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排序方式: 共有568条查询结果,搜索用时 218 毫秒
81.
82.
Arif M. Abdullah Xiuling Li Paul V. Braun John A. Rogers K. Jimmy Hsia 《Advanced functional materials》2020,30(14)
Self‐assembly of 3D structures presents an attractive and scalable route to realize reconfigurable and functionally capable mesoscale devices without human intervention. A common approach for achieving this is to utilize stimuli‐responsive folding of hinged structures, which requires the integration of different materials and/or geometric arrangements along the hinges. It is demonstrated that the inclusion of Kirigami cuts in planar, hingeless bilayer thin sheets can be used to produce complex 3D shapes in an on‐demand manner. Nonlinear finite element models are developed to elucidate the mechanics of shape morphing in bilayer thin sheets and verify the predictions through swelling experiments of planar, millimeter‐scaled PDMS (polydimethylsiloxane) bilayers in organic solvents. Building upon the mechanistic understandings, The transformation of Kirigami‐cut simple bilayers into 3D shapes such as letters from the Roman alphabet (to make “ADVANCED FUNCTIONAL MATERIALS”) and open/closed polyhedral architectures is experimentally demonstrated. A possible application of the bilayers as tether‐less optical metamaterials with dynamically tunable light transmission and reflection behaviors is also shown. As the proposed mechanistic design principles could be applied to a variety of materials, this research broadly contributes toward the development of smart, tetherless, and reconfigurable multifunctional systems. 相似文献
83.
Danielle M. Blumstein Daniel Mays Kim T. Scribner 《Journal of Great Lakes research》2018,44(1):149-156
Burbot (Lota lota) are the only freshwater member of the Cod like (Lotidae) family that have a circumpolar distribution and occupy the widest geographic distribution of all Laurentian Great Lakes fish species. Information regarding burbot spatial genetic structure and recruitment dynamics is critical for the development of effective management strategies. Although burbot are a species of conservation concern throughout their range, little demographic or behavioral information exists. We estimated levels of genetic diversity within, and the degree of spatial population structure between samples collected from Lake Michigan and tributaries of the Manistee River, MI. Measures of genetic diversity across 10 microsatellite loci were moderately high. Disparities between adult groups sampled in Lake Michigan and the Manistee River were notable for observed heterozygosity (0.662 vs 0.488) and allelic richness (11.7 vs 6.6). Significant levels of inter-population variance in microsatellite allele frequencies (FST 0.154 to 0.208) were detected between Lake Michigan and the Manistee River samples. Results indicate reproductive isolation between what plausibly may be riverine and lacustrine spawning life history types. Pedigree analyses for three cohorts sampled in the Manistee River revealed that a sizeable number of adults contributed reproductively to multiple cohorts, indicating spawning philopatry. While data were collected from restricted areas in lacustrine and river habitats, analyses revealing microgeographic genetic structuring, potentially attributed to life history polymorphisms, have significant implications for burbot management in the Great Lakes. 相似文献
84.
The metal-insulator phase transition in vanadium oxide makes it an attractive material for developing reconfigurable infrared optoelectronic components. In this paper, we present a tunable mid-infrared plasmonic patch antenna array based on vanadium oxide. The antennas consist of a circular gold patch array separated from a metallic ground plane by a film of vanadium dioxide. As the insulator-to-metal phase transition is thermally triggered, the resonances of the antenna array redshift with reduced absorbance before they are eventually switched off. The measured tuning range is about 10% of the resonant frequency, and the modulation depth in reflection is as high as 50%. A hysteresis loop in the tuning behavior is also observed. The XRD and XPS characterizations reveal a polycrystalline and multi-phase vanadium oxide. Our demonstrated tunable patch antennas hold promise for optical switching and modulating in mid-infrared applications. 相似文献
85.
Maxwell Wood Jimmy Jiahong Kuo Kazuki Imasato Gerald Jeffrey Snyder 《Advanced materials (Deerfield Beach, Fla.)》2019,31(35)
Materials with high zT over a wide temperature range are essential for thermoelectric applications. n‐Type Mg3Sb2‐based compounds have been shown to achieve high zT at 700 K, but their performance at low temperatures (<500 K) is compromised due to their highly resistive grain boundaries. Syntheses and optimization processes to mitigate this grain‐boundary effect has been limited due to loss of Mg, which hinders a sample's n‐type dopability. A Mg‐vapor anneal processing step that grows a sample's grain size and preserves its n‐type carrier concentration during annealing is demonstrated. The electrical conductivity and mobility of the samples with large grain size follows a phonon‐scattering‐dominated T?3/2 trend over a large temperature range, further supporting the conclusion that the temperature‐activated mobility in Mg3Sb2‐based materials is caused by resistive grain boundaries. The measured Hall mobility of electrons reaches 170 cm2 V?1 s?1 in annealed 800 °C sintered Mg3 + δSb1.49Bi0.5Te0.01, the highest ever reported for Mg3Sb2‐based thermoelectric materials. In particular, a sample with grain size >30 mm has a zT 0.8 at 300 K, which is comparable to commercial thermoelectric materials used at room temperature (n‐type Bi2Te3) while reaching zT 1.4 at 700 K, allowing applications over a wider temperature scale. 相似文献
86.
Qingran Zhang Yinguang Chen Jian Pan Rahman Daiyan Emma C. Lovell Jimmy Yun Rose Amal Xunyu Lu 《Small (Weinheim an der Bergstrasse, Germany)》2023,19(40):2302338
Electrochemical synthesis of hydrogen peroxide (H2O2) through the selective oxygen reduction reaction (ORR) offers a promising alternative to the energy-intensive anthraquinone method, while its success relies largely on the development of efficient electrocatalyst. Currently, carbon-based materials (CMs) are the most widely studied electrocatalysts for electrosynthesis of H2O2 via ORR due to their low cost, earth abundance, and tunable catalytic properties. To achieve a high 2e− ORR selectivity, great progress is made in promoting the performance of carbon-based electrocatalysts and unveiling their underlying catalytic mechanisms. Here, a comprehensive review in the field is presented by summarizing the recent advances in CMs for H2O2 production, focusing on the design, fabrication, and mechanism investigations over the catalytic active moieties, where an enhancement effect of defect engineering or heteroatom doping on H2O2 selectivity is discussed thoroughly. Particularly, the influence of functional groups on CMs for a 2e−-pathway is highlighted. Further, for commercial perspectives, the significance of reactor design for decentralized H2O2 production is emphasized, bridging the gap between intrinsic catalytic properties and apparent productivity in electrochemical devices. Finally, major challenges and opportunities for the practical electrosynthesis of H2O2 and future research directions are proposed. 相似文献
87.
Joshua C. Steele Kurt Mahoney Omer Karovic Larry W. Mays 《Water Resources Management》2016,30(5):1605-1620
The design of urban stormwater systems and sanitary sewer systems consists of solving two problems: generating a layout of the system and the pipe design which includes the crown elevations, slopes and commercial pipe sizes. A heuristic model for determining the optimal (minimum cost) layout and pipe design of a storm sewer network is presented. The hierarchical procedure combines a sewer layout model formulated as a mixed-integer nonlinear programming (MINLP) problem which is solved using the General Algebraic Modeling System (GAMS) and a simulated annealing optimization procedure for the pipe design of a generated layout was developed in Excel. The GAMS and simulated annealing models are interfaced through linkage of Excel and GAMS. The pipe design model is based upon the simulated annealing method to optimize the crown elevations and diameter of pipe segments in a storm sewer network using layouts generated using GAMS. A sample scenario demonstrates that using these methods may allow for significant costs saving while simultaneously reducing the time typically required to design and compare multiple storm sewer networks. 相似文献
88.
Robert S. Ayre
John R. Mays
《Computers & Structures》1971,1(4):511-534Examples of the transient dynamic response of various single-degree-of-freedom and many-degree-of-freedom simplified nonlinear structural systems are shown through a presentation of general equations of motion, nonlinear damping and restoring force functions, and the use of nonlinear-system response spectra. A few examples of response spectra are shown for widely different families of nonlinear systems having widely varying parameters. 相似文献
89.
A series of sodium poly(styrene sulfonate)-block-poly(4-tert-butylstyrene) (NaPSS-b-PtBS) copolymers and related homopolymers were characterized by Fourier transform infrared (FT-IR) and nuclear magnetic resonance (NMR) spectroscopy. The homopolymers included polystyrene (PS), poly(4-tert-butylstyrene) (PtBS), sodium poly(4-styrene sulfonate) (NaP4SS), sodium poly(styrene sulfonate) (NaPSS) with various sulfonation levels, and partially sulfonated PtBS (PtBSS). The structures of NaPSS and PtBSS were elucidated, and the effect of sulfonation level on the NaPSS FT-IR spectrum was studied. The characteristic peaks for NaPSS and PtBSS in FT-IR and NMR spectra were identified. 相似文献
90.