全文获取类型
收费全文 | 491篇 |
免费 | 36篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 15篇 |
综合类 | 1篇 |
化学工业 | 135篇 |
金属工艺 | 17篇 |
机械仪表 | 9篇 |
建筑科学 | 16篇 |
矿业工程 | 1篇 |
能源动力 | 26篇 |
轻工业 | 47篇 |
水利工程 | 9篇 |
石油天然气 | 4篇 |
无线电 | 67篇 |
一般工业技术 | 65篇 |
冶金工业 | 26篇 |
原子能技术 | 7篇 |
自动化技术 | 84篇 |
出版年
2024年 | 2篇 |
2023年 | 5篇 |
2022年 | 14篇 |
2021年 | 31篇 |
2020年 | 26篇 |
2019年 | 32篇 |
2018年 | 28篇 |
2017年 | 37篇 |
2016年 | 28篇 |
2015年 | 11篇 |
2014年 | 41篇 |
2013年 | 49篇 |
2012年 | 31篇 |
2011年 | 22篇 |
2010年 | 34篇 |
2009年 | 20篇 |
2008年 | 22篇 |
2007年 | 12篇 |
2006年 | 9篇 |
2005年 | 9篇 |
2004年 | 6篇 |
2003年 | 3篇 |
2002年 | 2篇 |
2001年 | 2篇 |
2000年 | 5篇 |
1999年 | 4篇 |
1998年 | 2篇 |
1997年 | 5篇 |
1996年 | 4篇 |
1995年 | 6篇 |
1994年 | 5篇 |
1993年 | 7篇 |
1992年 | 1篇 |
1991年 | 2篇 |
1990年 | 1篇 |
1989年 | 1篇 |
1988年 | 1篇 |
1987年 | 2篇 |
1986年 | 2篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1980年 | 1篇 |
1973年 | 2篇 |
排序方式: 共有529条查询结果,搜索用时 15 毫秒
71.
Mahmoud Moslehi-Fard Naser Alinejad Chapar Rasouli Asghar Sadigzadeh 《Journal of Fusion Energy》2012,31(4):346-351
Toroidal and Poloidal magnetic fields have an important effect on the tokomak topology. Damavand Tokomak is a small size tokomak characterized with k?=?1.2, B t?=?1T, R 0?=?36?cm, maximum plasma current is about 35?KA with a discharge time of 21?ms. In this experimental work, the variation of poloidal magnetic field on the torodial cross section is measured and analyzed. In order to measure the polodial magnetic field, 18 probes were installed on the edge of tokomak plasma with ?θ?=?18°, while a limiter was installed inside the torus. Plasma current, I p, induces a polodial magnetic field, B p, smaller than the torodial magnetic field B t. Magnetic lines B produced as a combination of B t and B p, are localized on the nested toroidal magnetic surfaces. The presence of polodial magnetic field is necessary for particles confinement. Mirnov oscillations are the fluctuations of polodial magnetic field, detected by magnetic probes. Disrupted instability in Tokomak typically starts with mirnov oscillations which appear as fluctuations of polodial magnetic field and is detected by magnetic probes. Minor disruptions inside the plasma can contain principal magnetic islands and their satellites can cause the annihilation of plasma confinement. Production of thin layer of turbulent magnetic field lines cause minor disruption. Magnetic limiter may cause the deformation of symmetric equilibrium configuration and chaotic magnetic islands reveal in plasma occurring in thin region of chaotic field lines close to their separatrix. The width of this chaotic layer in the right side of poloidal profile of Damavand Tokomak is smaller than the width in the left side profile because of Shafranov displacement. Ergodic region in the left side of profile develops a perturbation on the magnetic polodial field lines, B p, that are greater in magnitude than that in the right side, although the values of B p on the left side are smaller than that on the right side of the profile. The Left side of profile is close to the principal magnetic axis and the right side is away from Z axis of Tokamak. 相似文献
72.
Biomass should be considered as one of the promising sources of energy for mitigating greenhouse gas (GHG) emissions. Co-firing biomass with coal has become a solution for meeting the power crisis as well as to reduce the pollutant emissions. The biomass fuels typically found from woody to grassy and solid recovered fuels depending on its origin and properties. It is suggested that co-firing coal with biomass has a substantial effect on SOx and NOx emission level. The ashing process, fly ash quality depends on the conversion technology, capture technology and the properties of the biomass. In order to control the furnace efficiency and production, burnout, optimum injection of biomass sharing with specific information of particle ignition properties are also important. A number of small/laboratory scale and industrial scale experiments have been conducted by different researchers. Different experimental studies performed are reviewed, grouped and summarized based on the fuel processing technology, burnout performance, emission level, environmental aspect, ash information and deposit characteristics, effect of co-firing ratios and adoption of oxy-fuel co-firing. Overall, this paper will highlight existing technologies and emerging trends in co-firing of different types of biomass which will be helpful for future investigations. 相似文献
73.
M. H. Ehsani M. E. Ghazi P. Kameli F. S. Razavi 《Journal of Superconductivity and Novel Magnetism》2013,26(10):3151-3157
The Co-doped bilayered LaSr2Mn2O7 manganite at low Co concentrations (0–0.15) was synthesized by the sol–gel process. The X-ray diffraction (XRD) technique confirms phase formation for all the samples under investigation. The results of ac magnetic susceptibility measurements indicate the effect of Co doping on the magnetic ordering phases. The indications of charge ordering (CO) transitions were observed in all the prepared compounds. The CO magnetic phase transition temperature was observed systematically shift to lower temperatures as the Co concentration increases. There was an anomalous oscillating magnetic behavior in all samples with a few peaks before the CO temperature in the paramagnetic (PM) region so that with an increasing Co doping, the number of peaks and amplitude were decreased. Also, the ac susceptibility measurements were performed in the presence of an applied dc magnetic field to further study of this oscillating behavior. 相似文献
74.
Using the hyperbolic heat conduction model, thermal stresses generated within a rapidly heated thin metal plate are investigated numerically. The effects of different parameters such as the form, duration, amplitude, and penetration depth of the heating source on the temperature, thermal moment, deflection, and thermal stresses are studied. It is found that under ultra-fast heating of very thin plates, the hyperbolic heat conduction model must be adopted to model the thermal behavior. 相似文献
75.
There is considerable interest in the use of ruthenium as an ultrathin trench liner in damascene copper plating used to fabricate
on-chip interconnects. The problem is that when freshly deposited ruthenium films are exposed to air, their surfaces tend
to undergo spontaneous oxidation, and such deposits (as demonstrated here) are reluctant to undergo reduction. Copper deposition
in an acid plating bath occurs readily on the oxidized ruthenium, but the presence of oxide is known to have a detrimental
effect both on the copper superfilling process and copper adhesion at the Ru/Cu interface. 相似文献
76.
Virgin olive oil (VOO) based polyetheramide (PEtA) was developed from N-N′-bis(2-hydroxyl ethyl) olive fatty amide (HEOA) and orcinol through condensation polymerization. PEtA was further treated with toluylene 2,4-diisocynate (TDI) with different percentages (20–30 wt%) via addition polymerization to obtain poly(ether amide urethane) (PEtAU). The structural elucidation of HEOA, PEtA and PEtAU were carried out by FT-IR, 1H NMR and 13C NMR spectroscopic techniques. Physico-chemical and physico-mechanical properties of the material were investigated by standard methods. Thermal stability and curing behavior of virgin olive oil, HEOA, and PEtAU were assessed by thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC). The corrosion behavior was investigated by potentiodynamic polarization measurements in different corrosive environments (3.5 wt% HCl, 5 wt% NaCl, 3.5 wt% NaOH, tap water) at room temperature. The results showed that UPEtA coatings exhibit good physico-mechanical as well as corrosion resistance performance and can be safely used up to 200 °C. The work is an attempt for alternate utilization of olive oil. 相似文献
77.
M. Zamani M. Taghizadeh M. Naser Moghadasi B. S. Virdee 《Analog Integrated Circuits and Signal Processing》2012,71(1):143-150
In this letter, a 5th-Order single-loop low distortion Sigma–Delta Modulator (SDM) is implemented with the combination of
the comparator-based switched-capacitor (CBSC)-based and op-amp-based techniques for asymmetric digital subscriber line (ADSL)
applications. This structure, which uses integrator (CBSC-based) and IIR filter (op-amp-based) concurrently, has relatively
fewer feed-forward paths and modulator coefficients for sensitivity reduction to mismatch. To lower the power consumption
of the modulator, the integrators are implemented with CBSC, the IIR filter block is implemented by single OTA, and a passive
adder is used to realize the adder at the input of the 5-bit quantizer. The design purpose is minimizing the power consumption
while the dynamic performance maintains high. As shown in the simulation result, for a 2-MHz signal bandwidth, the modulator
achieves a dynamic range (DR) of 86.5 dB and a peak signal-to-noise and distortion ratio (SNDR) of 85 dB with an oversampling
ratio of 8. In addition it consumes 18.75 mW from a 1.8-V power supply at 32 MS/s, which obtains a figure of merit of 1.6e−3. 相似文献
78.
Naser Faisal Al Tannak 《化学与化工:英文版》2014,(5):524-529
Naloxone is a well-known opioid antagonist indicated for the treatment of CNS (central nervous system) and respiratory depression induced by natural or synthetic opioid in adults and neonates whose mothers have received opioids. While it has been reported that an injection of 0.2 mg/mL of naloxone hydrochloride is physically and chemically stable, data on photostability on continuous i.v. infusion of 0.2 mg/mL of naloxone hydrochloride has not been reported. Therefore, a method was required for assessment of naloxone hydrochloride photostability. A high performance LC-MS (liquid chromatography/mass spectrometry) method was established to evaluate the photostability of naloxone hydrochloride. Injections of naloxone hydrochloride in 0.9% sodium chloride were exposed to artificial light and stored at room temperature (22 ~C) and 37 ~C. Naloxone losses up to 9.79% of its initial concentration when exposed to light at room temperature for 192 h, but the degradation increased up to 14.91% as the storage temperature increase. The disappearance of naloxone hydrochloride was correlated with the appearance of nor-oxymorphonedegradant. Naloxone hydrochloride is photosensitive and degradation increased at highly temperature and light intensity. Therefore, naloxone i.v. infusion solutions should either be protected from light and/or be frequently replaced when being administered to patients. 相似文献
79.
Shahram?ArbabEmail author Parviz?Noorpanah Naser?Mohammadi Ahmad?Zeinolebadi 《Polymer Bulletin》2011,66(9):1267-1280
Investigation of structural development of acrylic fibers during the early stages of the wet-spinning process has great importance
both in carbon fiber and textile industries. The simultaneous effects of increasing polymer concentration, jet-stretching
and hot-drawing on porosity, morphology, and mechanical properties of wet-spun poly(acrylonitrile) fibers were studied. The
detailed microstructure of the voids was characterized by electron microscopy, porosimetry, and thermoporometry. The effects
of jet-stretching/hot-drawing on the overall porosity of the fibers were negligible below a threshold polymer concentration.
Increasing polymer concentration from 10 to 20 vol.% reduced the total porosity. Hot-drawing was more effective in reducing
the overall porosity of the fibers in comparison with jet-stretching. Stretching and drawing replaced the macrovoids by dense
ligaments but did not change the volume fraction of nanovoids, however, shifted nanovoids size distribution toward smaller
values. In general, Young’s modulus and elongation at break increased by decreasing overall porosity, however, they depended
also on the distribution of voids size and chain orientation along the fiber axis. Strength–diameter correlation showed a
good agreement with the Griffith’s theory. 相似文献
80.