全文获取类型
收费全文 | 640篇 |
免费 | 22篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 7篇 |
综合类 | 2篇 |
化学工业 | 120篇 |
金属工艺 | 33篇 |
机械仪表 | 18篇 |
建筑科学 | 12篇 |
矿业工程 | 6篇 |
能源动力 | 29篇 |
轻工业 | 29篇 |
水利工程 | 3篇 |
无线电 | 69篇 |
一般工业技术 | 156篇 |
冶金工业 | 76篇 |
原子能技术 | 3篇 |
自动化技术 | 100篇 |
出版年
2024年 | 3篇 |
2023年 | 6篇 |
2022年 | 13篇 |
2021年 | 15篇 |
2020年 | 9篇 |
2019年 | 6篇 |
2018年 | 23篇 |
2017年 | 15篇 |
2016年 | 15篇 |
2015年 | 13篇 |
2014年 | 24篇 |
2013年 | 47篇 |
2012年 | 15篇 |
2011年 | 34篇 |
2010年 | 30篇 |
2009年 | 38篇 |
2008年 | 39篇 |
2007年 | 17篇 |
2006年 | 21篇 |
2005年 | 20篇 |
2004年 | 18篇 |
2003年 | 12篇 |
2002年 | 20篇 |
2001年 | 12篇 |
2000年 | 11篇 |
1999年 | 18篇 |
1998年 | 25篇 |
1997年 | 14篇 |
1996年 | 15篇 |
1995年 | 9篇 |
1994年 | 9篇 |
1993年 | 2篇 |
1992年 | 13篇 |
1991年 | 7篇 |
1990年 | 9篇 |
1989年 | 5篇 |
1988年 | 5篇 |
1987年 | 6篇 |
1986年 | 2篇 |
1985年 | 11篇 |
1984年 | 3篇 |
1983年 | 4篇 |
1982年 | 4篇 |
1981年 | 3篇 |
1980年 | 9篇 |
1979年 | 3篇 |
1978年 | 3篇 |
1977年 | 3篇 |
1976年 | 3篇 |
1969年 | 1篇 |
排序方式: 共有663条查询结果,搜索用时 15 毫秒
651.
Eric S. Gratz Xiaofei Guan Jarrod D. Milshtein Uday B. Pal Adam C. Powell 《Metallurgical and Materials Transactions B》2014,45(4):1325-1336
The solid oxide membrane (SOM) process has been used at 1423 K to 1473 K (1150 °C to 1200 °C) to produce magnesium metal by the direct electrolysis of magnesium oxide. MgO is dissolved in a molten MgF2-CaF2 ionic flux. An oxygen-ion-conducting membrane, made from yttria-stabilized zirconia (YSZ), separates the cathode and the flux from the anode. During electrolysis, magnesium ions are reduced at the cathode, and Mg(g) is bubbled out of the flux into a separate condenser. The flux has a small solubility for magnesium metal which imparts electronic conductivity to the flux. The electronic conductivity decreases the process current efficiency and also degrades the YSZ membrane. Operating the electrolysis cell at low total pressures is shown to be an effective method of reducing the electronic conductivity of the flux. A two steel electrode method for measuring the electronic transference number in the flux was used to quantify the fraction of electronic current in the flux before and after SOM process operation. Potentiodynamic scans, potentiostatic electrolyses, and AC impedance spectroscopy were also used to characterize the SOM process under different operating conditions. 相似文献
652.
Trinetta V Vaidya N Linton R Morgan M 《International journal of food microbiology》2011,146(2):203-206
The increase in reported food-borne outbreaks linked with consumption of raw fruits and vegetables has motivated new research focusing on prevention of pre-harvest produce contamination. This study evaluates and compares the effectiveness of three non-thermal technologies, chlorine dioxide gas, ozone gas and e-beam irradiation, for inactivation of Salmonella enterica and Escherichia coli O157:H7 on pre-inoculated tomato, lettuce and cantaloupe seeds, and also their corresponding effect on seeds germination percentage after treatments. Samples were treated with 10 mg/l ClO2 gas for 3 min at 75% relative humidity, with 4.3 mg/l ozone gas for 5 min and with a dose of 7 kGy electron beam for 1 min. Initial load of pathogenic bacteria on seeds was ~ 6 log CFU/g. Results demonstrate that all treatments significantly reduce the initial load of pathogenic bacteria on seeds (p < 0.05). In particular, after ozone gas treatments 4 log CFU/g reduction was always observed, despite the seeds and/or microorganisms treated. ClO2 and e-beam treatments were noticeably more effective against Salmonella on contaminated tomato seeds, where 5.3 and 4.4 log CFU/g reduction were respectively observed. Germination percentage was not affected, except for cantaloupe seeds, where the ratio was significantly lowered after ClO2 treatments. Overall, the results obtained show the great applicability of these non-thermal inactivation techniques to control and reduce pathogenic bacteria contamination of seeds. 相似文献
653.
The RFID reader collision problem, in which an RFID reader's interrogation is interfered by other concurrent readers' transmission, is considered an important issue to reliable operation and thus to the wide‐spread deployment of RFID networks. In this paper, we present modeling and analysis of the RFID reader collision problem. We observe asymmetry between an RFID reader's and a tag's communication capabilities and develop an RFID radio model based on the asymmetry. By the model, we characterize the spatial reuse of RFID reader networks, and derive concurrent interrogation distance beyond which readers can transmit simultaneously without causing collision and the carrier sense threshold corresponding to the distance. We also examine the dual‐channel mode where available bandwidth is divided into two channels by which reader‐to‐tag communication and tag‐to‐reader communication are separated. We analyze and evaluate the performance of the dual‐channel mode in terms of spatial reuse and interrogation completion time. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
654.
Yujiao Lu Jing Wang Fulei Tang Uday P. Pratap Gangadhara R. Sareddy Krishnan M. Dhandapani Ana Capuano Zoe Arvanitakis Ratna K. Vadlamudi Darrell W. Brann 《International journal of molecular sciences》2022,23(10)
Hemoglobin (Hb) is the oxygen transport protein in erythrocytes. In blood, Hb is a tetramer consisting of two Hb-alpha (Hb-α) chains and two Hb-beta (Hb-β) chains. A number of studies have also shown that Hb-α is also expressed in neurons in both the rodent and human brain. In the current study, we examined for age-related regulation of neuronal Hb-α and hypoxia in the hippocampus and cerebral cortex of intact male and female mice. In addition, to confirm the role and functions of neuronal Hb-α, we also utilized lentivirus CRISPR interference-based Hb-α knockdown (Hb-α CRISPRi KD) in the non-ischemic and ischemic mouse hippocampus and examined the effect on neuronal oxygenation, as well as induction of hypoxia-inducible factor-1α (HIF-1α) and its downstream pro-apoptotic factors, PUMA and NOXA, and on neuronal survival and neurodegeneration. The results of the study revealed an age-related decrease in neuronal Hb-α levels and correlated increase in hypoxia in the hippocampus and cortex of intact male and female mice. Sex differences were observed with males having higher neuronal Hb-α levels than females in all brain regions at all ages. In vivo Hb-α CRISPRi KD in the mouse hippocampus resulted in increased hypoxia and elevated levels of HIF-1α, PUMA and NOXA in the non-ischemic and ischemic mouse hippocampus, effects that were correlated with a significant decrease in neuronal survival and increased neurodegeneration. As a whole, these findings indicate that neuronal Hb-α decreases with age in mice and has an important role in regulating neuronal oxygenation and neuroprotection. 相似文献
655.
Effects of moisture and UV exposure on liquid molded carbon fabric reinforced nylon 6 composite laminates 总被引:2,自引:0,他引:2
Liquid molding of thermoplastics has been limited by high resin viscosity, high temperature processing requirements, and a short processing window [Sibal PW, Camargo RE, Macosko CW. Designing nylon 6 polymerization for RIM. In: Proceedings of the second international conference on reactive processing of polymers, Pittsburgh, PA; 1982, p. 97–125.]. The processing parameters for vacuum assisted resin transfer molding (VARTM) developed by the authors and previously reported [Pillay S, Vaidya UK, Janowski GM. Liquid molding of carbon fabric-reinforced nylon matrix composite laminates. J Thermoplast Compos Mater 2005;18:509–27] have been adapted to process carbon/nylon 6 composite panels. The present work addresses the effects of moisture and ultraviolet (UV) exposure on the static and dynamic mechanical properties of carbon fabric reinforced, thermoplastic polyamide 6 matrix panels processed using VARTM. The Bao and Yee dual diffusivity model [Bao LR, Yee AF. Moisture diffusion and hygrothermal aging in bismaleimide matrix carbon fiber composites: Part II – Woven and hybrid composites. Compos Sci Technol 2002;62:2111–9] was applied to evaluate the moisture uptake for the C/PA6, fully immersed in distilled water at 100 °C. SEM results show that moisture exposure result in surface micro-cracks compromise of the fiber–matrix interface. The flexural strength is lowered by 45%, after exposure to moisture at 100 °C. UV exposure up to 600 h causes yellowing of the samples and an increase in crystallinity from 40% to 44%. 相似文献
656.
Kerehalli Vinayaka Prasad Rajashekhar Choudhari Hanumesh Vaidya Ashwini Bhat Isaac Lare Animasaun 《亚洲传热研究》2023,52(1):216-235
In recent years, a great deal of interest has been generated in modern micro- and nanotechnologies for micro/nano-electronic devices. These technologies are increasingly utilizing sophisticated fluid media to enhance performance. Among the new trends is the simultaneous adoption of nanofluids and biological micro-organisms. Motivated by bio-nanofluid vertical channel oxygenators in medical engineering, in the current work, a mathematical model is developed to examine the flow of mixed convective couple-stress nanofluids in a vertical channel with a transverse magnetic field, fluid viscosity that changes with temperature, and thermal conductivity. The non-Newtonian model follows Brownian motion and heat spread by nanoparticles in a fluid under coupled stress. Highly linked, nonlinear regulating equations are translated into nondimensional equations using relevant variables. The governing equations are then turned into a form with no dimensions. The Keller-box technique, a second-order finite difference method for solving second-order equations, is used to solve them numerically. On the other hand, the effects of different non-Newtonian flow parameters, such as the couple stress fluid parameter, the magnetic parameter, the variable fluid viscosity, the variable thermal conductivity parameters, the Brinkman number, the nanofluid and buoyancy parameters, and the rate of chemical reaction parameter, are carefully studied. The velocity, temperature, and concentration fields are calculated over a wide range of possible values for the relevant parameters. 相似文献
657.
Anil Kumar Shubham Bawa Jayanta Bera Uday Shankar Satyajit Sahu Anasuya Bandyopadhyay 《应用聚合物科学杂志》2023,140(1):e53242
In this study, Al(III)-metallopolymer is synthesized with our previously reported ligand to understand the difference in the interaction of the reported ligand with transition metal ions (Fe(II) and Cr(II) ions) and smaller cationic radius main group metal ion. Al(III)-metallopolymer is thoroughly characterized by different analytical techniques to understand the structure–property relationship. Surface morphological analyses reveal the formation of long nano-fiber strands on the respective substrates. This polymer has shown reversible redox behavior, which is ligand centric as no d-orbitals are available on the central metal ion for the electron push-pull mechanism. Al(III)-metallopolymer is fluorescent active, and it is shown a reversible change in absorption spectrum on the application of the appropriate potential. This ligand-based redox-switching also generates a bistable state when a metal–insulator(thin film of polymer)-metal sandwich device is probed in between ±1 V, and it is stable in the ambient condition to sustain several flip-flop cycles without any degradation for 103 s as observed from the experimental data. This work enlightens a new metallopolymer with a low value of SET-RESET voltage and a long retention time for the future memristive device, which can operate at very low voltage compared to conventional Si-based memory chips. 相似文献
658.
In this work, we propose a stateless blockchain called CompactChain, which compacts the entire state of the UTXO (Unspent Transaction Output) based blockchain systems into two RSA accumulators. The first accumulator is called Transaction Output (TXO) commitment which represents the TXO set. The second one is called Spent Transaction Output (STXO) commitment which represents the STXO set. In this work, we discuss three algorithms: (i) To update the TXO and STXO commitments by the miner. The miner also provides the proofs for the correctness of the updated commitments; (ii) To prove the transaction’s validity by providing a membership witness in TXO commitment and non-membership witness against STXO commitment for a coin being spent by a user; (iii) To update the witness for the coin that is not yet spent; The experimental results evaluate the performance of the CompactChain in terms of time taken by a miner to update the commitments and time taken by a validator to verify the commitments and validate the transactions. We compare the performance of CompactChain with the existing state-of-the-art works on stateless blockchains. CompactChain shows a reduction in commitments update complexity and transaction witness size which inturn reduces the mempool size and propagation latency without compromising the system throughput (Transactions per second (TPS)). 相似文献
659.
Scaling down the circuits of complementary metal oxide semiconductor increases the leakage current. Input vector control is an extremely popular method for controlling leakage without using any technological modification. However, it is less effective for larger logic depth circuits. Our study proposes a Worst Leakage State (WLS) free‐node algorithm based on gate replacement technique, in which, when the logic gate of a given circuit goes into WLS, it is replaced by a suitable variant of the gate which in turn reduces the leakage current in an idle mode of the circuit at the same input vector. These variants minimize leakage under WLS conditions. For replacement purpose, four variants (V1–V4) of a two‐input NAND gate are proposed. This technique is applied on different circuits and some benchmark circuits such as ISCAS'85 (C17) and ITC'99 (B01, B02 and B06) (total of 10 circuits), according to the proposed algorithm with variants V1–V4. The average total power is reduced to 15.04%, 15.04%, 35.7% and 31.5%, and the leakage current is reduced to 42.96%, 42.96%, 84.25% and 84.52%, respectively, for variants V1–V4. The average delay is decreased by 16.03% in V1 and V2 variants and increased by 7.74% and 13.16% for variants V3 and V4, respectively, as compared with the results of conventional circuits at 45‐nm Berkeley Predictive Technology Model technology. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
660.
Vikas S. Hakke Vividha K. Landge Shirish H. Sonawane G. Uday Bhaskar Babu Sivakumar Manickam Grzegorz Boczkaj 《加拿大化工杂志》2023,101(4):1815-1830
The complex structured starch particles were reduced to the nanoscale size range through hydrolysis utilizing low concentration acid assisted by ultrasound irradiation. The synthesized starch nanoparticles (SNPs) were characterized by transmission electron microscopy (TEM), Fourier-transform infrared (FTIR), and X-ray diffraction (XRD) techniques. The synthesized SNPs possessed surface activated entities, as many cationic functional groups were confirmed through the FTIR spectrum. Also, these SNPs were effectively utilized to separate heavy Cu metal ions from the synthetic ion solution. The SNPs were characterized using field emission scanning electron microscope (FESEM), X-ray photoelectron spectroscopy (XPS), and Brunauer–Emmett–Teller (BET) analysis for the surface modification after the adsorption process. The weak electrostatic interaction between the SNP surface and Cu ion was confirmed by the XPS spectrum and energy-dispersive X-ray spectroscopy. The maximum efficiency of Cu ions removal was about 93% at an optimal pH 5 and 25 mg/ml dosage. The adsorption equilibrium was obtained in 60 min. The nitrogen isotherm BET analysis of SNPs after adsorption shows a higher specific surface area of 18.552 m2/g, attributed to the interaction and presence of Cu ions on the SNP surface. The process feasibility was validated by the Langmuir isotherm model. The process exhibits pseudo-second-order adsorption kinetics and follows the Langmuir isotherm. The RL predicted by the Langmuir isotherm mechanism is 0.017, implying favourable adsorption. The process is reproducible and allows for the separation of heavy metal ions from the wastewater through biosorption effectively. 相似文献