全文获取类型
收费全文 | 425篇 |
免费 | 21篇 |
专业分类
电工技术 | 10篇 |
化学工业 | 159篇 |
金属工艺 | 6篇 |
机械仪表 | 7篇 |
建筑科学 | 4篇 |
矿业工程 | 1篇 |
能源动力 | 22篇 |
轻工业 | 39篇 |
无线电 | 18篇 |
一般工业技术 | 86篇 |
冶金工业 | 31篇 |
原子能技术 | 1篇 |
自动化技术 | 62篇 |
出版年
2023年 | 5篇 |
2022年 | 10篇 |
2021年 | 25篇 |
2020年 | 12篇 |
2019年 | 17篇 |
2018年 | 18篇 |
2017年 | 20篇 |
2016年 | 13篇 |
2015年 | 9篇 |
2014年 | 15篇 |
2013年 | 46篇 |
2012年 | 24篇 |
2011年 | 27篇 |
2010年 | 23篇 |
2009年 | 17篇 |
2008年 | 19篇 |
2007年 | 14篇 |
2006年 | 15篇 |
2005年 | 11篇 |
2004年 | 7篇 |
2003年 | 4篇 |
2002年 | 6篇 |
2001年 | 4篇 |
2000年 | 2篇 |
1999年 | 6篇 |
1998年 | 6篇 |
1997年 | 6篇 |
1996年 | 8篇 |
1995年 | 8篇 |
1994年 | 1篇 |
1993年 | 3篇 |
1991年 | 2篇 |
1990年 | 3篇 |
1989年 | 3篇 |
1988年 | 2篇 |
1987年 | 2篇 |
1986年 | 2篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1983年 | 2篇 |
1982年 | 5篇 |
1981年 | 2篇 |
1980年 | 2篇 |
1979年 | 2篇 |
1978年 | 3篇 |
1977年 | 6篇 |
1976年 | 2篇 |
1975年 | 1篇 |
1974年 | 1篇 |
1973年 | 2篇 |
排序方式: 共有446条查询结果,搜索用时 15 毫秒
1.
2.
Multimedia Tools and Applications - In the way of communication, facial expression act as non-verbal communication and play an important role in social interaction by providing some contextual... 相似文献
3.
4.
Ranjit Gharpurey Robert G. Meyer 《International Journal of Circuit Theory and Applications》1995,23(4):381-394
A technique is presented which allows efficient calculation of substrate-coupling macromodels in integrated circuits. the technique can be used to calculate node-to-node resistances or impedances in substrate models. Examples of the technique applied to several test structures are presented. 相似文献
5.
L. J. Singh S. Choudhury S. Singha Roy K. P. Ghatak 《Electrical Engineering (Archiv fur Elektrotechnik)》2005,87(1):1-9
An attempt is made to study the Einstein relation for the diffusivity–mobility ratio (DMR) in quantum wells (QWs) and quantum well wires (QWWs) of tetragonal compounds on the basis of a newly formulated electron energy spectrum taking into account the combined influences of the anisotropies in effective electron mass, the spin–orbit splitting, and the presence of crystal field splitting, respectively. The results for quantum-confined III–V compounds form a special case of our generalized analysis. The DMR has also been studied for QWs and QWWs of II–VI and IV–VI materials. Taking QWs and QWWs of CdGeAs2, InAs, CdS and PbSe as examples, it was found that the DMR increases with increasing carrier statistics and decreasing film thickness respectively in various oscillatory manners emphasizing the influence of dimensional quantizations and the energy band constants in different cases. An experimental method of determining the DMR in nanostructures with arbitrary dispersion laws has also been suggested and the present simplified analysis is in agreement with the suggested relationship. The well-known results for nanostructures with parabolic energy bands have also been obtained as special cases from this generalized analysis under certain limiting conditions. 相似文献
6.
7.
S. Sarkar P. K. Singha S. Dey M. Mohanty B. Adhikari 《Materials and Manufacturing Processes》2006,21(3):291-296
A polyester urethane was synthesized for use in a biodegradable scaffold. The polyurethane was synthesized in a two-step process: first, ester diol was synthesized from lactic acid and polyethylene glycol 400 (PEG 400), then it was polymerized with toluene diisocyanate using dibutyl tin dilaurate (DBTDL) as a catalyst to form a polyester urethane. Polyester urethane has tensile strength of 51-59 MPa and elongation at fracture of 369-439%. FTIR and XRD were used to confirm the formation and structure of the polymer. Hydrolytic degradation was studied in different alkali solutions and in saline water. In order to assess the cellular response of this material, cytotoxicity analysis was carried out against the cell line. 相似文献
8.
Phase diagrams for oil/methanol/ether mixtures 总被引:4,自引:4,他引:4
David G. B. Boocock Samir K. Konar Hanif Sidi 《Journal of the American Oil Chemists' Society》1996,73(10):1247-1251
One-phase transmethylations of vegetable oils with methanol to form methyl esters occur considerably faster than conventional
two-phase reactions. Addition of simple ethers is an efficient method for producing a single phase. Ternary phase diagrams
have been determined at 23°C for oil/methanol/ether mixtures; these are useful when applying the one-phase method across a
wide range of conditions. Soybean, canola, palm, and coconut oils were used in combination with five ethers, namely, tetrahydrofuran
(THF), 1,4-dioxane (DO), diethyl ether (DE), diisopropyl ether (DI), andtert-butyl methyl ether (TBM). All five ethers can produce miscibility for all methanol/oil compositions. The ether/methanol volumetric
ratios required for miscibility at a methanol/soybean or canola oil volumetric ratio of 0.20 (5.4 molar ratio) at 23°C are:
THF, 1.15; DO, 1.60; DE, 1.38 DI, 1.57; and TBM, 1.57. For THF, this results in one-phase mixtures that contain 65 vol% oil.
Soybean and canola oil form identical diagrams. Palm oil requires slightly less ether at the lower methanol concentrations,
but coconut oil requires considerably less across the whole concentration range. Acid-catalyzed reactions, when performed
at the boiling point of the most volatile component, require less ether than predicted from the diagrams. 相似文献
9.
Ranjit Prasad Vanja Pasanovic‐Zujo Rahul K. Gupta Ferenc Cser Sati N. Bhattacharya 《Polymer Engineering and Science》2004,44(7):1220-1230
Shear and extensional rheological measurements were conducted in conjunction with laser light scattering (LLS) on ethylene‐vinyl acetate copolymer (EVA) nanocomposites. The materials were prepared by melt‐mixing EVA and commercially acquired layered silicates. Wide Angle X‐Ray Scattering (WAXS) was used to ascertain the degree of layer swelling. This could be attributed to the intercalation of polymer chains into the interlayer of the silicates. The nanocomposites prepared were determined to be predominantly intercalated in nature. In shear rheological tests, the nanocomposites exhibited an increase in viscoelastic properties compared to the pure EVA. The extent of this property enhancement was not as pronounced as had been reported in many instances with respect to other polymer nanocomposites. This could be attributed to the absence of a network structure normally observed in an exfoliated system. The extensional rheological tests showed an increase in extensional flow properties. This was confirmed by the LLS, which indicated that the filled systems had higher deformability than the unfilled one. Polym. Eng. Sci. 44:1220–1230, 2004. © 2004 Society of Plastics Engineers. 相似文献
10.
Vinnie?Mao Samir?K.?Konar David?G.?B.?BoocockEmail author 《Journal of the American Oil Chemists' Society》2004,81(8):803-808
The base-catalyzed transmethylation of soybean oil has been studied under conditions whereby the reaction starts as a single
phase, but later becomes two phases as glycerol separates. Methanol/oil molar ratios of 6∶1 were used at 23°C. The catalysts
were sodium hydroxide (0.5, 1.0, and 2.0 wt%), potassium hydroxide (1.0 and 1.4 wt%), and sodium methoxide (0.5, 1.0, and
1.35 wt%), all concentrations being with respect to the oil. Oxolane (tetrahydrofuran) was used to form a single reaction
phase. The reactions deviated from homogeneous kinetics as glycerol separated, taking with it most of the catalyst. When 1.0
wt% sodium hydroxide was used, the methyl ester content reached 97.5 wt% after 4 h, compared with 85–90 wt% in the two-phase
reaction. Sodium hydroxide (1.0 wt%), sodium methoxide (1.35 wt%), and potassium hydroxide (1.4 wt%) gave similar results,
presumably because the same number of moles was used. The ASTM biodiesel specification for chemically bound glycerol was achieved
after only 3 min when 2.0 wt% sodium hydroxide was used. However, the standard was not achieved after 4 h when 1.0 wt% sodium
hydroxide was used, the MG content being 1.1–1.6 wt%. The use of 2.0 wt% catalyst is commercially impractical. 相似文献