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51.
The sciatic nerve of rats fed sunflower oil (6 mg 18∶3n−3/100 g of diet) presented dramatic alterations in the long chain
polyunsaturated fatty acids in comparison with those fed soy oil (130 mg 18∶3n−3/100 g of diet). In both 15-day-old and 60-day-old
animals fed sunflower oil, 22∶6n−3 (cervonic acid) was fourfold less, 22∶5n−6 was 10-fold greater; adrenic acid (22∶4n−6)
was slightly greater and arachidonic acid (20∶4n−6) was close to that in rats fed soy oil. The percentage distribution of
total polyunsaturated fatty acids as well as the individual saturated and monounsaturated fatty acids were the same in both
groups.
When the sunflower oil-fed animals were switched to a soy oil-containing diet for either 15 or 60 days, the percentage distribution
of 22∶6n−3 increased slowly to reach the control value 2.5 months later. Conversely 22∶5n−6 decreased slowly. The decay of
22∶5n−6 was more rapid than the increase of 22∶6n−3. 相似文献
52.
Potié A Baron T Dhalluin F Rosaz G Salem B Latu-Romain L Kogelschatz M Gentile P Oehler F Montès L Kreisel J Roussel H 《Nanoscale research letters》2011,6(1):187-9
The growth of semiconductor (SC) nanowires (NW) by CVD using Au-catalyzed VLS process has been widely studied over the past few years. Among others SC, it is possible to grow pure Si or SiGe NW thanks to these techniques. Nevertheless, Au could deteriorate the electric properties of SC and the use of other metal catalysts will be mandatory if NW are to be designed for innovating electronic. First, this article's focus will be on SiGe NW's growth using Au catalyst. The authors managed to grow SiGe NW between 350 and 400°C. Ge concentration (x) in Si1-xGex NW has been successfully varied by modifying the gas flow ratio: R = GeH4/(SiH4 + GeH4). Characterization (by Raman spectroscopy and XRD) revealed concentrations varying from 0.2 to 0.46 on NW grown at 375°C, with R varying from 0.05 to 0.15. Second, the results of Si NW growths by CVD using alternatives catalysts such as platinum-, palladium- and nickel-silicides are presented. This study, carried out on a LPCVD furnace, aimed at defining Si NW growth conditions when using such catalysts. Since the growth temperatures investigated are lower than the eutectic temperatures of these Si-metal alloys, VSS growth is expected and observed. Different temperatures and HCl flow rates have been tested with the aim of minimizing 2D growth which induces an important tapering of the NW. Finally, mechanical characterization of single NW has been carried out using an AFM method developed at the LTM. It consists in measuring the deflection of an AFM tip while performing approach-retract curves at various positions along the length of a cantilevered NW. This approach allows the measurement of as-grown single NW's Young modulus and spring constant, and alleviates uncertainties inherent in single point measurement. 相似文献
53.
Fabienne Levi-Acobas Dr. Pascal Röthlisberger Dr. Ivo Sarac Dr. Philippe Marlière Prof. Dr. Piet Herdewijn Dr. Marcel Hollenstein 《Chembiochem : a European journal of chemical biology》2019,20(24):3032-3040
The formation of artificial metal base pairs is an alluring and versatile method for the functionalization of nucleic acids. Access to DNA functionalized with metal base pairs is granted mainly by solid-phase synthesis. An alternative, yet underexplored method, envisions the installation of metal base pairs through the polymerization of modified nucleoside triphosphates. Herein, we have explored the possibility of using thiolated and pKa-perturbed nucleotides for the enzymatic construction of artificial metal base pairs. The thiolated nucleotides S2C, S6G, and S4T as well as the fluorinated analogue 5FU are readily incorporated opposite a templating S4T nucleotide through the guidance of metal cations. Multiple incorporation of the modified nucleotides along with polymerase bypass of the unnatural base pairs are also possible under certain conditions. The thiolated nucleotides S4T, S4T, S2C, and S6G were also shown to be compatible with the synthesis of modified, high molecular weight single-stranded (ss)DNA products through TdT-mediated tailing reactions. Thus, sulfur-substitution and pKa perturbation represent alternative strategies for the design of modified nucleotides compatible with the enzymatic construction of metal base pairs. 相似文献
54.
Dr. Wojciech Schönemann Dr. Jonathan Cramer Tobias Mühlethaler Dr. Brigitte Fiege Marleen Silbermann Dr. Said Rabbani Dr. Philipp Dätwyler Dr. Pascal Zihlmann Dr. Roman P. Jakob Dr. Christoph P. Sager Dr. Martin Smieško Dr. Oliver Schwardt Prof. Dr. Timm Maier Prof. Dr. Beat Ernst 《ChemMedChem》2019,14(7):749-757
Antimicrobial resistance has become a serious concern for the treatment of urinary tract infections. In this context, an anti-adhesive approach targeting FimH, a bacterial lectin enabling the attachment of E. coli to host cells, has attracted considerable interest. FimH can adopt a low/medium-affinity state in the absence and a high-affinity state in the presence of shear forces. Until recently, mostly the high-affinity state has been investigated, despite the fact that a therapeutic antagonist should bind predominantly to the low-affinity state. In this communication, we demonstrate that fluorination of biphenyl α-d -mannosides leads to compounds with perfect π–π stacking interactions with the tyrosine gate of FimH, yielding low nanomolar to sub-nanomolar KD values for the low- and high-affinity states, respectively. The face-to-face alignment of the perfluorinated biphenyl group of FimH ligands and Tyr48 was confirmed by crystal structures as well as 1H,15N-HSQC NMR analysis. Finally, fluorination improves pharmacokinetic parameters predictive for oral availability. 相似文献
55.
Clment De Saint Jores Clment Brandel Najla Gharbi Morgane Sanselme Pascal Cardinael Grard Coquerel 《化学工程与技术》2019,42(7):1500-1504
Since eutomer and distomer show different biological effects, access to pure enantiomers is essential. Preferential enrichment is a relatively new process of chiral resolution developed in the 90s. Extension of its scope was attempted with tryptophan ethyl ester hydrochloride. This salt meets one of the most important requirements for preferential enrichment, namely, a larger solubility for the pure enantiomers with reference to the racemic compound. But, due to the absence of a solid solution, this salt cannot perform preferential enrichment. This impossibility was endorsed by semi‐empirical molecular modeling. 相似文献
56.
Vincent Gernigon Mohammed A. Chekroun Arnaud Cockx Pascal Guiraud Jrme Morchain 《化学工程与技术》2019,42(8):1663-1669
The microalgae growth rate in photobioreactors responds with inertia to light stimuli. Here, light variations experienced by the algae are accessed through a coupling of an irradiance field calculation and a Lagrangian particle tracking. The response of algae to fluctuating light is then described by a relaxation model involving a single time constant, the value of which is identified from published data. The overall growth rate is calculated as the sum of individual growth rates of all particles. Instantaneous adaptation and full integration asymptotic behaviors are recovered whilst a finite time constant reveals that the overall growth rate is dependent both on mixing and light distribution. This methodology thus quantitatively relates the design parameters to the photobioreactor performance. 相似文献
57.
Raphaël Faure Fabrice RossignolClaire Bonhomme Alexandre MaîtreGrégory Etchegoyen Pascal Del GalloDaniel Gary 《Journal of the European Ceramic Society》2011,31(3):303-312
The manufacture and the characterisation of alumina foams as alternative catalysts supports for industrial steam reforming processes are presented here. The possibility of use of alumina foams as catalysts supports in such processes is evaluated by studying their resistance toward mechanical and chemical stresses. The alumina foams produced are characterised owing to their processing parameters (slurry infiltration, sintering temperature, template pore size). Their ability to work in hydrothermal atmosphere is assessed by characterising the evolution of microstructures and mechanical strengths upon aging. Thermodynamic studies of the stability of alumina in industrial steam reforming working conditions are performed and correlated to the experiments to demonstrate the stability of such a system. 相似文献
58.
Despite the powerful spectroscopic information it provides, Nuclear Magnetic Resonance (NMR) spectroscopy suffers from a lack of sensitivity, especially when dealing with nuclei other than protons. Even though NMR can be applied in a straightforward manner when dealing with abundant protons of organic molecules, it is very challenging to address biomolecules in low concentration and/or many other nuclei of the periodic table that do not provide as intense signals as protons. Dynamic Nuclear Polarization (DNP) is an important technique that provides a way to dramatically increase signal intensities in NMR. It consists in transferring the very high electron spin polarization of paramagnetic centers (usually at low temperature) to the surrounding nuclear spins with appropriate microwave irradiation. DNP can lead to an enhancement of the nuclear spin polarization by up to four orders of magnitude. We present in this article some basic concepts of DNP, describe the DNP apparatus at EPFL, and illustrate the interest of the technique for chemical applications by reporting recent measurements of the kinetics of complexation of 89Y by the DOTAM ligand. 相似文献
59.
Self-assembled monolayers (SAMs) of organic molecules are of exceptional technological importance since they represent a convenient, flexible, and simple system for tuning the chemical and physical properties of surfaces. The fine control of surface properties is directly dependent on the structure of mixed SAMs which is difficult to characterize at the nanoscale with usual techniques such as scanning probe microscopies. In this study, we report on a general method to investigate at the nanoscale the structure of molecular patterns which consist in SAMs of two components. Iron oxide nanoparticles (NPs) have been used as probing agents to study indirectly the structure of mixed SAMs. Mixed SAMs were prepared by the replacement of mercaptododecane (MDD) adsorbed by mercaptoundecanoic acid (MUA) molecules on gold substrates. Therefore, the SAM surface displays both chelating carboxylic terminal groups and non-chelating methylene terminal groups. As NPs have been previously demonstrated to specifically interact with carboxylic acid groups, the increasing density in NPs was correlated with the evolution of the COOH/CH(3) terminal groups ratio. Therefore the structure of mixed SAMs was studied indirectly as well as the kinetic of the replacement reaction and its mechanism. With this aim, we took advantage of the SPR properties of the gold substrate and of the high refractive index of iron oxide nanoparticles to follow their assembling on mixed SAMs as a time resolved study. The high sensitivity and tuning of the SPR signal over a wide range of wavelengths are correlated with the NP density. Furthermore, SEM combined with image analysis has allowed studying the replacement rate of MDD by MUA in SAMs. We took also advantages of the magnetic properties of NPs to evaluate qualitatively the replacement of thiol molecules. 相似文献
60.
Pascal Laurent Hary Razafindralambo Bernard Wathelet Christophe Blecker Jean-Paul Wathelet Michel Paquot 《Journal of surfactants and detergents》2011,14(1):51-63
Short chemical syntheses were developed to produce a new set of surfactants from uronic acids derived from widely available
raw materials. Three different strategies were used to synthesize uronic amide derivatives, the structures of which were totally
characterized by spectrometric methods (IR, MS, 1H-RMN and 13C-RMN). The best one, using an acid chloride as the synthetic intermediate, furnished the expected amides as a mixture of
anomers in 46–58% global yield. Surface-active properties (CMC, γcmc, Γmax, A
min) of homologous series of uronic acid N-alkylamides from C8 to C18 were also assessed. In general, these sugar-based surfactants exhibited good surface-activities,
and appeared as valuable nonionic surfactants compared to octylphenol 9–10 ethylene oxide condensate, the most well-known
nonionic surfactant. Increasing the alkyl chain length influenced the CMC values for both glucuronic and galacturonic N-alkylamide derivatives. The galacturonic N-alkylamides decreased γcmc at slower values than their counterpart’s glucuronic N-alkylamides. 相似文献