全文获取类型
收费全文 | 167篇 |
免费 | 12篇 |
专业分类
化学 | 163篇 |
力学 | 6篇 |
数学 | 5篇 |
物理学 | 3篇 |
综合类 | 2篇 |
出版年
2023年 | 2篇 |
2021年 | 6篇 |
2020年 | 8篇 |
2019年 | 3篇 |
2018年 | 3篇 |
2016年 | 3篇 |
2015年 | 6篇 |
2014年 | 6篇 |
2013年 | 3篇 |
2012年 | 5篇 |
2011年 | 9篇 |
2010年 | 5篇 |
2009年 | 3篇 |
2008年 | 10篇 |
2007年 | 11篇 |
2006年 | 12篇 |
2005年 | 8篇 |
2004年 | 16篇 |
2003年 | 11篇 |
2002年 | 7篇 |
2001年 | 2篇 |
2000年 | 10篇 |
1998年 | 1篇 |
1997年 | 4篇 |
1996年 | 4篇 |
1995年 | 1篇 |
1994年 | 4篇 |
1992年 | 4篇 |
1990年 | 1篇 |
1989年 | 1篇 |
1983年 | 2篇 |
1981年 | 4篇 |
1977年 | 1篇 |
1974年 | 1篇 |
1967年 | 2篇 |
排序方式: 共有179条查询结果,搜索用时 671 毫秒
61.
62.
Nayeli Ávila-Cisneros Susana Velasco-Lozano Sergio Huerta-Ochoa Jesús Córdova-López Miquel Gimeno Ernesto Favela-Torres 《Applied biochemistry and biotechnology》2014,174(5):1859-1872
A naturally immobilized biocatalyst with lipase activity was produced by Thermomyces lanuginosus on solid-state fermentation with perlite as inert support. Maxima lipase activities (22 and 120 U/g of dry matter, using p-nitrophenyl octanoate and trioctanoine, respectively, as substrates) were obtained after 72 h of solid culture, remaining nearly constant up to 120 h. Maxima lipase activity was found at 60 to 85 °C and pH 10. The biocatalyst was stable at 60 °C for at least 4 h of incubation and a pH from 7 to 10. Energy values of activation and deactivation of lipase were of 26 and 6.7 kJ/mol, respectively. The biocatalyst shows high selectivity for the release of the omega-3 polyunsaturated fatty acids, eicosapentaenoic (EPA) and docosahexaenoic acids (DHA), during the hydrolysis of sardine oil. The EPA/DHA ratio (16:6) released by this biocatalyst was superior to that obtained with the commercial preparations of T. lanuginosus. 相似文献
63.
Thermal desorption gas chromatography with mass spectrometry study of outgassing from polymethacrylimide foam (Rohacell®) 下载免费PDF全文
Enrique J. Carrasco‐Correa Jos M. Herrero‐Martínez Lina Consuegra Guillermo Ramis‐Ramos Rafael Mata Sanz Benito Gimeno Martínez Vicente E. Boria Esbert David Raboso García‐Baquero 《Journal of separation science》2015,38(17):3028-3037
Polymethacrylimide foams are used as light structural materials in outer‐space devices; however, the foam closed cells contain volatile compounds that are outgassed even at low temperatures. These compounds ignite as plasmas under outer‐space radiation and the intense radio‐frequency fields used in communications. Since plasmas may cause spacecraft fatal events, the conditions in which they are ignited should be investigated. Therefore, qualitative and quantitative knowledge about polymethacrylimide foam outgassing should be established. Using thermogravimetric analysis, weight losses reached 3% at ca. 200°C. Thermal desorption gas chromatography with mass spectrometry detection was used to study the offgassed compounds. Using successive 4 min heating cycles at 125°C, each one corresponding to an injection, significant amounts of nitrogen (25.3%), water (2.6%), isobutylene (11.3%), tert‐butanol (2.9%), 1‐propanol (11.9%), hexane (25.3%), propyl methacrylate (1.4%), higher hydrocarbons (11.3%), fatty acids (2.2%) and their esters (1.3%), and other compounds were outgassed. Other compounds were observed during the main stage of thermal destruction (220–280°C). A similar study at 175°C revealed the extreme difficulty in fully outgassing polar compounds from polymethacrylimide foams by baking and showed the different compositions of the offgassed atmosphere that can be expected in the long term. 相似文献
64.
J. Ortega Corresponding author J. A. Gallastegui C. L. Folcia J. Etxebarria N. Gimeno M. B. Ros 《Liquid crystals》2013,40(4):579-584
The second-order susceptibility tensor of three liquid crystals composed of banana-shaped molecules has been fully determined. The measurements were carried out in single domain samples, aligned by means of an electric field parallel to the cell surface. Special care was taken with the appropriate determination of the index mismatch between the fundamental and second harmonic waves. This was achieved by using samples of different thickness. This parameter is very important for obtaining reliable values of the second order susceptibility tensor components, and is seldom directly measured. The suitability of the experimental procedure was checked by comparing the results obtained for the reference compound P-8-O-PIMB with previously reported measurements for this material. The dij coefficients obtained in this work are in the range 1–4?pm?V?1 and are compared with other values obtained in previous reports. 相似文献
65.
66.
67.
Novel neutral biimidazolate or bibenzimidazolate palladium(II) and platinum(II) complexes of the type M(NN)2(dpe) [M = Pd, Pt; (NN)22? = BiIm2?, BiBzIm2?. dpe = 1,2-bis(diphenylphosphino) ethane] have been obtained by reacting MCl2(dpe) with TI2(NN)2. Complexes M(NN)2(dpe) which are Lewis bases react with HClO4 or [M(dpe)(Me2CO)2](ClO4)2 to yield, respectively, mononuclear cationic complexes of general formula [M{H2(NN)2](dpe) (M = Pd, Pt; H2(NN)2 = H2BiIm, H2BiBzIm) and homobinuclear palladium(II) or platinum(II) cationic complexes of the type [M2{μ - (NN)2}(dpe)2](ClO4)2. Reactions of M(BiBzIm)(dpe) with [Rh(COD) (Me2CO)X](ClO4) render similar heterobinuclear palladium(II)-rhodium(I) and platinum(II)-rhodium(I) cationic complexes, of general formula [(dpe)M(μ-BiBzIm)Rh(COD)](ClO4) (M = Pd, Pt; COD = 1,5-cyclooctadiene). Di- and mono-carbonyl derivatives [(dpe)M(μ-BiBzIm)Rh(CO)L](ClO4) (M = Pd, Pt; L = CO, PPh3) have also been prepared. The structures of the resulting complexes have been elucidated by conductance studies and IR spectroscopy. 相似文献
68.
Silver(I) complexes of N-thiophosphorylated bis(iminophosphorane) ligands: from monomers to polymers
Cadierno V Díez J García-Alvarez J Gimeno J 《Dalton transactions (Cambridge, England : 2003)》2007,(26):2760-2769
Treatment of diphosphines Ph(2)P(CH2)nPPh2 (n = 1, 2, 4, 6) and [Fe(eta5-C(5)H(4)PR'2)2] (R' = Ph, (i)Pr) with a two-fold excess of (RO)2P(=S)N3 (R = Et, Ph) results in the high-yield formation of the N-thiophosphorylated bis(iminophosphorane) derivatives (CH2)n[P{=NP(=S)(OR)2}Ph2]2 and Fe(eta5-C(5)H(4)[P{=NP(=S)(OR)2}R'2])2, respectively. The reactions of these ligands with AgSbF(6) in a 1 : 1 molar ratio have been investigated. The resulting silver(I) complexes, derived from the selective coordination of the P=S units, have been characterized by IR, NMR and MS (FAB) spectroscopy and, in selected cases, by X-ray crystallography. Monomeric, dimeric and polymeric solid-state structures, depending on the nature of the ligand backbone, have been found. 相似文献
69.
70.
Chaintreau A Cicchetti E David N Earls A Gimeno P Grimaud B Joulain D Kupfermann N Kuropka G Saltron F Schippa C 《Journal of chromatography. A》2011,1218(43):7869-7877
Previous publications investigated different data treatment strategies for quantification of volatile suspected allergens by GC/MS. This publication presents the validation results obtained on "ready to inject" samples under reproducibility conditions following inter-laboratory ring-testing. The approach is based on the monitoring of three selected ions per analyte using two different GC capillary columns. To aid the analysts a decisional tree is used for guidance during the interpretation of the analytical results. The method is evaluated using a fragrance oil concentrate spiked with all suspected allergens to mimic the difficulty of a real sample extract or perfume oil. At the concentrations of 10 and 100mg/kg, imposed by Directive 76/768/EEC for labeling of leave-on and rinse-off cosmetics, the mean bias is +14% and -4%, respectively. The method is linear for all analytes, and the prediction intervals for each analyte have been determined. To speed up the analyst's task, an automated data treatment is also proposed. The method mean bias is slightly shifted towards negative values, but the method prediction intervals are close to that resulting from the decisional tree. 相似文献