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11.
The effect of the reaction kinetics on the ionic conductivity for a comblike‐type polyether (MEO) electrolyte with lithium bis(trifluoromethane sulfonyl)imide (LiTFSI) was characterized by DSC, complex impedance measurements, and 1H pulse NMR spectroscopy. The ionic conductivity of these electrolytes was affected by the reaction condition of the methacrylate monomer and revealed by the glass transition temperature (Tg), spin–spin relaxation time (T2), steric effects of the terminal groups, and the number of charge carriers indicated by the VTF kinetic parameter. In this system, the electrolytes prepared by the reaction heating rate of 10°C/min of MEO–H and 15°C/min of MEO–CH3 showed maximum ionic conductivity, σi, two to three times higher in magnitude than that of the σi of the others at room temperature. As experimental results, the reaction kinetic rate affected the degree of conversion, the ionic conductivity, and the relaxation behaviors of polyether electrolytes. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 2149–2156, 2003 相似文献
12.
Dr. Yoshiaki Yasutake Dr. Taiki Nishioka Dr. Noriko Imoto Prof. Tomohiro Tamura 《Chembiochem : a European journal of chemical biology》2013,14(17):2284-2291
Vitamin D3 hydroxylase (Vdh) from Pseudonocardia autotrophica is a cytochrome P450 monooxygenase that catalyzes the two‐step hydroxylation of vitamin D3 (VD3) to produce 25‐hydroxyvitamin D3 (25(OH)VD3) and 1α,25‐dihydroxyvitamin D3 (1α,25(OH)2VD3). These hydroxylated forms of VD3 are useful as pharmaceuticals for the treatment of conditions associated with VD3 deficiency and VD3 metabolic disorder. Herein, we describe the creation of a highly active T107A mutant of Vdh by engineering the putative ferredoxin‐binding site. Crystallographic and kinetic analyses indicate that the T107A mutation results in conformational change from an open to a closed state, thereby increasing the binding affinity with ferredoxin. We also report the efficient biocatalytic synthesis of 25(OH)VD3, a promising intermediate for the synthesis of various hydroxylated VD3 derivatives, by using nisin‐treated Rhodococcus erythropolis cells containing VdhT107A. The gene‐expression cassette encoding Bacillus megaterium glucose dehydrogenase‐IV was inserted into the R. erythropolis chromosome and expressed to avoid exhaustion of NADH in a cytoplasm during bioconversion. As a result, approximately 573 μg mL?1 25(OH)VD3 was successfully produced by a 2 h bioconversion. 相似文献
13.
Yoichi Tominaga 《Polymer》2005,46(19):8113-8118
We have measured ionic conductivity of PEO-LiX [anion X=N(CF3SO2)2 (TFSI), ClO4, CF3SO3, BF4, NO3, and CH3SO3] polymer electrolytes in CO2 at pressures varied from 0.1 to 20 MPa. From the temperature dependence in supercritical CO2, a large increase in the conductivity for PEO-LiBF4 and LiCF3SO3 electrolytes has been observed. Permeation of the CO2 molecules gave rise to the plasticization for crystal domains in the electrolytes, which is related to the reduction in transition point of the Arrhenius plot corresponding to the melting of crystal PEO. Relation between the conductivity and CO2 reduced density revealed that the electrolytes containing fluorinated anions such as ‘CO2-philic’ BF4 and CF3SO3 increase in the conductivity with increasing the density. This indicates that the salt dissociation was promoted by the CO2 permeation and the Lewis acid-base interactions between fluorinated anions and CO2 molecules. 相似文献
14.
Yoichi Tominaga 《Electrochimica acta》2005,50(19):3949-3954
We have synthesized mesoporous silica (MPSi) as a novel type of inorganic filler for polyether-based electrolytes and have characterized the effect of addition on ionic conduction. Both poly(ethylene oxide) (PEO) and PMEO composites filled with MPSi showed higher ionic conductivity than the original and the composites filled with particle silica (pSiO2). It was considered that the increase is caused by the difference in the surface area between MPSi and pSiO2. In the PEO composites, the addition of MPSi gave rise to the reduction of crystal PEO and crystalline complex domains. The glass transition temperature of the PMEO composites increased with the addition of the MPSi, in spite that the conductivity increased with increasing the filler contents. It has been suggested that the Lewis acid-base interactions between ions, ether chains and filler surface strongly affect on the ionic conduction in the composite electrolytes. 相似文献
15.
Toshihiro Nagao Yuji Shimada Yoshie Yamauchi-Sato Takaya Yamamoto Masaaki Kasai Kentaro Tsutsumi Akio Sugihara Yoshio Tominaga 《Journal of the American Oil Chemists' Society》2002,79(3):303-308
A commercial product of CLA contains almost equal amounts of cis-9,trans-11 (c9,t11)-CLA and trans-10,cis-12 (t10,c12)-CLA. We attempted to enrich the two isomers by a two-step selective esterification using Candida rugosa lipase that acted on c9,t11-CLA more strongly than on t10,c12-CLA. An FFA mixture containing CLA isomers was esterified with an equimolar amount of lauryl alcohol in a mixture of 20%
water and the lipase. When the esterification of total FA reached 50%, two isomers were fractionated in a good yield: t10,c12-CLA was enriched in FFA, and c9,t11-CLA was recovered in lauryl esters. The FFA were esterified again to enrich t10,c12-CLA. At 27.3% esterification of total FA, the t10,c12-CLA content in FFA increased to 64.8 wt% with 89.3% recovery: The ratio of the content of t10,c12-CLA to that of two isomers was 95.9%. Lauryl esters obtained by the single esterification were employed for enrichment
of c9,t11-CLA. After the esters were hydrolyzed, the resulting FFA were esterified again with lauryl alcohol. At 62.0% esterification
of total FA, the c9,t11-CLA content in lauryl esters increased to 73.3 wt% with 79.4% recovery: The ratio of the content of c9,t11-CLA to that of two isomers was 95.6%. In a 600-g-scale purification, molecular distillation was effective in separating
the reaction mixture into lauryl alcohol, FFA, and lauryl ester fractions. 相似文献
16.
γ‐Butyrolactone (GBL)‐processable high modulus heat‐resistant materials were developed in this work. The polyaddition of an ester‐containing tetracarboxylic dianhydride, i.e. hydroquinone bis(trimellitate anhydride) (TAHQ), and 2,2′‐bis(trifluoromethyl)benzidine (TFMB) in GBL resulted in gelation in the initial reaction stage. The incorporation of a methyl group to TAHQ (M‐TAHQ) allowed polymerization with TFMB in GBL and led to a homogeneous poly(ester imide) (PEsI) precursor solution with a short pot life of 3 days, whereas a simple copolymerization approach using bulky/flexible comonomers to TAHQ/TFMB was less effective. PEsI precursors (PEsAAs) were prepared from TFMB, M‐TAHQ and a minor fraction of 4,4′‐(hexafluoroisopropylidene)diphthalic anhydride (6FDA) or a fluorene‐containing tetracarboxylic dianhydride. These PEsAA systems showed drastically improved GBL solution stability. In particular, the M‐TAHQ(80);6FDA(20)/TFMB copolymer system provided a PEsAA film with a very high light transmittance at 365 nm (>70%). A photosensitive film composed of this matrix resin and diazonaphthoquinone provided a clear positive‐tone pattern by development in a 2.38 wt% tetramethylammonium hydroxide aqueous solution at room temperature with a high dissolution contrast. The thermally cured PEsI film achieved a very high tensile modulus (>5 GPa) as the present target with other desirable properties, i.e. sufficient film flexibility, a relatively low coefficient of thermal expansion, a high Tg and low water absorption. The present materials can be promising candidates as novel buffer coat films in semiconductor applications. Copyright © 2011 Society of Chemical Industry 相似文献
17.
High‐strength regenerated cellulose fibers spun from 1‐butyl‐3‐methylimidazolium chloride solutions 下载免费PDF全文
High‐performance regenerated cellulose fibers were prepared from cellulose/1‐butyl‐3‐methylimidazolium chloride (BMIMCl) solutions via dry‐jet wet spinning. The spinnability of the solution was initially evaluated using the maximum winding speed of the solution spinning line under various ambient temperatures and relative humidities in the air gap. The subsequent spinning trials were conducted under various air gap conditions in a water coagulation bath. It was found that low temperature and low relative humidity in the air gap were important to obtain fibers with high tensile strength at a high draw ratio. From a 10 wt % cellulose/BMIMCl solution, regenerated fibers with tensile strength up to 886 MPa were prepared below 22 °C and relative humidity of 50%. High strengthening was also strongly linked with the fixation effect on fibers during washing and drying processes. Furthermore, an effective attempt to prepare higher performance fibers was conducted from a higher polymer concentration solution using a high molecular weight dissolving pulp. Eventually, fibers with a tensile strength of ~1 GPa and Young's modulus over 35 GPa were prepared. These tensile properties were ranked at the highest level for regenerated cellulose fibers prepared by an ionic liquid–based process. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45551. 相似文献
18.
Heterodimerization of Group I Ribozymes Enabling Exon Recombination through Pairs of Cooperative trans‐Splicing Reactions 下载免费PDF全文
Takahiro Tanaka Yusuke Hirata Yuto Tominaga Prof. Hiroyuki Furuta Dr. Shigeyoshi Matsumura Prof. Yoshiya Ikawa 《Chembiochem : a European journal of chemical biology》2017,18(16):1659-1667
Group I (GI) self‐splicing ribozymes are attractive tools for biotechnology and synthetic biology. Several trans‐splicing and related reactions based on GI ribozymes have been developed for the purpose of recombining their target mRNA sequences. By combining trans‐splicing systems with rational modular engineering of GI ribozymes it was possible to achieve more complex editing of target RNA sequences. In this study we have developed a cooperative trans‐splicing system through rational modular engineering with use of dimeric GI ribozymes derived from the Tetrahymena group I intron ribozyme. The resulting pairs of ribozymes exhibited catalytic activity depending on their selective dimerization. Rational modular redesign as performed in this study would facilitate the development of sophisticated regulation of double or multiple trans‐splicing reactions in a cooperative manner. 相似文献
19.
Inside Cover: Selective Manipulation of Discrete Mannosidase Activities in the Endoplasmic Reticulum by Using Reciprocally Selective Inhibitors (ChemBioChem 11/2017) 下载免费PDF全文
20.
Facile purification of tocopherols from soybean oil deodorizer distillate in high yield using lipase 总被引:16,自引:0,他引:16
Yuji Shimada Seiichi Nakai Masaharu Suenaga Akio Sugihara Motohiro Kitano Yoshio Tominaga 《Journal of the American Oil Chemists' Society》2000,77(10):1009-1013
Tocopherols have been purified from deodorizer distillate produced in the final deodorization step of vegetable oil refining
by a process including molecular distillation. Deodorizer distillate contains mainly tocopherols, sterols, and free fatty
acids (FFA); the presence of sterols hinders tocopherol purification in good yield. We found that Candida rugosa lipase recognized sterols as substrates but not tocopherols, and that esterification of sterols with FFA could be effected
with negligible influence of water content. Enzymatic esterification of sterols with FFA was thus used as a step in tocopherol
purification. High boiling point substances including steryl esters were removed from soybean oil deodorizer distillate by
distillation, and the resulting distillate (soybean oil deodorizer distillate tocopherol concentrate; SODDTC) was used as
a starting material for tocopherol purification. Several factors affecting esterification of sterols were investigated, and
the reaction conditions were determined as follows: A mixture of SODDTC and water (4∶1, w/w) was stirred at 35°C for 24 h
with 200 U of Candida lipase per 1 g of the reaction mixture. Under these conditions, approximately 80% of sterols was esterified, but tocopherols
were not esterified. After the reaction, tocopherols and FFA were recovered as a distillate by molecular distillation of the
oil layer. To enhance further removal of the remaining sterols, the lipase-catalyzed reaction was repeated on the distillate
under the same reaction conditions. As a result, more than 95% of the sterols was esterified in total. The resulting reaction
mixture was fractionated to four distillates and one residue. The main distillate fraction contained 65 wt% tocopherols with
low contents of FFA and sterols. In addition, the residue fraction contained high-purity steryl esters. Because the process
presented in this study includes only organic solvent-free enzymatic reaction and molecular distillation, it is feasible as
a new industrial purification method of tocopherols.
This work was presented at the Biocatalysis symposium in April 2000, held at the 91st Annual Meeting and Expo of the American
Oil Chemists Society, San Diego, CA. 相似文献