全文获取类型
收费全文 | 1894篇 |
免费 | 50篇 |
国内免费 | 6篇 |
专业分类
电工技术 | 31篇 |
综合类 | 2篇 |
化学工业 | 750篇 |
金属工艺 | 64篇 |
机械仪表 | 52篇 |
建筑科学 | 56篇 |
矿业工程 | 12篇 |
能源动力 | 83篇 |
轻工业 | 102篇 |
水利工程 | 3篇 |
石油天然气 | 2篇 |
武器工业 | 3篇 |
无线电 | 136篇 |
一般工业技术 | 247篇 |
冶金工业 | 46篇 |
原子能技术 | 7篇 |
自动化技术 | 354篇 |
出版年
2023年 | 9篇 |
2022年 | 75篇 |
2021年 | 106篇 |
2020年 | 24篇 |
2019年 | 34篇 |
2018年 | 49篇 |
2017年 | 46篇 |
2016年 | 73篇 |
2015年 | 47篇 |
2014年 | 64篇 |
2013年 | 139篇 |
2012年 | 99篇 |
2011年 | 97篇 |
2010年 | 110篇 |
2009年 | 76篇 |
2008年 | 92篇 |
2007年 | 70篇 |
2006年 | 53篇 |
2005年 | 58篇 |
2004年 | 52篇 |
2003年 | 50篇 |
2002年 | 44篇 |
2001年 | 34篇 |
2000年 | 21篇 |
1999年 | 26篇 |
1998年 | 18篇 |
1997年 | 22篇 |
1996年 | 28篇 |
1995年 | 17篇 |
1994年 | 24篇 |
1993年 | 19篇 |
1992年 | 11篇 |
1991年 | 18篇 |
1990年 | 21篇 |
1989年 | 10篇 |
1988年 | 21篇 |
1987年 | 18篇 |
1986年 | 12篇 |
1985年 | 15篇 |
1984年 | 23篇 |
1983年 | 24篇 |
1982年 | 18篇 |
1981年 | 23篇 |
1980年 | 14篇 |
1979年 | 13篇 |
1978年 | 8篇 |
1977年 | 9篇 |
1975年 | 7篇 |
1974年 | 3篇 |
1973年 | 2篇 |
排序方式: 共有1950条查询结果,搜索用时 0 毫秒
41.
Andrzej Piasecki 《Advanced Synthesis \u0026amp; Catalysis》1987,329(4):579-586
The direct condensation reaction of prop-2-enal or but-2-enal with mixture of n-aliphatic alcohol and ethylene glycol, in the presence of p-toluenesulphonic acid as catalyst, leads to a complex mixture of saturated, unsaturated, cyclic and linear acetals, moreover, 2-(2-alkoxy-alkyl)-1,3-dioxolanes are the main reaction products. The detailed investigations for n-butanol showed that unsaturated cyclic acetals: 2-vinyl-1,2-dioxolane 1a or 2-(1-propenyl)-1,3-dioxolane 1b , as well as unsaturated linear acetals: 1,1-dibutoxy-prop-2-en 2a or 1,1-dibutoxy-but-2-en 2b are intermediate reaction products. Additionally, it was found in final products presence of eight by-products: 5-butoxy- 4a or 5-butoxy-7-methyl-1,4-dioxepane 4b , 1,1,3-tributoxypropane 5a or 1,1,3-tributoxybutane 5b , 2-[2-(2-hydroxyethoxy)ethyl]- 6a or 2-[2-(2-hydroxyethoxy)propyl]-1,3-dioxolane 6b , 5-(2-hydroxyethoxy)-7-methyl-1,4-dioxepane 7b , 1,3-dibutoxy-1-(2-hydroxyethoxy)-propane 8a or 1,3-dibutoxy-1-(2-hydroxyethoxy)-butane 8b , 1,1-dibutoxy-3-(2-hydroxyethoxy)-propane 9a or 1,1-dibutoxy-3-(2-hydroxyethoxy)-butane 9b , 3-butoxy-1,1-bis-(2-hydroxyethoxy)-propane 10a or 3-butoxy-1,1-bis-(2-hydroxyethoxy)-butane 10b , and 1-butoxy-1,3-bis-(2-hydroxyethoxy)-propane 11a or 1-butoxy-1,3-bis-(2-hydroxyethoxy)-butane 11b , respectively. 相似文献
42.
Krystyna Bogdanowicz-Szwed Andrzej Policht 《Advanced Synthesis \u0026amp; Catalysis》1984,326(5):721-728
The reaction of enamines 1 derivatives of cyclohexanon- or cycloheptanon-2-carboxylic acid anilides with malononitrile gave in the first step 2-phenylcarbamoyl-cycloalkylideno-malononitriles 3 , which in turn were converted into 1-oxo-2-phenyl-3-amino-4-cyano-cycloalkenoisoquinolines 4 . Enamines containing an adjacent diphenylamidino group 6 reacted with malononitrile giving 1-phenylimino-2-phenyl-3-amino-4-cyano-cycloalkenoisoquinolines 7 . The alkaline hydrolysis of 7 yielded 1-phenylamino-3-oxo-4-cyano-cycloalkenoisoquinoline 8 . 相似文献
43.
A comprehensive meta‐analysis on dietary flavonoid and lignan intake and cancer risk: Level of evidence and limitations 下载免费PDF全文
44.
Agnieszka Drd Adrianna Sawiska-Brych Dominika Kubera Magdalena Kimsa-Dudek Joanna Magdalena Gola Jolanta Adamska Celina Kruszniewska-Rajs Arkadiusz Matwijczuk Dariusz Karcz Wojciech Dbrowski Andrzej Stepulak Mariusz Gago 《International journal of molecular sciences》2022,23(23)
4-(5-methyl-1,3,4-thiadiazole-2-yl) benzene-1,3-diol (C1) and 4-[5-(naphthalen-1-ylmethyl)-1,3,4-thiadiazol-2-yl] benzene1,3-diol (NTBD) are representative derivatives of the thiadiazole group, with a high antimycotic potential and minimal toxicity against normal human fibroblast cells. The present study has proved its ability to synergize with the antifungal activity of AmB. The aim of this work was to evaluate the cytotoxic effects of C1 or NTBD, alone or in combination with AmB, on human renal proximal tubule epithelial cells (RPTECs) in vitro. Cell viability was assessed with the MTT assay. Flow cytometry and spectrofluorimetric techniques were used to assess the type of cell death and production of reactive oxygen species (ROS), respectively. The ELISA assay was performed to measure the caspase-2, -3, and -9 activity. ATR-FTIR spectroscopy was used to evaluate biomolecular changes in RPTECs induced by the tested formulas. The combinations of C1/NTBD and AmB did not exert a strong inhibitory effect on the viability/growth of kidney cells, as evidenced by the negligible changes in the apoptotic/necrotic rate and caspase activity, compared to the control cells. Both NTBD and C1 displayed stronger anti-oxidant activity when combined with AmB. The relatively low nephrotoxicity of the thiadiazole derivative combinations and the protective activity against AmB-induced oxidative stress may indicate their potential use in the therapy of fungal infections. 相似文献
45.
The p-chlorophenyl glycidyl ether was polymerized in the presence of Al(OiPr)3, ZnCl2, SnCl4, BuOK, KOH and by the Al(OiPr)3ZnCl2 1:1 initiator system. Analysis of the 13C n.m.r. spectra of the poly(p-chlorophenyl glycidyl ethers) obtained has made it possible to determine their tacticity and the content of the head-to-tail and head-to-head linkages in the polymer chain. 相似文献
46.
A Monte Carlo method was used for a computer simulation of radiation-induced solid state polymerization. The propagation of polymer chains was simulated by means of self-avoiding random walks on a tetrahedral lattice. The initiation and termination of the chains were modelled by pseudorandom processes. The influence of conditions of the in-source process on the post-polymerization kinetics and on the degree of polymerization of the polymers was studied. 相似文献
47.
Determination of the ash yield and the mineral matter content of brown coals by density measurements
Edward Chruściel Wit Jagusztyn Andrzej Kreft Andrzej Lenda Wojciech Przybylowicz Jan Woźniak 《Fuel》1983,62(3):389-390
A method of measuring the density of bed-moist brown coals based on their plastic properties is described and the feasibility of using the method for determination of the ash yield of the coal is evaluated. 相似文献
48.
Andrzej Kreft Edward Chrus̀ciel Bohdan Dziunikowski Jan Gyurcsak Stefan Kalita Andrzej Lenda Wojciech Przybylowicz Jan Woźniak 《Fuel》1984,63(9):1281-1284
A method for the simultaneous determination of calorific value Qr, ash yieldAr and total water content Wrt of soft brown coals is described. The method involves instrumental analysis of brown coal samples using neutron thermalization and gamma back-scattering techniques. Over 80 coal samples (1.1 kg) were analysed, having Qrvalues up to 15.5 MJ kg?1,Ar ranging from 3.6 to 76.1 wt% and Wrt ranging from 11.4 to 61.7 wt%. A comparison of the results from the instrumental method with those of standard laboratory analyses is given, followed by a discussion of the accuracy of the method and of possible ways for improving it. 相似文献
49.
Promising hybrid processes for ethanol dewatering consist of different combinations of distillation with adsorption and/or vapour permeation. This paper presents an analysis and optimisation of these hybrid processes using non-equilibrium models and an evolutionary algorithm. Four different membrane assisted configurations are compared with a benchmark process consisting of distillation and pressure swing adsorption. In total 12 cases were investigated while assuming different feed and product compositions at different production capacities: three ethanol mass fractions in feed 45, 80, 92 wt.%, two product purities 99.6, 99.95 wt.% and two production capacities 25,000, 250,000 m3/year. The influence of decisive operating and structural variables on important target variables such as total membrane area is demonstrated. Finally, the processes are evaluated regarding operating costs and energy consumption depending on product purity and production capacity. The operating costs of the membrane assisted configurations differ only in a small range of −3% to 6% from those of the benchmark. The energy consumption of the membrane assisted configurations without distillation is up to 30% lower compared to the benchmark. Especially the combination of vapour permeation and adsorption is a promising alternative allowing for producing ethanol with high purities at lower operating pressures compared to the vapour permeation as stand alone process. 相似文献
50.
Steven Hall Andrzej W. Pacek Adam J. Kowalski Mike Cooke David Rothman 《Chemical Engineering Research and Design》2013
The effect of scale, processing conditions, interfacial tension and viscosity of the dispersed phase on power draw and drop size distributions in three in-line Silverson rotor–stator mixers was investigated with the aim to determine the most appropriate scaling up parameter. The largest mixer was a factory scale device, whilst the smallest was a laboratory scale mixer. All the mixers were geometrically similar and were fitted with double rotors and standard double emulsor stators. 1 wt.% silicone oils with viscosities of 9.4 mPa s and 339 mPa s in aqueous solutions of surfactant or ethanol were emulsified in single and multiple pass modes. The effect of rotor speed, flow rate, dispersed phase viscosity, interfacial tension and scale on drop size distributions was investigated. 相似文献