全文获取类型
收费全文 | 1485篇 |
免费 | 49篇 |
国内免费 | 9篇 |
专业分类
电工技术 | 123篇 |
综合类 | 4篇 |
化学工业 | 420篇 |
金属工艺 | 49篇 |
机械仪表 | 43篇 |
建筑科学 | 38篇 |
矿业工程 | 1篇 |
能源动力 | 61篇 |
轻工业 | 116篇 |
水利工程 | 4篇 |
石油天然气 | 4篇 |
无线电 | 101篇 |
一般工业技术 | 285篇 |
冶金工业 | 120篇 |
原子能技术 | 36篇 |
自动化技术 | 138篇 |
出版年
2023年 | 5篇 |
2022年 | 19篇 |
2021年 | 36篇 |
2020年 | 12篇 |
2019年 | 11篇 |
2018年 | 28篇 |
2017年 | 19篇 |
2016年 | 35篇 |
2015年 | 28篇 |
2014年 | 53篇 |
2013年 | 83篇 |
2012年 | 79篇 |
2011年 | 115篇 |
2010年 | 56篇 |
2009年 | 74篇 |
2008年 | 90篇 |
2007年 | 76篇 |
2006年 | 56篇 |
2005年 | 67篇 |
2004年 | 64篇 |
2003年 | 51篇 |
2002年 | 43篇 |
2001年 | 44篇 |
2000年 | 20篇 |
1999年 | 25篇 |
1998年 | 39篇 |
1997年 | 28篇 |
1996年 | 21篇 |
1995年 | 20篇 |
1994年 | 32篇 |
1993年 | 27篇 |
1992年 | 12篇 |
1991年 | 20篇 |
1990年 | 14篇 |
1989年 | 21篇 |
1988年 | 16篇 |
1987年 | 15篇 |
1986年 | 7篇 |
1985年 | 8篇 |
1984年 | 6篇 |
1983年 | 4篇 |
1982年 | 8篇 |
1981年 | 8篇 |
1980年 | 12篇 |
1979年 | 13篇 |
1978年 | 7篇 |
1977年 | 7篇 |
1976年 | 4篇 |
1974年 | 3篇 |
1972年 | 1篇 |
排序方式: 共有1543条查询结果,搜索用时 31 毫秒
141.
Ken Furusawa Hideharu Sugihara Kiichiro Tsuji Yasunori Mitani 《Electrical Engineering in Japan》2007,158(1):36-45
In recent years, energy storage systems have increasingly been expected as a means of load leveling of the annual load factor. Of course there is an effect of installing the energy storage systems at the substation. But some customers operate their storage system in an integrated way and it also has an effect of increasing the load factor. In this paper the authors proposed that the energy storage systems on the customer side be used for congestion relief on transmission networks. However, it is not clear which kind of customer has the effect of relieving transmission line congestion. First, this paper assumes the authors determine the optimal configuration of energy equipment including energy storage systems. We propose a new contract whereby electric utility subsidizes a part of the entrance cost of the energy storage systems and customers change the output pattern of energy storage according to the request of the electric utility. This paper evaluates the possibility that the contract gives merit to both the electric utility and the customer. © 2006 Wiley Periodicals, Inc. Electr Eng Jpn, 158(1): 36–45, 2007; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20299 相似文献
142.
Turn-on characteristics of GaAs MESFETs are simulated when the gate and the drain voltages are changed abruptly, and quasi-pulsed I-V curves are derived from them. It is discussed how the slow current transients (lag phenomena) and the pulsed I-V curves are affected by the existence of substrate traps and surface states. It is also discussed how the characteristics are influenced by impact ionization of carriers. 相似文献
143.
Summary
Introduction of simple alkyl groups at the C-2 nitrogen of chitin and some properties of the resulting N-alkyl-chitins have been examined. Chitosan was fully deacetylated and treated with three kinds of aldehydes, formaldehyde,
acetaldehyde, and pentanal. The Schiff bases of chitosan, whose extents of substitution were dependent on the amount of aldehydes,
were reduced with sodium cyanoborohydride to N-alkylated chitosans. The N-alkyl-chitosans were then transformed into the corresponding N-alkyl-chitins by acetylation with acetic anhydride followed by transesterification to remove partly formed O-acetyl groups. The resulting N-methyl-, ethyl-, and pentyl-chitins were amorphous and showed improved affinity for organic solvents.
Received: 13 December 2001/Revised version: 11 January 2002/Accepted: 17 January 2002 相似文献
144.
School of Engineering, Duke University, Durham, North Carolina, 27706. The status of wafer bonding technology especially for
silicon-on-insulator (SOI) materials is reviewed. General advantages of wafer bonding as well as specific problems of wafer
bonding, such as interface bubble formation, and solutions for these problems are discussed. The specific requirements for
SOI materials in terms of SOI layer thickness and the appropriate thinning procedures are dealt with. Interface properties
such as bonding strength and electrical properties are also reviewed. Various device results are mentioned. 相似文献
145.
Tomoyuki Kawaguchi Yasuhiro Rachi Wataru Sugimoto Yasushi Murakami Yoshio Takasu 《Journal of Applied Electrochemistry》2006,36(10):1117-1125
Highly dispersed ternary PtRuRh/C anode catalysts for direct methanol fuel cells were prepared with various contents and their electro-catalytic activities towards methanol oxidation at 25 °C and 60 °C were examined to investigate the influence of the catalyst composition. Electrocatalysts were prepared by a co-impregnation method using ethanolic solutions of metal precursors and carbon black followed by pyrolysis under reducing conditions. X-ray diffraction analysis revealed that the fcc peaks shifted to higher diffraction angles with increasing Rh content, indicating the alloying of Rh into the fcc structure. In terms of the mass specific current density, the activity towards methanol oxidation differed significantly depending on the catalysts composition and cell temperature. The catalyst prepared at a ratio of Pt:Ru:Rh = 1:1:2 exhibited the highest activity at 60 °C of 155 A (g-Pt)−1 at 0.5 V vs. RHE. 相似文献
146.
The spreading behavior of N,N'-dialkylacrylamide (dAAs) monomers on a water surface is investigated by measurement of surface pressure-area isotherms as a function of alkyl chain length and temperature. The monolayers of dAAs can be classified into three types. (I) N,N'-dioctadecylacrylamide (dODA) shows a rapid increase in surface pressure indicating formation of a rigid condensed monolayer; (II) the isotherm of N,N'-dihexadecylacrylamide (dHDA) has a plateau region in surface pressure corresponding to a phase transition from a expanded form to a condensed form, which corresponds to gel-liquid crystal phase transition often observed in biomembranes; and (III) the dialkylacrylamides with alkyl chain length shorter than the hexadecyl group form expanded monolayers with no condensed monolayer at any temperature. The similar three kinds of monolayers are also observed in the isotherms for dHDA monolayer as a function of temperature. It is found that two carbon elongation in double alkyl chains causes the same effect on the monolayer induced by about 10 °C cooling. Under various conditions, only liquid condensed monolayers are transferred on to a solid support, yielding the monomer LB films, practically, of dODA at any temperature and dHDA at low temperature. The polymerization of those LB films by UV irradiation was ascertained by the electronic absorption spectra. 相似文献
147.
Noritada Kaji Akio Oki Ryo Ogawa Yuzuru Takamura Takahiro Nishimoto Hiroaki Nakanishi Yasuhiro Horiike Manabu Tokeshi Yoshinobu Baba 《Israel journal of chemistry》2007,47(2):161-169
The various potential factors affecting the performance of nanopillar chips on DNA separation were investigated from the viewpoints of both numerical calculations and actual experiments. To yield higher performance and replace the conventional DNA separation techniques such as microchip electrophoresis, the phenomenon specific to the nanopillar chips should be deeply understood. In this paper, although various factors affecting the performance of the nanopillar chips are considered, we focused on the effect of electroosmotic flow, which is particularly noticeable in quartz-made nanopillar chips. High-resolution separation of DNA was realized when an electroosmotic flow was suppressed by simply using a higher concentration of buffer, but DNA separation failed in the presence of an electroosmotic flow. It was confirmed from the numerical simulations and the direct observations that the deformation of DNA band during the injection process was induced by electroosmotic flow and consequently led to a poor resolution. 相似文献
148.
Determination of optimal sending voltage profile in distribution systems with distributed generators
Yasuhiro Hayashi Junya Matsuki Ryoji Suzuki Eiji Muto 《Electrical Engineering in Japan》2007,161(2):16-24
Sending voltage profile of distribution feeder is controlled by changing a tap of distribution transformer. In a distribution network with distributed generators, for reasons of effect of reversed flows from them and existence of a great number of sending voltage profile candidates, it is not easy to control sending voltage profile within the acceptable voltage limit. In this paper, in order to determine the optical sending voltage profile of distribution transformer in a distribution network with distributed generators, the authors propose a new method to determine the optimal sending voltage profile so as to minimize the total number of tap position's change per day under constraints of acceptable voltage limit. In the proposed method, after calculating acceptable range of three‐phase voltage of distribution feeder, the optimal profile of tap position within the calculated acceptable voltage range is determined among these candidates by using reduced ordered binary decision diagram (ROBDD) which is an efficient enumeration algorithm. In order to check the validity of the proposed method, numerical simulations are carried out for a distribution network model with a distributed generator. © 2007 Wiley Periodicals, Inc. Electr Eng Jpn, 161(2): 16–24, 2007; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20393 相似文献
149.
Superplasticity in ceramics 总被引:1,自引:0,他引:1
It is now recognized that superplasticity is a potential deformation process in ceramics. This review summarizes the major characteristics of superplasticity and examines the reports of both transformation and structural superplasticity in ceramic and other non-metallic materials. It is shown that there are both similarities to and differences from metals. Similarities include the variation of strain rate with stress and grain size, but an important difference is the necessity to consider the role of intergranular glassy phases in ceramics. Superplasticity is also important in intermetallic compounds, and in geological materials where there is evidence for superplastic deformation both in laboratory experiments and in natural deformation. 相似文献
150.
A method for the stereospecific analysis of triacyl-sn-glycerols by high-performance liquid chromatography (HPLC) on a chiral column is described. Triacyl-sn-glycerols were partially degraded with ethyl magnesium bromide, and the monoacylglycerols produced were separated as 1- and
2-monoacylglycerol fractions by thin-layer chromatography on boric acid-impregnated silica gel plates. The 1-monoacylglycerols
were resolved intosn-1 andsn-3 monoacylglycerol fractions by HPLC on a chiral column (Sumichiral OA-4100) after derivatization with 3,5-dinitrophenyl
isocyanate. Fatty acid methyl esters obtained from the original triacyl-sn-glycerols, 1- and 2-monoacylglycerol fractions, andsn-1 andsn-3 monoacylglycerol fractions were analyzed by gas chromatography on open-tubular columns. Stereospecific acyl distributions
in triacyl-sn-glycerols were calculated from the data. The acyl distributions of several oils were obtained. The method is rapid, simple
and gave reproducible results. 相似文献