全文获取类型
收费全文 | 273篇 |
免费 | 19篇 |
专业分类
电工技术 | 4篇 |
化学工业 | 64篇 |
金属工艺 | 1篇 |
机械仪表 | 6篇 |
建筑科学 | 6篇 |
矿业工程 | 1篇 |
能源动力 | 12篇 |
轻工业 | 24篇 |
水利工程 | 1篇 |
无线电 | 27篇 |
一般工业技术 | 64篇 |
冶金工业 | 24篇 |
原子能技术 | 2篇 |
自动化技术 | 56篇 |
出版年
2024年 | 1篇 |
2023年 | 5篇 |
2022年 | 23篇 |
2021年 | 18篇 |
2020年 | 22篇 |
2019年 | 15篇 |
2018年 | 26篇 |
2017年 | 16篇 |
2016年 | 20篇 |
2015年 | 17篇 |
2014年 | 8篇 |
2013年 | 14篇 |
2012年 | 9篇 |
2011年 | 12篇 |
2010年 | 7篇 |
2009年 | 10篇 |
2008年 | 6篇 |
2007年 | 7篇 |
2006年 | 3篇 |
2005年 | 2篇 |
2004年 | 2篇 |
2003年 | 2篇 |
2002年 | 3篇 |
1998年 | 1篇 |
1997年 | 3篇 |
1996年 | 1篇 |
1995年 | 2篇 |
1994年 | 5篇 |
1993年 | 2篇 |
1991年 | 2篇 |
1990年 | 1篇 |
1989年 | 1篇 |
1988年 | 2篇 |
1987年 | 4篇 |
1985年 | 3篇 |
1984年 | 4篇 |
1983年 | 3篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1977年 | 3篇 |
1976年 | 1篇 |
1974年 | 2篇 |
1972年 | 1篇 |
1969年 | 1篇 |
排序方式: 共有292条查询结果,搜索用时 0 毫秒
1.
Khalid Mahmood Zia Mehdi Barikani Ijaz Ahmad Bhatti Mohammad Zuber Haq Nawaz Bhatti 《应用聚合物科学杂志》2008,109(3):1840-1849
A series of polyurethane (PU) elastomers was prepared by the reaction of poly(?‐caprolactone) and 4,4′‐diphenylmethane diisocyanate, which was extended with a series of chain extenders (CEs) having 2–10 methylene units in their structure. The completion of the reaction was confirmed by Fourier transform infrared spectroscopy. The chemical structures of the synthesized PU samples were characterized with Fourier transform infrared, 1H‐NMR, and 13C‐NMR spectroscopy, and the thermal properties were determined by thermogravimetric analysis, DSC, and dynamic mechanical thermal analysis techniques. The mechanical properties were also studied and are discussed. The thermogravimetric analysis and DSC analysis showed that CE length had a considerable effect on the thermal properties of the prepared samples. The dynamic mechanical thermal analysis and damping peaks were also affected by the number of methylene units in the CE length. The elastomer extended with 1,2‐ethane diol exhibited optimum thermal properties, whereas the elastomer based on 1,10‐decane diol displayed the worst thermal properties. Tensile strength and elongation at break decreased with increasing CE length, whereas hardness showed the opposite trend. The glass‐transition temperature moved toward lower temperatures with increasing CE length. The decrease in the glass‐transition temperature and tensile properties were interpreted in terms of decreasing hard segments and increasing chain flexibility. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 相似文献
2.
Trygve Burchardt Pascal GouérecEmilio Sanchez-Cortezon Zia KarichevJames H Miners 《Fuel》2002,81(17):2151-2155
ZeTek Power recently introduced mass manufacturable and cost effective alkaline fuel cells on the market. Today's research is focused on further improvement both in terms of performance increase and cost reduction. This research is classically performed using small (4 cm2) experimental electrodes in the half-cell configuration. This allows the primary electrochemical losses in an anode or cathode to be determined independently. Additional performance losses occur when one integrates large electrodes into a module of 24 cells and in a stack comprised of many modules. By comparing the performance of half-cell experiments to that of modules, these losses can be distinguished and addressed. The information thus obtained, both for the small electrodes and in up-scaling is vital if one is to identify the key areas in which improvement is possible and where to focus future research. Furthermore, the identification of the losses in a module and system allows us to predict the final performance from half-cell measurements of a new laboratory scale experimental electrode. 相似文献
3.
Dynamic mechanical and longitudinal sonic velocity measurements have been made on a series of semi-1-IPNs in which the network component is a polyurethane and the linear constituent a copolymer of methyl acrylate and ethyl acrylate. Dynamic mechanical analysis reveals phase separation. The shifting of the polyurethane glass transition in both the tan δ? and the E″–temperature plots indicates that some mixing occurs. The longitudinal sonic velocity results indicate that the polyurethane is present as a continuous phase in all the materials investigated. 相似文献
4.
The process of isothermal annealing of nodular monoclinic crystals of isotactic polypropylene (iPP) was analyzed by atomic force microscopy (AFM) and temperature-modulated differential scanning calorimetry (TMDSC). Initially nodular and mesomorphic domains were obtained by controlled melt-crystallization at high cooling rate. Subsequent heating triggers transition from mesomorphic to monoclinic structure, and melting of unstable nodules. Annealing allows re-crystallization, which is recognized by enlargement of domains from initially about 20 nm to about 35 and 55 nm after annealing at 393 and 433 K, respectively. Furthermore, the re-crystallization process is connected with a slight change of the aspect ratio of crystals. The isothermal re-crystallization of the liquid is superimposed by aggregation of crystals, to yield blocky, and string-like objects. The direct analysis of structure on isothermal annealing by AFM is for the first time compared with the isothermal decrease of the apparent specific heat capacity, or change of enthalpy, monitored by TMDSC. The apparent specific heat capacity decreases during annealing with an identical non-linear time dependence as the directly observed growth of the crystal size. Analysis of the annealing processes at different temperatures yields proportionality between the increase of the crystal size and the reduction of the apparent specific heat capacity. 相似文献
5.
Liu Daobin Wu Chuanqiang Chen Shuangming Ding Shiqing Xie Yaofeng Wang Changda Wang Tao Haleem Yasir A. ur Rehman Zia Sang Yuan Liu Qin Zheng Xusheng Wang Yu Ge Binghui Xu Hangxun Song Li 《Nano Research》2018,11(4):2217-2228
Nano Research - Atomically dispersed catalysts have attracted attention in energy conversion applications because their efficiency and chemoselectivity for special catalysis are superior to those... 相似文献
6.
Sulphur dioxide loadings over megacity Lahore (Pakistan) and adjoining region of Indo-Gangetic Basin
Zia ul-Haq Salman Tariq Muhammad Ali Khalid Mahmood Asim Daud Rana 《International journal of remote sensing》2016,37(13):3021-3041
This article presents spatial and temporal variations of planetary boundary layer (PBL) sulphur dioxide (SO2) over megacity Lahore and adjoining region, a typical representative area in the Indo-Gangetic Basin (IGB) largely influenced by transported volcanic SO2 from Africa, Middle East, and southern Europe, by using data retrieved from satellite-based Ozone Monitoring Instrument (OMI) during October 2004–September 2015. We find a positive trend of 2.4% per year (slope 0.01 ± 0.005 with y-intercept 0.35 ± 0.03 Dobson Unit (DU), correlation coefficient r = 0.55 and 2-tailed p-value at 0.1) of OMI-SO2 column with the average value of 0.4 ± 0.05 DU. Strong seasonality of OMI-SO2 column is observed over the region linked with local meteorology, patterns of anthropogenic emissions, crop residue burning, and vegetation cover. There exists a seasonal high value in winter 0.56 ± 0.24 DU with a peak in December 0.67 ± 0.26 DU. The seasonal lowest value is observed to be 0.29 ± 0.11 DU in wet summer with minimum value in July 0.25 ± 0.06 DU. High growth rates of OMI-SO2 column over the study region have been observed in January, June, October, and December ranging from 5.7% to 11.6% per year. Satellite data show elevated OMI-SO2 columns in 2007, 2008, 2011, and 2012 largely contributed by trans-boundary volcanic SO2. A detailed analysis of volcanic SO2 transported from Africa and Middle East (Jabal Al-Tair, Dalaffilla, and Nabro volcanoes) over the study area is presented. Air mass trajectories suggest the presence of long-range transported volcanic SO2 at high altitude levels over Lahore and IGB region during the volcanic episodes. The SO2 enhancements in PBL during winter season are generally due to significant vertical downdraft of high-altitude volcanic SO2. For the first time, we present significant influence of volcanic SO2 from southern Europe (Mt. Etna volcano) reaching over the study area. Daily mean OMI-SO2 levels up to 21.4, 10.0, 5.6, and 2.4 DU have been noticed due to the eruptions from Dalaffilla, Mt. Etna, Nabro, and Jabal Al-Tair volcanoes, respectively. 相似文献
7.
Khan Z Balch T Dellaert F 《IEEE transactions on pattern analysis and machine intelligence》2006,28(12):1960-1972
In several multitarget tracking applications, a target may return more than one measurement per target and interacting targets may return multiple merged measurements between targets. Existing algorithms for tracking and data association, initially applied to radar tracking, do not adequately address these types of measurements. Here, we introduce a probabilistic model for interacting targets that addresses both types of measurements simultaneously. We provide an algorithm for approximate inference in this model using a Markov chain Monte Carlo (MCMC)-based auxiliary variable particle filter. We Rao-Blackwellize the Markov chain to eliminate sampling over the continuous state space of the targets. A major contribution of this work is the use of sparse least squares updating and downdating techniques, which significantly reduce the computational cost per iteration of the Markov chain. Also, when combined with a simple heuristic, they enable the algorithm to correctly focus computation on interacting targets. We include experimental results on a challenging simulation sequence. We test the accuracy of the algorithm using two sensor modalities, video, and laser range data. We also show the algorithm exhibits real time performance on a conventional PC 相似文献
8.
9.
Spatial channel models are often proposed for modeling the angular aspects of mobile radio channel in picocell, microcell, and macrocellular environments. These models are validated through comparison with available measurement results. The comparisons are usually based on the fitness of their pdfs of angle of arrival to the histogram of occurrences of the signals over an angular span, given in the measurement data. This paper presents a comparison of the notable scattering models with various spatial channel measurements. The paper suggests criteria for the comparative analysis of the previously proposed spatial channel models and measurements on the basis of their fading statistics. Quantitative analysis of the considered models and the field measurements is also presented using multipath shape factors i.e. angle spread, the angular constriction and direction of maximum fading. Based on the obtained shape factors, fading statistics like level crossing rates, average fade duration, auto-covariance and coherence distance are evaluated. Effect of increasing Doppler spread on the level crossing rates and average fade duration is also elaborated in detail. 相似文献
10.
Qamer Zia Davide Tranchida René Androsch Holger Schönherr 《Journal of Materials Science》2012,47(7):3040-3045
In this study the effects of crystal habit, crystallinity and superstructure on the modulus of elasticity of isotactic polypropylene
films were analyzed by atomic force microscope (AFM) nanoindentation. The modulus of elasticity, evaluated on the nanometer
scale by AFM, showed a qualitatively similar dependence on the crystal habit, crystallinity and superstructure as the modulus
of elasticity measured by dynamic-mechanical analysis and tensile testing. The observed values of both the surface stiffness
measured by AFM and the macroscopic/bulk stiffness were distinctly larger in the presence of non-isometric lamellae organized
in spherulite than in the presence of isometric nodular crystals, not organized in a spherulitic superstructure. The experimental
data showed that the modulus of elasticity is not primarily influenced by the presence or absence of spherulite but by the
molecular-deformation constraint associated to the crystal habit. 相似文献