全文获取类型
收费全文 | 661篇 |
免费 | 37篇 |
国内免费 | 3篇 |
专业分类
电工技术 | 4篇 |
综合类 | 3篇 |
化学工业 | 154篇 |
金属工艺 | 19篇 |
机械仪表 | 11篇 |
建筑科学 | 15篇 |
能源动力 | 41篇 |
轻工业 | 37篇 |
水利工程 | 6篇 |
无线电 | 62篇 |
一般工业技术 | 170篇 |
冶金工业 | 56篇 |
原子能技术 | 7篇 |
自动化技术 | 116篇 |
出版年
2024年 | 5篇 |
2023年 | 9篇 |
2022年 | 25篇 |
2021年 | 36篇 |
2020年 | 30篇 |
2019年 | 22篇 |
2018年 | 39篇 |
2017年 | 36篇 |
2016年 | 32篇 |
2015年 | 22篇 |
2014年 | 27篇 |
2013年 | 67篇 |
2012年 | 29篇 |
2011年 | 43篇 |
2010年 | 32篇 |
2009年 | 31篇 |
2008年 | 26篇 |
2007年 | 21篇 |
2006年 | 22篇 |
2005年 | 14篇 |
2004年 | 20篇 |
2003年 | 14篇 |
2002年 | 13篇 |
2001年 | 7篇 |
2000年 | 5篇 |
1999年 | 4篇 |
1998年 | 7篇 |
1997年 | 7篇 |
1996年 | 10篇 |
1995年 | 2篇 |
1994年 | 4篇 |
1993年 | 8篇 |
1992年 | 2篇 |
1991年 | 3篇 |
1990年 | 1篇 |
1989年 | 1篇 |
1987年 | 3篇 |
1985年 | 4篇 |
1984年 | 1篇 |
1983年 | 2篇 |
1982年 | 3篇 |
1981年 | 6篇 |
1980年 | 1篇 |
1978年 | 2篇 |
1976年 | 1篇 |
1974年 | 1篇 |
1958年 | 1篇 |
排序方式: 共有701条查询结果,搜索用时 15 毫秒
41.
Mahesh Tripunitara Tom Messerges 《Computer》2007,40(2):104-106
Cryptography-based alternatives are the most appropriate long-term solution to the micropayment problem, especially compared to the business solution of restructuring transaction fees. We acknowledge that the business solution is easier to deploy in the short term. Cryptography-based solutions face tremendous deployment challenges: they need more market testing, they significantly change payment-ecosystem processes, their legal implications are unclear, and they require new kinds of devices and processes for merchants. Nonetheless, the long-term payoff of investing in such sound solutions are be tremendous 相似文献
42.
Swapan K. Bhattacharya Mahesh G. Varadarajan Premjeet Chahal Gopal C. Jha Rao R. Tummala 《Journal of Electronic Materials》2007,36(3):242-244
To realize embedded resistors on multilayer benzocyclobutene (BCB) either on-chip or on-board, a low-cost large format electroless
process for deposition of NiP and NiWP thin-film resistors using both low-temperature (25°C) and high-temperature (90°C) baths
has been developed. The electroless process exhibits uniform resistor thickness in the submicron range and offers low profile
and excellent adhesion to the BCB dielectric layer. The resistor films also act as a seed layer for direct electroplating
of copper traces. The NiP alloys can also be tailored to a variable temperature coefficient of resistance (TCR) with different
alloy compositions. The electroless process can be adopted in the PCB manufacturing industries with no additional investment.
This article is the first report on electroless plated thin film resistors on low loss BCB dielectric. 相似文献
43.
During the last 20 years, new philosophies such as the Theory of Constraints (TOC) and Activity-Based Management (ABM) have emerged as viable, distinct alternatives for measuring and improving the performance of world-class manufacturing companies. In the early phase of their evolution, these philosophies differed fundamentally in their approaches; but there is increasing evidence that both philosophies have now evolved to a stage where an integrated framework can be developed for enhancing cross-functional coordination, thereby improving organizational performance. In this paper, a general framework is presented that integrates the basic concepts, as well as recent advances of TOC and ABM philosophies, into a cohesive framework that can be used to guide performance improvement initiatives . A successful implementation in a world-class manufacturing company is described to validate the framework and to demonstrate that these philosophies can indeed work together in positive ways. Insights are provided into the reasons for implementing such an integrative framework, e.g. identifying the most profitable mix of products, allocating scarce resources optimally, establishing priorities for process improvements, analysing the strategic investment (or expansion) alternatives, and exploiting new market segments. 相似文献
44.
Mahesh Chandra Alok Kalra Pradeep K. Sharma Hirdesh Kumar Rajinder S. Sangwan 《Biomass & bioenergy》2010,34(5):805-811
The production of cellulases by Trichoderma citrinoviride fermented on marc of Artemisia annua, and bioconversion of the same marc by produced cellulase system was studied. The effects of pretreatments, substrate concentration, particle size, initial pH, temperature and concentration of the medium components on production of FPase, endoglucanase and β-glucosidase were monitored and comparatively evaluated. Among the three pretreatment processes, alkali hydrolysis with autoclaving was found to be most suitable for production of all the three enzymes. Optimum production of FPase, endoglucanase and β-glucosidase was obtained at 96 h, 96 h and 72 h of fermentation period, respectively. Substrate concentration of 1% with particle size between 200 μm and 475 μm gave the higher yields. Higher production of all the three enzymes was obtained with initial pH value of 5.5, temperature of 28 °C and 75% of mineral salt solution. Partially purified enzyme system obtained by optimized fermentation procedure, was applied for saccharification. Forty six percent of saccharification was noticed after 48 h of incubation on alkali hydrolyzed and autoclaved substrate which was 3.26 fold more than that of unpretreated substrate. 相似文献
45.
46.
Chloromethylated styrene-divinylbenzene copolymer was chemically modified with ethylenediaminetetraacetic acid ligand. Catalytically
active polymer containing Ru(III) moieties were synthesized from this polymeric ligand. They were characterized using FTIR,
UV-vis, SEM, ESR and TGA. Other physico-chemical properties such as bulk density, surface area, moisture content and swelling
behaviour in different solvents were also studied. The polymer bound complex was used to study hydrogenation of 1-hexene ton-hexane under mild conditions. Influence of [1-hexene], [catalyst], temperature and nature of the solvent on the rate of the
reaction was investigated. A rate expression is proposed based on the observed initial rate data. Recycling efficiency of
the catalyst has also been studied. 相似文献
47.
48.
Polybenzimidazoles containing different contents of pendant nitrophenoxy groups were prepared by condensation of 3,3′‐diamino‐benzidine with a mixture of 3,5‐dicarboxyl‐4′‐nitro diphenyl ether and isophthalic acid (IPA) in different ratios in polyphosphoric acid. The polymers are soluble in polar aprotic solvents, they have inherent viscosities in the range of 0.75–1.10 dL g?1 and they form tough and transparent films on solution casting. They have good thermal stability with initial decomposition temperature ranging from 380 to 416°C in nitrogen, good tensile strength ranging from 56 to 65 MPa and reasonably good oxidative stability. Phosphoric acid uptake of these polymers is low compared with PBI and membranes doped with phosphoric acid exhibit good proton conductivity in the range of 6.6× 10?3 to 1.9× 10?2 S/cm at 25°C and 1.2× 10?2 to 4.9× 10?2 S/cm at 175°C, compared with 3.9× 10?3 S/cm at 25°C and 3.2× 10?2 S/cm at 175°C for PBI. These membranes are suitable for applications as polymer electrolyte for fuel cell and presumably for gas separation at high temperature. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 相似文献
49.
Pandurang N. Honkhambe Mahesh V. Biyani Nagendra S. Bhairamadgi Prakash P. Wadgaonkar Manikrao M. Salunkhe 《应用聚合物科学杂志》2010,117(5):2545-2552
Two bisphenols, viz., 4,4′‐[1‐(2‐naphthalenyl)ethylidene]bisphenol and 4,4′‐[1‐(2‐naphthalenyl) ethylidene]bis‐3‐methylphenol were prepared by condensation of commercially available 2‐acetonaphthanone with phenol and o‐cresol, respectively. A series of new aromatic polyesters containing pendent naphthyl units was synthesized by phase‐transfer‐catalyzed interfacial polycondensation of these bisphenols with isophthaloyl chloride, terephthaloyl chloride, and a mixture of isophthaloyl chloride/terephthaloyl chloride (50 : 50 mol %). Inherent viscosities of polyesters were in the range 0.83–1.76 dL g−1, while number average molecular weights (Mn) were in the range 61,000–235,000 g mol−1. Polyesters were readily soluble in organic solvents such as dichloromethane, chloroform, tetrahydrofuran, m‐cresol, pyridine, N,N‐dimethylformamide, N,N‐dimethylacetamide, and 1‐methyl‐2‐pyrrolidinone at room temperature. Tough, transparent, and flexible films were cast from a solution of polyesters in chloroform. X‐Ray diffraction measurements displayed a broad halo at 2θ ≅ 19° indicating the amorphous nature of polyesters. Glass transition temperatures of polyesters were in the range 209–259°C. The temperature at 10% weight loss (T10), determined by TGA in nitrogen atmosphere, of polyesters was in the range 435–500°C indicating their good thermal stability. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 相似文献
50.
Mahesh N. Varma 《Fuel》2010,89(7):1641-31
Biodiesel was synthesized in supercritical fluids by two routes: non-catalytically in supercritical alcohols and by enzyme catalysis in supercritical carbon dioxide. Two oils, sesame oil and mustard oil, and two alcohols, methanol and ethanol, were used for the synthesis. Complete conversion was observed for synthesis in supercritical alcohols whereas only a maximum of 70% conversion was observed for the enzymatic synthesis in supercritical carbon dioxide. For the synthesis in supercritical alcohols, the activation energies and pseudo-first order rate constants were determined. For the reactions in supercritical carbon dioxide, a mechanism based on ping pong bi-bi was proposed and the kinetic parameters were determined. 相似文献