全文获取类型
收费全文 | 663篇 |
免费 | 76篇 |
国内免费 | 52篇 |
专业分类
电工技术 | 65篇 |
综合类 | 38篇 |
化学工业 | 116篇 |
金属工艺 | 36篇 |
机械仪表 | 36篇 |
建筑科学 | 77篇 |
矿业工程 | 16篇 |
能源动力 | 21篇 |
轻工业 | 44篇 |
水利工程 | 18篇 |
石油天然气 | 61篇 |
武器工业 | 12篇 |
无线电 | 70篇 |
一般工业技术 | 75篇 |
冶金工业 | 26篇 |
原子能技术 | 4篇 |
自动化技术 | 76篇 |
出版年
2024年 | 5篇 |
2023年 | 18篇 |
2022年 | 35篇 |
2021年 | 36篇 |
2020年 | 33篇 |
2019年 | 21篇 |
2018年 | 20篇 |
2017年 | 36篇 |
2016年 | 23篇 |
2015年 | 33篇 |
2014年 | 24篇 |
2013年 | 44篇 |
2012年 | 63篇 |
2011年 | 58篇 |
2010年 | 42篇 |
2009年 | 43篇 |
2008年 | 54篇 |
2007年 | 29篇 |
2006年 | 31篇 |
2005年 | 18篇 |
2004年 | 21篇 |
2003年 | 22篇 |
2002年 | 13篇 |
2001年 | 9篇 |
2000年 | 13篇 |
1999年 | 7篇 |
1998年 | 2篇 |
1997年 | 7篇 |
1996年 | 8篇 |
1995年 | 3篇 |
1994年 | 2篇 |
1993年 | 5篇 |
1992年 | 3篇 |
1991年 | 4篇 |
1990年 | 1篇 |
1988年 | 2篇 |
1987年 | 1篇 |
1986年 | 2篇 |
排序方式: 共有791条查询结果,搜索用时 15 毫秒
31.
结合作者自己管理的建设项目,基于能量意外释放理论,对该类型项目个体防护装备的分类和选择提出了自己的看法,也对类似项目具有借鉴意义。 相似文献
32.
对于多级分离过程的模拟通常都采用平衡级模型,而实际化工过程的非理想性使其应用受到了很大限制。本文引入非平衡级模型,采用修正的PSRK物性方法用Aspen plus软件对低温甲醇洗流程的吸收塔及CO2解吸塔进行模拟研究,并将其模拟结果与平衡级模型作对比。该模型下对吸收塔及CO2解吸塔的模拟结果都与设计值吻合很好。并将该流程吸收塔的非平衡级模型计算结果与本文作者教研组前期工作中研究的吸收塔的非平衡级模型结果作对比。研究结果表明,非平衡级模型可以应用于低温甲醇洗流程的模拟计算,为低温甲醇洗流程的设计计算提供了可靠的技术支持。 相似文献
33.
Functionalized ionic liquids containing ethyoxyl groups were synthesized and immobilized on magnetic silica nanoparticles(MSNP) prepared by two steps,i.e.,Fe3O4 synthesis and silica shell growth on the surface.This magnetic nanoparticle supported ionic liquid(MNP-IL) were applied in the immobilization of penicillin G acylase(PGA).The MSNPs and MNP-ILs were characterized by the means of Fourier transform infrared spectroscopy(FTIR),scanning electron microscopy(SEM),transmission electron microscopy(TEM),and vibrating sample magnetometer(VSM).The results showed that the average size of magnetic Fe3O4 nanoparticles and MSNPs were ~10 and ~90 nm,respectively.The saturation magnetizations of magnetic Fe3O4 nanoparticles and MNP-ILs were 63.7 and 26.9 A?m2?kg?1,respectively.The MNP-IL was successfully applied in the immobilization of PGA.The maximum amount of loaded enzyme was about 209 mg?g?1(based on carrier),and the highest enzyme activity of immobilized PGA(based on ImPGA) was 261 U?g?1.Both the amount of loaded enzyme and the activity of ImPGA are at the same level of or higher than that in previous reports.After 10 consecutive operations,ImPGA still main-tained 62% of its initial activity,indicating the good recovery property of ImPGA activity.The ionic liquid modified magnetic particles integrate the magnetic properties of Fe3O4 and the structure-tunable properties of ionic liquids,and have extensive potential uses in protein immobilization and magnetic bioseparation.This work may open up a novel strategy to immobilize proteins by ionic liquids. 相似文献
34.
35.
36.
37.
利用腈纶废丝合成絮凝剂PAN—DCD 总被引:10,自引:0,他引:10
本文以腈纶废丝为原料与双氰双胺在碱性溶液中反应,成功地制得含有多种活性基因的聚合物PAN-DCD,并用于染料废水脱色及炼油厂废水除油,除酚的处理研究,与常规使用的几种絮凝剂进行处理结果对照,实验结果表明:该产品单独使用处理效果明显优于其他絮凝剂,与聚铝复合使用处理效果更为理想。 相似文献
38.
A novel nanocomposite catalyst was prepared from immobilization of aluminum oxide hydroxide onto the attapulgite. Characterizations with scanning electron microscopy (SEM) and wide angle X‐ray diffraction (XRD) of the as‐prepared catalyst revealed that AlO(OH) nanoparticles were distributed on the attapulgite. Thermogravimetric analysis‐infrared spectrometry (TGA‐IR) of the mixture prepared by mixing of bishydroxy ethylene terephthalate (BHET) and the catalyst indicated that attapulgite‐supported aluminum oxide hydroxide catalyst can catalyze BHET polycondensation under the applied conditions. A kinetic model for determining the activation energy has been applied to evaluate the catalyst activity. The catalyst activity was examined through comparative experiments, and the results showed that the new catalyst exhibited higher activity for BHET polycondensation under identical reaction conditions, and the viscosity‐average molecular weight of poly(ethylene terephthalate) (PET) product obtained was increased about 2000 g/mol. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013 相似文献
39.
Aqueous-based inorganic–organic hybrid coating materials comprising self-assembled nanophase particles (SNAP) were investigated for their potential to confer high gas barrier performance to flexible polymeric substrates, particularly to improve suitability of the substrates as encapsulation materials for organic photovoltaic (OPV) devices. Potential benefits of this approach include versatility in barrier coating formulation to achieve specific barrier properties, and application of coatings in a reel-to-reel process under ambient conditions. The present study focused on enhancement of the oxygen barrier performance of polypropylene (PP) substrates by applying SNAP-based coatings with and without the addition of an oxygen scavenging additive. SNAP particles were characterised using 29Si NMR and dynamic light scattering, and coatings were analysed using atomic force microscopy and X-ray photoelectron spectroscopy. SNAP particle preparation and coating formulation was optimised with respect to oxygen transmission rate (OTR) of the coating on PP, and mechanical properties of the coating solution. In the absence of oxygen scavenger, the lowest OTR attained for the SNAP-based coatings was 0.87 cm3 mil m−2 day−1 atm−1. The OTR was further reduced to 0.22 cm3 mil m−2 day−1 atm−1 on addition of 9,10-anthraquinone-2,6-dissulfonic acid (AQDS) into the coating as an oxygen scavenger. These results represent a decrease in OTR by 4 orders of magnitude compared with uncoated PP, and the oxygen barrier obtained by addition of AQDS surpasses the performance of many plastic materials considered to be high oxygen barriers in the food and pharmaceutical industries. 相似文献
40.
D-泛酸(维生素B5)是一种重要的维生素,在饲料、化妆品和制药行业均有广阔的市场。酮泛解酸是泛酸生物合成途径的中间体,易内酯化为酮基泛解酸内酯,后者可立体选择性地转化为D-泛解酸,并进一步用于D-泛酸的生产。本工作提供了一种采用α-酮基异戊酸与甲醛经羟醛反应合成酮泛解酸的新方法。其中,反应物α-酮基异戊酸可由葡萄糖原料经发酵法生产。结果表明,以葡萄糖为碳源,经克雷伯氏肺炎杆菌发酵能高水平生产D-泛酸生物合成途径的关键前体—α-酮基异戊酸。采用商品α-酮基异戊酸开发一种新型的酮泛解酸合成方法;分析合成反应机理,确定总反应级数为1.87;经条件优化确定酮泛解酸合成反应的最佳pH=13,最佳温度为45℃,此条件下酮泛解酸转化率达83.5%。调节酮泛解酸溶液pH至强酸性,有助于其内酯化合成酮基泛解酸内酯。之后采用前述优化的方法,由流加发酵制备的25.2 g/L α-酮基异戊酸合成酮泛解酸19.9 g/L。最后通过异丁醇萃取、活性炭脱色、浓缩结晶方法进行产物提纯,调节酮基泛解酸内酯溶液pH在7~10范围内可使其开环转化回酮泛解酸。最终得到酮泛解酸及其内酯的纯品。本研究建立了以葡萄糖为原料通过α-酮基异戊酸中间体生产酮泛解酸的方法。该方法结合生物发酵和化学合成过程,采用廉价原料,具有绿色高效的特点,有望用于工业化生产泛酸。 相似文献