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Hydrodynamics,mass transfer,and photocatalytic phenol selective oxidation reaction kinetics in a fixed TiO2 microreactor 下载免费PDF全文
Matic Krivec Andrej Pohar Blaž Likozar Goran Dražić 《American Institute of Chemical Engineers》2015,61(2):572-581
Photocatalytic phenol dissociation was studied in a microreactor, with a TiO2 layer immobilized on the reactor inner walls. Experiments were conducted for various residence times, initial concentrations, pH values, and UV light irradiation intensities. The intermediates and products (catechol, hydroquinone, and resorcinol) were quantitatively investigated to determine the predominant reaction pathways for the investigated anatase catalyst. A three‐dimensional mathematical model was used to simulate the heterogeneous photocatalysis reaction conditions with Langmuir–Hinshelwood mechanism, considering the adsorption/desorption thermodynamic equilibria, and for kinetic parameter estimation via regression analysis. The effectiveness factor, Thiele modulus, and the correction function were calculated to determine the pore diffusion effects. The value of pH had the dramatic effect of lowering the reaction rate due to the competitive adsorption of hydroxide ions and protons on the catalyst surface. A phenol conversion of 79.5% was achieved at the residence time of 7.22 min, but without total mineralization. © 2014 American Institute of Chemical Engineers AIChE J, 61: 572–581, 2015 相似文献
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Tomas Prosek Andrej Nazarov Marie-Georges Olivier Catherine Vandermiers Dorothe Koberg Dominique Thierry 《Progress in Organic Coatings》2010
The effect of topcoat properties on the tendency of painted materials to blistering was studied. Six topcoats were applied on identical panels of hot-dip galvanized steel painted with a polyester primer. The tendency to blistering was assessed under the conditions of permanent condensation in a Q-panel condensation test at 60 °C. Internal tensile stress and stress development in organic coatings during temperature and relative humidity cycling were investigated by the cantilever curvature method. Although blisters originated from the metal/polymer interface, the extent of blistering was strongly influenced by the topcoat. Available data suggest that it may increase with the coating thickness, glass transition temperature (Tg) and thermal expansion properties. Connection was found between the internal tensile stress formed in topcoats during the paint film preparation and the extent of blistering. A hypothesis that stress-assisted interfacial bond hydrolysis was responsible for blister initiation is proposed. Other experiments suggested that local paint buckling over non-adherent sites can be caused by plastic deformation of the paint due to relief of compressive stress generated at elevated temperature or by ingress of water. 相似文献
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Schwudke D Oegema J Burton L Entchev E Hannich JT Ejsing CS Kurzchalia T Shevchenko A 《Analytical chemistry》2006,78(2):585-595
Data-dependent acquisition of MS/MS spectra from lipid precursors enables to emulate the simultaneous acquisition of an unlimited number of precursor and neutral loss scans in a single analysis. This approach takes full advantage of rich fragment patterns in tandem mass spectra of lipids and enables their profiling by complex (Boolean) scans, in which masses of several fragment ions are considered within a single logical framework. No separation of lipids is required, and the accuracy of identification and quantification is not compromised, compared to conventional precursor and neutral loss scanning. 相似文献
107.
The influence of alloying on the ignition and flammability was studied. One end of a cylindrical specimen was exposed to a free diffusion flame. Ignition required at least partial melting. Burning extinguished once the flame was withdrawn. Specimen tips of pure Mg, AZ61, and AZ91 ignited upon prolonged flame exposure. There was smouldering and delayed ignition for Mg-1Y. There was no ignition for Mg-5Y specimen tips, attributed to a protective surface oxide containing Y. The results indicate that (i) vigorous burning requires a continued supply of Mg vapour, and (ii) a critical alloy concentration is required to change ignition behaviour. 相似文献
108.
Variable gap penalty for protein sequence-structure alignment 总被引:1,自引:0,他引:1
Madhusudhan MS Marti-Renom MA Sanchez R Sali A 《Protein engineering, design & selection : PEDS》2006,19(3):129-133
The penalty for inserting gaps into an alignment between two protein sequences is a major determinant of the alignment accuracy. Here, we present an algorithm for finding a globally optimal alignment by dynamic programming that can use a variable gap penalty (VGP) function of any form. We also describe a specific function that depends on the structural context of an insertion or deletion. It penalizes gaps that are introduced within regions of regular secondary structure, buried regions, straight segments and also between two spatially distant residues. The parameters of the penalty function were optimized on a set of 240 sequence pairs of known structure, spanning the sequence identity range of 20-40%. We then tested the algorithm on another set of 238 sequence pairs of known structures. The use of the VGP function increases the number of correctly aligned residues from 81.0 to 84.5% in comparison with the optimized affine gap penalty function; this difference is statistically significant according to Student's t-test. We estimate that the new algorithm allows us to produce comparative models with an additional approximately 7 million accurately modeled residues in the approximately 1.1 million proteins that are detectably related to a known structure. 相似文献
109.
Kaicheng Zhang Andrej Vincze Ezzeldin Metwalli Jiyun Zhang Chao Liu Wei Meng Boxue Zhang Jingjing Tian Thomas Heumueller Zhiqiang Xie Junsheng Luo Andres Osvet Tobias Unruh Larry Lüer Ning Li Christoph J. Brabec 《Advanced functional materials》2023,33(42):2303455
Mixed lead and tin (Pb/Sn) hybrid perovskites exhibit a great potential in fabricating all-perovskite tandem devices due to their easily tunable bandgaps. However, the energy deficit and instability in Pb/Sn perovskite solar cells (PSCs) constrain their practical applications, which renders defect passivation engineering indispensable to develop highly efficient and long-term stable PSCs. Herein, the mechanisms of strain tailoring and defect passivation in Pb/Sn PSCs by 2D ligands are investigated. The 2D ligands include electroneutral cations with long alkyl chain (LAC), iodates with relatively short alkyl chain (SAC) and their mixtures. This study reveals that LAC ligands facilitate the relaxation of tensile strain in perovskite films while SAC ligands cause strain buildup. By mixing LAC/SAC ligands, tensile strain in perovskite films can be balanced which improves solar cell performance. PSCs with admixed β-guanidinopropionic acid (GUA)/phenethylammonium iodide (PEAI) exhibit enhanced open circuit voltage and fill factor, which is attributed to reduced nonradiative recombination losses in the bulk and at the interfaces. Furthermore, the operational stability of PSCs is slightly improved by the mixed 2D ligands. This work reveals the mechanisms of 2D ligands in strain tailoring and defect passivation toward efficient and stable narrow-bandgap PSCs. 相似文献
110.
Fabio Chizzolini Alexandra D. Kent Luiz F. M. Passalacqua Andrej Lupták 《Chembiochem : a European journal of chemical biology》2021,22(12):2098-2101
A mechanism of nucleoside triphosphorylation would have been critical in an evolving “RNA world” to provide high-energy substrates for reactions such as RNA polymerization. However, synthetic approaches to produce ribonucleoside triphosphates (rNTPs) have suffered from conditions such as high temperatures or high pH that lead to increased RNA degradation, as well as substrate production that cannot sustain replication. Previous reports have demonstrated that cyclic trimetaphosphate (cTmp) can react with nucleosides to form rNTPs under prebiotically-relevant conditions, but their reaction rates were unknown and the influence of reaction conditions not well-characterized. Here we established a sensitive assay that allowed for the determination of second-order rate constants for all four rNTPs, ranging from 1.7×10−6 to 6.5×10−6 M−1 s−1. The ATP reaction shows a linear dependence on pH and Mg2+, and an enthalpy of activation of 88±4 kJ/mol. At millimolar nucleoside and cTmp concentrations, the rNTP production rate is sufficient to facilitate RNA synthesis by both T7 RNA polymerase and a polymerase ribozyme. We suggest that the optimized reaction of cTmp with nucleosides may provide a viable connection between prebiotic nucleotide synthesis and RNA replication. 相似文献