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51.
《Journal of the European Ceramic Society》2014,34(16):4373-4381
From the characterization of a series compositions with general stoichiometry as Ca1−xZr1−xSm2xTi2O7 (0.00 ≤ x ≤ 1.00), the phase evolution between zirconolite (CaZrTi2O7) and pyrochlore type Sm2Ti2O7 has been elucidated. All the compositions were prepared by high temperature solid state reaction and characterized by powder X-ray diffraction (XRD) and electron probe for microanalyses (EPMA). Three major phase fields, namely two layer (2-M) or four layer (4-M) monoclinic zirconolite and cubic pyrochlore structure types were observed in this system. In addition, a feeble amount of perovskite type phase is found to coexist with zirconolite phase. 4-M zirconolite phase is observed as single phase field at the composition with x = 0.30 and 0.35, while cubic pyrochlore phase is observed as single phase at the compositions with x ≥ 0.60. Further, the composition and microstructure of coexisting phases are verified by back scattered electron image and EPMA studies. 相似文献
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M. G. Roig J. F. Bello S. Rodriguez J. F. Kennedy D. W. Taylor 《Polymer International》1996,39(1):17-30
Alkaline phosphatase from human placenta has been chemically immobilized on a hydrophilic cross-flow microfiltration membrane made from poly(vinylidene difluoride) (PVDF) derivatized with 1,1′-carbonyldiimidazole. The physicochemical characterization of the immobilized biocatalyst paid special attention to the irreversibility of the bonding of the enzyme to the support, the effects of pH, temperature and ionic strength on this activity, the existence of limitations of internal and external diffusion for H+, substrate and/or products, and the kinetic behavior (intrinsic and/or effective) of the immobilized enzyme. With respect to enzyme stability, patterns of hysteresis or memory are proposed, to account for a catalytic activity affected by previous experimental events and situations. The intrinsic kinetic behaviour, rate versus substrate concentration in the absence of diffusional restrictions, was analysed graphically and numerically (by non-linear regression and by utilizing the F statistical test for model discrimination), postulating a minimum rational rate equation of 2:2 degree in substrate concentration. In concordance, a mechanistic kinetic scheme for the catalytic enzyme action has been postulated. 相似文献
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Jong-Min Park Mi Yeon Kim Joachim Jose Min Park 《International journal of molecular sciences》2022,23(1)
A regenerable immunoaffinity layer comprising covalently immobilized orientation-controlled antibodies was developed for use in a surface plasmon resonance (SPR) biosensor. For antibody orientation control, antibody-binding Z-domain-autodisplaying Escherichia coli (E. coli) cells and their outer membrane (OM) were utilized, and a disuccinimidyl crosslinker was employed for covalent antibody binding. To fabricate the regenerable immunoaffinity layer, capture antibodies were bound to autodisplayed Z-domains, and then treated with the crosslinker for chemical fixation to the Z-domains. Various crosslinkers, namely disuccinimidyl glutarate (DSG), disuccinimidyl suberate (DSS) and poly (ethylene glycol)-ylated bis (sulfosuccinimidyl)suberate (BS(PEG)5), were evaluated, and DSS at a concentration of 500 μM was confirmed to be optimal. The E. coli-cell-based regenerable HRP immunoassay was evaluated employing three sequential HRP treatment and regeneration steps. Then, the Oms of E. coli cells were isolated and layered on a microplate and regenerable OM-based HRP immunoassaying was evaluated. Five HRP immunoassays with four regeneration steps were found to be feasible. This regenerable, covalently immobilized, orientation-controlled OM-based immunoaffinity layer was applied to an SPR biosensor, which was capable of quantifying C-reactive protein (CRP). Five regeneration cycles were repeated using the demonstrated immunoaffinity layer with a signal difference of <10%. 相似文献
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生物菌固定化研究对生物脱硫技术的推广应用具有重要的意义。本文以实验室筛选的、符合4S脱硫代谢途径的Rhodococcus sp.H.412为研究对象,二苯并噻吩(DBT)为生物催化脱硫模拟化舍物,考察了脱硫菌Rhodococcus sp.H.412的固定化操作条件和使用条件。试验结果表明:在交联温度为4℃,交联剂氯化钙溶液浓度为0.10mmol/L,海藻酸钠质量分数为3.0%,添加剂硅藻土质量分数为1.0%,菌胶比(菌体湿重:胶体体积)为1:20的条件下,用8号医用针头造粒,可以得到具有较高的脱硫活性、较好的机械强度和传质性能的固定化细胞颗粒。固定化细胞相对游离细菌而言,具有较高的温度适应能力和较宽的pH适应范围。 相似文献
59.
Xin Yuan Yu Liu Fan Cao Panliang Zhang Jian Ou Kewen Tang 《American Institute of Chemical Engineers》2020,66(9):e16292
Enzyme immobilization enhances the catalytic activity and stability of the enzyme, and also improves reusability. Metal–organic frameworks (MOFs), which possess diversified structures and porosity, have been used as excellent carriers for enzyme immobilization. Pseudomonas fluorescens lipase (PFL) has been successfully immobilized onto MOFs by covalent cross-linking to obtain a series of immobilized lipase (PFL@MOFs). PFL@MOFs are used for catalytic enantioselective hydrolysis of 2-(4-hydroxyphenyl) propionic acid ethyl ester enantiomers (2-HPPAEE) in aqueous medium and transesterification of 4-methoxymandelic acid enantiomers (4-MMA) in organic medium. The experimental results indicated that PFL@Uio-66(Zr) exhibits excellent enzymatic catalysis performances and high enantioselectives. In addition, to improve catalytic activity and reusability, PFL is modified by the polyethylene glycol (PEG) to prepare PEG-modified lipase (PFL-PEG), then PFL-PEG is immobilized onto Uio-66(Zr) to prepare PFL-PEG@Uio-66(Zr), demonstrating better reusability and catalytic activity compared with PFL@Uio-66(Zr). 相似文献
60.
采用发酵性丝孢酵母菌处理精炼大豆油废水,首先利用海藻酸钠和所制备的Fe3O4磁性载体分别对酵母菌进行固定化,然后分别用酵母菌、磁性载体、海藻酸钠固定化酵母菌和磁性载体固定化酵母菌来处理精炼大豆油废水。对处理结果进行对比分析,结果显示:4种物质中,磁性载体固定化酵母菌对精炼大豆油废水处理36 h时效果最佳。pH值6.0比较适合磁性载体固定化酵母菌的生长,处理36 h的废水中的酵母菌的OD600值为19.78。通过研究不同pH值和不同接种量条件对磁性载体固定化酵母菌处理精炼大豆油废水的情况,得到处理废水的较优条件:废水pH值6.0,酵母菌接种量10%,处理时间36 h,此条件下废水的化学需氧量(COD)值为2 430 mg/L。 相似文献