes, Nanotubes and Carbon Nanostructures》2020,28(10):769-780
AbstractIn this study, hazelnut shell and walnut shell which are the agricultural wastes existent abundantly in many countries were pyrolyzed at different temperatures in the temperature range of 400–700?°C in order to optimize the physicochemical properties of biochars. The biochars with large surface area were used to removal of lead (Pb2+) ions, one of the most important heavy metal pollutant, from aqueous solutions. The characterization of raw biomass and also biochars produced by pyrolysis were performed using FT-IR, BET, SEM, partial and elemental analysis techniques. In order to determine the adsorption characteristics of both biochars, batch adsorption experiments were carried out under different experimental conditions. The optimum conditions were determined by investigating the effect of adsorption parameters (initial heavy metal concentration, temperature, adsorbent amount, pH, contact time and mixing speed) for efficient removal of Pb2+ ions from aqueous solution. The experimental results were investigated in terms of Langmuir, Freundlich and Temkin isotherm models. Together with the calculated thermodynamic parameters, the adsorption mechanism was tried to be explained. In order to determine the kinetic model of the adsorption process, the experimental data were applied to pseudo first-order, pseudo second-order and intra-particle diffusion model, and the model constants were investigated. 相似文献
34.
R. Ertan Anli Nilüfer Vural Simge Demiray Behic Mert 《Journal of the Institute of Brewing》2006,112(3):267-274
The biogenic amine content of beers available in Turkey, both domestic production and imported products, was investigated. A total of 17 domestic and 13 imported beers were evaluated in terms of 8 different biogenic amines (histamine, tyramine, spermine, spermidine, 2‐phenylethylamine, putrescine, tryptamine and cadaverine). HPLC methodology with pre‐column derivatization and photodiode array detection after derivatization with dansyl chloride was used for quantification. In addition, the evolution of important amines such as histamine, tyramine, putrescine and cadaverine were investigated during different storage conditions by response surface methodology. The results indicated that both storage temperature and storage time were important factors affecting biogenic amine content. Histamine and putrescine increased during storage, but then decreased after reaching a maximum level after six weeks. With the biogenic amines tyramine and cadaverine, the amounts increased during the entire storage period. At higher storage temperatures, the formation of biogenic amines increased. 相似文献
35.
The aim of this study was to investigate the effect of using dynamic geometry software (GeoGebra) on the eighth-grade students' conceptual understanding and the retention of learning regarding linear equations and slope. In this study, a quasi-experimental design with pre-test, post-test and delayed post-test was employed. This study was conducted with 52 eighth-grade Turkish students (experimental group, n = 25; control group, n = 27). While GeoGebra software-supported instruction was carried out in the experimental group, textbook-based direct instruction was continued in the control group. Data were collected with the conceptual understanding test (CUT) which consists of 38 questions including open-ended, multiple choice and fill in the blanks. CUT was applied to the experimental and control groups as a pre-test and post-test at both the beginning and the end of the instruction, respectively. Seven weeks after the instruction, CUT was applied to both groups as a retention test. Data were analysed through SPSS 17.0 statistical software by using a t-test and ANCOVA test. It was indicated in the study results that GeoGebra software-supported instruction for eighth-grade students regarding linear equations and slope did significantly improve both their conceptual understanding and retention of learning in comparison to textbook-based direct instruction. 相似文献
36.
Serdal Terzi Mustafa Karaşahin Süleyman Gökova Mustafa Tahta Nihat Morova İsmail Uzun 《Neural computing & applications》2013,23(3-4):989-997
The core drilling method has often been used to determine the current status of asphalt concretes. However, this method is destructive so causes damage to the asphalt concretes. In addition, this method causes localized points of weakness in the asphalt concretes and is time consuming. In recent years, non-destructive testing methods have been used for pavement thickness estimation, determination of elasticity modulus, and density and moisture measurements. In this study, the above-mentioned non-destructive and destructive tests with data obtained by applying the Marshall stability to the same asphalt concretes were estimated using the artificial neural networks approach. 相似文献
37.
Sevgi Asliyuce Lokman Uzun Ridvan Say Adil Denizli 《Reactive and Functional Polymers》2013,73(6):813-820
In this study, we applied the epitope imprinting approach to prepare molecularly imprinted monolithic cryogels for immunoglobulin G (IgG) recognition. In this respect, we imprinted Fab fragments of IgG molecules instead of intact protein molecules via two different non-covalent interactions. In the first approach, we directly coordinated Fab fragments with N-methacryloyl-L-histidine (MAH), polymerizable derivative of L-histidine, but for the second, we used cupric ions [Cu(II)] as mediator between MAH and Fab fragments. The monolithic cryogels were characterized by Fourier transform infrared (FTIR) spectroscopy, swelling test, and scanning electron microscopy. Then, the monolithic cryogels were used for Fab fragment adsorption from aqueous solution while evaluating the factors such as pH and Fab fragment concentration affecting on adsorption process in continuous set-up. After that, monolithic cryogels were used for IgG adsorption by varying pH, IgG concentration, flowrate, and temperature in appropriate ranges. Maximum IgG adsorption capacities were determined as 32.4 mg/g and 49.0 mg/g for directly coordinated cryogel (MIPDirect) and Cu(II) assisted cryogel (MIPCu(II) assisted), respectively. Non-imprinted monolithic cryogels were also prepared for control purposes. In addition to Fab fragments and IgG molecules, albumin and Fc fragment of IgG molecules were used as competitor biomolecules in order to investigate the selectivity gained by imprinting process. Relative selectivity constants were calculated as 1.47, 2.64 and 3.89 for MIPDirect and 2.90, 8.98, and 11.51 for MIPCu(II) assisted for Fab/IgG, Fab/Fc, and Fab/albumin as biomolecule pairs, respectively. The desorption efficiency and reusability of MIPCu(II) assisted cryogel were better than that of MIPDirect. The results reported here showed that the metal ion assistance improved the selectivity features of the imprinted cryogels and allowed to study under milder conditions with enhanced adsorptive properties. 相似文献
38.
Yusuf Ziya Akpinar Ismail Hakki Uzun Betul Yilmaz Numan Tatar 《Journal of Adhesion Science and Technology》2013,27(11):1096-1106
Objective: The purpose of this preliminary clinical study was to evaluate the effect of novel impression valve system (IVS) on adhesion force of different impression materials to edentulous maxilla. Background data: Impression materials and techniques have an important role in complete denture success. During the functional impression with an individual impression tray (IIT), high adhesive forces exist between edentulous ridge and impression material. Removing the IIT from the mouth with minimal force provides the most accurate and non-deformed impression. Materials and methods: This study included twenty maxillary edentulous patients (n?=?20). Patients who had palatal torus, anatomic undercut, gagging reflex, and flabby ridges were excluded from the study. The age range of the participants was 55–70. All patients gave written informed consent. Two impression materials – zinc oxide eugenol (ZOE) and alginate – were used as experimental material. The digital dynamometer was used to determine the adhesion force of impression materials with and without IVS to edentulous maxilla. The mean values of the adhesion forces were analyzed using the Wilcoxon signed-ranks test (α = 0.05). Results: The effect of IVS on adhesion force was found to be statistically significant (p < 0.05). There were also statistical differences between the ZOE and alginate groups (p < 0.05). Conclusions: The IVS is useful to remove the functional impression from the mouth without any deformation and detaching in cases which high adhesive force occurs. 相似文献
39.
Two donor-acceptor-donor types of π-conjugated monomers were synthesized using Stille coupling reaction. Both monomers were found to produce electroactive polymers upon electrochemical oxidation. The effects of different donor substituents on the polymers' electrochemical and spectroelectrochemical properties were examined. Optical characterization revealed that the band gaps of poly(2-(2,3-dihydrobenzo[b][1,4]dioxin-6-yl)-3-(2,3-dihydrobenzo[b][1,4]dioxin-7-yl)-5,8-di(thiophen-2-yl)quinoxaline) (PDBQTh) and poly(2-(2,3-dihydrobenzo[b][1,4]dioxin-6-yl)-3-(2,3-dihydrobenzo[b][1,4]dioxin-7-yl)-5-(2,3-dihydrothieno[3,4-b][1,4]dioxin-5-yl)-8-(2,3-dihydrothieno[3,4-b][1,4]dioxin-7-yl)quinoxaline) (PDBQEd) were 1.5 eV and 1.3 eV, respectively. PDBQEd reveals two distinct absorption bands as expected for this type of donor-acceptor-donor polymer at 423 and 738 nm, while PDBQTh has a single absorption band at 630 nm. The colorimetry analysis revealed that while PDBQTh has a blue color, PDBQEd showed a green color in the neutral state. PDBQEd revealed reversible n-doping. 相似文献
40.
In this study, we focused on the preparation and characterization of poly(ethylene glycol) (PEG)/poly(methyl methacrylate) (PMMA) blends as novel form‐stable phase‐change materials (PCMs) for latent‐heat thermal energy storage (LHTES) applications. In the blends, PEG acted as a PCM when PMMA was operated as supporting material. We subjected the prepared blends at different mass fractions of PEG (50, 60, 70, 80, and 90% w/w) to leakage tests by heating the blends over the melting temperature of the PCM to determine the maximum encapsulation ratio without leakage. The prepared 70/30 w/w % PEG/PMMA blend as a form‐stable PCM was characterized with optical microscopy and Fourier transform infrared spectroscopy. The thermal properties of the form‐stable PCM were measured with differential scanning calorimetry (DSC). DSC analysis indicated that the form‐stable PEG/PMMA blend melted at 58.07°C and crystallized at 39.28°C and that it had latent heats of 121.24 and 108.36 J/g for melting and crystallization, respectively. These thermal properties give the PCMs potential LHTES purposes, such as for solar space heating and ventilating applications in buildings. Accelerated thermal cycling tests also showed that the form‐stable PEG/PMMA blend as PCMs had good thermal reliability and chemical stability. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 相似文献