全文获取类型
收费全文 | 2435篇 |
免费 | 58篇 |
国内免费 | 16篇 |
学科分类
工业技术 | 2509篇 |
出版年
2024年 | 3篇 |
2023年 | 5篇 |
2022年 | 41篇 |
2021年 | 43篇 |
2020年 | 48篇 |
2019年 | 15篇 |
2018年 | 28篇 |
2017年 | 18篇 |
2016年 | 35篇 |
2015年 | 34篇 |
2014年 | 61篇 |
2013年 | 92篇 |
2012年 | 135篇 |
2011年 | 195篇 |
2010年 | 99篇 |
2009年 | 89篇 |
2008年 | 58篇 |
2007年 | 171篇 |
2006年 | 187篇 |
2005年 | 158篇 |
2004年 | 144篇 |
2003年 | 116篇 |
2002年 | 131篇 |
2001年 | 129篇 |
2000年 | 118篇 |
1999年 | 88篇 |
1998年 | 73篇 |
1997年 | 52篇 |
1996年 | 21篇 |
1995年 | 11篇 |
1994年 | 60篇 |
1993年 | 19篇 |
1992年 | 8篇 |
1991年 | 5篇 |
1989年 | 13篇 |
1988年 | 5篇 |
1987年 | 1篇 |
排序方式: 共有2509条查询结果,搜索用时 15 毫秒
1.
A series of polyethylene glycol-linked Gemini fatty alcohol phosphate surfactants (GFAP) were prepared with long chain n-alkanol (C = 8, 12, 16, 18), polyethylene glycol (PEG-200, PEG-400, PEG-600, PEG-800, PEG-1000) and phosphorus oxychloride (POCl3). The structure of the prepared surfactants was characterized by Fourier transform infrared spectrometer (FT-IR). The surfactants were employed for the modification of chrome-tanned leather. The morphological changes of chrome-tanned leather and modified chrome-tanned leather were observed by scanning electron microscopy (SEM). The relationship between the alkyl chain length and molecular weight of the PEG and the hydrophobicity, softness, mechanical strength of modified chrome-tanned leather was also discussed. The experimental results showed that the mechanical strength and softness of modified chrome-tanned leather were enhanced with an increase of alkyl chain length, while the hydrophobicity, mechanical strength and softness were decreased with an increase of molecular weight of the PEG. The hydrophobicity, mechanical strength and softness of modified chrome-tanned leather were optimized for an alkyl chain length of 16. Therefore, 16–200 Gemini phosphate surfactants with an alkyl chain length of 16 and a PEG molecular weight of 200 have a good comprehensive modification effect on Chrome-tanned leather, the tensile strength, tear strength and softness of modified chrome-tanned leather are 57.07 N mm−2, 79.49 N mm−1, 9.73 mm, respectively. 相似文献
2.
3.
Leather manufacturing involves a crucial energy-intensive drying stage in the finishing process to remove its residual moisture and generates important heat gradients. The numerical model presented in this study has been developed to describe the drying process of porous medium: bovine leather that undergoes deformation due to shrinkage. The mathematical formulation of fundamental heat, mass and momentum transfers’ phenomena during drying summarizes a two-dimensional model considering elastic behavior of bovine leather. The evolution of moisture content, temperature, and mechanical stresses during drying was discussed. The model was validated with experimental results. Numerical simulations show good agreement with experimental results. The study shows that the elastic model keeps the stress sign at the final stage of drying. The deformations induce tensional stresses near the surface equilibrated by compressive stresses within the product. They reached their maximum for normal stresses equal to 5.97 and 3.52?MPa at around 2145 and 868?s, respectively, for normal stresses along x and y directions and then decrease. 相似文献
4.
Chelsea Sullivan Algy Kazlauciunas James T. Guthrie 《Color research and application》2020,45(2):362-373
The objective of this study is to determine if men would follow the “red effect” when choosing colors for women to wear on a date, and also to determine if the colors that men would wear when going on a date would be the same as the colors that females (their date) would wish them to wear. A set of psychophysical data was generated from this experiment, where participants were asked to rank a set of 10 colored samples based on preference for each question asked. There were three different sets of colored samples. The set of colored samples given to the participant depended on the question. A total of five questions were asked. Scaling analysis was done on the data to organize a set of items according to preferences providing values, an interval scale (Z values), that correspond to the relative perceptual differences among the stimuli. The Z values were graphed to show the general preference of colors for women to wear, and the preference of colors for men to wear. A Spearman's rank-order correlation coefficient (SRCC) was calculated comparing each individual's rank order with the mean rank order for that specific question. An average Spearman's rank order was calculated for each question and each gender in order to determine the variability in answers. Scaling results indicate that men follow the “red effect,” but women preferred to wear other colors such as turquoise, blue, or yellow depending on the outfit. Males and females agreed that no matter the colored bottoms (denim or black), blue was the preferred color top for men to wear. SRCC results showed a lot of variability between individual answers and the mean answer indicating that participants' rankings did not necessarily agree with general color preferences presented in the scaling analysis. While scaling analysis might suggest certain color preferences such as men following the “red effect” and women preferring to wear blue, the poor correlation found using SRCC between the individual answers and the mean rank orders suggests that color preferences for each individual are inherently unique. 相似文献
5.
6.
GB/T 30398-2013《皮革和毛皮化学试验致敏性分散染料的测定》中规定了皮革和毛皮中的致敏性分散染料的测定方法,按照GB/T 30398-2013标准用HPLC法测定皮革中可萃取致敏性分散染料,以分散黄3为例,分析了测试过程中不确定度的来源,对各不确定度分量进行评定及合成,并计算得出合成不确定度和扩展不确定度。结果表明,对本测试方法影响较大的不确定度分量是标准物质配制。在重复测定的条件下,测定结果的不确定度仅与溶液中的致敏性分散染料浓度有关。 相似文献
7.
8.
Senem Kamiloglu Esra Capanoglu 《International Journal of Food Science & Technology》2014,49(4):1027-1039
In this study, to evaluate the in vitro bioaccessibility of eight different pekmez and pestil samples, total phenolics, flavonoids, proanthocyanidins, anthocyanins and antioxidant capacity were determined at different phases of simulated gastrointestinal (GI) digestion. For the analysis of antioxidant activity, four different methods were used including 2,2‐azinobis(3‐ethylbenzothiazoline)‐6‐sulfonic acid, 1,1‐diphenyl‐2‐picrylhydrazil, ferric reducing antioxidant power and cupric ion reducing antioxidant capacity. The results revealed that the dialysed fraction (IN) represented 12–50%, 3–17% and 3–72% of the total phenolics, flavonoids and proanthocyanidins, respectively. Moreover, total antioxidant capacity of IN fraction was 2–57% of the initial values obtained for pekmez and pestil samples. To identify the influence of simulated in vitro GI digestion on total anthocyanins, only black mulberry molasses (pekmez) and plum leather (pestil) were analysed and according to the results no anthocyanins were detected in the IN fraction for both samples. The present study presented a detailed insight of bioaccessibility of polyphenols in various pekmez and pestil samples. 相似文献
9.
10.