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91.
    
Photocatalytic nitrogen fixation is a promising strategy for ammonia synthesis under mild conditions by using solar energy, but N2 activation remains a great challenge. Herein, we demonstrate that a Z-scheme g-C3N4/WO3 heterojunction possessing abundant nitrogen vacancies exhibits the highly enhanced activity for photocatalytic N2 fixation through efficient nitrogen molecular activation compared with pristine NVs-g-C3N4 and WO3 photocatalysts. The construction of the internal electric field induced by Z-scheme NVs-g-C3N4/WO3 heterojunction allows a rapid charge carrier separation and simultaneously maintains the powerful redox ability of photogenerated charge carriers, defined by the covalent C O bond. Moreover, nitrogen vacancy plays a crucial role in the adsorption/activation of N2, which substantially facilitates the hydrogenation to generate NH3. According to experimental and theoretical investigations, photocatalytic N2 fixation on NVs-g-C3N4/WO3 composites is proposed to be energetically favorable in the alternating pathway. This study offers an alternative way for the design of efficient photocatalysts for photocatalytic N2 fixation.  相似文献   
92.
    
This study presented a controlled oxygen vacancy formation on stabilization of tetragonal zirconia particles via a nonthermal atmospheric pressure plasma jet (APPJ) with varying the supplied power. The characteristic analyses based on X-ray diffraction, field emission scanning electron microscopy, high-resolution transmission electron microscopy (HR-TEM), Raman, ultraviolet–visible spectroscopy, and ultraviolet photoemission spectroscopy confirm the existence of oxygen vacancies in tetragonal zirconia particles. Production of oxygen vacancies in the prepared zirconia powder is related to the presence of surface defects by observing HR-TEM and further decreases the bandgap as indicated by optical characterization. Thus, it can be anticipated that the research of defect engineering is a promising way to improve the optoelectronic and photocatalytic performance of oxide material via the APPJ method.  相似文献   
93.
    
Transition metal chalcogenides (TMCs) are widely used in photocatalytic fields such as hydrogen evolution, nitrogen fixation, and pollutant degradation due to their suitable bandgaps, tunable electronic and optical properties, and strong reducing ability. The unique 2D malleability structure provides a pre-designed platform for customizable structures. The introduction of vacancy engineering makes up for the shortcomings of photocorrosion and limited light response and provides the greatest support for TMCs in terms of kinetics and thermodynamics in photocatalysis. This work reviews the effect of vacancy engineering on photocatalytic performance based on 2D semiconductor TMCs. The characteristics of vacancy introduction strategies are summarized, and the development of photocatalysis of vacancy engineering TMCs materials in energy conversion, degradation, and biological applications is reviewed. The contribution of vacancies in the optical range and charge transfer kinetics is also discussed from the perspective of structure manipulation. Vacancy engineering not only controls and optimizes the structure of the TMCs, but also improves the optical properties, charge transfer, and surface properties. The synergies between TMCs vacancy engineering and atomic doping, other vacancies, and heterojunction composite techniques are discussed in detail, followed by a summary of current trends and potential for expansion.  相似文献   
94.
    
Anion exchange reaction tunes the band gap of halide perovskites, which proceeds by the migration of the ions through the halide vacancies. This study reports the preparation of the heterojunction perovskite microrods by optically controlled localized halide vacancy filling, and halide exchange leading to color tuning in the MAPbBr3 microrod crystals. The exchange reaction is homogeneously suppressed by treating the crystal with a halide precursor solution, whereas the reaction is locally inhibited at the specific site of a crystal by filling the halide vacancies using a tightly focused beam of a near-infrared laser. By controlling the density of halide vacancies at the specific site of the crystal, the rate of nonradiative recombination of charge carriers in the crystal is controlled. This halide vacancy filling by the remote-controlled reaction helps to locally control the crystal quality and photoluminescence for designing perovskite-based high-quality photovoltaic and optoelectronic devices.  相似文献   
95.
    
In this study, nanoparticle-assembled Bi25FeO40 materials were synthesized by a novel and simple process, and their microstructure was regulated by different methods of adding Bi3+ and Fe3+. The novel nanoparticle-assembled tetrakaidekahedron Bi25FeO40 materials exhibited more oxygen vacancy and larger specific surface area than irregular or cubic-like Bi25FeO40 microcrystals and revealed better photo-Fenton catalytic oxidation activity toward degrading Rhodamine B (RhB) pollutants. These novel materials activated H2O2 in visible light to produce non-free radicals 1O2 and hole (h+) active oxidative species that dominated the catalytic degradation of RhB. Complete degradation of RhB was achieved after 1 h. The possible reaction mechanisms of the photo-Fenton catalytic system are discussed in detail by radical scavenging tests, X-ray phosphorescence analysis, and electron paramagnetic resonance spectroscopy. The results provided a way to rationally explore and construct photo-Fenton catalysts for wastewater treatment.  相似文献   
96.
    
Photocatalytic nitrogen reduction represents a viable technology for green ammonia synthesis under mild conditions. However, the performance of the photocatalysts is typically limited by high charge carrier recombination and low adsorption and activation of nitrogen molecules. Herein, Bi/Bi2Sn2O7 (Bi/BSO) heterojunction nanocomposites are prepared via a one-step hydrothermal method, where NaOH etching of oxygen vacancies in the Bi─O bonds of Bi2Sn2O7 (BSO) is exploited for the in situ formation of metallic Bi and hence Schottky junctions with the semiconducting BSO. This leads to a high separation rate of photogenerated charge carriers. Consequently, compared to the pure-phase BSO, the Bi/BSO heterostructures exhibit markedly enhanced ammonia production, reaching an optimum rate of 284.5 µmol g−1 h−1, where the rectifying contact between the semiconducting BSO and metallic Bi facilitates directional BSO to Bi electron transfer, leading to enrichment of photogenerated electrons at the active sites of metallic Bi. First-principles calculations confirm the alteration of active sites and the guided electron flow by the Schottky junctions and surface oxygen vacancies. Results from this study offer an effective paradigm of structural engineering in manipulating the photocatalytic activity of bismuth-based pyrochlore materials toward nitrogen fixation to ammonia.  相似文献   
97.
    
The metal–insulator (MI) transition of vanadium dioxide (VO2) is effectively modulated by oxygen vacancies, which decrease the transition temperature and insulating resistance. Oxygen vacancies in thin films can be driven by oxygen transport using electrochemical potential. This study delves into the role of crystallographic channels in VO2 in facilitating oxygen transport and the subsequent tuning of electrical properties. A model system is designed with two types of VO2 thin films: (100)- and (001)-oriented, where channels align parallel and perpendicular to the surface, respectively. Growing an oxygen-deficient TiO2 layer on these VO2 films prompted oxygen transport from VO2 to TiO2. Notably, in (001)-VO2 film, where oxygen ions move along the open channels, the oxygen migration deepens the depleted region beyond that in (100)-VO2, leading to more pronounced changes in metal-insulator transition behaviors. The findings emphasize the importance of understanding the intrinsic crystal structure, such as channel pathways, in controlling ionic defects and customizing electrical properties for applications.  相似文献   
98.
    
Even lithium-rich manganese oxides (LRMOs) are considered as promising cathode materials for next-generation lithium-ion batteries, their commercialization is hindered mainly by the low initial Coulombic efficiency, poor cyclability and unexpected capacity fade. Here, a synergistic modification strategy by using both F doping and weak organic acid surface treatment is proposed to improve the electrochemical performances of LRMOs significantly. Optimized Li1.2Mn0.54Ni0.13Co0.13O1.95F0.05 sample with surface oxygen vacancy defects and thin carbon coating layer exhibits profound electrochemical performances, for example, discharging capacities of 298.6 and 212.5 mAh g−1 at 0.1 C and 1 C rate, respectively. In addition, it can own an initial Coulombic efficiency of 84.4%, which is much higher than that of untreated sample. In situ X-ray diffraction analysis implies that synergistic modification can enhance the skeleton stability of LRMOs , especially at a high state of charge. Galvanostatic intermittent titration technique analysis suggests that as-developed synergistic modification can accelerate the lithium ions diffusion. Theoretical calculations reveal that substituted F and oxygen vacancy defects can diminish the diffusion energy barrier of Li+ ions. This work provides a new synergistic modification strategy to improve the comprehensive properties of LRMO cathode effectively.  相似文献   
99.
Innovation of highly active cathode is of great significance to the development of protonic ceramic fuel cells (PCFCs). Herein, tailoring oxygen vacancies in Zn-doped Ba0·95La0·05FeO3?δ (BLFZ) perovskite is proved to be beneficial for promoting the formation of proton defects. Hydration ability of the triple conducting BLFZ perovskites is confirmed by electrical conductivity relaxation (ECR). The results demonstrate that BLFZ exhibits a proton surface exchange coefficient of 1.34 × 10?3 cm s?1 at 600 °C, which greatly extends active sites from the electrolyte/cathode interface to the entire electrode. Mechanism and process elementary steps of the oxygen reduction reaction (ORR) of BLFZ-BaCe0.7Zr0·1Y0.1Yb0.1O3?δ (BCZYYb) are detailedly studied. It is found that the rate-determining step of ORR is surface dissociative adsorption of oxygen on BLFZ-BCZYYb cathode. A maximum power density of 673 mW cm?2 at 700 °C is achieved and BLFZ-BCZYYb based single-cell shows no obvious degradation at 600 °C for 200 h. The good performance is ascribed to the rapid proton diffusion of BLFZ-BCZYYb composite electrode by regulating the oxygen vacancies.  相似文献   
100.
    
Graphite carbon nitride (g-C3N4) has caught far-ranging concern for its masses of advantages, for instance, the unique graphite-like two-dimensional lamellar structure, low cost, nontoxic, suitable bandgap of 2.7 eV and favorable stability. Whereas owing to the shortcomings of low solar absorptivity and fast recombination of photo-induced charge pairs, the overall quantum efficiency of photocatalysis for g-C3N4 is suboptimal, resulting in limited practicality of g-C3N4 (GCN). In our study, modified g-C3N4 materials (HCN) with ample carbon vacancies (CVs) were obtained through calcinating of g-C3N4 in H2 atmosphere. Higher specific surface area and more active sites of HCN were induced by roasting of g-C3N4 in H2. CVs that occurred in the N-(C3) bond lead to the reduction of electron density around N, thus narrowing the bandgap of HCN-3h and enlarging corresponding light response capability. Under the synergistic function of abundant pore construction and CVs on HCN, the photo-excited e?/h+ pairs can be memorably separated and transferred, which is favorable to photocatalytic efficiency. Among HCN, the HCN-3h sample has the highest H2 generation rate of 4297.9 μmol h?1 g?1, which achieves 2.3-fold higher than that of GCN (1291.7 μmol h?1 g?1). This paper brings forward a meaningful method of boosting the photocatalytic performance of photocatalysts by constructing abundant CVs.  相似文献   
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