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41.
Synthesis of Ternary Titanium Aluminum Carbides Using Self-Propagating High-Temperature Synthesis Technique 总被引:6,自引:0,他引:6
Micha opaciski Jan Puszynski Jerzy Lis 《Journal of the American Ceramic Society》2001,84(12):3051-3053
Different ternary carbide phases, namely Ti3 AlC2 , Ti3 AlC, and Ti2 AlC, were successfully synthesized in a self-sustaining regime. Direct reactions among elemental powders of titanium, aluminum, and carbon are strongly exothermic, and the resulting reaction products consist of binary carbides and they are partially molten. The use of TiAl, instead of elemental titanium and aluminum, significantly reduces the combustion temperature. As a result, ternary titanium aluminum carbide phases are formed. In addition, the combustion-synthesized products are not sintered and easy to deagglomerate. Reaction conditions and X-ray diffraction patterns of different ternary phases formed in a self-sustaining regime are presented. 相似文献
42.
Annamaria Duszová Radoslav Halgaš Marek Bľanda Pavol Hvizdoš František Lofaj Ján Dusza Jerzy Morgiel 《Journal of the European Ceramic Society》2013,33(12):2227-2232
WC–Co cemented carbide has been investigated using instrumented indentation with maximum applied loads from 0.1 to 10 mN. The hardness and indentation modulus of individual phases and the influence of crystallographic orientation of WC on the hardness and indentation modulus have been studied. The hardness of the Co binder was approximately 10 GPa and that of WC grains up to 50 GPa with relatively large scatter under the indentation load of 1 mN. Investigation of the role of crystallographic orientation of WC grains on hardness at 10 mN load revealed average values of HITbasal = 40.4 GPa (EITbasal = 674 GPa) and HITprismatic = 32.8 GPa (EItprismatic = 542 GPa), respectively. The scatter in the measured values at low indentation loads is caused by the effects of surface and sub-surface characteristics (residual stress, damaged region) and at higher loads by “mix-phase” volume below the indenter. 相似文献
43.
Jerzy Haber 《Topics in Catalysis》2009,52(8):970-981
Modern civilization, whose spectacular development took place in the second half of XX century as the result of scientific
and information revolution has six characteristic features: (1) it is a mass civilization, (2) it is mobile, (3) it is global,
(4) it is free of the spectre of famine, (5) it is built on informatics, (6) human lifespan is steadily prolonged. In order
to achieve these goals it was necessary to invent thousands new materials and to find out methods of their fast and cheap
production in large quantities. The unique possibility of the fast and selective production of the desired chemical molecules,
required to obtain a material with defined properties, is offered by catalysis. Catalysis comprises technological processes
of the largest scale, such as catalytic cracking of billions tons of crude oil per year and smallest scale enzymatic reactions
with micrograms of product formed with 100% chemo-, regio- and stereoselectivity. With the rapidly growing earth’s population
increasingly important becomes not only the production of materials needed in our modern society, but also the destruction
of undesired by-products of its activities, making the application of catalysis to pollution control one of important tasks.
The progress of catalysis, both science and technology, was in the last 50 years driven by the development in five fields:
(1) new materials, particularly those based on the principle of molecular imprinting (use of templates), (2) application of
new surface science techniques to identify active sites and surface reaction intermediates, (3) quantum chemical modeling
of elementary steps of catalytic reactions, (4) design of new reactors, (5) development of computational catalysis, (6) development
of new ways for carrying catalytic reactions, (7) biocatalysis using enzymes, modified by mutagenesis and recombination techniques
to make them selective and active in conditions of the desired technological process. Application of molecular sieves, catalytic
antibodies, metallocene catalysts, asymmetric catalysis, fuel cells, control of automotive exhaust are described and pending
change of the paradigm of catalysis is discussed. 相似文献
44.
The enthalpies of thermal dissociation (ΔdH) and formation (ΔfH) found in the literature as well as the crystal lattice energies (Ec) of inorganic and organic hexahalogenohafnates (MI2(or MII)HfX2−6; MI and MII denote monovalent and divalent cations respectively and X denotes a halogen) are reviewed and discussed. The enthalpies of formation of the salts were evaluated using the above-mentioned ΔdH values and known enthalpies of formation of products of decomposition. Combination of the enthalpies of formation of hexahalogenohafnates thus obtained or those of the literature with the literature values of the enthalpy of formation of cations and theoretically determined enthalpies of formation of HfX2−6 (or electrostatic lattice energies of the salts) afforded lattice energies of the salts (or enthalpies of formation of gaseous HfX2−6). Values of ΔfH were also assessed taking theoretically obtained electrostatic lattice energies of the salts and enthalpies of formation of HfX2−6 and literature or theoretically determined values of the enthalpy of formation of gaseous cations. The independent sets of crystal lattice energies and thermochemical radii for HfX2−6 were obtained following the Kapustinskii—Yatsimirskii approach. Combination of the latter method with the thermochemical cycle afforded information on the influence of the dimensions of ions on the thermodynamic stability of hexahalogenohafnates with respect to dissociation and oxidation processes. The thermochemical quantities of experimental and theoretical origin correlate with each other reasonably well, thus increasing their reliability. 相似文献
45.
David B. Knorr Sc.D. Jerzy A. Szpunar Ph.D. 《JOM Journal of the Minerals, Metals and Materials Society》1994,46(9):42-48
Thin films are important in a variety of applications, including optical, magnetic,and electronic devices. The origin of microstructure in films formed by physical vapor deposition depends primarily on the homologous deposition temperature, which determines the grain structure and substructure. Texture is coupled to grain structure development through several kinetic parameters, principally surface diffusivity and interfacial energy. The representation of such fiber textures is facilitated by simplified pole intensity versus tilt angle plots rather than entire pole figures. The reliability of thin film interconnection materials such as aluminum alloys is heavily leveraged on both texture and grain structure. The properties of thin magnetic films depend on both the crystallographic texture and the grain shape anisotropy. 相似文献
46.
Magdalena Misiura Tomasz Guszczyn Ilona Oscilowska Weronika Baszanowska Jerzy Palka Wojciech Miltyk 《International journal of molecular sciences》2021,22(2)
Although the role of platelet-rich plasma (PRP) in tissue regeneration has been confirmed in many studies, the mechanism of this process is still not fully understood. Human keratinocytes (HaCaT) cells were used as an experimental model for studies on the effects of PRP on cell proliferation, migration, collagen biosynthesis, prolidase activity, and its expression and anabolic signaling. The activation of epidermal growth factor receptor (EGFR), β1-integrin, and insulin-like growth factor-1 receptor (IGF-1R) by PRP were investigated by western blot and immunocytochemistry. It has been found that PRP induced keratinocytes migration and proliferation through activation of cell cycle progression and EGFR downstream signaling. Similar biological effects were achieved by an addition to the culture medium of prolidase (PEPD), a ligand of EGFR (PRP is a rich source of PEPD–2 ng/mL). PRP-dependent stimulation of collagen biosynthesis was accompanied by an increase in the expression of NF-κβ, IGF-1R-downstream signaling proteins, and PEPD activity. The data suggest that PRP activates a complex of growth factors and adhesion receptors that stimulate cell proliferation, migration, and collagen biosynthesis. PRP induces PEPD-dependent human keratinocyte proliferation through activation of the EGFR receptor. Our study provides a novel mechanism of PRP-dependent wound healing. 相似文献
47.
Electropolishing and passivation of NiTi shape memory alloy 总被引:2,自引:0,他引:2
Electropolishing of NiTi alloy has been investigated. The influence of polishing bath composition and the operating conditions instead of the conditions of the process on the quality of the surface, evaluated by AFM and SEM methods, was established. Morphologically uniform surfaces were obtained only in the case of solutions containing hydrofluoric and sulfuric acids. Electropolished samples were sterilized and thermally passivated, then their corrosion resistance was measured in Tyrode's physiological solution. It was established that already after the electropolishing the corrosion resistance of NiTi alloy increases due to the spontaneously formed TiO2 layer. The increase of the thickness of the layer during sterilization and thermal passivation causes further increase in the corrosion resistance. 相似文献
48.
Sweeney JD Silk PJ Gutowski JM Wu J Lemay MA Mayo PD Magee DI 《Journal of chemical ecology》2010,36(12):1309-1321
The male-produced aggregation pheromones of Tetropium fuscum (F.) and T. cinnamopterum Kirby were identified as (2S,5E)-6,10-dimethyl-5,9-undecadienol by chemical analysis, synthesis, electronantennography, and field trapping; the compound
is here renamed “fuscumol”. The effect of fuscumol chirality, alone or with host volatiles, and fuscumol release rate on Tetropium spp. was tested in field-trapping experiments in Nova Scotia and Poland. Both (S)-fuscumol and racemic fuscumol synergized trap catches of male and female T. fuscum, T. cinnamopterum, and T. castaneum (L.) when combined with a blend of host monoterpenes and ethanol. Without added host volatiles, fuscumol was either unattractive
(in Nova Scotia) or only slightly so (in Poland). (R)-Fuscumol, alone or in combination with host volatiles, did not elicit increases in trap capture of any Tetropium species, relative to the controls. Fuscumol synergized attraction of both sexes to host volatiles, thus indicating it acts
as an aggregation pheromone. Sex ratio was often female-biased in traps baited with fuscumol plus host volatiles, and was
either unbiased or male-biased in traps with host volatiles alone. In traps with host volatiles and racemic fuscumol, mean
catches of Tetropium species were unaffected by fuscumol release rates ranging from 1 to 32 mg/d. The attraction of three different Tetropium species to the combination of (S)-fuscumol and host volatiles suggests that cross-attraction may occur where these species are sympatric, and that reproductive
isolation possibly occurs via differences in close-range cues. These results have practical applications for survey and monitoring
of T. fuscum, a European species established in Nova Scotia since at least 1980, and for early detection of T. castaneum, a European species not presently established in North America. 相似文献
49.
50.
Janina Tokarz Gabriele Mller Anna Artati Simone Huber Anja Zeigerer Bert Blaauw Jerzy Adamski Kenneth Allen Dyar 《International journal of molecular sciences》2021,22(15)
Biological aging research is expected to reveal modifiable molecular mechanisms that can be harnessed to slow or possibly reverse unhealthy trajectories. However, there is first an urgent need to define consensus molecular markers of healthy and unhealthy aging. Established aging hallmarks are all linked to metabolism, and a ‘rewired’ metabolic circuitry has been shown to accelerate or delay biological aging. To identify metabolic signatures distinguishing healthy from unhealthy aging trajectories, we performed nontargeted metabolomics on skeletal muscles from 2-month-old and 21-month-old mice, and after dietary and lifestyle interventions known to impact biological aging. We hypothesized that common metabolic signatures would highlight specific pathways and processes promoting healthy aging, while revealing the molecular underpinnings of unhealthy aging. Here, we report 50 metabolites that commonly distinguished aging trajectories in all cohorts, including 18 commonly reduced under unhealthy aging and 32 increased. We stratified these metabolites according to known relationships with various aging hallmarks and found the greatest associations with oxidative stress and nutrient sensing. Collectively, our data suggest interventions aimed at maintaining skeletal muscle arginine and lysine may be useful therapeutic strategies to minimize biological aging and maintain skeletal muscle health, function, and regenerative capacity in old age. 相似文献