首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   133篇
  免费   10篇
  国内免费   16篇
电工技术   2篇
综合类   3篇
化学工业   35篇
金属工艺   3篇
机械仪表   14篇
矿业工程   2篇
轻工业   24篇
石油天然气   1篇
武器工业   2篇
无线电   34篇
一般工业技术   26篇
冶金工业   1篇
原子能技术   2篇
自动化技术   10篇
  2024年   1篇
  2022年   3篇
  2021年   1篇
  2020年   3篇
  2018年   3篇
  2017年   2篇
  2016年   4篇
  2015年   5篇
  2014年   11篇
  2013年   9篇
  2012年   13篇
  2011年   12篇
  2010年   5篇
  2009年   6篇
  2008年   12篇
  2007年   16篇
  2006年   6篇
  2005年   9篇
  2004年   5篇
  2003年   3篇
  2002年   3篇
  2001年   7篇
  2000年   4篇
  1999年   4篇
  1998年   3篇
  1997年   2篇
  1996年   1篇
  1995年   1篇
  1994年   1篇
  1993年   1篇
  1992年   2篇
  1988年   1篇
排序方式: 共有159条查询结果,搜索用时 0 毫秒
1.
Thermal characterization of maleic anhydride‐styrene‐allyl propionate (MA‐St‐AP) terpolymer and its ester derivatives named as n‐alkyl maleate and shown as nPr MA‐St‐AP, nBu MA‐St‐AP, nPn MA‐St‐AP, and nBz MA‐St‐AP was carried out. The thermal characterization was performed using thermal analysis techniques such as TGA, DTA, DSC, and TMA. Different results were observed between the original terpolymer and its ester derivatives. Thermal stabilities of the terpolymer and its ester derivatives were compared by using various measurements plotted as TGA, DTA, DSC, and TMA curves. The increase in the alcohols' carbon numbers added to the original terpolymer results in ester derivatives with different thermal stability behavior. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 600–604, 2007  相似文献   
2.
基于卡尔曼滤波的水下近距目标运动分析   总被引:1,自引:0,他引:1  
为跟踪水下近距目标,设计采用被动声纳平台获得目标的方位数据,用扩展卡尔曼滤波算法对测量数据进行目标运动分析来实现.建立了目标相对观测平台在固定深度做直线运动时的理论模型,针对非线性测量方程,采用雅可比矩阵来近似处理.采用标准卡尔曼滤波进行了实例仿真.结果表明,该方法将估计误差控制在8%以下,并有较好的稳定性.  相似文献   
3.
溶胶-凝胶法制备的纳米In2O3气敏性能研究   总被引:10,自引:0,他引:10  
以氯化铟为前驱体 ,通过溶胶 -凝胶法制备了纳米In2 O3 颗粒 .经TG -DSC热分析表明 :In(OH) 3 在 2 72 9℃附近脱水形成In2 O3 .经XRD ,TEM等手段表征的结果显示 :所合成的纳米In2 O3属立方晶型 ,晶粒尺寸约 2 0nm .气敏性能测试结果表明 :纳米In2 O3 气敏元件对TMA及NH3 灵敏度高 .通过与某公司提供的粒度为 3.0 77μm的In2 O3 制成的气敏元件比较得知 ,纳米In2 O3 气敏元件对TMA的灵敏度提高特别明显 .  相似文献   
4.
Aim of the work was to identify sulfide-producers isolated from tuna and swordfish and to evaluate some physiological characteristics, particularly those that could be related to spoiling potential.16S rDNA sequencing revealed Shewanella baltica as the main species, followed by Serratia spp. and other Shewanella species, while RAPD- and rep-PCR analyses indicated the presence of several biotypes. Shewanella baltica and Shewanella putrefaciens showed rapid growth at 4 and 8 °C, production of TMA and H2S, amino acids decarboxylation and proteolytic activity also at refrigeration temperatures, therefore being potentially able to modify texture and sensory characteristics of finfish. Extracellular DNAse activity and growth in presence of high salt concentrations can provide a competitive advantage in unfavourable environments.Our data provide new insights into specific metabolic features of Shewanella spp., rarely studied before, such as extracellular DNAse activity and amino acid decarboxylating activity. Moreover, our results highlight the clear necessity of more specific media and research methods to count H2S-producing bacteria.  相似文献   
5.
针对大口径离轴非球面系统加工与装调的难点,提出了非球面光学系统共基准加工与检测的方法,对该方法的基本原理和实现过程进行了分析和研究。当光学系统的主镜和第三镜面形的RMS值优于λ/10(λ=632.8nm)时,对主镜和第三镜进行共基准装调和测试,并进行背板一体化装嵌,然后利用离子束对其进行一体化共基准加工。结合工程实例,对一大口径非球面系统口径为724mm×247mm的非球面主镜和口径为632mm×205mm的第三镜进行了共基准加工与检测,最终利用离子束共基准一体化精抛光得到主镜和第三镜面形的RMS值分别为0.019λ和0.017λ,满足光学成像。  相似文献   
6.
This note reconsiders the marginal density of a threshold moving average process and proposes a simple yet effective numerical algorithm to implement that by solving an associated integral equation. This algorithm can also be applied to calculate stationary probability density or distribution functions of a few other types of nonlinear stationary stochastic processes numerically.  相似文献   
7.
Biochemical, microbiological and sensory changes during shelf‐life at ?1 °C were determined in shrimp (Panaeus aztecus) previously dipped in ascorbic acid, citric acid, potassium sorbate and 4‐hexyl resorcinol solutions using face‐centred central composite design. Microbiological count, trimethylamine and hypoxantine production were measured. The lowest level of the total psychrotrophic bacteria, hypoxantine and trimethylamine were found in samples dipped in all containing chemicals solutions comparing to control treatment. Sensory studies showed that treatment A (ascorbic acid 4.50, citric acid 0.12, potassium sorbate 18.60 and 4‐hexyl resorcinol 0.25, all g L?1) and B (ascorbic acid 4.37, citric acid 1.26, potassium sorbate 7.03 and 4‐hexyl resorcinol 0.25, all g L?1) did not alter the typical sensory features of shrimp and were effective at delaying the bitter off‐flavour formation for 26 days. This study constitutes a promising alternative to extent shelf‐life of shrimp kept at ?1 °C without freezing.  相似文献   
8.
Stable bituminous foams have been obtained by using a 35/50 penetration grade bitumen and a reactive prepolymer (MDI-PPG) synthesized by the reaction of polymeric 4,4′-diphenylmethane diisocyanate (MDI) with a low molecular weight polypropylene glycol (PPG). In a first step, MDI-PPG and bitumen were allowed to react for up to 7 days. Foams were then obtained by adding an excess of water. The results obtained point out important changes in the material colloidal structure, as a consequence of the reactions between the –NCO groups and bitumen most polar fractions. Modification led to bituminous foams with low density and improved in-service properties (higher elasticity and resistance to deformation at high in-service temperatures, reduced thermal susceptibility and better flexibility at low temperatures), demonstrating their adequacy to be used in building applications. Properties were enhanced by subjecting the material to longer periods of curing prior to promote foaming.  相似文献   
9.
This study was carried out to evaluate the chemical changes and sensory attributes of Pacific saury (Cololabis saira), brined (12% NaCl brine solution) or marinated (12% NaCl + 2% acetic acid; or 12% NaCl + 3% acetic acid solutions) followed by vacuum-packaging and storage at 4 °C for 90 days. The chemical analysis revealed a significant reduction in the pH value, total volatile bases nitrogen (TVBN), and trimethylamine (TMA) contents in marinated versus brined fillets. Lipid oxidation, as indicated by the 2-thiobarbituric acid (TBA) values, was significantly delayed in marinated fillets in comparison with the brined fillets. The growth rate of psychrotrophic bacteria was significantly (P < 0.05) reduced in marinated versus brined fillets. No significant differences were detected for the sensory attributes between the two marinating conditions although the overall acceptability was significantly higher in marinated versus brined fish. Both conditions of the marinating process resulted in an extension of the shelf life of the product to more than 90 days versus only 60 days for the control brined fillets. The study concluded that marination of Pacific saury can delay the undesirable chemical changes, retard lipid oxidation, improve the sensory attributes and extend the shelf life of the product during refrigerated storage.  相似文献   
10.
The quality of rotational molded products is strongly affected by the sintering behavior of the powders used in the process. In turn, for a given material, the sintering behavior of polymer powders is dependent on the size and the shape of particles obtained in the milling apparatus. The quality of powders for rotational molding is usually determined by means of size distribution, dry flow, and bulk density tests. However, these tests do not provide insight into the relationship between the shape of powders, the milling conditions, and the sintering behavior during the rotational molding cycle. Nevertheless, the application of mathematical tools to powder analysis can significantly improve the efficiency of the grinding process, looking not only at the size but also at the shape of the powder. This can in turn result in a higher reliability of rotational molding and in better performances of the products obtained in processes dominated by the sintering behavior of polymer powders. In this work the grinding process of recycled high‐density polyethylene was analyzed using a quantitative approach to the shape and size of the powders. In particular, shape factors, capable of characterizing powders obtained in different milling conditions, were studied. Finally, the influence of the powders' shape and size on sintering behavior was studied by thermomechanical analysis. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 449–460, 2004  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号