全文获取类型
收费全文 | 49篇 |
免费 | 7篇 |
专业分类
化学工业 | 24篇 |
金属工艺 | 1篇 |
轻工业 | 7篇 |
无线电 | 1篇 |
一般工业技术 | 4篇 |
冶金工业 | 19篇 |
出版年
2023年 | 1篇 |
2022年 | 2篇 |
2021年 | 3篇 |
2020年 | 1篇 |
2019年 | 4篇 |
2018年 | 3篇 |
2017年 | 3篇 |
2015年 | 1篇 |
2013年 | 2篇 |
2012年 | 3篇 |
2011年 | 1篇 |
2010年 | 2篇 |
2008年 | 2篇 |
2005年 | 1篇 |
2004年 | 2篇 |
2003年 | 1篇 |
2000年 | 1篇 |
1999年 | 1篇 |
1998年 | 6篇 |
1997年 | 6篇 |
1996年 | 1篇 |
1995年 | 1篇 |
1993年 | 1篇 |
1992年 | 1篇 |
1991年 | 1篇 |
1987年 | 1篇 |
1983年 | 2篇 |
1976年 | 1篇 |
1972年 | 1篇 |
排序方式: 共有56条查询结果,搜索用时 240 毫秒
1.
Poly(amide-carbonate)s and poly(amide-thiocarbonate)s derived from the diphenol-amides N-(2,6-dichloro-4-nitrophenyl)-2,2-bis(hydroxyphenyl)-propylamide (I), N-(2,6-dichloro-4-nitrophenyl)-3,3-bis(hydroxyphenyl)-butylamide (II), and N-(2,6-dichloro-4-nitrophenyl)-4,4-bis(hydroxyphenyl)-pentylamide (III), and phosgene or thiophosgene, have been synthesized under phase transfer conditions using several quaternary ammonium salts
as phase transfer catalysts. Benzyltriethylammonium chloride (BTEAC) was effective in practically all cases due the hydrophilicity
of this catalysts.
Received: 21 February 1997/Revised: 28 April 1997/Accepted: 30 April 1997 相似文献
2.
Ferro R. Rodriguez J.A. Jimenez I. Cirera A. Cerda J. Morante J.R. 《IEEE sensors journal》2005,5(1):48-52
A novel NO/sub 2/ sensor based on (CdO)/sub x/(ZnO)/sub 1-x/ mixed-oxide thin films deposited by the spray pyrolysis technique is developed. The sensor response to 3-ppm NO/sub 2/ is studied in the range 50/spl deg/C-350/spl deg/C for three different film compositions. The device is also tested for other harmful gases, such as CO (300 ppm) and CH/sub 4/ (3000 ppm). The sensor response to these reducing gases is different at different temperatures varying from the response typical for the p-type semiconductor to that typical for the n-type semiconductor. Satisfactory response to NO/sub 2/ and dynamic behavior at 230/spl deg/C, as well as low resistivity, are observed for the mixed-oxide film with 30% Cd. The response to interfering gas is poor at working temperature (230/spl deg/C). On the basis of this study, a possible sensing mechanism is proposed. 相似文献
3.
4.
Monoterpenes such as limonene and perillyl alcohol (PA) are currently under investigation for their chemotherapeutic properties
which have been tied to their ability to affect protein isoprenylation. Because PA affects the synthesis of isoprenoids’ such
as ubiquinone’ and cholesterol is the end product of the synthetic pathway from which this isoprenoid pathway branches’ we
investigated the effects of this compound upon cholesterol metabolism in the colonic adenocarcinoma cell line SW480. PA (1
mM) inhibited incorporation of 14C-mevalonate into 21–26 kDa proteins by 25% in SW480 cells. Cholesterol (CH) biosynthesis was assessed by measuring the incorporation
of 14C-acetate and 14C-mevalonate into 27-carbon-sterols. Cells treated with PA (1 mM) exhibited a fourfold increase in the incorporation of 14C-acetate but not 14C-mevalonate into cholesterol. Mevinolin (lovastatin)’ an inhibitor of 3-hydroxy-3-methylglutaryl-CoA (HMG-CoA) reductase’
at 2 μM concentration’ inhibited CH synthesis from 14C-acetate by 80%. Surprisingly’ concurrent addition of mevinolin and PA did not significantly alter the stimulatory effects
of PA. As observed differences in 14C-acetate and 14C-mevalonate precursor labeling could indicate PA affects early pathway events’ the effects of this monoterpene on HMG-CoA
reductase activity were evaluated. Unexpectedly’ 1 mM PA did not stimulate activity of this enzyme. Consistent with its action
as a reversibly bound inhibitor’ in washed microsomes’ 2 μM mevinolin pretreatment increased reductase protein expression
causing a 12.7 (±2.4)-fold compensatory HMG-CoA reductase activity increase; concurrent treatment with 1 mM PA attenuated
this to a 5.3 (±0.03)-fold increase. Gas chromatographic analysis confirmed CH was the major lipid present in the measured
thin-layer chromatography spot. Since 14C-acetate incorporation into free fatty acid and phospholipid pools was not significantly affected by PA treatment’ nonspecific
changes in whole acetate pool sizes were not indicated. Because increases in endogenous CH synthesis should result in compensatory
changes in exogenous sterol utilization’ the effects of PA upon low density lipoprotein (LDL) receptor activity were evaluated.
Consistent with the observed increases in CH synthesis’ 1 mM PA decreased 125I-LDL internalization to 50% of the fetal bovine serum control; concurrent addition of 2 μM mevinolin attenuated this effect
to a reduction of 80% of the control value. Data suggest that in certain colonic tumor cells PA strongly affects cholesterol
metabolism via a mechanism of action that is insensitive to the HMG-CoA reductase inhibitor mevinolin. 相似文献
5.
Hemoglobin I (HbI) from the claim Lucina pectinata is a unique heme protein that binds and transfers hydrogen sulfide (H2S) to a symbiotic bacteria. The metcyano, metaquo, carbon monoxy, oxy, and deoxy complexes of HbI were studies by resonance Raman (RR) spectroscopy, and the metacyano and carbon monoxy complexes were also studied by 1H-NMR. The results indicate a unique orientation of the heme 2-vinyl group relative to other heme proteins. The RR spectra of the HbICO, metHbICN, metHbIH2O, HbIO2 and deoxyHbI heme derivatives show a band at 1621 cm-1 and a shoulder at 1626 cm-1, indicative of an out-of-plane position for one of the vinyls relative to the other one. Spin-lattice relaxation properties of protons in the metHbICN complex also suggest a unique orientation for the heme 2-vinyl group of HbI. The longitudinal relaxation time (T1) for the 2-H alpha, 2-H beta c, and H beta t protons are 120 ms, 115 ms, and 135 ms, respectively. The data from both techniques suggest an out-of-plane and trans-oriented 2-vinyl group, and an in-plane and cis-oriented 4-vinyl group for the low-spin complexes of HbI. These results imply that the electron withdrawing character of the out-of-plane vinyl group contributes to the stability of the heme Fe+3 oxidation state, facilitates the binding of the H2S ligand, and promotes the stability of this ferric H2S complex. 相似文献
6.
Significant energy savings in conventional distillation trains can be achieved by (i) altering the processing sequence, and (ii) performing intercolumn energy matches through an appropriate choice of the column pressures. Prior works have shown that the best thermally-coupled distillation systems usually feature near-minimum utility costs. By choosing the least utility cost as the design target, the synthesis of a heat-integrated distillation train is formulated as a mixed-integer linear programming problem to find simultaneously all the best separation strategy, column pressures and HX-network. Every feasible high-order intercolumn heat match is considered in the model. The search for the global optimum is made by applying a standard branch-and-bound technique for MILP problems. The proposed formulation has successfully been applied to a five-component mixture separation problem. 相似文献
7.
Jaime Cerda Arthur W. Westerberg David Mason Bodo Linnhoff 《Chemical engineering science》1983,38(3):373-387
This paper formulates the minimum utility calculation for a heat exchanger network synthesis as a “transportation problem” from linear programming, allowing one to develop an effective interactive computing aid for this problem. The approach is to linearize cooling/heating curves and partition the only at potential pinch points. In this formulation user imposed constraints are readily included, the latter permitting selected stream/stream matches disallowed in total or in part.By altering the formulation of the objective function, the paper also shows how to solve a minimum utility cost problem, where each utility is available at a single temperature level. A procedure is included to handle a utility which passes through a temperature change when being used.Extending the partitioning procedure permits the formulation to accommodate match dependent approach temperatures, an extension which is useful when heat transfer through a third fluid only is allowed for some matches. 相似文献
8.
This paper presents an algorithm which is readily computer implementable for the synthesis of heat exchanger networks. The algorithm permits the user to impose constraints disallowing in part or in total the matching of any of the stream pairs. Earlier work showed how to discover minimum utility use for these restricted match problems. Constraining utility use to any feasible limit desired, this paper shows how to discover networks requiring the fewest stream/stream matches and among those to discover networks of simply topology. If required, the algorithm will generate cyclic and/or split stream networks. The algorithm involves the formulation, solving and post processing of a series of linear “transportation” problems. Such problems are linear programming problems of special structure which can be solved extremely rapidly using existing computer codes. 相似文献
9.
Yadira D. Cerda‐Sumbarda Ivan Zapata‐Gonzalez Angel Licea‐Claverie Arturo Zizumbo‐Lopez Luis F. Ramos‐de Valle Adriana Espinoza‐Martínez 《Polymer Engineering and Science》2019,59(1):170-181
The preparation of poly(hexylacrylate)core‐poly(ethyleneglycol methacrylate)shell (PHA‐co‐PEGMA) nanogels, to be used as fillers in nanocomposite hydrogels, is reported. Stable nanogels with particle sizes between 90–300 nm were obtained varying the conditions of synthesis. The synthesis recipe of the nanogels could be easily scaled up. Purified and dispersed nanogels in aqueous solution were used as soft fillers for poly(2‐hydroxyethyl methacrylate) (PHEMA) hydrogels, crosslinked with ethylene glycol dimethacrylate (EGDMA). The obtained nanocomposite hydrogels exhibit a larger swelling capacity and a higher thermal stability in comparison with the non‐filled PHEMA hydrogels. Young, storage, and lost moduli, increase largely, in the better case up to 72.5% in the swollen state; while in the dry state the storage modulus increase up to 4.7 fold with a very low load on nanogels (0.64 wt%); resulting in biomaterials with improved properties with potential applications in medical devices. POLYM. ENG. SCI., 59:170–181, 2019. © 2018 Society of Plastics Engineers 相似文献
10.