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排序方式: 共有209条查询结果,搜索用时 33 毫秒
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32.
Effect of water content on product distribution in electrochemical chlorination of c-hexene in nitromethane solution was studied. Formation of 1-chloro, c-hexanone which occurs at the beginning of electrolysis is more effective at lower water content. 相似文献
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The optically active isomers of carbisocaine [1-methyl-2-diethylaminoethyl ester of 2-(n)-heptyloxycarbonilic acid] were prepared. The blocking activity of equimolar concentrations of the carbisocaine and its corresponding enantiomers was tested on isolated rat sciatic nerves. There were no significant differences between the anesthetic action of racemic form and enantiomers, however, lower activity for the (--)-enantiomer was observed. The results may indicate negligible stereoselectivity of action of highly lipophilic local anesthetic carbisocaine in the excitable membrane. 相似文献
35.
Min Yan Attila Csík Chun-Chuan Yang Yun Luo Tamás Fodor Shinn-Jyh Ding 《Ceramics International》2018,44(16):19665-19671
Veneering ceramics should be strongly bonded to zirconia core in order to achieve successfully long-term clinical practice. Indeed, to pursue the high zirconia core–veneering ceramic bonding is still a concerned issue. In this regard, this study was to treat zirconia surface using a 3?wt% Si3N4 solution in 4?M NaOH and to investigate the effect of soaking time (5, 10, and 20 days) on the surface properties of zirconia and shear bond strength between zirconia and veneering ceramics. The residual veneering ceramics on zirconia surfaces and failure modes were also examined after fracture. The results showed that the phase composition of zirconia before and after surface modification was not changed. The elemental mapping and depth profiling consistently revealed the soaking-time-dependent Si content on the zirconia surface. The surface roughness of zirconia was significantly (P?<?0.05) increased with the increasing soaking time. When zirconia was treated for 10 days, the shear bond strength value of 27.4?MPa was significantly (P?<?0.05) higher than the control (18.6?MPa), associated with greater remaining amounts of veneering ceramics on the zirconia surface. The failure mode of the treated zirconia was almost the mixed failure. On the basis of the data, surface modification using Si3N4 in NaOH solution for zirconia core could be a simple and effective method for enhancing the veneering ceramic–zirconia bonding. 相似文献
36.
Máté Szabados Zsófia Csákó Bohumil Kotlík Helena Kazmarová Anna Kozajda Anja Jutraz Andreja Kukec Peter Otorepec Arianna Dongiovanni Andrea Di Maggio Stefano Fraire Tamás Szigeti 《Indoor air》2021,31(4):989-1003
The indoor air quality (IAQ) was investigated in sixty-four primary school buildings in five Central European countries (Czech Republic, Hungary, Italy, Poland, and Slovenia). The concentration of volatile organic compounds, aldehydes, PM2.5 mass, carbon dioxide, radon, as well as physical parameters were investigated during the heating period of 2017/2018. Significant differences were identified for the majority of the investigated IAQ parameters across the countries. The median indoor/outdoor ratios varied considerably. A comprehensive evaluation of IAQ in terms of potential health effects and comfort perception was performed. Hazard quotient values were below the threshold value of 1 with one exception. In contrast, 31% of the school buildings were characterized by hazard index values higher than 1. The maximum cumulative ratio approach highlighted that the concern for non-carcinogenic health effects was either low or the health risk was driven by more substances. The median excess lifetime cancer risk values exceeded the acceptable value of 1 × 10−6 in the case of radon and formaldehyde. PM2.5 mass concentration values exceeded the 24 h and annual guideline values set by the World Health Organization in 56 and 85% of the cases, respectively. About 80% of the schools could not manage to comply with the recommended concentration value for carbon dioxide (1000 ppm). 相似文献
37.
Belay A Ruzgas T Csöregi E Moges G Tessema M Solomon T Gorton L 《Analytical chemistry》1997,69(17):3471-3475
An analysis system is described for the determination of the neurotoxin β-N-oxalyl-l-α,β-diaminopropionic acid (β-ODAP). The system is based on liquid chromatographic separation of β-ODAP from interfering amino acids on an anion exchange column coupled with an amperometric enzyme electrode for the registration of β-ODAP. The electrode is based on a graphite rod modified with an Os(2+/3+) redox polymer cross-linked with l-glutamate oxidase and horseradish peroxidase. This LC-bienzyme electrode analytical system enabled monitoring of as low as 4 μM β-ODAP (injection volume 100 μL). The β-ODAP content in real grass pea samples was measured to range between 3.3 and 5.2 g kg(-)(1) in dry grass pea. 相似文献
38.
Stephan Kastner Anne-Kathrin Dietel Florian Seier Shaunak Ghosh Daniel Weiß Oliwia Makarewicz Andrea Csáki Wolfgang Fritzsche 《Small (Weinheim an der Bergstrasse, Germany)》2023,19(33):2207953
The development of rapid, simple, and accurate bioassays for the detection of nucleic acids has received increasing demand in recent years. Here, localized surface plasmon resonance (LSPR) spectroscopy for the detection of an antimicrobial resistance gene, sulfhydryl variable β-lactamase (blaSHV), which confers resistance against a broad spectrum of β-lactam antibiotics is used. By performing limit of detection experiments, a 23 nucleotide (nt) long deoxyribonucleic acid (DNA) sequence down to 25 nm was detected, whereby the signal intensity is inversely correlated with sequence length (23, 43, 63, and 100 nt). In addition to endpoint measurements of hybridization events, the setup also allowed to monitor the hybridization events in real-time, and consequently enabled to extract kinetic parameters of the studied binding reaction. Performing LSPR measurements using single nucleotide polymorphism (SNP) variants of blaSHV revealed that these sequences can be distinguished from the fully complementary sequence. The possibility to distinguish such sequences is of utmost importance in clinical environments, as it allows to identify mutations essential for enzyme function and thus, is crucial for the correct treatment with antibiotics. Taken together, this system provides a robust, label-free, and cost-efficient analytical tool for the detection of nucleic acids and will enable the surveillance of antimicrobial resistance determinants. 相似文献
39.
Metal nanostructures are promising novel labels for microarray-based biomolecular detection. Additional silver deposition on the surface-bound labels strongly enhances the sensitivity of the system and can lead to continuous metal areas, which enable an electrical readout especially for simple and robust point-of-care analyses. In this paper, atomic force microscopy (AFM) was used to study different routes of metal deposition on labelled DNA-DNA duplexes in electrode gaps. Besides the well-established metal-induced silver enhancement, a recently introduced enzymatic silver deposition was applied and proved highly specific. The in situ characterization was especially focused on the nanostructure percolation-the moment at which the nanoparticulate film becomes continuous and electrically conducting. The formation of conducting paths, continuous from one electrode to the other, was followed by complementary electrical measurements. Thereby, a percolation threshold was determined for the surface coverage with metal structures, i.e.?the required metallized area to achieve conductance. Complementary graphic simulations of the growth process and graphic 'conductance measurements' were developed and proved suitable to model the metal deposition and electrical detection. This may help to design electrode arrays and identify optimum enhancement parameters (required seed concentration and shell growth) as well as draw quantitative conclusions on the existing label (i.e.?analyte) concentration. 相似文献
40.
Zsoldos-Mády V Csámpai A Szabó R Mészáros-Alapi E Pásztor J Hudecz F Sohár P 《ChemMedChem》2006,1(10):1119-1125
Some new glycosides of 3-ferrocenyl-1-(4'-hydroxyphenyl)-prop-2-en-1-one were prepared and transformed into the corresponding pyrazoline and pyrazole derivatives. Using methyl-hydrazine, formation of regioisomers was observed. DDQ was found to be a mild and efficient reagent for the pyrazoline-pyrazole dehydroaromatization process. The structure of the new compounds was proved by IR and NMR spectroscopy. The in vitro antitumor activity of the substances was investigated against human leukemia (HL-60) cells by the MTT method. Among these new compounds some chalcone derivatives (3 a, 3 b, 5 a, and 5 b) showed attractive in vitro antitumor effects on human leukemia cells. These molecules contained ferrocenyl moieties and a p-hydroxy-phenolic ring or a size-independent apolar substitution of that. 相似文献