全文获取类型
收费全文 | 3371篇 |
免费 | 89篇 |
国内免费 | 15篇 |
专业分类
电工技术 | 54篇 |
综合类 | 8篇 |
化学工业 | 652篇 |
金属工艺 | 119篇 |
机械仪表 | 103篇 |
建筑科学 | 46篇 |
矿业工程 | 15篇 |
能源动力 | 176篇 |
轻工业 | 182篇 |
水利工程 | 30篇 |
石油天然气 | 6篇 |
无线电 | 549篇 |
一般工业技术 | 830篇 |
冶金工业 | 340篇 |
原子能技术 | 28篇 |
自动化技术 | 337篇 |
出版年
2024年 | 10篇 |
2023年 | 41篇 |
2022年 | 76篇 |
2021年 | 157篇 |
2020年 | 80篇 |
2019年 | 84篇 |
2018年 | 121篇 |
2017年 | 85篇 |
2016年 | 101篇 |
2015年 | 73篇 |
2014年 | 110篇 |
2013年 | 206篇 |
2012年 | 130篇 |
2011年 | 181篇 |
2010年 | 144篇 |
2009年 | 154篇 |
2008年 | 141篇 |
2007年 | 110篇 |
2006年 | 110篇 |
2005年 | 85篇 |
2004年 | 64篇 |
2003年 | 67篇 |
2002年 | 55篇 |
2001年 | 61篇 |
2000年 | 64篇 |
1999年 | 53篇 |
1998年 | 105篇 |
1997年 | 58篇 |
1996年 | 52篇 |
1995年 | 50篇 |
1994年 | 62篇 |
1993年 | 59篇 |
1992年 | 54篇 |
1991年 | 57篇 |
1990年 | 45篇 |
1989年 | 28篇 |
1988年 | 29篇 |
1987年 | 32篇 |
1986年 | 30篇 |
1985年 | 23篇 |
1984年 | 32篇 |
1983年 | 20篇 |
1982年 | 27篇 |
1981年 | 13篇 |
1980年 | 24篇 |
1979年 | 21篇 |
1978年 | 10篇 |
1977年 | 18篇 |
1976年 | 23篇 |
1973年 | 8篇 |
排序方式: 共有3475条查询结果,搜索用时 296 毫秒
21.
Samuel L. Manzello Richard G. Gann Scott R. Kukuck Kuldeep Prasad Walter W. Jones 《火与材料》2007,31(5):297-310
A gypsum wall assembly was exposed to an intense real‐scale compartment fire. For the wall assembly, temperatures were measured at the exposed face, within the stud cavity, and at the unexposed face during the fire exposure. Total heat flux gauges were used to measure the temporal variation of the energy incident on the walls, and cameras, both visual and infrared, were used to image the unexposed face of the wall assembly during the fire exposure. The behaviour of the wall assembly under the fire load is discussed as are current model results for a simulation of the fire test. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
22.
The removal of Cu(II) by adsorption on fly ash has been found to be concentration, pH and temperature dependent. The kinetics of adsorption indicates the process to be diffusion controlled. The Langmuir constants have been calculated at different temperatures, and the adsorption has been found to be endothermic (ΔH = 15.652 kcal mol?1). The maximum removal is observed at pH 8.0, and variation in adsorption with pH has been explained on the basis of surface ionisation and complexation. 相似文献
23.
Sipra Mahapatra Turaga P. Prasad 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》1992,53(2):201-203
Hydrolysis of Fe(OH)SO4 was carried out in the presence of metallic iron in order to prevent the formation of iron(III) oxides with strongly bonded sulphate. Under the conditions of the experiment, the products were found to be mixtures of ?-Fe2O3 and α-FeOOH. The occluded sulphate, if any, could be easily washed out with water. The hydrolysis reaction passes through an equilibrium state before coming to completion. The entropy with enthalpy of the hydrolysis corresponding to the equilibrium state were found to be 4 e.u. and 0·5 kJ/mol, respectively. The activation energy of the hydrolysis reaction was found to be 21 kJ/mol. 相似文献
24.
The present study was aimed at understanding the response of 2014 Al alloy dispersed with graphite particles in various corrosive environments. Marine (sodium chloride) as well as acidic media were selected for the purpose with a view to widen the range of utility of the composite for applications where such environments may be encountered. Studies were also extended to characterize the corrosion resistance of the composite in fresh as well as used lubricating oils to explore the possibilities of using it in bearing, bushing and such other applications. The corrosion behaviour of the base alloy processed under identical conditions was also examined in the above media to see the influence of graphite addition in the alloy. In order to assess the role of the matrix microstructure, the composite as well as the base alloy was subjected to corrosion in heat-treated as well as-cast conditions. It was observed that the specimens suffered from the maximum rate of corrosion in acid, while sodium chloride produced the minimum corrosion rate. Oil in both used and fresh conditions revealed a negligibly small extent of corrosion. The composite was found to show a higher rate of corrosion than the base alloy under identical test conditions. This was attributed to the dispersoid/matrix interfacial corrosion in the case of the graphitic aluminium alloy. Heat treatment of the composite and the base alloy was found to lower the rate of corrosion in the environments tested. Microstructural modifications of the matrix and possible relief of residual stresses were thought to be responsible for the lower rate of corrosion in the heat-treated condition. 相似文献
25.
Safety,liveness and fairness in temporal logic 总被引:1,自引:0,他引:1
A. Prasad Sistla 《Formal Aspects of Computing》1994,6(5):495-511
In this paper we present syntactic characterization of temporal formulas that express various properties of interest in the verification of concurrent programs. Such a characterization helps us in choosing the right techniques for proving correctness with respect to these properties. The properties that we consider include safety properties, liveness properties and fairness properties. We also present algorithms for checking if a given temporal formula expresses any of these properties.This work is partly supported by NSF grant CCR-9212183. A preliminary version of this paper appeared in the Fourth ACM Symposium on Principles of Distributed Computing. 相似文献
26.
New spectrophotometric methods for the assay of some antioxidants have been developed using potassium permanganate and metol (p-N-methyl amino phenol). Metol is oxidised at pH 3.0 with potassium permanganate and coupled with antioxidants to give λmax at 560 nm for propyl gallate and gallic acid and 510nm for butylated hydroxy anisole. The method is simple, sensitive, reproducible and accurate within ±1% and applicable to the assay of antioxidants (gallic acid, propyl gallate and butylated hydroxy anisole) in oils and fats. 相似文献
27.
28.
F. D. McDaniel B. L. Doyle C. H. Seager D. S. Walsh G. Vizkelethy D. K. Brice C. Yang P. Rossi M. Nigam M. El Bouanani G. V. Ravi Prasad J. C. Schwartz L. T. Mitchell J. L. Duggan 《Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms》2002,190(1-4):1-10
A new ion beam analysis-based, single ion technique called the time to first photon has been developed to measure the decay of the luminescence signal of phosphors. Such measurements are currently needed to study luminescence decay mechanisms following high-density excitations and to identify strongly luminescent phosphor coatings with short lifetimes for ion photon emission microscopy (IPEM). The samples for this technique consist of thin phosphor layers placed or coated on the surface of PIN diodes. Single ions from an accelerator strike this sample and simultaneously create ion beam induced luminescence (IBIL) from the phosphor that is measured by a single-photon-detector, and an ion beam induced charge collection (IBICC) signal in the PIN diode. In this case, the IBICC signal provides the start pulse and the IBIL signal the stop pulse to a time to amplitude converter. It is straightforward to show that this approach also measures a signal proportional to activity versus time with an accuracy of 5% as long as the number of detected photons per ion is less than 0.1, which usually requires the use of absorbers for the IBIL detector or electronic discrimination for the IBIL signals. Details of the new analysis are given together with examples of luminescence decay measurements of several ceramic phosphors being considered to coat IPEM samples. IPEM is currently being developed at Sandia National Laboratory (SNL), the University of North Texas in Denton, and the Universities and INFN of Padova and Torino. 相似文献
29.
A.Varada Rajulu G. Babu Rao B. Ravi Prasad Rao A. Madhu Sudana Reddy Jiasong He Jun Zhang 《应用聚合物科学杂志》2002,84(12):2216-2221
Studies on some properties such as the density, the degradation temperatures, the morphology and the spectral features of the ligno‐cellulose fiber Hildegardia were carried out in both untreated and alkali treated form. The fibers are found to have good morphology and moderate initial and final degradation temperatures. On alkali treatment, the lignin was found to be eliminated. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 2216–2221, 2002 相似文献
30.
J. S. Zabinski M. S. Donley S. V. Prasad N. T. McDevitt 《Journal of Materials Science》1994,29(18):4834-4839
The synthesis and characterization of tungsten disulphide (WS2) films grown on 440C stainless steel substrates using the 248 nm line from a KrF excimer laser are reported. Film properties could be adjusted by controlling substrate temperature and by laser or thermal anneals. X-ray photoelectron spectroscopy, glancing angle XRD, Raman spectroscopy and high-resolution scanning electron microscopy were used to evaluate film chemistry, crystallinity and morphology. Films grown at room temperature were amorphous, near stoichiometric, and had a multiplicity of chemical states. Local order and bonding were improved most dramatically through post-deposition laser anneals. Crystallite size could be increased by raising the substrate temperature during deposition and, to a lesser degree, by post-deposition thermal anneals. Local disorder was observed within the larger crystallites compared to those that were laser annealed. Crystallinity was induced in amorphous films by mechanical rubbing at room temperature under conditions where frictional heating was negligible. The degree of control over film properties provided by PLD demonstrates its value for growing/designing tribological coatings. 相似文献