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71.
叙述了30万~60万千瓦汽轮机叶片用钢AISI403(1Cr12Mo)的生产工艺以及Ni、Mo和热处理工艺对钢的机械性能的影响。当Ni、Mo含量分别不小于0.3%时,钢的机械性能满足PDS技术条件的要求。 相似文献
72.
In this report, the results of preliminary research on L-alanine/ESR electron dosimeters are described. They include the designs of modelling tools and experimental capsules, the preparation and irradiation of very thin dosimeters, the measurement of ESR signal spectrum and the calibration method. The physical, chemical and dosimetric properties of the alanine free radical dosimeters, such as the smallest thickness, average density, lowest detectable limit, repeatability of the method, reproducibility resulted in directivity and location in resonance cavity, linearity regions as well as relative scattering of the response to identical doses, are summarized. 相似文献
73.
74.
本文研究了组氨酸和精氨酸对胸腺嘧啶的辐射保护机理。用ESR方法和分子轨道计算确证其辐射保护是由于电子清除和从胸腺嘧啶阴离子向碱性氨基酸的转移。碱性氨基酸的亲电子性能随质子化程度而异,在pH=7的条件下,组氨酸对胸腺嘧啶的辐射保护机理可能是电子转移与氢原子转移的协同过程。 相似文献
75.
Coal liquefaction experiments are described which were carried out to dissolve a subbituminous coal in low and high hydrogen content solvents, in which liquid samples were periodically withdrawn and examined by electron spin resonance spectroscopy. The objectives of this study were to gain information on the free radical processes involved in coal liquefaction, to determine the relative effectiveness of two solvents (H-donor and non-donor) in influencing the radical processes involved in coal liquefaction and to investigate changes in radical concentration on storage. 相似文献
76.
Hana Kim Jeong Yong Moon Hyeonji Kim Dong-Sun Lee Moonjae Cho Hyung-Kyoon Choi Young Suk Kim Ashik Mosaddik Somi Kim Cho 《Food chemistry》2010
The antioxidant and antiproliferative properties of flesh and peel of mango (Mangifera indica L.) were investigated. The cytoprotective effect of mango flesh and peel extracts on oxidative damage induced by H2O2 in a human hepatoma cell line, HepG2, were determined, and the underlying mechanism was examined by a single-cell electrophoresis assay (comet assay). Treatment of HepG2 cell with mango peel extract prior to oxidative stress was found to inhibit DNA damage. The free radical scavenging activities of mango flesh and peel extracts were evaluated by electron spin resonance (ESR). The mango peel extract exhibited stronger free radical scavenging ability on 1,1-diphenyl-2-picrylhydrazyl (DPPH) and alkyl radicals than mango flesh extract, regardless of ripeness. Similarly, peel extract exhibited significant antiproliferative effect against all tested cancer cell lines, compared to that of flesh extract, in a dose-dependent manner. The result also showed that the antiproliferative activity of mango flesh and peel extracts correlated with their phenolic and flavonoid contents. Thus, mango peel, a major by-product obtained during the processing of mango product, exhibited good antioxidant activity and may serve as a potential source of phenolics with anticancer activity. 相似文献
77.
通过对非真空感应炉+电渣炉工艺生产的1Cr21Ni5Ti电渣锭出现的表面气孔问题进行多方调查分析,指出减少电渣锭中H的来源是控制电渣锭气孔产生的关键要素,并在后续生产中采取了相关措施,电渣锭气孔问题得到了有效遏止。 相似文献
78.
Electron spin resonance (ESR) spectroscopy is able to directly measure the chemical species with unpaired electrons and has been widely used in a number of research fields. This review focused on its application in nutraceutical and food research. Current status of ESR in free radical scavenging capacity estimation, food oxidative stability evaluation, Cu(2+) chelating capacity determination were summarized. Also discussed was the potential of ESR spin-label oximetry technique in examination of lipid peroxidation and oxygen diffusion-concentration products in liposomes, oxygen transport and depletion, and membrane structure and dynamic properties. In addition, ESR application in identifying and estimating irradiated foods including meat, fruits, vegetables, spices, cereal grains, and oil seeds was reviewed. Finally, the potential use of ESR technique in investigating microstructure change, phase transition and viscosity related properties during food formulation, processing, and storage was briefly mentioned, along with its potential in determination of radio-stability of food components. This review may provide some fundamental knowledge of ESR and its application in nutraceutical and food research. 相似文献
79.
The self-prepared pectin hydroxamic acid has been reported to have antioxidant activities [Yang, S. S., Cheng, K. D., Lin, Y. S., Liu, Y. W., & Hou, W. C. (2004). Pectin hydroxamic acids exhibit antioxidant activities in vitro. Journal of Agricultural and Food Chemistry, 52, 4270–4273]. In this study, the galacturonic acid (GalA), the monomer unit of the pectin polymer, was esterified with acidic methanol (1 N HCl) at 4 °C with gentle stirring for 5 days to get galacturonic acid methyl ester which was further reacted with alkaline hydroxylamine to get galacturonyl hydroxamic acid (GalA–NHOH). The GalA–NHOH was used to test the antioxidant and antiradical activities in the comparison with GalA. The scavenging activities of GalA–NHOH against DPPH radicals (half-inhibition concentration, IC50, was 82 μM), hydroxyl radicals detected by electron spin resonance (IC50 was 0.227 nM in the comparison with Trolox of 0.433 μM), superoxide radicals (IC50 was 830 μM) were determined. The protection activities of GalA–NHOH against hydroxyl radicals-mediated calf thymus DNA damages, linoleic acid peroxidation and peroxynitrite-mediated dihydrorhodamine 123 oxidations were also investigated. It was found that the GalA–NHOH exhibited dose-dependently antioxidant activity and few or none was found in GalA. The GalA–NHOH was used to evaluate the suppressed activity of nitric oxide (NO) productions of RAW264.7 cells in the presence of lipopolysaccharide (LPS, 100 ng/ml) as inducers. It was found that GalA–NHOH (0.02–0.1 mg/ml) could dose-dependently suppress the NO productions (expressed as nitrite concentrations) in RAW264.7 cells without significant cytotoxicity. 相似文献
80.
~(60)Co-γ射线对粳米黏度的影响及机理分析 总被引:1,自引:0,他引:1
ZOU Zhen-you PENG Xiao-peng LI Xing ZHANG Kai-xiang WANG Fang WANG Guo-xiang TAN Yuan-yuan FU Jun-jie 《食品科学》2008,(12)
为明确大米辐照后黏度下降的原因,将粳米粒放在不同剂量的60Co-γ射线下辐照后观察了淀粉粒的形态与结构,测量了蒸煮黏度、碱溶蛋白分子量种类以及自由基含量的变化。结果表明,随辐照加强,粳米的蒸煮黏度的数值自213cPs单调降低到21cPs;淀粉组织崩解碎裂;蛋白质碎片增多,生成了35kD以下的小蛋白片段和肽;自由基增多,ESR信号增强;大米受γ射线辐照时,其成分物质中的电子从原有轨道激发电离,生成电子未配对的自由基,与淀粉、蛋白质等反应,导致后者断裂;以及辐射的生热效应使淀粉和其它成分膨胀产生的应力使大米结构崩解,也是粳米黏度降低的部分原因。 相似文献