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排序方式: 共有572条查询结果,搜索用时 15 毫秒
51.
Yan Duan Shengnan Sun Yuanmiao Sun Shibo Xi Xiao Chi Qinghua Zhang Xiao Ren Jingxian Wang Samuel Jun Hoong Ong Yonghua Du Lin Gu Alexis Grimaud Zhichuan J. Xu 《Advanced materials (Deerfield Beach, Fla.)》2019,31(12)
Developing highly active electrocatalysts for oxygen evolution reaction (OER) is critical for the effectiveness of water splitting. Low‐cost spinel oxides have attracted increasing interest as alternatives to noble metal–based OER catalysts. A rational design of spinel catalysts can be guided by studying the structural/elemental properties that determine the reaction mechanism and activity. Here, using density functional theory (DFT) calculations, it is found that the relative position of O p‐band and MOh (Co and Ni in octahedron) d‐band center in ZnCo2?xNixO4 (x = 0–2) correlates with its stability as well as the possibility for lattice oxygen to participate in OER. Therefore, it is testified by synthesizing ZnCo2?xNixO4 spinel oxides, investigating their OER performance and surface evolution. Stable ZnCo2?xNixO4 (x = 0–0.4) follows adsorbate evolving mechanism under OER conditions. Lattice oxygen participates in the OER of metastable ZnCo2?xNixO4 (x = 0.6, 0.8) which gives rise to continuously formed oxyhydroxide as surface‐active species and consequently enhances activity. ZnCo1.2Ni0.8O4 exhibits performance superior to the benchmarked IrO2. This work illuminates the design of highly active metastable spinel electrocatalysts through the prediction of the reaction mechanism and OER activity by determining the relative positions of the O p‐band and the MOh d‐band center. 相似文献
52.
Y. Balcaen N. Radutoiu J. Alexis J.-D. Beguin L. Lacroix D. Samélor C. Vahlas 《Surface & coatings technology》2011,206(7):1684-1690
This study focuses on the implementation of different aluminum oxide coatings processed by metal-organic chemical vapor deposition from aluminum tri-isopropoxide on commercial Ti6Al4V titanium alloy to improve its high temperature corrosion resistance. Films grown at 350 °C and at 480 °C are amorphous and correspond to formulas AlOOH, and Al2O3, respectively. Those deposited at 700 °C are composed of γ-Al2O3 nanocrystals dispersed in a matrix of amorphous alumina. Their mechanical properties and adhesion to the substrates were investigated by indentation, scratch and micro tensile tests. Hardness and rigidity of the films increase with increasing deposition temperature. The hardness of the coatings prepared at 350 °C and 480 °C is 5.8 ± 0.7 GPa and 10.8 ± 0.8 GPa respectively. Their Young's modulus is 92 ± 8 GPa (350 °C) and 155 ± 6 GPa (480 °C). Scratch tests cause adhesive failures of the films grown at 350 °C and 480 °C whereas cohesive failure is observed for the nanocrystalline one, grown at 700 °C. Micro tensile tests show a more progressive cracking of the latter films than on the amorphous ones. The films allow maintaining good mechanical properties after corrosion with NaCl deposit during 100 h at 450 °C. After corrosion test only the film deposited at 700 °C yields an elongation at break comparable to that of the as processed samples without corrosion. The as established processing–structure–properties relation paves the way to engineer MOCVD aluminum oxide complex coatings which meet the specifications of the high temperature corrosion protection of titanium alloys with regard to the targeted applications. 相似文献
53.
Shifting the focus from futuristic visions, Alfredo Brillembourg and Hubert Klumpner with Alexis Kalagas of interdisciplinary design practice Urban-Think Tank urge us to ‘forget about utopia’, for in the most part the urban environment of 2050 is already built. Architects’ sights need to be set on the sometimes grim and unfolding reality of favelas and the world's informal cities. 相似文献
54.
55.
Stefania De Rosa Paolo Branchini Valentina Spampinato Alexis Franquet Rossella Yivlialin Lamberto Duo Gianlorenzo Bussetti Luca Tortora 《Nano Research》2022,(2):1120-1127
A detailed stratigraphic investigation of the intercalation mechanism when graphite electrodes are immersed inside diluted perchloric(HClO4)and sulfuric(H2SO4)electrolytes is obtained by comparing results when graphite crystals are simply immersed in the same acid solutions.By combining time-of-flight secondary ion mass spectrometry(ToF-SIMS)and in-situ atomic force microscopy(AFM),we provide a picture of the chemical species involved in the intercalation reaction.The depth intensity profile of the ion signals along the electrode crystal clearly shows a more complex mechanism for the intercalation process,where the local morphology of the basal plane plays a crucial role.Solvated anions are mostly located within the first tens of nanometers of graphite,but electrolytes also diffuse inside the buried layers for hundreds of nanometers,the latter process is also aided by the presence of mesoscopic crystal defects.Residual material from the electrolyte solution was found localized in well-defined circular spots,which represent preferential interaction areas.Interestingly,blister-like micro-structures similar to those observed on the highly oriented pyrolytic graphite(HOPG)surface were found in the buried layers,confirming the equivalence of the chemical condition on the graphite surface and in the underneath layers. 相似文献
56.
Hervais-Adelman Alexis; Davis Matthew H.; Johnsrude Ingrid S.; Carlyon Robert P. 《Canadian Metallurgical Quarterly》2008,34(2):460
Speech comprehension is resistant to acoustic distortion in the input, reflecting listeners' ability to adjust perceptual processes to match the speech input. This adjustment is reflected in improved comprehension of distorted speech with experience. For noise vocoding, a manipulation that removes spectral detail from speech, listeners' word report showed a significantly greater improvement over trials for listeners that heard clear speech presentations before rather than after hearing distorted speech (clear-then-distorted compared with distorted-then-clear feedback, in Experiment 1). This perceptual learning generalized to untrained words suggesting a sublexical locus for learning and was equivalent for word and nonword training stimuli (Experiment 2). These findings point to the crucial involvement of phonological short-term memory and top-down processes in the perceptual learning of noise-vocoded speech. Similar processes may facilitate comprehension of speech in an unfamiliar accent or following cochlear implantation. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
57.
Stein Catherine H.; Abraham Kristen M.; Bonar Erin E.; Leith Jaclyn E.; Kraus Shane W.; Hamill Alexis C.; Gumber Shinakee; Hoffmann Erica; Fogo Wendy R. 《Canadian Metallurgical Quarterly》2011,25(3):449
The present intergenerational study examined the perceived impact of the recent U.S. economic crisis on a sample of 68 young adult–parent dyads. The relative contribution of perceived economic pressure, reports of adult child–parent relationship quality, and concerns about the economic future in accounting for variation in self-reports of psychological distress for adult children and their middle-aged parents were examined. Parents' concerns about their children's economic future accounted for variation in their reports of anxiety and depressed mood above and beyond that of perceived economic pressures and their views of the parent–child relationship. In contrast, for young adults, reports of personal economic pressure were generally related to self-reported anxiety and depressed mood. Implications of findings for research and practice are discussed. (PsycINFO Database Record (c) 2011 APA, all rights reserved) 相似文献
58.
Alexis De Vos 《Electronic Notes in Theoretical Computer Science》2010,253(6):17-22
Conventional logic gates (e.g. AND gates) cannot be used for building a reversible computer. An appropriate design approach is necessary. Both small building blocks and a more complex circuit in MOS technology are presented. Today, these are useful in low-power digital electronics. Tomorrow, these may be useful in quantum computers. 相似文献
59.
Rika E. Anderson Alexis D. Ostrowski Danielle E. Gran Jesse D. Fowler Alan R. Hopkins Randy M. Villahermosa 《Polymer Bulletin》2008,61(5):563-568
Summary Various diameters of polyaniline (PANI) nanofibers were easily made by varying the sweep rate in the
electrochemical polymerization of the aniline monomer. At a sweep rate of 5 mV/s, the PANI nanofibers have
an average diameter of 450 nm with a median of 440 nm. The fibers are short, on the order of a few microns
in length, and exhibit a branched geometry. Increasing the sweep rate to 50 mV/s produced longer nanofibers
with a smaller average diameter of 200 nm. Nanofibers synthesized at 100 mV/s were noted to be smaller
with an average and median diameter of 100 nm. These results illustrate the ease in which the morphology
of nanostructured PANI can be altered and indicate that the method has the potential to create multi-diameter
fibers or mixed-morphology materials. 相似文献
60.
The C2 products formed over Ru during Fischer-Tropsch synthesis often lie well below the Anderson-Schulz-Flory line describing the C4+ products. This has led to speculation that either the surface precursor to C2 hydrocarbons is exceptionally long lived, or that the ethylene formed by CO hydrogenation readsorbs and thereby reenters the chain growth process. In this study, the role of ethylene readsorption on the dynamics of chain initiation and growth is investigated using13CO/H2 and12C2H4 to differentiate between the carbon sources. Ethylene addition is found to suppress the rate of methanation and increase the rates of formation of C3+ hydrocarbons. Ethylene serves as an effective chain initiator, as well as a source of C1 monomer species which participate in chain propagation. No evidence is seen, though, for the participation of C2 species in chain propagation. 相似文献