全文获取类型
收费全文 | 1863篇 |
免费 | 194篇 |
国内免费 | 120篇 |
专业分类
电工技术 | 27篇 |
综合类 | 129篇 |
化学工业 | 743篇 |
金属工艺 | 5篇 |
机械仪表 | 5篇 |
建筑科学 | 457篇 |
矿业工程 | 139篇 |
能源动力 | 171篇 |
轻工业 | 93篇 |
水利工程 | 155篇 |
石油天然气 | 116篇 |
武器工业 | 1篇 |
无线电 | 2篇 |
一般工业技术 | 80篇 |
冶金工业 | 47篇 |
原子能技术 | 3篇 |
自动化技术 | 4篇 |
出版年
2024年 | 1篇 |
2023年 | 17篇 |
2022年 | 48篇 |
2021年 | 40篇 |
2020年 | 65篇 |
2019年 | 48篇 |
2018年 | 42篇 |
2017年 | 54篇 |
2016年 | 82篇 |
2015年 | 84篇 |
2014年 | 99篇 |
2013年 | 93篇 |
2012年 | 129篇 |
2011年 | 134篇 |
2010年 | 109篇 |
2009年 | 133篇 |
2008年 | 101篇 |
2007年 | 98篇 |
2006年 | 116篇 |
2005年 | 94篇 |
2004年 | 85篇 |
2003年 | 61篇 |
2002年 | 60篇 |
2001年 | 48篇 |
2000年 | 36篇 |
1999年 | 37篇 |
1998年 | 24篇 |
1997年 | 16篇 |
1996年 | 14篇 |
1995年 | 17篇 |
1994年 | 10篇 |
1993年 | 5篇 |
1992年 | 7篇 |
1991年 | 3篇 |
1990年 | 2篇 |
1989年 | 4篇 |
1988年 | 7篇 |
1987年 | 8篇 |
1986年 | 2篇 |
1985年 | 33篇 |
1984年 | 48篇 |
1983年 | 23篇 |
1982年 | 36篇 |
1979年 | 4篇 |
排序方式: 共有2177条查询结果,搜索用时 15 毫秒
1.
Sekove Vodo Kunihiko Uemura Mitsutoshi Nakajima Marcos A. Neves 《International Journal of Food Science & Technology》2021,56(12):6697-6706
Synthetic emulsifiers in food industries are being replaced with a customer-friendly food ingredient that is derived from biomass using sustainable green technologies. After hydrothermal liquefaction treatment, raw bagasse (21%), pith (26%), and rind portions (25%) were obtained with reduced ash contents. As aqueous extracts, with oligosaccharides and lignin residues, it was used in the preparation of oil-in-water emulsions with 5% soybean oil. Results showed that the emulsions stabilised the oil droplets with particle size between 11 and 17 µm by steric repulsion with raw bagasse-stabilised emulsion showing a better stability at 25 °C (31 days). It was demonstrated that raw bagasse extracts, without alteration, maybe a potential unconventional source for food-grade emulsifiers by integrating a versatile thermochemical conversion of waste without the use of chemicals. 相似文献
2.
3.
4.
Nils von Preetzmann Philipp Eckmann Adriaan M. H. van der Veen Jianrong Li Markus Richter 《American Institute of Chemical Engineers》2021,67(4):e17128
Exact knowledge of natural gas composition is essential in custody transfer to determine the energy content of the delivery. However, for liquefied natural gas (LNG), a reliable composition determination is difficult. Here, we describe the design of a laboratory-scale reference liquefier that enables the validation and calibration of optical spectroscopy sensors by providing them with a sample of metrologically traceable composition. Hence, it is crucial to avoid fractionation of the sample during liquefaction. This is realized by supercritical liquefaction of a reference gas mixture in conjunction with a special vapor–liquid-equilibrium (VLE) cell. As this is a demanding high-pressure application, low-pressure condensation as liquefaction method was also assessed. Through experimental investigations and VLE calculations, preservation of the composition of the produced liquid sample during condensation was studied. We conclude that under optimized conditions, validation, and calibration measurements of optical sensors can be performed on condensed liquids, which, however, needs further confirmation. 相似文献
5.
Hua Zhao Michael S Franklin 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2020,95(9):2301-2310
Coal is the most abundant fossil fuel. Direct combustion of low- and medium-rank coals causes alarming environmental impacts. Therefore, it is crucial for coal to undergo pretreatments before its efficient utilization [such as coal to liquid (CTL) processes]. Conventional pretreatment methods suffer from several limitations including the use of volatile organic solvents, environmental hazards, strong reaction conditions (e.g. high temperature and pressure), consumption of large quantities of nonrecoverable chemicals (e.g. bases used in aqueous alkaline digestion), or being only effective for specific coals. On the other hand, coal pretreatment by nonvolatile ionic liquids (ILs) could lead to partial coal dissolution/swelling and structure disruption, which is a critical step before coal liquefaction, hydrogenation, pyrolysis or the inhibition of oxidation/combustion. In addition, ILs are suitable solvents for extracting sulfur compounds from coal, asphaltenes from Direct Coal Liquefaction Residues (DCLR) and phenolic compounds from coal tar. This review will discuss these aspects of coal pretreatments by ILs, and identify how ILs could lead to a cleaner and more efficient utilization of coal resources. © 2020 Society of Chemical Industry 相似文献
6.
与采用低温费托合成主产油品技术相比,产品更为多元化和高值化的高温费托合成技术在目前市场环境下显示出非常明显的优势。本文综述了高温费托合成技术的发展历程及其最新进展,重点介绍了高温费托合成过程中的核心问题,主要包括高温费托合成工艺、固定流化床反应器、费托合成催化剂;介绍了高温费托合成产物分布与特性,讨论了高温费托合成产物的加工路线,并对高温费托合成煤间接液化的工业应用前景和产业化方向进行了展望。结果表明:高温费托合成技术具有产物附加值高、兼顾油品和化学品、技术发展成熟等优势,产物中轻组分含量高、碳数分布较窄、高附加值的α-烯烃含量高;精细化、高端化、差异化加工是实现高温费托合成产物高值化利用的关键。 相似文献
7.
高能量密度燃料是为新型高性能飞行器提供动力保障的关键,其合成及应用研究具有重要的前瞻性和重大战略意义。煤炭是我国的主体能源和重要原料,通过煤直接转化获取的煤基油,充分保留了煤中特有的环状分子化学结构,具有良好的热安定性和较高的能量密度,被认为是高超音速飞行器的优选燃料。以煤直接液化工艺生产的煤液化石脑油馏分为起始原料,通过富集轻质芳烃、化学合成、催化加氢稳定和产物分离提纯等方法制备煤基高能量密度燃料,并对其产物进行分子结构表征和性能评价。结果表明,煤直接液化生产的石脑油馏分是一种优异的催化重整原料,经催化重整富集轻质芳烃后,其轻质芳烃质量分数高达71.05%。Diels-Alder化学合成主产物是由多个封闭环平面组成且具有空间立体构型的二环或三环烃类物质,质量分数为46.18%,因分子内存在较大的张力能,结构紧凑,其拥有更大的密度和体积热值。煤基高能量密度燃料的密度和体积热值分别为0.8990 g/cm3与38.06 MJ/L,均大大超过现行的国内石油基喷气燃料(RP-3和RP-6)、煤基大比重喷气燃料、美国和俄罗斯军用标准。与单一纯物质合成高能量密度燃料(JP-10和T-10)比较,其密度与体积热值偏小。究其原因主要是轻质芳烃的富集度仅为71.05%,需进一步提高其轻质芳烃质量分数。另外,制备的煤基高能量密度燃料种类复杂,其主产物质量分数仅46.18%,下一步可重点调控合成产物的分子构型和纯化分离。 相似文献
8.
《International Journal of Hydrogen Energy》2022,47(86):36582-36592
High energy consumption is considered to be one of the most persistent problems in liquid hydrogen (LH2) plants. The combination of heat exchanger and ortho-para (O–P) hydrogen conversion has attracted considerable attention as a cutting-edge technology to reduce energy consumption. The flow and heat transfer characteristics of O–P hydrogen conversion catalyst-filled spiral wound heat exchanger (SWHE) were investigated in this study in two steps. In the first step, pressure-drop experiments were performed in a tube filled with porous media. The results indicated that the pressure drop was overestimated when using Ergun's equation. Therefore, a new empirical pressure-drop correlation for a channel filled with O–P catalyst was formulated. Subsequently, a novel heat transfer model was established based on this correlation for further numerical simulations. The distributions of the temperature, pressure, and para hydrogen content in a catalyst-filled tube were determined. In addition, the influence of the flow rate on the heat exchange coefficient and outlet para hydrogen was clarified; it was found that, with an increase in the flow rate, the heat exchange coefficient increased, whereas the outlet para hydrogen content decreased. At a flow rate of 0.5 m3/h, the para hydrogen content increased by 44% after hydrogen flowed through the channel filled with the O–P catalyst. Furthermore, a prediction model for the para hydrogen content with a flow rate range of 0–1.5 m3/h was derived. This study provides promising theoretical evidence for the engineering application of SWHEs filled with O–P catalysts in large-scale hydrogen liquefaction units. 相似文献
9.
10.
爆震条件下淤积砂基础的抗液化安全评价 总被引:1,自引:0,他引:1
三峡二期高土石围堰座落在极易液化的新淤积砂基础上,故在基坑钻爆开挖过程所诱发的爆破震动作用下对该淤积砂基础进行抗液化安全评价极具工程意义。本文利用爆震条件下一期围堰淤积砂基础中动孔隙水压力实测资料,结合二期围堰的静力有限元计算成果,设法对二期围堰淤积砂基础是否液化作出科学的评估。 相似文献