全文获取类型
收费全文 | 390篇 |
免费 | 31篇 |
国内免费 | 20篇 |
专业分类
电工技术 | 10篇 |
综合类 | 41篇 |
化学工业 | 27篇 |
金属工艺 | 7篇 |
机械仪表 | 19篇 |
建筑科学 | 47篇 |
矿业工程 | 6篇 |
能源动力 | 7篇 |
轻工业 | 67篇 |
水利工程 | 8篇 |
石油天然气 | 11篇 |
无线电 | 22篇 |
一般工业技术 | 25篇 |
冶金工业 | 7篇 |
原子能技术 | 6篇 |
自动化技术 | 131篇 |
出版年
2024年 | 1篇 |
2023年 | 1篇 |
2022年 | 3篇 |
2021年 | 7篇 |
2020年 | 7篇 |
2019年 | 6篇 |
2018年 | 6篇 |
2017年 | 8篇 |
2016年 | 9篇 |
2015年 | 11篇 |
2014年 | 21篇 |
2013年 | 24篇 |
2012年 | 19篇 |
2011年 | 28篇 |
2010年 | 23篇 |
2009年 | 27篇 |
2008年 | 20篇 |
2007年 | 22篇 |
2006年 | 23篇 |
2005年 | 30篇 |
2004年 | 25篇 |
2003年 | 21篇 |
2002年 | 17篇 |
2001年 | 10篇 |
2000年 | 7篇 |
1999年 | 15篇 |
1998年 | 6篇 |
1997年 | 7篇 |
1996年 | 5篇 |
1995年 | 7篇 |
1994年 | 8篇 |
1993年 | 3篇 |
1992年 | 3篇 |
1991年 | 1篇 |
1990年 | 2篇 |
1989年 | 1篇 |
1988年 | 2篇 |
1987年 | 1篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1955年 | 2篇 |
排序方式: 共有441条查询结果,搜索用时 31 毫秒
31.
针对无导光板LED平板灯具设计中常规扩 散板对斜入射光线透过率低的问题,基于几何光 学和Fresnel公式,设计了一种具有高效抑制斜入射光线Fresnel反射的表面微结构扩散板, 并推导了获得 高光传输效率的三棱柱微结构参数计算公式。采用Solidworks软件进行建模,并结合TraceP ro软件对所设计 的扩散板进行光线追迹仿真,分析了扩散板微结构参数对光传输效率和照明面照度均匀度的 影响。结果表 明,入射表面微结构不等腰三棱柱的尺寸和形状、出射表面半凹球面微透镜直径对斜入射光 线传输效率都 有较大影响;参数优化后的扩散板,在距离出光面 1mm处的照明面上的光传输效率为0.92,照度均匀度为 96.8%,并且不同距离照明面上的照度均匀度均能达到80%以上 。根据理论分析得出的优化参数制作扩散板,得到传输效率为0.91。 相似文献
32.
This work compares three different global sensitivity analysis techniques, namely the state-dependent parameter (SDP) modelling, the random balance designs, and the improved formulas of the Sobol’ sensitivity indices. These techniques are not yet commonly known in the literature. Strengths and weaknesses of each technique in terms of efficiency and computational cost are highlighted, thus enabling the user to choose the more suitable method depending on the computational model analysed. Two test functions proposed in the literature are considered. Computational costs and convergence rates for each function are compared and discussed. 相似文献
33.
《Food Control》2016
The sparkling wine protection against air is of interest for maintaining its sensorial profile and it is achieved through the use of antioxidants while disgorging. Sulfur dioxide (SO2) is commonly added, but its amount should be limited due to human health problems. The suitability of three polyphenols-based commercial formulas containing plant gallic and ellagic acids extracted from grape (Vitis vinifera L.) (AO1), plant ellagic acid and gum arabic (AO2), and plant gallic, ellagic acids and Saccharomyces cerevisiae cell-wall fractions (AO3) was evaluated after 7 months storage (at 15 °C and 25 °C) of disgorged sparkling white wine. The phenolic composition of these formulas was investigated through spectrophotometric measurements. Moreover, the phenols were characterized and quantified by HPLC-MS analyses. The sotolon concentration and the absorbance values at 420 nm were determined in wines. The HPLC-MS analysis showed that the formula AO1 mainly contained gallotannins, ellagic tannins and flavan-3-ols, while AO2 had high levels of flavan-3-ols and gallotannins. Flavan-3-ols were the only phenols found in AO3. The addition of these formulas increased the yellow hue. Sotolon was higher than the perception threshold in the samples with AO2 and at trace amount in the samples with both AO1 and AO3 only stored at 25 °C. The tested antioxidant formulas seemed to be less effective of SO2 for the storage of sparkling white wine. However, the investigation of phenolics in antioxidant formulas could be helpful for the proper choice of a potential substitute of SO2 due to increase interest in sulfur-free wine production. 相似文献
34.
王长元 《西安工业学院学报》1988,(4)
本文构造了一种混合样条函数,它是用一次多项式函数及指数函数的结合来表示的。文章给出了这种混合样条的一般表达式,并证明插值问题解的存在性定理和误差估计定理,由此说明这种样条函数具有良好的逼近度和物理背景。 相似文献
35.
An Algorithm to Evaluate Quantified Boolean Formulae and Its Experimental Evaluation 总被引:1,自引:0,他引:1
Marco Cadoli Marco Schaerf Andrea Giovanardi Massimo Giovanardi 《Journal of Automated Reasoning》2002,28(2):101-142
The high computational complexity of advanced reasoning tasks such as reasoning about knowledge and planning calls for efficient and reliable algorithms for reasoning problems harder than NP. In this paper we propose Evaluate, an algorithm for evaluating quantified Boolean formulae (QBFs). Algorithms for evaluation of QBFs are suitable for experimental analysis of problems that belong to a wide range of complexity classes, a property not easily found in other formalisms. Evaluate is a generalization of the Davis–Putnam procedure for SAT and is guaranteed to work in polynomial space. Before presenting the algorithm, we discuss several abstract properties of QBFs that we singled out to make it more efficient. We also discuss various options that were investigated about heuristics and data structures and report the main results of the experimental analysis. In particular, Evaluate is orders of magnitude more efficient than a nested backtracking procedure that resorts to a Davis–Putnam algorithm for handling the innermost set of quantifiers. Moreover, experiments show that randomly generated QBFs exhibit regular patterns such as phase transition and easy-hard-easy distribution. 相似文献
36.
合取范式(CNF)公式H到F的同态φ是一个从H的文字集合到F的文字集合的映射,并保持补运算和子句映到子句.同态映射保持一个公式的不可满足性.一个公式是极小不可满足的是指该公式本身不可满足,而且从中删去任意一个子句后得到的公式可满足.MU(1)是子句数与变元数的差等于1的极小不可满足公式类.一个三元组(H,φ,F)称为的一个来自H的同态证明,如果φ是一个从H到F的同态.利用基础矩阵的方法证明了:一个不可满足公式F的树消解证明,可以在多项式时间内转换成一个来自MU(1)中公式的同态证明.从而,由MU(1)中的公式构成的同态证明系统是完备的,并且由MU(1)中的公式构成的同态证明系统与树消解证明系统之间是多项式等价的. 相似文献
37.
林柏钢 《信息工程大学学报》2002,3(2):17-19
本文给出一个与孙子定理(中国剩余定理)相并行的对偶理论-孙子互余定理,用以解决一元一次互余式组通解的问题。同时还给出互余式组与同余式组的一个等价转换定理。这是一个值得研究的对偶规律,而且具有一定的普遍意义,是对孙子定理的进一步扩展和补充。 相似文献
38.
A recurrent formula and an ordinary formula are proposed for the number of Hamiltonian paths on special digraphs generated by a chain metric on n-permutations. 相似文献
39.
Blanca Viadel Sara PeralesReyes Barberá María Jesús LagardaRosaura Farré 《Food chemistry》2007,102(3):925-931
The bioavailability of iron from milk-based infant formulas was estimated by an in vitro system including enzymatic digestion, iron uptake by Caco-2 cells and ferritin determination via an enzymoimmunoassay (ELISA). Positive correlations (p < 0.01) were found between the Fe(II) added to Caco-2 cells and ferritin synthesis and between the amount of dialyzed iron added to the cell culture and ferritin synthesis. The comparison of the bioavailability of iron from different milk-based formulas showed that adapted formulas having the same composition but differing in the iron salts added yielded similar ferritin levels. The same happened with follow-up formulas differing only in the presence or absence of bifidobacterium added. However, significant differences in the amount of ferritin synthesized were recorded between the two analyzed toddler formulas. Such differences could be attributed firstly to the ascorbic acid content and perhaps also to the manufacturing process involved, because one formula was in liquid form while the other was powdered. 相似文献
40.
Pilar Manglano María Jesús Lagarda María Dolores Silvestre Carmen Vidal Gonzalo Clemente Rosaura Farr 《European Journal of Lipid Science and Technology》2005,107(11):815-823
A study is made of the effects of storage (time and temperature) on the lipid fraction of four milk‐based adapted infant formulas with basically the same composition, though differing in the iron salt added (lactate or sulfate) and/or the vitamin E source (α‐tocopherol or α‐tocopherol acetate). Peroxide value, hydroperoxide C18 percentage and thiobarbituric acid‐reactive substance (TBARS) content were used as indicators of lipid peroxidation. Fat contents remained stable throughout storage. Peroxide values increased from the first storage month and were affected by storage time, although they exhibited irregular behavior. Storage time and temperature affected hydroperoxide percentage, which was seen to be the earliest indicator of lipid oxidation, being measurable in newly manufactured formulas. TBARS values were only affected by storage time. No statistically significant differences were found among the four infant formulas for any of the lipid oxidation indicators. 相似文献