全文获取类型
收费全文 | 2833篇 |
免费 | 91篇 |
国内免费 | 9篇 |
专业分类
电工技术 | 44篇 |
综合类 | 1篇 |
化学工业 | 697篇 |
金属工艺 | 58篇 |
机械仪表 | 59篇 |
建筑科学 | 49篇 |
矿业工程 | 3篇 |
能源动力 | 91篇 |
轻工业 | 201篇 |
水利工程 | 12篇 |
石油天然气 | 7篇 |
无线电 | 299篇 |
一般工业技术 | 523篇 |
冶金工业 | 566篇 |
原子能技术 | 27篇 |
自动化技术 | 296篇 |
出版年
2023年 | 26篇 |
2022年 | 53篇 |
2021年 | 75篇 |
2020年 | 70篇 |
2019年 | 65篇 |
2018年 | 85篇 |
2017年 | 60篇 |
2016年 | 62篇 |
2015年 | 57篇 |
2014年 | 78篇 |
2013年 | 174篇 |
2012年 | 105篇 |
2011年 | 107篇 |
2010年 | 75篇 |
2009年 | 87篇 |
2008年 | 84篇 |
2007年 | 74篇 |
2006年 | 83篇 |
2005年 | 58篇 |
2004年 | 43篇 |
2003年 | 44篇 |
2002年 | 45篇 |
2001年 | 22篇 |
2000年 | 41篇 |
1999年 | 64篇 |
1998年 | 200篇 |
1997年 | 135篇 |
1996年 | 101篇 |
1995年 | 60篇 |
1994年 | 63篇 |
1993年 | 58篇 |
1992年 | 38篇 |
1991年 | 31篇 |
1990年 | 22篇 |
1989年 | 42篇 |
1988年 | 33篇 |
1987年 | 30篇 |
1986年 | 26篇 |
1985年 | 22篇 |
1984年 | 20篇 |
1983年 | 18篇 |
1982年 | 30篇 |
1981年 | 31篇 |
1980年 | 26篇 |
1979年 | 21篇 |
1978年 | 17篇 |
1977年 | 29篇 |
1976年 | 41篇 |
1974年 | 15篇 |
1973年 | 24篇 |
排序方式: 共有2933条查询结果,搜索用时 359 毫秒
71.
Nanoclays for polymer nanocomposites, paints, inks, greases and cosmetics formulations, drug delivery vehicle and waste water treatment 总被引:2,自引:0,他引:2
Hasmukh A. Patel Rajesh S. Somani Hari C. Bajaj Raksh V. Jasra 《Bulletin of Materials Science》2006,29(2):133-145
An overview of nanoclays or organically modified layered silicates (organoclays) is presented with emphasis placed on the
use of nanoclays as the reinforcement phase in polymer matrices for preparation of polymer/layered silicates nanocomposites,
rheological modifier for paints, inks and greases, drug delivery vehicle for controlled release of therapeutic agents, and
nanoclays for industrial waste water as well as potable water treatment to make further step into green environment. A little
amount of nanoclay can alter the entire properties of polymers, paints, inks and greases to a great extent by dispersing 1nm
thick layered silicate throughout the matrices. The flexibility of interlayer spacing of layered silicates accommodates therapeutic
agents which can later on be released to damaged cell. Because the release of drugs in drug-intercalated layered materials
is controllable, these new materials have a great potential as a delivery host in the pharmaceutical field. The problem of
clean water can be solved by treating industrial and municipal waste water with organoclays in combination with other sorbents
like activated carbon and alum. Organoclays have proven to be superior to any other water treatment technology in applications
where the water to be treated contains substantial amounts of oil and grease or humic acid. 相似文献
72.
Shuangqun Zhao Xishan Xie Gaylord D. Smith Shailesh J. Patel 《Materials & Design》2006,27(10):1120-1127
INCONEL alloy 740 is a newly developed Ni–Cr–Co–Mo–Nb–Ti–Al superalloy in the application to ultra-supercritical boilers with steam temperatures up to 700 °C. By means of scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), micro-chemical phase analyses, and corrosion-resisting test, this paper investigates the structure stability of the alloy at elevated temperature and concentrates on coal ash corrosion performance of the alloy under the simulated coal ash/flue gas condition. Experimental results show that the most important structure instabilities of the alloy during prolonged aging are γ′ coarsening, γ′ to η transformation and G phase formation at grain boundary. The performance of corrosion resistance of the alloy would meet the requirement of ultra-supercritical boiler tubes. The phase computation by means of Thermo-Calc has been adopted in chemical composition modification for structure stability improvement. Two suggested new modified alloys in adjustment of the Al and Ti contents and in control of Si level, and also in maintenance of Cr content of the alloy were designed and melted for experimental investigation. These two modified alloys exhibit more stable microstructure during 760 °C long time aging. 相似文献
73.
F. Abdollahi H.A. Talebi R.V. Patel 《Mechatronics, IEEE/ASME Transactions on》2006,11(4):488-495
This paper presents an approach for stable identification of multivariable nonlinear system dynamics using a multilayer feedforward neural network. Unlike most of the previous neural network identifiers, the proposed identifier is based on a nonlinear-in-parameters neural network (NLPNN). Therefore, it is applicable to systems with higher degrees of nonlinearities. Both parallel and series-parallel models are used with no a priori knowledge about the system dynamics. The method can be considered both as an online identifier that can be used as a basis for designing a neural network controller as well as an offline learning scheme for monitoring the system states. A novel approach is proposed for the weight updating mechanism based on the modification of the backpropagation (BP) algorithm. The stability of the overall system is shown using Lyapunov's direct method. To demonstrate the performance of the proposed algorithm, an experimental setup consisting of a three-link macro-micro manipulator (M/sup 3/) is considered. The proposed approach is applied to identify the dynamics of the experimental robot. Experimental and simulation results are given to show the effectiveness of the proposed learning scheme. 相似文献
74.
C. Ji N. Chubun R.G. Broeke J. Cao Y. Du S.J.B. Yoo K.Y. Liou J.R. Lothian S. Vatanapradit S.N.G. Chu B. Patel W.S. Hobson W.T. Tsang 《Photonics Technology Letters, IEEE》2006,18(4):625-627
We report a 10-GHz colliding pulse mode-locked laser fabricated with integrated active-passive waveguides. The laser fabrication adopted a deep reactive ion etching and single-step metal-organic vapor phase epitaxy regrowth process for forming the buried heterostructure waveguide. Clean output pulses resulted from laterally tilting the active-passive interface and effectively suppressing residual back-reflections at the interface. Hybrid mode-locking resulted in a synchronized transform-limited sech/sup 2/optical waveform. Pulsewidth, chirp, timing jitter, and frequency-locking range were investigated through systematic device biasing condition optimization. 相似文献
75.
K. K. Makhija Arabinda Ray R. M. Patel U. B. Trivedi H. N. Kapse 《Bulletin of Materials Science》2005,28(1):9-17
A sensor for ammonia gas and ethanol vapour has been fabricated using indium oxide thin film as sensing layer and indium tin
oxide thin film encapsulated in poly(methyl methacrylate) (PMMA) as a miniature heater. For the fabrication of miniature heater
indium tin oxide thin film was grown on special high temperature corning glass substrate by flash evaporation method. Gold
was deposited on the film using thermal evaporation technique under high vacuum. The film was then annealed at 700 K for an
hour. The thermocouple attached on sensing surface measures the appropriate operating temperature.
The thin film gas sensor for ammonia was operated at different concentrations in the temperature range 323–493 K. At 473 K
the sensitivity of the sensor was found to be saturate. The detrimental effect of humidity on ammonia sensing is removed by
intermittent periodic heating of the sensor at the two temperatures 323K and 448 K, respectively. The indium oxide ethanol
vapour sensor operated at fixed concentration of 400 ppm in the temperature range 293–393 K. Above 373 K, the sensor conductance
was found to be saturate. With various thicknesses from 150–300 nm of indium oxide sensor there was no variation in the sensitivity
measurements of ethanol vapour. The block diagram of circuits for detecting the ammonia gas and ethanol vapour has been included
in this paper. 相似文献
76.
Kaushik Patel Jagdish Prajapati Rajiv Vaidya S. G. Patel 《Bulletin of Materials Science》2005,28(5):405-410
Single crystals of the lamellar compound, ZrSe3, were grown by chemical vapour transport technique using iodine as a transporting agent. The grown crystals were characterized
with the help of energy dispersive analysis by X-ray (EDAX), which gave confirmation about the stoichiometry. The optical
band gap measurement of as grown crystals was carried out with the help of optical absorption spectra in the range 700–1450
nm. The indirect as well as direct band gap of ZrSe3 were found to be 1.1 eV and 1.47 eV, respectively. The resistivity of the as grown crystals was measured using van der Pauw
method. The Hall parameters of the grown crystals were determined at room temperature from Hall effect measurements. Electrical
resistivity measurements were performed on this crystal in the temperature range 303–423 K. The crystals were found to exhibit
semiconducting nature in this range. The activation energy and anisotropy measurements were carried out for this crystal.
Pressure dependence of electrical resistance was studied using Bridgman opposed anvils set up up to 8 GPa. The semiconducting
nature of ZrSe3 single crystal was inferred from the graph of resistance vs pressure. The results obtained are discussed in detail. 相似文献
77.
Possible Phase Transition at Low mK Temperatures in Liquid Helium Mixture Films Adsorbed on Graphite
F. Ziouzia H. Patel J. Nyéki B. P. Cowan J. Saunders 《Journal of Low Temperature Physics》2004,134(1-2):79-84
We report heat capacity and magnetisation measurements of 3He adsorbed on the surface of graphite plated with three atomic layers of 4He. For 3He coverages n 3>4 nm?2 the heat capacity corresponds to a 2D Fermi fluid. The inferred hydrodynamic mass of the 3He quasiparticles is 1.38±0.05 m3. The 3He effective mass ratio increases with coverage to 2.4 at n 3=4 nm?2, due to Fermi liquid interactions. The heat capacity isotherm exhibits a steplike increase centred on n 3=4.5 nm?2, similar to that previously observed on four layers of 4He. This is associated with the population of the first excited Andreev surface bound state. However, in the present case, as n 3 is increased through the step a pronounced anomalous feature develops in the temperature dependence of the heat capacity, around 10 mK. Below 5 mK the heat capacity is approximately linear in temperature. With n 3=7 nm?2, we find that this behaviour is very sensitive to small changes in the 4He third layer coverage, around the completed third layer. Measurements of the 3He magnetisation,, by continuous wave NMR methods, find a significant increase with decreasing temperature below around 20 mK. Together the data suggest that a phase transition takes place in the film at low mK temperatures. 相似文献
78.
Hey DS Key MH Mackinnon AJ MacPhee AG Patel PK Freeman RR Van Woerkom LD Castaneda CM 《The Review of scientific instruments》2008,79(5):053501
A calibration of three types of GafChromic radiochromic film (HS, MD-55, and HD-810) was carried out on the Crocker Nuclear Laboratory's 76 in. cyclotron at UC Davis over doses ranging from 0.001 to 15 kGy. The film was digitized with a scanning microdensitometer with which it was scanned twice with two different filters to increase the film's effective dynamic range. We demonstrate how this calibrated film can be used to measure the spectrum and total energy of a laser generated proton beam. This technique was applied to an experiment on the 10 J, 100 fs Callisto laser at Lawrence Livermore National Laboratory. The resulting proton spectrum was compared to that obtained by simultaneous measurement of Ti nuclear activation; the two methods give the same proton beam slope temperature and agree in number of protons to within 27%. 相似文献
79.
Ion beam extraction from two different ion sources with single aperture triode extraction columns was simulated with the particle beam transport codes PBGUNS and IGUN. For each ion source, the simulation results are compared to experimental data generated on well-equipped test stands. Both codes reproduced the qualitative behavior of the extracted ion beams to incremental and scaled changes to the extraction electrode geometry observed on the test stands. Numerical values of optimum beam currents and beam emittance generated by the simulations also agree well with test stand data. 相似文献
80.
This paper describes the synthesis of phosphorus‐containing polyester‐urethanes and their applications in nanoclay composites and coatings. Polyester was prepared by the reaction of bis(bisphenol‐A) monophenyl phosphonate, maleic anhydride and phthalic anhydride. The polyester was reacted with various diols such as ethylene glycol, diethylene glycol and propylene glycol to obtain polyester polyols. Synthesized polyester polyols were characterized by chemical analysis and instrumental analysis and was used further to react with different isocyanates to develop polyester‐urethanes. The synthesized polyester‐urethanes were blended with organo‐modified montmorillonite nanoclay (1 wt%, 3 wt% and 5 wt%) and were cast in a mold and coated on mild steel panels. The thermal stability of neat polyester‐urethane and the nanoclay composites was determined by thermogravimetric analysis. The flame retardant properties of cast films and their composites were determined by the limiting oxygen index and UL‐94 test methods. The physical and mechanical properties of coatings such as pot life, drying properties, scratch hardness, pencil hardness, impact resistance, adhesion and flexibility were investigated. The chemical resistance properties of the coatings were also determined in different reagents. The data reveal that the polyester‐urethane nanoclay composites with 3 wt% clay hold promise for use in effective flame retardant coatings. © 2013 Society of Chemical Industry 相似文献