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71.
吸附-聚合物修饰组合固定化Candida antarctica脂肪酶研究 总被引:1,自引:0,他引:1
通过吸附法联合PEG非共价修饰,研发了一种固定化南极假丝酵母脂肪酶(Candida antarctica lipase)的新方法,可以有效提高固定化酶在非水介质中的催化活性。最佳固定化条件为硅藻土:酶粉(W/W)=8,PEG4000:酶粉(W/W)=0.6,缓冲液pH7.5。采用三油酸甘油酯与甲醇的转酯化反应,测定了固定化酶的转酯活性。结果表明,固定化酶同时加入PEG进行非共价修饰,可显著提高固定化酶的转酯活力。PEG修饰的固定化酶转酯比活是未经PEG修饰的固定化酶的4.1倍,转酯酶活回收率为604.8%,说明PEG两性分子的特性对制备用于非水介质的固定化酶有重要作用。该固定化方法可显著提高Candida antarctica脂肪酶在非水介质中的催化效率,且固定化方法简单、成本低,具有工业应用价值。 相似文献
72.
用二-十二烷基-N-D-葡萄糖酸-L-谷氨酸酯对来源于Candida cylindrucea的脂肪酶包衣后应用于水-有机溶剂体系中催化选择性水解布洛芬甲酯制备S-(+)-布洛芬。考察了体系的有机溶剂种类和体积分数、温度、pH值等因素对转化率和对映选择性的影响。结果表明,在布洛芬甲酯为100 mmol,脂包衣脂肪酶250 mg/mL,pH值为7.5,温度为40℃,N,N-二甲基甲酰胺(DMF)体积分数在20%时,15 h后催化的转化率可达48.3%,对映选择率达465。动力学研究表明脂包衣脂肪酶在水-DMF混合体系中其酶促反应符合米氏方程,其米氏常数Km是水相中没有包衣酶的1/2,最大反应速度vm ax是它的1.4倍。 相似文献
73.
S.?P.?J.?Namal Senanayake Fereidoon?ShahidiEmail author 《Journal of the American Oil Chemists' Society》2002,79(10):1003-1013
This study utilized γ-linolenic acid (18∶3n−6; GLA)-rich borage oil (BO) and evening primrose oil (EPO) for the synthesis
of structured lipids (SL) and compared the oxidative stability of the products with those of unmodified BO and EPO as controls.
Immobilized Novozym 435 lipase from Candida antarctica was used as the biocatalyst for SL production. BO or EPO eas enzymatically modified with docosahexaenoic acid (22∶6n−3; DHA),
as the acyl donor, to produce SI. The SI were characterized and their oxidative stabilities evaluated. Among the oils examined,
SL gave rise to higher quantities (P≤0.05) of conjugated dienes, TBARS, and headspace volatiles as compared to their unmodified counterparts. Results indicated
that modified oils were less stable than their unmodified counterparts. The double bond index (DBI) and methylene bridge index
(MBI) of oils decreased (P<0.05) during oxidation in the more unsaturated oils. An attempt was made to correlate various parameters of oxidation with
DBI and MBI of oils; correlation coefficients (−r) were within the range of 0.574–0.973. This suggests that indicators such as DBI and MBI can reflect oxidative stability
of oils. 相似文献
74.
Lipase-catalyzed alcoholysis of soy phospholipids was investigated to simultaneously make lysophospholipids and fatty acid
esters of individual alcohols. Alcoholysis was carried out by stirring a mixture of soy phospholipids and individual alcohols
in equimolar proportions with 10% (by weight of reactants) Mucor miehei lipase at 55°C for 24 h. The products were isolated by column chromatography after removal of the lipase. Lysophospholipids
(in 69–78% molar yield) were obtained from soy phospholipids, and the yield of esters of various alcohols also conformed nearly
with theoretical yields. 相似文献
75.
Chemo-enzymatic synthesis of amino acid-based surfactants 总被引:5,自引:0,他引:5
Rao Valivety Paula Jauregi Iqbal Gill Evgeny Vulfson 《Journal of the American Oil Chemists' Society》1997,74(7):879-886
The application of lipases to the synthesis of amino acid-based surfactants was investigated. Low yields (2–9%) were obtained
in the acylation of free amino acids, such as l-serine and l-lysine, as well as their ethyl esters and amides with fatty acids, owing in part to low miscibility of the reactants. When
the N-carbobenzyloxy (Cbz)-l-amino acids were used in an effort to improve miscibility of the amino acid derivatives with the acyl donor, a dramatic improvement
was observed for N-Cbz-l-serine (92% yield) but not for N
α-Cbz- or N
ζ-Cbz-l-lysine (7 and 2% yield, respectively). As an alternative, and efficient synthesis of N
ζ-acyl-l-lysines was developed, based on the regiospecific chemical acylation of copper(II) lysinate. In pursuit of a general route
to amino acid-fatty acid surfactants, the utility of a polyol linker was investigated. Thus, the glycerol ester of N
α′
N
ζ-di-Cbz-l-lysine was prepared and evaluated as a substrate for acylation. As expected, this and other glycer-1-yl esters of N-protected amino acids were excellent substrates for lipase-catalyzed acylation. Their reaction with myristic acid in the
presence of Novozyme resulted in the regioselective acylation of the primary hydroxyl group of the glycerol moiety to afford
the corresponding 1-O-(N-Cbz-l-aminoacyl)-3-O-myris-toylglycerols with conversions of 50–90%. These were readily deprotected to give a range of 1-O-(aminoacyl)-3-O-myristoyl-glycerols with overall yields of 27–71%. 相似文献
76.
Mohamed M. Soumanou Uwe T. Bornscheuer Rolf D. Schmid 《Journal of the American Oil Chemists' Society》1998,75(6):703-710
Structured triacylglycerides with medium-chain fatty acids (caprylic acid) in sn1- and sn3-positions and a long-chain unsaturated fatty acid (oleic or linoleic acid) in the sn2-position of glycerol (MLM) were synthesized by lipase catalysis in a two-step process. First, pure 2-monoacylglycerides
(2-MG) were synthesized by alcoholysis of triacylglycerides (triolein, trilinolein, or peanut oil) in organic solvents with
1,3-regiospecific lipases (from Rhizomucor miehei, Rhizopus delemar, and Rhizopus javanicus). The 2-MG were purified by crystallization and obtained in up to 71.8% yield. These 2-MG were esterified in a second reaction
with caprylic acid in n-hexane to form almost pure MLM. For 2-MG obtained from peanut oil, the final product contained more than 90% caprylic acid
in the sn1- and sn3-positions, whereas the sn2-position was composed of 98.5% unsaturated long-chain fatty acids. Reaction conditions for both steps were optimized with
respect to source and immobilization of lipase, water activity, and solvent. 相似文献
77.
Lipase-catalyzed modification of borage oil: Incorporation of capric and eicosapentaenoic acids to form structured lipids 总被引:2,自引:0,他引:2
Casimir C. Akoh Charment O. Moussata 《Journal of the American Oil Chemists' Society》1998,75(6):697-701
Two immobilized lipases, nonspecific SP435 from Candida antarctica and sn-1,3 specific IM60 from Rhizomucor miehei, were used as biocatalysts for the restructuring of borage oil (Borago officinalis L.) to incorporate capric acid (10:0, medium-chain fatty acid) and eicosapentaenoic acid (20:5n-3) with the free fatty acids
as acyl donors. Transesterification (acidolysis) reactions were carried out in hexane, and the products were analyzed by gas-liquid
chromatography. The fatty acid profiles of the modified borage oil were different from that of unmodified borage oil. Higher
incorporation of 20:5n-3 (10.2%) and 10:0 (26.3%) was obtained with IM60 lipase, compared to 8.8 and 15.5%, respectively,
with SP435 lipase. However, SP435 lipase was able to incorporate both 10:0 and 20:5n-3 fatty acids at the sn-2 position, but the IM60 lipase did not. Solvents with log P values between 3.5 and 4.5 supported the acidolysis reaction better than those with log P values between −0.33 and 3.0. 相似文献
78.
固定化假丝酵母99-125脂肪酶催化酯化脂肪酸低碳醇酯反应条件的研究 总被引:9,自引:2,他引:9
以硅藻土和纺织品为载体 ,采用吸附法制备固定化脂肪酶 ,研究了固定化假丝酵母 99 1 2 5脂肪酶在有机溶剂中催化脂肪酸低碳醇酯酯化合成过程中 ,有机溶剂性质、脂肪酸与低碳醇的结构、pH值、反应温度和体系含水量、低碳醇的抑制作用等因素对酯化过程的影响。试验结果表明 :底物低碳醇需要采用流加方式加入体系 ,石油醚是最适宜的有机溶剂 ,脂肪酸与醇的碳链越长 ,越易于酯化 ;固定化脂肪酶对直链醇的选择性优于支链醇。以石油醚为有机溶剂 ,在反应温度为 40℃、pH值为 7时 ,硬脂酸与甲醇的酯化率达 95 % ;反应后期应除去体系中的水以避免酶失活。固定化酶间歇催化油酸与甲醇的酯化时 ,重复使用 1 5次 (每次 2 4h) ,其操作半衰期约为 360h。 相似文献
79.
80.
Murielle Schmitt-Rozieres Guillaume Vanot Valérie Deyris Louis-Claude Comeau 《Journal of the American Oil Chemists' Society》1999,76(5):557-562
γ-Linolenic acid (Z,Z,Z-6,9,12-octadecatrienoic acid), a very important polyunsaturated fatty acid is found in the free fatty acid fraction prepared
by the hydrolysis of borage oil. Our aim was to enrich this fraction in γ-linolenic acid using selective esterification. Candida rugosa lipase was used as catalyst after immobilization on the following ion-exchange resins: Amberlite IRC50, IRA35, IRA93, and
Duolite A7, A368, A568. In every case, immobilization modified the lipae’s specificity: palmitic, stearic, oleic, and linoleic
acids were preferentially esterified compared to γ-linolenic acid, thus allowing a γ-linolenic acid enrichment of 3.0. 相似文献