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María Dolores López‐Ramírez Ulises Miguel García‐Ventura Fabricio Omar Barroso‐Muñoz Juan Gabriel Segovia‐Hernández Salvador Hernández 《化学工程与技术》2016,39(2):271-275
The esterification of oleic acid and methanol using sulfuric acid as a homogeneous catalyst is studied in reactive‐separation systems. The conversion of the free fatty acid was investigated in two different experiments with the molar ratio of methanol/oleic acid, amount of catalyst, temperature, and reaction time as variables. The conversion of the free fatty acid was found to depend strongly on the molar ratio of methanol/oleic acid. The reaction time had a direct effect on the conversion of the free fatty acid, and this conversion decreased with higher temperature. These results were valuable for a preliminary study on biodiesel production, using an acid homogeneous catalyst in a reactive dividing‐wall distillation column. 相似文献
63.
Fairly uniform microspheres of poly(styrene‐co‐methyl methacrylate) were prepared by employing a microporous glass membrane [Shirasu porous glass (SPG)]. The single‐step SPG emulsification, the emulsion composed mainly of monomers, hydrophobic additives, and an oil‐soluble initiator, suspended in the aqueous phase containing a stabilizer and inhibitor, was then transferred to a reactor, and subsequent suspension polymerization followed. The droplets obtained were polymerized at 75°C under a nitrogen atmosphere for 24 h. The uniform poly(styrene‐co‐methyl methacrylate) microspheres with diameters ranging from 7 to 14 μm and a narrow particle‐size distribution with a coefficient of variation close to 10% were prepared by using SPG membrane with a pore size of 1.42 μm. The effects of the crosslinking agent and hydrophobic additives on the particle size, particle‐size distribution, and morphologies were investigated. It was found that the particle size decreased with a narrower size distribution when the additives were changed from long‐chain alkanes to long‐chain alcohols and long‐chain esters, respectively. Various microspheres with different morphologies were obtained, depending on the composition of the oil phase. The spherical poly(styrene‐co‐methyl methacrylate) particles without phase separation were obtained when using an adequate amount of the crosslinking agent and methyl palmitate as an additive. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 1013–1028, 2000 相似文献
64.
维生素C棕榈酸酯是一种新型、脂溶性、无毒无害多功能的营养性抗氧化剂,近几年被国际上认可为一种新型食品添加剂.研究表明它的抗氧化效果明显比常用的抗氧化剂BHA、BHT、TBHQ等效果要好,还能与VE等抗氧化剂作用产生增效作用,仅仅需要加入少量,即可对食品起到保鲜作用,而且能延长食品贮存时间,增加食品的营养,安全可靠.因而广泛地应用于油脂、含油食品、医药、保健品化妆品等领域.实验以维生素C和棕榈酸为原料,硫酸为催化剂,直接酯化法合成维生素C棕榈酸酯.研究了反应时间、反应温度、维生素C与棕榈酸物质量的比、催化剂用量等工艺条件对产品收率的影响.工艺条件优化基础上,研究不同抗氧化增效剂对产品收率的影响.产品最终收率达到74.52%,产品质量符合GB16314-1996标准. 相似文献
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The novel hybrid polyoxazoline‐grafted multiwalled carbon nanotubes (POZO‐grafted MWNTs) were synthesized by the reaction of partially hydrolyzed polyoxazolines (Hydrolyzed‐POZO) and MWNTs having carboxylic acid groups (MWNT‐COOH) in the presence of DCC as a condensing agent. Hydrolyzed‐POZO (degree of hydrolysis, 20.2 mol % by 1H‐NMR) were produced from the hydrolysis of polyoxazolines in an aqueous NaOH solution at reflux for 72 h. MWNT‐COOH were prepared by acid treatment of pristine MWNTs. The composition, structure, thermal property, and surface morphology of the novel hybrid POZO‐grafted MWNTs were fully characterized by FT‐IR, Raman, 1H‐NMR, DSC, TGA, SEM, and TEM. The obtained POZO‐grafted MWNTs are well soluble in various organic solvents and water. It was observed that the glass transition temperature (Tg) of POZO‐grafted MWNTs was lower than that of Hydrolyzed‐POZO due to the absence of hydrogen bonding interactions between Hydrolyzed‐POZO itself caused by the incorporation with MWNTs. It was also found that Hydrolyzed‐POZO was homogeneously attached to the surfaces of MWNTs through the “grafting‐to” method. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 相似文献
67.
Shou-Yi Li Zhen-Lai Liu Gen-Xiang Xiang Bao-Hong Ma Xiao-Ding Meng Yong-Lin He 《Ceramics International》2019,45(1):767-776
Herein, a novel hierarchical TiO2 pinecone-like structure (TPS) has been successfully fabricated for the first time by self-assembling anodic oxidation methods on the Ti plate. Then it was constructed that a series of CdS-TPS nanocomposites with different cycles CdS modifying by a successive ionic layer adsorption and reaction (SILAR) after different temperature annealing in air. The structures and properties of the CdS-TPS were investigated by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Current-voltage (I-V), ultraviolet-visible (UV–vis/DRS). The results shown that the optical properties of the CdS-TPS could be rationally tailored by adjusting the CdS-modified cycles and annealing temperature, which significantly enhanced photocatalytic activity. To be used in photocatalytic organic pollutant removal after optimizing both the CdS modification cycles and annealing temperature. The 15-CdS-TPS-500?°C exhibited significantly improved photocatalytic activities of methyl orange (MO) degradation under simulated sunlight irradiation. With 180?min, 85% of the MO (0.05?mM/L, 5?mL) was photodegraded and its kinetic constant reached to 0.0104?min?1, which is the 3.0 times and 3.6 times quicker than that of 5-CdS-TPS-500?°C and 15-CdS-TPS-0?°C, respectively. This could be ascribed to the result of the synergy effects of the suitable quantity of CdS nanoparticles modifier, the special surface structure, excellent crystallinity, higher electrical conductivity, and band structure matching. The possible photocatalytic mechanism of the CdS-TPS sample is investigated as well. 相似文献
68.
Enzymatic Synthesis and Antioxidant Activity of 1‐Caffeoylglycerol Prepared from Alkyl Caffeates and Glycerol 下载免费PDF全文
Xiang‐Yun Meng Yan Xu Jin‐Xian Wu Chang‐Tong Zhu Dong‐Yang Zhang Guo‐Hua Wu Fu‐An Wu Jun Wang 《Journal of the American Oil Chemists' Society》2018,95(2):149-159
Caffeic acid (CA) as a strong antioxidant has lower solubility in nonpolar media, which limits its application in the food industry. To increase the lipophilicity of CA, 1‐caffeoylglycerol (1‐CG) was synthesized by lipase‐catalyzed transesterification of alkyl caffeates in solvent‐free system and its antioxidant capacity was investigated. Methyl caffeate was screened as the appropriate substrate from tested alkyl caffeates with a yield of 90.63%. Ethyl acetate was used for extracting 1‐CG from enzymatic reactants and could be easily recycled. The produced 1‐CG had 2.5‐ and 10‐fold lower values of half maximal inhibitory concentration (IC50) (10.86 and 3.99 μM) than butylated hydroxyanisole by 1,1‐diphenyl‐2‐picrylhydrazyl radical scavenging and β‐carotene‐linoleic acid assays, respectively. Thus, 1‐CG is an excellent antioxidant for application in the functional food industry. Using alkyl caffeates and glycerol as substrates to produce 1‐CG catalyzed by immobilized lipase in a solvent‐free system is a simple, selective, and safe bioprocess that can readily be achieved in the food industry, and the product 1‐CG could be widely applied in food, nutraceutical, and biotechnological products. 相似文献
69.
Piyanud Jantawasu Thammanoon Sreethawong Sumaeth Chavadej 《Chemical engineering journal (Lausanne, Switzerland : 1996)》2009,155(1-2):223-233
In this work, nanocrystalline mesoporous-assembled TiO2 photocatalyst was synthesized by a sol–gel process with the aid of a structure-directing surfactant and employed for the photocatalytic degradation of methyl orange azo dye (monoazo dye), as compared to various commercially available non-mesoporous-assembled TiO2 powders. The experimental results showed that the synthesized mesoporous-assembled TiO2 nanocrystal calcined at 500 °C provided superior decolorization and degradation performance to the non-mesoporous-assembled commercial TiO2 powders. In addition, several operational parameters affecting the decolorization and degradation of methyl orange, namely photocatalyst dosage, initial dye concentration, H2O2 concentration, and initial solution pH, were systematically investigated, using the mesoporous-assembled TiO2 nanocrystal. The optimum conditions were a photocatalyst dosage of 7 g/l, an initial dye concentration of 5 mg/l, a H2O2 concentration of 0.5 M, and an initial solution pH of 4.7, exhibiting the highest decolorization rate of methyl orange. 相似文献
70.