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71.
Polymerization shrinkage of methacrylate‐based dental composites remains a major concern in restorative dentistry. Cyclic monomers that undergo ring‐opening polymerization are known to exhibit reduced polymerization shrinkage compared to methacrylates. In this article, the synthesis of four crosslinking 1,1‐disubstituted 2‐vinylcyclopropanes bearing rigid spacers is described. These monomers were synthesized by esterification of 1‐ethoxycarbonyl‐2‐vinylcyclopropane‐1‐carboxylic acid with the corresponding diols. The photopolymerization kinetics of these monomers was investigated by photo‐differential scanning calorimeter using bis(4‐methoxybenzoyl)diethylgermane as the photoinitiator. The synthesized vinylcyclopropanes (VCPs) were shown to be more reactive than the frequently used reactive diluent triethylene glycol dimethacrylate. Composites based on these VCPs showed good mechanical properties and exhibited a significantly reduced volumetric shrinkage and shrinkage stress compared to a corresponding dimethacrylate‐based restorative material. This work highlights the excellent potential of VCPs as alternatives to methacrylates in the development of low‐shrinkage dental composites. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45577. 相似文献
72.
Design of S‐Allylcysteine in Situ Production and Incorporation Based on a Novel Pyrrolysyl‐tRNA Synthetase Variant 下载免费PDF全文
Dr. Matthias P. Exner Tilmann Kuenzl Tuyet Mai T. To Zhaofei Ouyang Sergej Schwagerus Michael G. Hoesl Prof. Dr. Christian P. R. Hackenberger Prof. Dr. Marga C. Lensen Prof. Dr. Sven Panke Prof. Dr. Nediljko Budisa 《Chembiochem : a European journal of chemical biology》2017,18(1):85-90
The noncanonical amino acid S‐allyl cysteine (Sac) is one of the major compounds of garlic extract and exhibits a range of biological activities. It is also a small bioorthogonal alkene tag capable of undergoing controlled chemical modifications, such as photoinduced thiol‐ene coupling or Pd‐mediated deprotection. Its small size guarantees minimal interference with protein structure and function. Here, we report a simple protocol efficiently to couple in‐situ semisynthetic biosynthesis of Sac and its incorporation into proteins in response to amber (UAG) stop codons. We exploited the exceptional malleability of pyrrolysyl‐tRNA synthetase (PylRS) and evolved an S‐allylcysteinyl‐tRNA synthetase (SacRS) capable of specifically accepting the small, polar amino acid instead of its long and bulky aliphatic natural substrate. We succeeded in generating a novel and inexpensive strategy for the incorporation of a functionally versatile amino acid. This will help in the conversion of orthogonal translation from a standard technique in academic research to industrial biotechnology. 相似文献
73.
Cover Picture: Design of S‐Allylcysteine in Situ Production and Incorporation Based on a Novel Pyrrolysyl‐tRNA Synthetase Variant (ChemBioChem 1/2017) 下载免费PDF全文
74.
Dr. Julien Orts Dr. Marielle Aulikki Wälti Dr. Dhiman Ghosh Dr. Silvia Campioni Dr. Sven J. Saupe Prof. Roland Riek 《Chembiochem : a European journal of chemical biology》2019,20(9):1161-1166
Amyloid fibrils are pathological hallmarks of various human diseases, including Parkinson's, Alzheimer's, amyotrophic lateral sclerosis (ALS or motor neurone disease), and prion diseases. Treatment of the amyloid diseases are hindered, among other factors, by timely detection and therefore, early detection of the amyloid fibrils would be beneficial for treatment against these disorders. Here, a small molecular fluorescent probe is reported that selectively recognize the fibrillar form of amyloid beta(1–42), α-synuclein, and HET-s(218–289) protein over their monomeric conformation. The rational design of the reporters relies on the well-known cross-β-sheet repetition motif, the key structural feature of amyloids. 相似文献
75.
Soodkhet Pojprapai Zhenhua Luo Bj?rn Clausen Sven C. Vogel Donald W. Brown Jennifer Russel Mark Hoffman 《Acta Materialia》2010,58(6):1897-1908
The performance of ferroelectric ceramics is governed by the ability of domains to switch. A decrease in the switching ability can lead to degradation of the materials and failure of ferroelectric devices. In this work the dynamic properties of domain reorientation are studied. In situ time-of-flight neutron diffraction is used to probe the evolution of ferroelastic domain texture under mechanical cyclic loading in bulk lead zirconate titanate ceramics. The high sensitivity of neutron diffraction to lattice strain is exploited to precisely analyze the change of domain texture and strain through a full-pattern Rietveld method. These results are then used to construct a viscoelastic model, which explains the correlation between macroscopic phenomena (i.e. creep and recovered deformation) and microscopic dynamic behavior (i.e. ferroelastic switching, lattice strain). 相似文献
76.
Sven van der Gijp Johan E. ten Elshof Oliver Steigelmann Henk Verweij 《Journal of the American Ceramic Society》2000,83(10):2610-2612
The influence of mechanical stress and chemical homogeneity on the permittivity of BaTi0.9 Zr0.1 O3 ceramics prepared from mixed-oxide and hydrothermal powders was studied. To reduce stress, liquid-phase sintering was applied in conjunction with a low heating rate to stimulate the formation of large grains. The influence of chemical homogeneity was studied by variations in sintering temperatures and times. For both types of ceramics, the dielectric constant at the Curie temperature was influenced by both factors, but to a different extent. In the mixed oxide ceramic, chemical homogeneity played a more prominent role, while internal stress appeared to exert a larger influence in the hydrothermal ceramics. The dielectric constant at the Curie temperature could be increased by 5%–10% by an annealing treatment at 200°C, followed by slow cooling. 相似文献
77.
The mechanical power that is transferred to a liquid via the shaft of an agitator is obtained from a measurement of the electrical power flowing into the electric motor within an accuracy of less than 5%. The accuracy obtained is limited by the calibration procedure. As the implementation of an electric power measurement is both simple and comparatively inexpensive, the technique is suitable for a continuous monitoring of the power used by agitators in the process industries. 相似文献
78.
Strohm E Herzner G Kaltenpoth M Boland W Schreier P Geiselhardt S Peschke K Schmitt T 《Journal of chemical ecology》2008,34(5):575-583
Females of the European beewolf, Philanthus triangulum, possess a large glove-shaped gland in the head, the postpharyngeal gland (PPG). They apply the content of the PPG to their
prey, paralyzed honeybees, where it delays fungal infestation. Here, we describe the chemical composition of the gland by
using combined GC-MS, GC-FTIR, and derivatization. The PPG of beewolves contains mainly long-chain unsaturated hydrocarbons
(C23–C33), lower amounts of saturated hydrocarbons (C14–C33), and minor amounts of methyl-branched hydrocarbons (C17–C31).
Additionally, the hexane-soluble gland content is comprised of small amounts of an unsaturated C25 alcohol, an unknown sesquiterpene,
an octadecenylmethylester, and several long-chain saturated (C25, C27) and unsaturated (C23–C27) ketones, some of which have
not yet been reported as natural products. Surprisingly, we found a dimorphism with regard to the major component of the PPG
with some females having (Z)-9-pentacosene, whereas others have (Z)-9-heptacosene as their predominant component. The biological relevance of the compounds for the prevention of fungal growth
on the prey and the significance of the chemical dimorphism are discussed. 相似文献
79.
Today's automation industry is driven by the need for an increased productivity, higher flexibility, and higher individuality, and characterized by tailor-made and more complex control solutions. In the processing industry, logic controller design is often a manual, experience-based, and thus an error-prone procedure. Typically, the specifications are given by a set of informal requirements and a technical flowchart and both are used to be directly translated into the control code. This paper proposes a method in which the control program is constructed as a sequential function chart (SFC) by transforming the requirements via clearly defined intermediate formats. For the purpose of analysis, the resulting SFC can be translated algorithmically into timed automata. A rigorous verification can be used to determine whether all specifications are satisfied if a formal model of the plant is available which is then composed with the automata model of the logic controller (LC). 相似文献
80.
It has been shown that it is possible to decrease fuel-NOx produced from NH3 using catalytic combustion of a synthetic gasified biomass at fuel-lean conditions. In a certain temperature regime where the conversion of fuel components, such as CO, H2 and CH4, is low and conversion of NH3 is high, it is suggested that the formed NOx is reduced by the remaining fuel components, mainly hydrocarbons. With oxide catalysts only ca. 10% of the NH3 was converted to NOx, the rest to N2. It has also been shown that the ignition sequence of CO, H2 and CH4 varied for different catalysts and different experimental conditions, and that methane coupling and methanation reactions occurred before ignition of CH4. 相似文献