全文获取类型
收费全文 | 1304篇 |
免费 | 81篇 |
国内免费 | 5篇 |
专业分类
电工技术 | 25篇 |
综合类 | 1篇 |
化学工业 | 439篇 |
金属工艺 | 39篇 |
机械仪表 | 36篇 |
建筑科学 | 49篇 |
矿业工程 | 5篇 |
能源动力 | 51篇 |
轻工业 | 191篇 |
水利工程 | 5篇 |
石油天然气 | 2篇 |
武器工业 | 1篇 |
无线电 | 80篇 |
一般工业技术 | 238篇 |
冶金工业 | 26篇 |
原子能技术 | 9篇 |
自动化技术 | 193篇 |
出版年
2023年 | 5篇 |
2022年 | 54篇 |
2021年 | 95篇 |
2020年 | 35篇 |
2019年 | 46篇 |
2018年 | 50篇 |
2017年 | 48篇 |
2016年 | 70篇 |
2015年 | 46篇 |
2014年 | 65篇 |
2013年 | 144篇 |
2012年 | 81篇 |
2011年 | 81篇 |
2010年 | 65篇 |
2009年 | 63篇 |
2008年 | 44篇 |
2007年 | 37篇 |
2006年 | 39篇 |
2005年 | 26篇 |
2004年 | 30篇 |
2003年 | 20篇 |
2002年 | 25篇 |
2001年 | 8篇 |
2000年 | 11篇 |
1999年 | 12篇 |
1998年 | 14篇 |
1997年 | 15篇 |
1996年 | 14篇 |
1995年 | 7篇 |
1994年 | 8篇 |
1993年 | 11篇 |
1992年 | 5篇 |
1991年 | 6篇 |
1990年 | 7篇 |
1989年 | 3篇 |
1987年 | 10篇 |
1986年 | 3篇 |
1985年 | 15篇 |
1984年 | 13篇 |
1983年 | 8篇 |
1982年 | 16篇 |
1981年 | 4篇 |
1980年 | 6篇 |
1979年 | 3篇 |
1978年 | 3篇 |
1977年 | 6篇 |
1976年 | 7篇 |
1975年 | 3篇 |
1971年 | 1篇 |
1967年 | 1篇 |
排序方式: 共有1390条查询结果,搜索用时 15 毫秒
81.
Two series of experiments of hydroprocessing of light gas oil - rape oil mixtures were carried out. The reactor feed was composed of raw material: first series — 10 wt.% rape oil and 90 wt.% of diesel oil; second series — 20 wt.% rape oil and 80 wt.% of diesel oil. 相似文献
82.
D. Trefon-Radziejewska J. Bodzenta T. Łukasiewicz 《International Journal of Thermophysics》2013,34(5):813-819
Thermal diffusivities of pure and doped gadolinium calcium oxoborate (GdCOB) single crystals were measured as a function of the temperature along optical indicatrix axes X, Y, and Z. Three GdCOB samples were investigated, chemically pure single crystal, the one doped with 4 at% of Nd and the next one doped with 7 at% of Yb. Measurements were carried out for temperature range 40 °C to 300 °C. Determination of the thermal diffusivity based on an analysis of thermal wave propagation in the sample. For a detection of temperature disturbance propagating in the sample the mirage effect was used. Obtained results show that the thermal diffusivity decreases with the increase of sample temperature for all investigated crystals. The GdCOB single crystals reveal a strong anisotropy. The thermal diffusivity along Y direction has the highest value while values obtained in X and Z axes are much lower. Dopants cause decrease in the thermal diffusivity for all investigated directions. 相似文献
83.
Agnieszka Łącz Łukasz Łańcucki Radosław Lach Bartosz Kamecki Ewa Drożdż 《International Journal of Hydrogen Energy》2018,43(18):8999-9005
Series of single-phase materials with assumed formula SrTi1?xCrxO3 (where x = 0, 1, 4, 6 mol.%) were obtained by sol-gel method. The structure and microstructure of materials were characterised by X-ray diffraction and scanning electron microscopy methods. Moreover, the study of electrical properties and evaluation of chemical stability in CO2/H2O atmosphere was performed by electrochemical impedance spectroscopy and thermogravimery methods, respectively. The possibility of participation of Cr-doped strontium titanate in oxidation–reduction processes was analysed by temperature-programed reduction (TPR) and temperature-programed oxidation (TPOx) measurements. The changes of lattice parameters together with XPS analysis, the Seebeck coefficient measurements results and TPR profiles obtained for SrTi1?xCrxO3 materials prove the presence of chromium on +3 and +6 oxidation stages. Thus, chromium can be treated as both acceptor- and donor-type dopant in the SrTiO3 structure. The Cr3+/Cr6+ ratio strongly affects the electrical properties, as the change of conduction mechanism was observed. The results of performed stability test clearly indicate that incorporation of chromium into SrTiO3 structure results with decrease of chemical stability in CO2 atmosphere. 相似文献
84.
Vibration analysis of machines operating under non-stationary operational conditions requires special attention. This refers to the necessity of use of order tracking algorithms together with additional advanced signal processing methods, especially when faults indicators of interest are located in resonance frequency ranges. 相似文献
85.
Renata Cegielska-Radziejewska Grzegorz Lesnierowski Tomasz Szablewski Jacek Kijowski 《European Food Research and Technology》2010,231(6):959-964
Lysozyme (N-acetyl-muramyl-hydrolase E.C. 3.2.1.17) is a low-molecular enzyme (14,400 Da) found in body secretions, systemic
fluids and tissues of humans and animals. Antibacterial activity of lysozyme monomer is limited first of all to Gram-positive
bacteria, which is connected with the structure of the cell wall. This enzyme catalyzes hydrolysis of β-glycoside bonds (1–4),
releasing N-acetylglucosamine and N-acetylmuramic acid. The spectrum of antibacterial activity of lysozyme may be extended
thanks to modifications of the enzyme. The aim of the study was to assess antibacterial activity, hydrolytic activity and
surface hydrophobicity of different forms of lysozyme. Chemical and thermo-chemical modification of lysozyme was performed,
and the antibacterial action of lysozyme monomer and modified preparations were compared. It was found that in comparison
with monomer and the control, all modified preparations exhibit effective action against Gram (−) bacteria Pseudomonas fluorescens. A particularly effective action was found in case of lysozyme subjected to thermo-chemical modification, which was characterized
by the highest proportion of oligomeric forms and the highest hydrophobicity. 相似文献
86.
The impact of liberalisation of the electricity market on the hard coal mining sector in Poland 总被引:1,自引:0,他引:1
The liberalisation of the electricity market changed the conditions of operation not only for the power industry, but also for related sectors. One of the particularly sensitive industries in Poland is coal mining, which is the result of coal-based structure of electricity generation. As it is more difficult, in the liberalised market, to burden consumers with all the costs, electricity producers are eager to transfer the risk of operation to the suppliers. That increases uncertainty about the future of the hard coal industry. The aim of this paper was to quantitatively estimate the impact that liberalisation of the electricity markets may have on the coal mining sector in Poland. First of all, the possible areas of that impact were identified. Then the model, which involved detailed relations in the impact areas identified, was developed and employed to evaluate the performance of the mining sector. The comparison of scenarios of a monopolistic electricity sector with a liberalised one enabled an estimation of the scale of the impact on the mining sector to be made. The results showed that liberalisation causes decreased coal consumption and decreased operating profits in coal companies. However, some savings in electricity costs are possible for coal producers. 相似文献
87.
X-ray Photoelectron Spectroscopy (XPS) was used to study the influence of low energy Ar+ ion bombardment, electron bombardment and Pt deposition on the SrTiO3 (STO) single crystal electronic structure. Atomic composition changes were found and attributed to chemical reconstruction of the STO surface. A clear correlation between the presence of conducting, low Ti oxidation states in valence band and core level changes was detected. A strong effect caused by electron irradiation was ascribed to the electroreduction process. The influence of lanthanum doping on surface instability of STO was also discussed. The La doped sample (STO: 3,75% La) was found to be modified upon Pt metal deposition to a higher degree than pure STO crystal. 相似文献
88.
M. Ławryńczuk 《化学工程与技术》2009,32(10):1578-1587
A nonlinear Model Predictive Control (MPC) algorithm and its application to a distillation column are described. The algorithm uses a neural model of the process that is linearized online around the current operating point. The algorithm is computationally efficient because the control policy is calculated explicitly without any optimization. The algorithm requires online repetition of a matrix decomposition task and the solution of linear equations. The obtained solution is projected onto the admissible set of constraints imposed on the magnitude and the increment of the manipulated variables. For the distillation column considered, the control accuracy is comparable not only to that obtained in MPC with online linearization and quadratic programming but also to that obtained in nonlinear MPC, which is based on full nonlinear optimization repeated at each sampling instant. 相似文献
89.
Dr.-Ing. habil. T. Łobos Dr.-Ing. A. Wordoffa 《Electrical Engineering (Archiv fur Elektrotechnik)》1987,70(6):389-399
Contents Using thyristor and thyristor-diode a.c. choppers causes distortion of currents and voltages in electrical power networks. In this paper the currents in three-phase, three-wire circuits with thyristor and thyristor-diode a.c. choppers are analysed, making allowances for asymmetrical phase-angle triggering. The computation results of the extinction angles versus firing angles, phase shift angles of the load and degree of asymmetry are shown. The d.c. and harmonic components of the current waveforms were calculated by applying Fourier analysis. The computation results of the magnitudes, which are characteristic of deformed waveforms are also presented.
Übersicht Der Einsatz von Thyristoren und Thyristordioden verursacht Verzerrungen von Strömen und Spannungen in elektrischen Versorgungsnetzen. In diesem Beitrag werden Stromverläufe in Drehstromnetzen unter Berücksichtigung unsymmetrischer Ansteuerung durch Thyristoren analysiert. Die errechneten Abhängigkeiten des Löschwinkels von der Phasenlage der Last und der Unsymmetrie der Ansteuerung werden dargestellt. Mit Hilfe der Fourieranalyse werden Gleichstromanteil und Oberschwingungen der Ströme ermittelt. Berechnet und dargestellt werden auch andere Größen, die für nichtlinear verzerrte Vorgänge charakteristisch sind.相似文献
90.
Frydrychowski AF Gumiński W Rojewski M Kaczmarek J Juzwa W 《IEEE transactions on bio-medical engineering》2002,49(8):887-904
This paper presents technical foundations for a new technique of near-infrared transillumination-backscattering sounding, which is designed to enable noninvasive detection and monitoring of changes in the width of the subarachnoid space (SAS) and magnitude of cerebrovascular pulsation in humans. The key novelty of the technique is elimination of influence of blood flow in the scalp on the signals received from two infrared sensors-proximal and distal. A dedicated digital algorithm is used to estimate on line the ratio of the powers of received signals, referred to as two-sensor distal-to-proximal received power quotient, TQ (t). The propagation duct for NIR radiation reaching the distal sensor is the SAS filled with translucent cerebrospinal fluid. Information on slow fluctuations of the average width of the SAS is contained in the slow-variable part of the TQ (t), called the subcardiac component, and in TQ itself. Variations in frequency and magnitude of faster oscillations of the width of that space around the baseline value, dependent on cerebrovascular pulsation, are reflected in instantaneous frequency and envelope of the fast-variable component. Frequency and magnitude of the cerebrovascular pulsation depend on the action of the heart, so this fast-variable component is referred to as the cardiac component. 相似文献