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排序方式: 共有143条查询结果,搜索用时 15 毫秒
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Pure chromium oxidized at 900 °C at low oxygen partial pressure (10?12 atm) gives duplex Cr2O3 scale with an internal part made of equiaxed grains and exhibiting an n-type conduction, and an external part made of columnar grains and exhibiting a p-type conduction. Spalled regions occurring during cooling have been studied with photoelectrochemical techniques at a microscale. New information in the form of a specific image (structural quality image) could be obtained and revealed a level of structural defect density in the internal chromia subscale higher than that measured in the non-spalled region. The results complement the spallation scenario proposed in part I of this work. 相似文献
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This study investigated the combination of chemical and ultrasonic regeneration (Sono-Fenton), used for regenerating granular activated carbon (GAC) saturated with Rhodamine B (RB). This process was modeled and optimized using response surface methodology (RSM) based on central composite design (CCD). Effective parameters on regeneration efficiency such as pH, concentration of hydrogen peroxide (H2O2), and time of ultrasonic irradiation were optimized and modeled using the reduced quadratic method. The fitness of the model was checked by the determination coefficient (R2?=?0.9978). At optimum condition, the effective parameters of pH?=?3.84, concentration of H2O2?=?38.28 (mM), and time of ultrasonic irradiation?=?23.11(min), maximum regeneration efficiency (87.88%) was achieved, the results of which were obtained after four-time sequential adsorption–regeneration cycles were acceptable. Desorption and degradation of RB were conducted through the generation of active species, including hydroxyl radicals and high-energy ultrasound. The regeneration efficiency was increased using this combination method. In conclusion, the Sono-Fenton method is suggested to be used more widely in regeneration processes. 相似文献
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To speed up data‐intensive programs, two complementary techniques, namely nested loops parallelization and data locality optimization, should be considered. Effective parallelization techniques distribute the computation and necessary data across different processors, whereas data locality places data on the same processor. Therefore, locality and parallelization may demand different loop transformations. As such, an integrated approach that combines these two can generate much better results than each individual approach. This paper proposes a unified approach that integrates these two techniques to obtain an appropriate loop transformation. Applying this transformation results in coarse grain parallelism through exploiting the largest possible groups of outer permutable loops in addition to data locality through dependence satisfaction at inner loops. These groups can be further tiled to improve data locality through exploiting data reuse in multiple dimensions. 相似文献
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Multimedia Tools and Applications - Cryptography is the process by which a readable message is converted into cipher-text unintelligible to an eavesdropper. With the advent of the internet,... 相似文献
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Behrouz Parsa Moghaddam José António Tenreiro Machado 《Journal of scientific computing》2017,71(3):1351-1374
This paper proposes accurate and robust algorithms for approximating variable order fractional derivatives of arbitrary order. The proposed schemes are based on finite difference approximations. We compare the performance of algorithms by introducing a new formulation of experimental convergence order. Two initial value problems are considered and solved by means of the proposed methods. Numerical results are provided justifying the usefulness of the proposed methods. 相似文献
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A quantitative metallographic assessment of the evolution of porosity during processing and creep in single crystal Ni‐base super alloys 下载免费PDF全文
H. Buck P. Wollgramm A. B. Parsa G. Eggeler 《Materialwissenschaft und Werkstofftechnik》2015,46(6):577-590
The present work reviews previous research on the evolution of porosity. It presents new results from a detailed study on the evolution of porosity during casting, heat treatment and creep of a single crystal Ni‐base superalloy subjected to uniaxial tensile creep at 1050 °C and 160 MPa in [001] and [110] directions. A quantitative metallographic study was performed on carefully polished metallographic cross sections, monitoring sampling fields of 4500 × 1000 µm2 using the back scatter contrast of an analytical scanning electron microscope; evolutions of pore sizes and pore form factors were analyzed and all important details which were previously revealed in a synchrotron study could be reproduced. In addition, it was observed that micro cracks form at larger cast pores. They interlink and thus initiate final rupture. The [110] tensile creep tests showed lower rupture strains than the [001] experiments. In agreement with earlier work, this can be rationalized on the basis of aligned porosity along primary dendrites. 相似文献
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We present the transport unaware link improvement protocol (TULIP), which dramatically improves the performance of TCP over
lossy wireless links, without competing with or modifying the transport- or network-layer protocols. TULIP is tailored for
the half-duplex radio links available with today's commercial radios and provides a MAC acceleration feature applicable to
collision-avoidance MAC protocols (e.g., IEEE 802.11) to improve throughput. TULIP's timers rely on a maximum propagation
delay over the link, rather than performing a round-trip time estimate of the channel delay. The protocol does not require
a base station and keeps no TCP state. TULIP is exceptionally robust when bit error rates are high; it maintains high goodput,
i.e., only those packets which are in fact dropped on the wireless link are retransmitted and then only when necessary. The
performance of TULIP is compared against the performance of the Snoop protocol (a TCP-aware approach) and TCP without link-level
retransmission support. The results of simulation experiments using the actual code of the Snoop protocol show that TULIP
achieves higher throughput, lower packet delay, and smaller delay variance.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献