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排序方式: 共有485条查询结果,搜索用时 15 毫秒
71.
L. Funes S. Fernández-Arroyo O. Laporta A. Pons E. Roche A. Segura-Carretero A. Fernández-Gutiérrez V. Micol 《Food chemistry》2009
Phenylpropanoids are the main class of compounds from lemon verbena which have shown a wide biological activity, verbascoside being the most abundant one. In this work, the composition of a lemon verbena extract was elucidated by HPLC-ESI-MS/MS and one flavone and one methoxylated phenylpropanoid were found in this source for the first time. The antioxidant activity of the lemon verbena extract was fully characterised by several methodologies. Unexpectedly, the extract was especially active in lipophilic environments and lipid peroxidation inhibition assay, as it was found for pure verbascoside. The lemon verbena extract, containing verbascoside as its major bioactive compound, was acutely administered to rats and verbascoside was the only metabolite detected in plasma samples as measured by HPLC mass spectrometry. The correlation between the highest verbascoside concentration in plasma and maximum plasma antioxidant capacity was observed at 20 min as measured by different techniques, i.e. minimum malondialdehyde (MDA) generation, highest ferric-reducing ability of plasma (FRAP value) and maximum superoxide dismutase activity (SOD). Therefore, the in vitro measurements of the antioxidant activity of lemon verbena extract may significantly support the antioxidant activity observed in vivo in this work. Moreover, neither evidence of acute oral toxicity nor adverse effects were observed in mice when the lemon verbena extract containing 25% verbascoside was used at a dosage of 2000 mg/kg. 相似文献
72.
The antioxidant activities of coconut oil extracted under hot and cold conditions were compared. The coconut oil extracted under hot conditions (HECO) contained more phenolic substances than the coconut oil extracted under cold conditions (CECO). The antioxidant potential of HECO was higher than that of CECO as demonstrated by DPPH assay, deoxyribose assay and in vivo assay of serum antioxidant capacity. It is the common belief that virgin coconut oil extracted under cold conditions preserves several thermally unstable antioxidants and, as a result, better beneficial qualities can be expected for virgin coconut oil. However, high temperatures used in the hot extraction of coconut oil favour the incorporation of more thermally stable phenolic antioxidants into coconut oil. Therefore, the consumption of HECO may result in the better improvement of antioxidant related health benefits compared with the consumption of CECO. 相似文献
73.
在以过氧化氢为氧化剂的二甲基硫醚液相氧化反应体系中,对空心钛硅分子筛(HTS)的催化性能进行了系统研究,详细考察了催化剂存在与否以及催化剂用量、反应时间、反应物料配比及溶剂用量等不同反应条件变化对二甲基硫醚温和液相氧化反应的影响。研究发现,在温和反应条件下,HTS催化二甲基硫醚氧化反应中主要产物是二甲基亚砜和二甲基砜。经优化后,能够获得较好的氧化二甲基硫醚制备二甲基亚砜的反应效果,在二甲基硫醚转化率超过99%的情况下,二甲基亚砜选择性可达95%以上。 相似文献
74.
Simona PotoracMarcel Popa Vasilica MaierGabriela Lisa Liliana Verestiuc 《Materials science & engineering. C, Materials for biological applications》2012,32(2):236-243
New hydrogels based on maleic anhydride (MA) modified collagen were prepared with the aim of overcoming the high degradation rate displayed by collagen that is not otherwise chemically crosslinked. Semi-interpenetrated matrices were obtained by free radical polymerization of maleilated collagen (CM) and 2-hydroxyethyl methacrylate (HEMA) in the presence of ammonium persulfate (APS) and N,N,N′,N′-tetramethylethylenediamine (TEMED) as initiating system. The resulting matrices (CMH) had a sharp decrease in degradation, when compared to pure collagen. FTIR and H1 NMR spectroscopies were used to confirm the incorporation of MA on the collagen peptide chains. The final composition of CMH was found to be strongly dependent by the concentration of maleilated collagen. The morphology of the hydrogels was studied by Scanning electron microscopy (SEM) and the macro-gel structure was confirmed. Water uptake of the synthetised hydrogels is influenced by both composition and the porosity of the matrices. 相似文献
75.
从糯米、籼米和粳米3种类型大米中分离提取支链淀粉,采用特征黏度法和激光光散射法研究支链淀粉在二甲亚砜(DMSO)纯溶液和DMSO水溶液中的分子构象。结果表明:籼米、粳米支链淀粉的分子特性较为相似,均与糯米支链淀粉的分子特性有较大差异。以糯米支链淀粉的重均分子质量和旋转半径最大,分支度最高,交点质量浓度最小,分子链更易伸展。大米支链淀粉在DMSO中的分子构象与DMSO水溶液的体积分数以及自身的重均分子质量、分支度和质量浓度有关。在DMSO纯溶液中,大米支链淀粉的分子构象接近球形。在DMSO水溶液中,籼米和粳米支链淀粉的分子构象几乎不受自身质量浓度影响,均接近星形;而糯米支链淀粉分子构象受自身质量浓度影响较大,在极低质量浓度条件下表现为硬球结构,稍高质量浓度条件下表现为柔性球结构。 相似文献
76.
以复合固体酸SO4^2-/Fe2O3-TiO2为多相催化剂,通过环己酮和乙二醇反应合成了环己酮缩乙二醇。探讨SO4^2-/Fe2O3-TiO2对缩酮反应的催化活性,较系统地研究了酮醇物质的量比,催化剂用量,反应时间诸因素对产品收率的影响。实验表明:SO4^2-/Fe2O3-TiO2是合成环己酮缩乙二醇的良好催化剂,在酮醇物质的量比为1:1.5,催化剂用量为反应物料总质量的2%,带水剂选用环己烷,反应时间1.5h的条件下,环己酮缩乙二醇的收率可达92.7%。 相似文献
77.
Mitsugu Watanabe Hirotoshi Fuda Shigeki Jin Toshihiro Sakurai Shu-Ping Hui Seiji Takeda Takayuki Watanabe Takao Koike Hitoshi Chiba 《Food chemistry》2012
3,5-Dihydroxy-4-methoxybenzyl alcohol (DHMBA), an antioxidant isolated from the Pacific oyster (Crassostrea gigas), was studied in a cell-based fluorometric antioxidant assay using human hepatocyte-derived cells (C3A) and diphenyl-1-pyrenylphosphine (DPPP) as a fluorescent probe. In comparison with two hydrophilic antioxidants, DHMBA showed the stronger inhibition of DPPP-mediated fluorescence than chlorogenic acid and l-ascorbic acid: at a concentration of 320 μM of DPPP, the inhibition was 26.4 ± 2.6%, 11.1 ± 1.2%, and 0 ± 2.0% for DHMBA, chlorogenic acid, and l-ascorbic acid, respectively (mean ± SD, n = 4). Their relative oxygen radical absorbance capacities (ORAC) were dissociated with their cell-based antioxidant activities: 1.47 ± 0.40, 4.57 ± 0.30, and 0.53 ± 0.13 μmol TE/μmol for DHMBA, chlorogenic acid, and l-ascorbic acid, respectively (mean ± SD, n = 4). The amphiphilicity of DHMBA was better than chlorogenic acid and l-ascorbic acid might underlie this dissociation. Since the C3A cells are human hepatoma-derived cells, DHMBA might be useful in the prevention and treatment of liver diseases by involving an oxidation process. 相似文献
78.
Ananta Kumar MishraSaswata Bose Tapas KuilaNam Hoon Kim Joong Hee Lee 《Progress in Polymer Science》2012,37(6):842-869
Proton-exchange membrane fuel cells have emerged as a promising emission free technology to fulfill the existing power requirements of the 21st century. Nafion® is the most widely accepted and commercialized membrane to date and possesses excellent electrochemical properties below 80 °C, under highly humidified conditions. However, a decrease in the proton conductivity of Nafion® above 80 °C and lower humidity along with high membrane cost has prompted the development of new membranes and techniques. Addition of inorganic fillers, especially silicate-based nanomaterials, to the polymer membrane was utilized to partially overcome the aforementioned limitations. This is because of the lower cost, easy availability, high hydrophilicity and higher thermal stability of the inorganic silicates. Addition of silicates to the polymer membrane has also improved the mechanical, thermal and barrier properties, along with water uptake of the composite membranes, resulting in superior performance at higher temperature compared to that of the virgin membrane. However, the degrees of dispersion and interaction between the organic polymer and inorganic silicates play vital roles in improving the key properties of the membranes. Hence, different techniques and solvent media were used to improve the degrees of nanofiller dispersion and the physico-chemical properties of the membranes. This review focuses mainly on the techniques of silicate-based nanocomposite fabrication and the resulting impact on the membrane properties. 相似文献
79.
Andrea Z. Dalla Valle Ilaria Mignani Anna Spinardi Fabio Galvano Salvatore Ciappellano 《European Food Research and Technology》2007,225(2):167-172
Total polyphenols, carotenoids and vitamin C were assessed in three different peaches cultivars (Prunus persica): ‘Luisa Berselli’ (LB), ‘Stark Earlyglo’ (SE) and ‘Maria Serena’ (MS). Total antioxidant capacity of fruits and plasma antioxidant
activity after ingestion of fruits were determined as Trolox equivalent antioxidant capacity (TEAC) and as plasma total radical-trapping
potential (TRAP) respectively. The amount of polyphenols, carotenoids and vitamin C resulted to be generally similar in the
three cultivars. TEAC, measured from harvest to 7 days postharvest, resulted to be influenced mainly by vitamin C content,
whereas polyphenols and carotenoids seemed to play a secondary role. Although TEAC was similar in the three cultivars, only
LB significantly increased the TRAP in human plasma at 1, 2 and 4 h after ingestion of peaches. Sugar moiety, condensed and
glycoside phenols are suggested to be involved in the higher effect on plasma TRAP of LB. 相似文献
80.
J. Prasad RaoKurt E. Geckeler 《Progress in Polymer Science》2011,36(7):887-913