全文获取类型
收费全文 | 363篇 |
免费 | 23篇 |
专业分类
电工技术 | 3篇 |
综合类 | 1篇 |
化学工业 | 139篇 |
金属工艺 | 16篇 |
机械仪表 | 9篇 |
建筑科学 | 7篇 |
能源动力 | 15篇 |
轻工业 | 27篇 |
水利工程 | 4篇 |
石油天然气 | 1篇 |
无线电 | 25篇 |
一般工业技术 | 69篇 |
冶金工业 | 26篇 |
原子能技术 | 2篇 |
自动化技术 | 42篇 |
出版年
2023年 | 7篇 |
2022年 | 20篇 |
2021年 | 14篇 |
2020年 | 9篇 |
2019年 | 11篇 |
2018年 | 8篇 |
2017年 | 6篇 |
2016年 | 18篇 |
2015年 | 12篇 |
2014年 | 15篇 |
2013年 | 25篇 |
2012年 | 22篇 |
2011年 | 25篇 |
2010年 | 21篇 |
2009年 | 19篇 |
2008年 | 4篇 |
2007年 | 17篇 |
2006年 | 7篇 |
2005年 | 11篇 |
2004年 | 8篇 |
2003年 | 8篇 |
2002年 | 8篇 |
2001年 | 2篇 |
1999年 | 3篇 |
1998年 | 2篇 |
1997年 | 4篇 |
1996年 | 7篇 |
1995年 | 3篇 |
1994年 | 2篇 |
1993年 | 3篇 |
1992年 | 5篇 |
1991年 | 3篇 |
1990年 | 2篇 |
1989年 | 3篇 |
1988年 | 2篇 |
1987年 | 2篇 |
1984年 | 2篇 |
1983年 | 3篇 |
1980年 | 2篇 |
1979年 | 2篇 |
1977年 | 3篇 |
1976年 | 2篇 |
1974年 | 5篇 |
1973年 | 2篇 |
1970年 | 5篇 |
1968年 | 8篇 |
1967年 | 2篇 |
1965年 | 2篇 |
1960年 | 1篇 |
1957年 | 1篇 |
排序方式: 共有386条查询结果,搜索用时 15 毫秒
61.
A density of neutral hydrogen atoms was systematically measured in the MESOX solar plasma reactor at different MW powers and flow rates. The H-atom density was measured by a gold fibre optics catalytic probe. The H-atom density was in general increasing with increasing MW power. At a pressure of 40 Pa and a power of 500 W it was about 3.5 × 1021 m−3 and at a power of 1000 W it was about 4.1 × 1021 m−3. A degree of dissociation of hydrogen molecules was between 3% and 20% depending on pressure and power. A maximum degree of dissociation was obtained at a pressure of 40 Pa and 1000 W, while the lowest one at 130 Pa and 500 W. 相似文献
62.
Dennis Haake Joerg Klatte Aleksander Grah Michael E. Dreyer 《Microgravity science and technology》2010,22(2):129-138
An open capillary channel is a structure that establishes a liquid flow path when the capillary pressure caused by surface
tension forces dominates in comparison to the hydrostatic pressure induced by gravitational or residual accelerations. To
maintain a steady flow through the channel the capillary pressure of the free surface has to balance the pressure difference
between the liquid and the surrounding constant pressure gas phase. Due to convective and viscous momentum transport the pressure
along the flow path of the liquid decreases and causes the free surface to bend inwards. The maximum flow rate through the
channel is reached when the free surface collapses and gas ingestion occurs near the outlet. This stability limit depends
on the geometry of the channel and the properties of the liquid. In this paper we present an experimental setup which is used
in the low-gravity environment of the Bremen Drop Tower. Experiments with convective dominated systems have been performed
where the flow rate was increased up to the maximum value. In comparison to this we present a one-dimensional theoretical
model to determine important characteristics of the flow, such as the free surface shape and the limiting flow rate. Furthermore
we present an explanation for the mechanism of flow rate limitation for these flow conditions which is similar to the choking
problem for compressible gas flows. 相似文献
63.
New design of electric double layer capacitors with aqueous LiOH electrolyte as alternative to capacitor with KOH solution 总被引:1,自引:0,他引:1
Activated carbon (AC) fiber cloths and a hydrophobic microporous polypropylene (PP) membrane, both modified with lithiated acetone oligomers, were used as electrodes and a separator in electric double layer capacitors (EDLCs) with aqueous lithium hydroxide (LiOH) as the electrolyte. Electrochemical characteristics of EDLCs were investigated by cyclic voltammetry (CV), galvanostatic charge-discharge cycle tests and impedance spectroscopy (EIS), compared with a case of the capacitor with aqueous potassium hydroxide (KOH) as an electrolyte. As a result, the capacitor with LiOH aqueous solution and a modified separator and electrodes was found to exhibit higher specific capacitance, maximum energy stored and maximum power than that with KOH aqueous solution. 相似文献
64.
Katarina Vojisavljević Goran Branković Tatjana Srećković Aleksander Rečnik Zorica Branković 《Journal of the European Ceramic Society》2010,30(2):485-488
Ultrathin PZT film was prepared using a chemical solution deposition method from polymeric citrate precursors. The PZT solution was spin-coated on an amorphous silica layer formed on a Si(1 0 0) substrate. The films were thermally treated from the substrate side with a low heating rate (1°/min) up to 700 °C and finally annealed for 10 h. Ultrathin PZT films without microstructural instability were prepared in spite of high temperature and long annealing time. AFM and HRTEM investigations revealed the formation of a well-developed dense microstructure consisting of spherical crystallites (4–7 nm). Low roughness (2.2 nm) of a ~26 nm thick layer was obtained for a two-layered PZT film. The grazing incidence X-ray diffraction (GIXRD) measurements confirmed the polycrystalline structure of ultrathin PZT films. Also, GIXRD and electron energy dispersive X-ray (EDS) analysis showed that compositional variations were smaller than expected, in spite of the long annealing time. 相似文献
65.
A process of plasma‐initiated grafting of acrylic acid on commercial porous polypropylene membrane was studied. The influence of parameters of the plasma (power, gas pressure, time plasma‐sample distance, sample arrangement) and grafting (solvent composition, monomer concentration, time, inhibitor presence) on the degree of grafting, amount of homopolymer produced and surface electrical resistance was determined. A degree of grafting up to 18 mmol/g was obtained, which resulted in sample resistance as low as 30 mΩ cm2. The molecular weight of AAc homopolymer that can be assumed as equal to the MW of grafted chains, ranged from 25,000 to 50,000,000 da. SEM and water permeability measurements show that grafting causes filling of the pores, which, however, does not stop K+ ions from penetrating the membrane. The performance of nickel‐cadmium cells with acrylic acid grafted membranes as separator is also presented. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 相似文献
66.
Barbara Mendrek Łukasz Sieroń Marcin Libera Mario Smet Barbara Trzebicka Aleksander L. Sieroń Andrzej Dworak Agnieszka Kowalczuk 《Polymer》2014
Core-shell type stars synthesized via atom transfer radical polymerization were used for the delivery of nucleic acids. The interior of the stars consisted of hyperbranched poly(arylene oxindole), while the arms were composed of poly(N,N-dimethylaminoethyl methacrylate). The length of the star arms varied in degree of polymerization (DP) from 14 to 98. The hydrodynamic radius of the structures measured in water indicated the presence of small aggregates, while isolated stars ranging in size from 14 to 29 nm were seen in organic solvent. The phase transition temperatures of the stars in water, measured in basic conditions, were shifted to lower values with increasing DP of the arms. Stable polyplexes of stars with plasmid DNA were formed. Their size varied from 300 nm to 400 nm, depending upon the DP of arms. The zeta potential of the polyplexes was positive, which facilitated their cellular uptake. The DP of the arms influenced the transfection efficiency of HT-1080 cells, demonstrating that stars are promising candidates for synthetic gene vectors. 相似文献
67.
Jan Blaszczak Jolanta Zimoch Wieslaw Hreczuch Aleksander Matuszewski Jan Szymanowski 《Journal of surfactants and detergents》1999,2(1):29-37
Surface and interfacial tension isotherms for narrow-range distribution ALFOL 1214 alcohol oxyethylates were determined and compared with those obtained for broad-range alcohol oxyethylates. Various adsorption parameters were estimated. The effectiveness of surface tension reduction decreases when the length of polyoxyethylene hydrophile increases. Micellization is observed at log cmc ranging from −4.7 to −3.3. Effects of the length and distribution of the polyoxyethylene chain on cmc are very small. A minimum of A min/N av 0.5 is obtained for N av=8, where A min and N av denote the minimum interfacial area occupied by a statistical molecule at the saturated interface and the average degree of oxyethylation, respectively. The interface becomes saturated at pC 20=−5.61±0.35, where pC 20 denotes the logarithm of concentration required to obtain the surface pressure equal to 20 mNm−1. The highest and lowest values of the surface excess at saturation and the free energy of adsorption, respectively, are obtained for an average degree of oxyethylation equal to 8. Parameters are correlated with the average degree of oxyethylation and the oxyethylene chain distribution parameter according to empirical second-order polynomials. Small differences in adsorption abilities at the water/air interface are only observed for narrow- and broad-range distributed oxyethylates. The differences become important for adsorption at the hexadecane/water interface. The lowest values of interfacial tension are obtained for narrow-range oxyethylates with N av=7 and 8. The Krefeld fabric detergency tests indicated that the best detergency was observed for alcohol oxyethylates with N av=5–7. Narrow-range oxyethylates exhibit somewhat better washing abilities than the broad-range products. No relationship between detergency of alcohol oxyethylates and their abilities to adsorb at the water/air and water/hydrocarbon interfaces is observed. 相似文献
68.
A gas chromatograph coupled with an atomic emission detector was used to identify and to determine the products formed on oxidation of sulfur mustard. The oxidation rate and the resulting oxidates were studied in relation to oxidant type and reaction medium parameters. Hydrogen peroxide, sodium hypochlorite, sodium perborate, potassium monopercarbonate, ammonium peroxydisulfate, potassium peroxymonosulfate (oxone), and tert-butyl peroxide were used as oxidants. Oxidations were run in aqueous media or in solvents of varying polarities. The oxidation rate was found to be strongly related to oxidant type: potassium peroxymonosulfate (oxone) and sodium hypochlorite were fast-acting oxidants; sodium perborate, hydrogen peroxide, ammonium peroxydisulfate, and sodium monopercarbonate were moderate oxidants; tert-butyl peroxide was the slowest-acting oxidant. In non-aqueous solvents, the oxidation rate was strongly related to solvent polarity. The higher the solvent polarity, the faster the oxidation rate. In the acid and neutral media, the mustard oxidation rates were comparable. In the alkaline medium, oxidation was evidently slower. A suitable choice of the initial oxidant-to-mustard concentration ratio allowed to control the type of the resulting mustard oxidates. As the pH of the reaction medium was increased, the reaction of elimination of hydrogen chloride from mustard oxidates becomes more and more intensive. 相似文献
69.
70.