全文获取类型
收费全文 | 918篇 |
免费 | 84篇 |
国内免费 | 65篇 |
学科分类
工业技术 | 1067篇 |
出版年
2024年 | 4篇 |
2023年 | 10篇 |
2022年 | 22篇 |
2021年 | 37篇 |
2020年 | 25篇 |
2019年 | 28篇 |
2018年 | 33篇 |
2017年 | 26篇 |
2016年 | 31篇 |
2015年 | 35篇 |
2014年 | 38篇 |
2013年 | 46篇 |
2012年 | 41篇 |
2011年 | 64篇 |
2010年 | 50篇 |
2009年 | 51篇 |
2008年 | 44篇 |
2007年 | 35篇 |
2006年 | 26篇 |
2005年 | 25篇 |
2004年 | 49篇 |
2003年 | 46篇 |
2002年 | 62篇 |
2001年 | 73篇 |
2000年 | 41篇 |
1999年 | 19篇 |
1998年 | 14篇 |
1997年 | 9篇 |
1996年 | 12篇 |
1995年 | 5篇 |
1994年 | 10篇 |
1993年 | 6篇 |
1992年 | 7篇 |
1991年 | 5篇 |
1990年 | 5篇 |
1989年 | 4篇 |
1988年 | 5篇 |
1987年 | 1篇 |
1986年 | 3篇 |
1985年 | 1篇 |
1984年 | 5篇 |
1983年 | 4篇 |
1982年 | 2篇 |
1981年 | 1篇 |
1980年 | 2篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1976年 | 2篇 |
1927年 | 1篇 |
排序方式: 共有1067条查询结果,搜索用时 15 毫秒
52.
53.
Selective hydrogenation of nitriles to imines over a multifunctional heterogeneous Pt catalyst 下载免费PDF全文
Jilan Long Biaolin Yin Yingwei Li Lianjie Zhang 《American Institute of Chemical Engineers》2014,60(10):3565-3576
Imines and their derivatives are versatile synthetic intermediates for the industrial preparation of both bulk and fine chemicals and for pharmaceuticals, but preparing these compounds efficiently through direct hydrogenation of nitriles are hindered by overhydrogenation to secondary amines. Here we report a highly efficient multifunctional catalyst system for selective hydrogenation coupling of nitriles to secondary imines using a heterogeneous Pt catalyst that was deposited on a nickel‐based metal‐organic framework (MOF) containing DABCO. The catalyst showed excellent synergy in promoting the hydrogenation of a variety of nitriles, giving significantly improved activity and selectivity (up to >99% yield) even under atmospheric pressure of H2. It is suggested that the Lewis base (DABCO) sites on the Ni‐MOF inhibit further hydrogenation of the imines. The influence of H2 pressure, reactant concentration, stirring speed, and reaction temperature was investigated. The kinetics and mechanism of hydrogenation of benzonitrile (BN) by the Pt/Ni‐MOF catalyst has been studied. The reaction showed a first‐order dependence on both BN concentration and H2 pressure. A kinetic model was proposed based on the mechanism of nitriles hydrogenation and compared with experimental observations. © 2014 American Institute of Chemical Engineers AIChE J, 60: 3565–3576, 2014 相似文献
54.
Päivi Mäki-Arvela Mika Mikkola Jarl Hemming Kari Eränen Stefan Willför Dmitry Yu. Murzin 《Journal of the American Oil Chemists' Society》2014,91(6):1035-1046
Mixtures of fatty acids and rosin acids are industrially important products utilized as a raw material for several purposes. Their thermal properties, especially cold stability and crystallization behavior is also important. Several fatty acid and rosin acid mixtures both from industrial products and from commercially available fatty and rosin acids were prepared and treated for 30 min at 80 °C under an inert atmosphere. Thereafter, the mixture was cooled to the desired temperature. Determination of the cloud point, chemical analysis of liquid and solid phase, thermal analysis by differential scanning calorimetry as well as morphology analysis by scanning electron microscopy were performed. The results revealed that crystallization was more rapid when it occurred at 10 °C compared to 25 °C. The crystal sizes increased with decreasing the crystallization temperature. Furthermore, crystals were of irregular shape and agglomerated when rapid cooling of the mixture occurred. Chemical analysis revealed that liquid phase was enriched with stearic acid, whereas crystals contained large amounts of abietic, dehydroabietic and linoleic acids. The cloud point of the mixtures increased with increasing amount of stearic and rosin acids. Dehydroabietic acid addition improved the cold stability of the synthetic fatty acid–rosin acids mixture. 相似文献
55.
橘皮精油中的主要成分D-柠檬烯具有较强的去污能力、抑菌功效以及天然芳香味。本研究以橘皮精油为有效成分,研制了一种绿色环保型洗衣液。通过单因素试验研究了洗衣液配方中AES、AEO-7的初步配比及质量分数,并采用正交试验优化了洗衣液中各组分的配比:D-柠檬烯15%,AEO-7 14%,AES 8%,乙醇8%,柠檬酸钠2%,KCl 0.25%,余量为蒸馏水。将含D-柠檬烯的洗衣液与市售LB洗衣液进行了去污效果、发泡力、pH值对比测试。结果表明,所制备的洗衣液洗涤效果优于市售LB洗衣液(去污比值大于1)。 相似文献
56.
Physical properties of sweet corn kernels have been evaluated as a function of kernel moisture content, varying from 9.12 to 17.06% (db). In the moisture range, kernel length, width, thickness, and geometric mean diameter increased linearly from 9.87 to11.09 mm, 7.41 to 9.25 mm, 3.25 to 4.37 mm, and 6.18 to 7.62 mm, respectively, with increase in moisture content from 9.12–17.06%. The sphericity index, kernel volume, kernel surface area, and thousand seed weight increased linearly from 62.6 to 68.8, 93.8 to 194.3 mm3, 120.1 to 182.9 mm2, and 220 to 268 gr, respectively. Apparent density and bulk density decreased linearly from 1.315 to 1.232 g/cm3 and 0.765 to 0.698 g/cm3, respectively, while bulk porosity increased from 41.8 to 43.3%. The highest static coefficient of friction was found on the plywood surface. The static coefficient of friction increased from 0.680 to 0.891, 0.605 to 0.741, and 0.530 to 0.644 for plywood, galvanized iron, and aluminum surfaces, respectively. The angle of repose increased linearly from 30.2 to 35.2° with the increase of moisture content. 相似文献
57.
Gábor Erős Zsuzsanna Kurgyis István Balázs Németh Eszter Csizmazia Szilvia Berkó Piroska Szabó-Révész Lajos Kemény Erzsébet Csányi 《Journal of surfactants and detergents》2014,17(1):67-70
Dermal or transdermal medication may lead to irritant contact dermatitis. However, little information is available on the irritant effect of surfactants which are applied in topical formulations. Our aim was to examine the irritant effect of the most frequent compounds in topical products. A murine model was applied. The following compounds were examined: sodium lauryl sulphate (SLS), polyethoxylated (40EO) hydrogenated castor oil and sucrose laurate. SLS led to severe erythema, increase in transepidermal water loss (TEWL) and induced necrosis and accumulation of neutrophylic granulocytes and lymphocytes. Exposure to sucrose laurate resulted in an elevation of TEWL, but histology did not reveal impairment of the skin structure. Application of polyethoxylated (40EO) hydrogenated castor oil was not accompanied by tissue damage. Special attention should be paid to the irritant effect of SLS. Polyethoxylated (40EO) hydrogenated castor oil seems to be a non-irritant agent and sucrose laurate is also a promising candidate for application in topical preparations. 相似文献
58.
汽车油罐车检定时需要用分段线性内插法编制容量表,手工计算工作量大,容易出错。本文设计了汽车油罐车容量编制程序,大大提高了工作效率。 相似文献
59.
60.
Coverage path planning for UAVs based on enhanced exact cellular decomposition method 总被引:3,自引:0,他引:3
In this paper, an enhanced exact cellular decomposition method to plan the coverage path of UAVs in a polygon area is proposed. To be more specific, the contributions of the paper are: firstly, the turning motion of UAVs is shown to be less efficient from the viewpoints of route length, duration and energy. Secondly, the problem of coverage Path Planning (CPP) in a convex polygon area is transformed to width calculation of the convex polygon, and a novel algorithm to calculate the widths of convex polygons with time complexity of O(n) is developed. The path of the least number of turns for an UAV based on the widths of convex polygons is devised. Thirdly, a convex decomposition algorithm for minimum width sum based on the greedy recursive method which revolves around decomposing the concave area into convex subregions is developed. It is proved that the algorithm is a polynomial time algorithm. To avoid unnecessary back and forth motion, some entirely adjacent subregions are combined. Finally, comparing different weights of two joint-points, a subregion connection algorithm based on minimum traversal of weighted undirected graph is proposed to connect the coverage paths of the subregions. Simulation results show that the proposed method is feasible and effective. 相似文献