全文获取类型
收费全文 | 1391篇 |
免费 | 67篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 11篇 |
综合类 | 2篇 |
化学工业 | 307篇 |
金属工艺 | 11篇 |
机械仪表 | 18篇 |
建筑科学 | 44篇 |
矿业工程 | 2篇 |
能源动力 | 49篇 |
轻工业 | 222篇 |
水利工程 | 4篇 |
石油天然气 | 3篇 |
无线电 | 73篇 |
一般工业技术 | 143篇 |
冶金工业 | 400篇 |
原子能技术 | 9篇 |
自动化技术 | 162篇 |
出版年
2023年 | 11篇 |
2022年 | 37篇 |
2021年 | 62篇 |
2020年 | 27篇 |
2019年 | 30篇 |
2018年 | 36篇 |
2017年 | 32篇 |
2016年 | 26篇 |
2015年 | 27篇 |
2014年 | 37篇 |
2013年 | 67篇 |
2012年 | 65篇 |
2011年 | 56篇 |
2010年 | 44篇 |
2009年 | 44篇 |
2008年 | 46篇 |
2007年 | 35篇 |
2006年 | 46篇 |
2005年 | 37篇 |
2004年 | 29篇 |
2003年 | 31篇 |
2002年 | 30篇 |
2001年 | 18篇 |
2000年 | 21篇 |
1999年 | 27篇 |
1998年 | 85篇 |
1997年 | 55篇 |
1996年 | 38篇 |
1995年 | 20篇 |
1994年 | 20篇 |
1993年 | 25篇 |
1992年 | 13篇 |
1991年 | 9篇 |
1990年 | 12篇 |
1989年 | 6篇 |
1988年 | 20篇 |
1987年 | 14篇 |
1986年 | 11篇 |
1985年 | 18篇 |
1984年 | 16篇 |
1983年 | 8篇 |
1982年 | 15篇 |
1981年 | 12篇 |
1980年 | 14篇 |
1979年 | 17篇 |
1978年 | 9篇 |
1977年 | 18篇 |
1976年 | 26篇 |
1975年 | 10篇 |
1960年 | 5篇 |
排序方式: 共有1460条查询结果,搜索用时 31 毫秒
21.
Fernando Corvillo Laura Gonzlez-Snchez Alberto Lpez-Lera Emilia Arjona Giovanni Ceccarini Ferruccio Santini David Araújo-Vilar Rebecca J Brown Joan Villarroya Francesc Villarroya Santiago Rodríguez de Crdoba Teresa Caballero Pilar Nozal Margarita Lpez-Trascasa 《International journal of molecular sciences》2021,22(12)
22.
A suite of density-differentiated macerals from several coals was analysed by Fourier transform infrared spectroscopy to obtain information on the nature and magnitude of the variations exhibited by the various maceral fractions. The most characteristic change between maceral groups was the variation in aliphatic hydrogen content, with exinite ? vitrinite ? inertinite. Since the separation technique (density gradient centrifugation) generally provided a number of fractions within a maceral group region, some of these were also analysed. In a series of density fractions from a low rank vitrinite, it was found that the aliphatic hydrogen content decreased as the density increased. The inertinites also exhibited a decrease in aliphatic hydrogen. The inertinite C—O bands had extinction coefficients different from those of vitrinites or exinites. The data suggest that quite profound variations in organic structure as determined by FT-i.r. spectroscopy can exist within a maceral group, so that for the most critical work on coals it is necessary to take this into account. 相似文献
23.
B. O. Solomon M. D. Oner L. E. Erickson S. S. Yang 《American Institute of Chemical Engineers》1984,30(5):747-757
Pirt's model for microbial growth and product formation are reparameterized to obtain multiresponse models with common parameters. The dependent variables in the models are related through the available electron and carbon balance constraints. Covariance adjustment is used to reduce the growth model to a unit variate linear model with covariates. Therefore, standard multiple regression programs can be used to obtain combined point and interval estimates of true biomass energetic yield, true product yield and maintenance coefficient. This approach may yield “better” estimates than the maximum likelihood approach when an appropriately selected subset of covariates is used. Nonlinear estimation procedures are also considered; these procedures are efficient with few responses; however, as the number of responses per observation increase, they may require a lot of computing time. For illustration several data from the biochemical engineering literature are analyzed by the proposed methods. 相似文献
24.
Graeme Moad Ezio Rizzardo David H. Solomon Athelstan L. J. Beckwith 《Polymer Bulletin》1992,29(6):647-652
Summary A method is described for determining the absolute rate constants for the first few propagation steps in radical polymerization. The procedure involves a product analysis of the oligomeric alkoxyamines formed when an initiator is decomposed in monomer containing a very low concentration of a nitroxide radical scavenger. The method is illustrated with analysis of data for methyl acrylate. The rate constants for the first two propagation steps for polymerization of this monomer,k
p(1) andk
p(2), are at least an order of magnitude greater thank
p(average). Values of the absolute rate constants for reactions of phenyl and primary alkyl radicals with methyl acrylate are also estimated. 相似文献
25.
Solomon Guadie Worku Chunxiang XuAuthor VitaeJining ZhaoAuthor Vitae Xiaohu HeAuthor Vitae 《Computers & Electrical Engineering》2014
Cloud computing poses many challenges on integrity and privacy of users’ data though it brings an easy, cost-effective and reliable way of data management. Hence, secure and efficient methods are needed to ensure integrity and privacy of data stored at the cloud. Wang et al. proposed a privacy-preserving public auditing protocol in 2010 but it is seriously insecure. Their scheme is vulnerable to attacks from malicious cloud server and outside attackers regarding to storage correctness. So they proposed a scheme in 2011 with an improved security guarantee but it is not efficient. Thus, in this paper, we proposed a scheme which is secure and with better efficiency. It is a public auditing scheme with third party auditor (TPA), who performs data auditing on behalf of user(s). With detail security analysis, our scheme is proved secure in the random oracle model and our performance analysis shows the scheme is efficient. 相似文献
26.
Alfonso Ranalli Luciano Pollastri Stefania Contento Emilia Iannucci Lucia Lucera 《European Journal of Lipid Science and Technology》2003,105(2):57-67
The influence of the olive paste malaxation time on the composition and the industrial output of oil was investigated. To this purpose, three Italian olive varieties (Leccino, Dritta, Caroleo) were processed with a centrifugal system for six malaxation periods (0, 15, 30, 45, 60 and 75 min). The concentrations of the majority of the oil constituents changed during the malaxation. However, these changes were not significant for all of them: the contents of β‐carotene, the major xanthophylls, chlorophylls a and b, pheophytins a and b in the oils increased progressively with increasing malaxing times, whereas the contents of simple and hydrolysable phenols (secoiridoid derivatives), o‐diphenols and total phenols decreased. A significant increase in total volatiles and green volatiles of the lipoxygenase cascade (C6 aldehydes, C6 alcohols, C5 alcohols and C5 carbonyls) was detected. An opposite trend was observed for the green C6 esters. As a result, the global analytical quality, flavour, aroma and shelf‐life of the oils were negatively affected. The oil yield increased substantially up to 45 min of paste malaxation times. Beyond 60 min, the yields tended to decrease. 相似文献
27.
The tert‐butoxy radical‐facilitated grafting of methyl methacrylate (MMA) onto commercial polypropylene (PP) pellets and fiber was investigated in heterogeneous conditions similar to practical systems. Free‐radical grafting of several other monomers onto PP fiber was also investigated. Also, preliminary data from the grafting of MMA onto poly(ethylene terephthalate) pellets is presented. The PP‐graft‐PMMA residues were detected by solid‐state 13C‐NMR and photoacoustic IR spectroscopy. There was a good correlation between the degree of grafting (DG) determined from these spectroscopic techniques and the results from gravimetric methods. A maximum grafting efficiency of over 50% was found, whereas DG (20%) remained constant at various PP pellet, initiator, and monomer concentrations. However, at relatively low PP fiber concentrations, the DG was 27%; the increase was most likely due to the greater surface area of the fiber. There was also a reduction in DG (14%) at relatively low initiator concentrations. The reaction conditions were altered to favor grafting by the addition of more polymer substrate. When the ratio of tert‐butoxy radicals to PP was decreased, more of the substrate remained unmodified, and empirical calculations showed the formation of grafts with up to 40 monomer units. At high initiator concentrations, calculations showed that the graft residues were 1–2 units long. Therefore, variation of the polymer, initiator, and monomer concentrations was shown to have a significant effect on grafting. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 898–915, 2002 相似文献
28.
This paper focuses on the robust stability analysis of a class of linear systems including multiple delays subjected to constant or time‐varying perturbations. The approach considered makes use of appropriate stability radius concepts (dynamic, static) and relies on a feedback interconnection interpretation of the uncertain system. Various computable bounds on stability radii are obtained that exploit the structure of the problem. Systems including perturbations on both system matrices and delays are also dealt with. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
29.
30.
Monday Eze Charles Okunbor Deborah Aleburu Olubukola Adekola Ibrahim Ramon Nneka Richard-Nnabu Oghenetega Avwokuruaye Abisola Olayiwola Rume Yoro Esomu Solomon 《计算机系统科学与工程》2022,41(2):595-609
This work demonstrates in practical terms the evolutionary concepts and computational applications of Parametric Curves. Specific cases were drawn from higher order parametric Bezier curves of degrees 2 and above. Bezier curves find real life applications in diverse areas of Engineering and Computer Science, such as computer graphics, robotics, animations, virtual reality, among others. Some of the evolutionary issues explored in this work are in the areas of parametric equations derivations, proof of related theorems, first and second order calculus related computations, among others. A Practical case is demonstrated using a graphical design, physical hand sketching, and programmatic implementation of two opposite-faced handless cups, all evolved using quadratic Bezier curves. The actual drawing was realized using web graphics canvas programming based on HTML 5 and JavaScript. This work will no doubt find relevance in computational researches in the areas of graphics, web programming, automated theorem proofs, robotic motions, among others. 相似文献