全文获取类型
收费全文 | 1364篇 |
免费 | 106篇 |
国内免费 | 3篇 |
专业分类
电工技术 | 14篇 |
化学工业 | 397篇 |
金属工艺 | 24篇 |
机械仪表 | 58篇 |
建筑科学 | 43篇 |
矿业工程 | 6篇 |
能源动力 | 93篇 |
轻工业 | 151篇 |
水利工程 | 10篇 |
石油天然气 | 16篇 |
无线电 | 116篇 |
一般工业技术 | 209篇 |
冶金工业 | 59篇 |
原子能技术 | 10篇 |
自动化技术 | 267篇 |
出版年
2024年 | 2篇 |
2023年 | 21篇 |
2022年 | 48篇 |
2021年 | 62篇 |
2020年 | 44篇 |
2019年 | 58篇 |
2018年 | 54篇 |
2017年 | 69篇 |
2016年 | 59篇 |
2015年 | 41篇 |
2014年 | 69篇 |
2013年 | 136篇 |
2012年 | 101篇 |
2011年 | 116篇 |
2010年 | 94篇 |
2009年 | 91篇 |
2008年 | 77篇 |
2007年 | 58篇 |
2006年 | 58篇 |
2005年 | 33篇 |
2004年 | 28篇 |
2003年 | 30篇 |
2002年 | 22篇 |
2001年 | 15篇 |
2000年 | 11篇 |
1999年 | 6篇 |
1998年 | 7篇 |
1997年 | 9篇 |
1996年 | 9篇 |
1995年 | 4篇 |
1994年 | 4篇 |
1993年 | 6篇 |
1992年 | 8篇 |
1991年 | 1篇 |
1990年 | 3篇 |
1989年 | 2篇 |
1988年 | 3篇 |
1987年 | 5篇 |
1985年 | 3篇 |
1983年 | 2篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1976年 | 1篇 |
1974年 | 1篇 |
排序方式: 共有1473条查询结果,搜索用时 218 毫秒
161.
162.
Melissa A. Ruivo Rafael R. Pacheco Maicon Sebold Marcelo Giannini 《Microscopy research and technique》2019,82(10):1756-1767
The purpose of this study was to evaluate the surface roughness (Ra), and the morphology and composition of filler particles of different composites submitted to toothbrushing and water storage. Disc‐shaped specimens (15 mm × 2 mm) were made from five composites: two conventional (Z100?, and Filtek? Supreme Ultra Universal, 3M), one “quick‐cure” (Estelite ∑ Quick, Tokuyama), one fluoride‐releasing (Beautiful II, Shofu), and one self‐adhering (Vertise Flow, Kerr) composite. Samples were finished/polished using aluminum oxide discs (Sof‐Lex, 3M), and their surfaces were analyzed by profilometry (n = 5) and scanning electron microscopy (SEM; n = 3) at 1 week and after 30,000 toothbrushing cycles and 6‐month water storage. Ra data were analyzed by two‐way analysis of variance and Tukey's test (α = 0.05). Filler particles morphology and composition were analyzed by SEM and X‐ray dispersive energy spectroscopy, respectively. Finishing/polishing resulted in similar Ra for all the composites, while toothbrushing and water storage increased the Ra of all the tested materials, also changing their surface morphology. Beautifil II and Vertise Flow presented the highest Ra after toothbrushing and water storage. Filler particles were mainly composed of silicon, zirconium, aluminum, barium, and ytterbium. Size and morphology of fillers, and composition of the tested composites influenced their Ra when samples were submitted to toothbrushing and water storage. 相似文献
163.
Marcelo Frota BAZHUNI Mahsa KAMALI Ali GHAHREMANINEZHAD 《Frontiers of Structural and Civil Engineering》2019,13(3):741
The properties of binary and ternary cement pastes containing glass powder (GP) were examined. Hydration at early age was evaluated using semi-adiabatic calorimetry and at late ages using non-evaporable water content and thermogravimetric analysis. The transport characteristic was assessed by measuring electrical resistivity. The binary paste with slag showed the highest hydration activity compared to the binary pastes with GP and fly ash (FA). The results indicated that the pozzolanic behavior of the binary paste with GP was less than that of the binary pastes with slag or FA at late ages. An increase in the electrical resistivity and compressive strength of the binary paste with GP compared to other modified pastes at late ages was observed. It was shown that GP tends to increase the drying shrinkage of the pastes. Ternary pastes containing GP did not exhibit synergistic enhancements compared to the respective binary pastes. 相似文献
164.
A numerical study of the combustion of lean methane/air mixtures in a porous media burner is performed using novelty geometry, cylindrical annular space. The combustion process takes place in the porous space located between two pipes, which are filled with alumina beads of 5.6 mm diameter forming a porosity of 0.4. The outer tube diameter of 3.82 cm is isolated; meanwhile the inner tube of 2 cm in diameter is covered by a continuous set of thermoelectric elements (TE) for transforming heat energy into electricity. To achieve and maintain the proper temperature gradient on TE, convective heat losses are considered from the TE. Computer simulations focus on the two-dimensional (2D) temperature analysis and displacement dynamics of the combustion front inside the reactor, depending on the values of the filtration velocity (0.1 to 1.0 m/s), the heat loss coefficient from the internal cylinder (400–1500 W/m2/K), and the fuel equivalence ratio (0.06– 0.5). The conditions that maximized the overall performance of the process of energy conversion are: 0.7 m/s of the filtration velocity, 0.363 of the fuel equivalence ratio and 1500 W/(m2·K) of the heat transfer coefficient from the internal cylinder, to obtain 2.05 V electrical potential, 21 W of electrical power, and 5.64% of the overall process efficiency. The study shows that the cylindrical annular geometry can be used for converting the energy of combustion from lean gas mixtures into electricity, with a performance similar to the specified by manufacturers of thermoelectric elements (TE). 相似文献
165.
166.
Fabiana Carmanini Ribeiro Flávio Meira Borém Gerson Silva Giomo Renato Ribeiro De Lima Marcelo Ribeiro Malta Luisa Pereira Figueiredo 《Journal of Stored Products Research》2011,47(4):341-348
The objective of this study was to evaluate the physical, chemical, and sensory qualities of green coffee beans (Coffea arabica L.) during storage in different types of packaging. Coffee was stored from October 2008 to September 2009 in a warehouse of the Agriculture Society Ltda. (SAAG) in Santana da Vargem, southern Minas Gerais State, Brazil. The treatments in the factorial design consisted of two types of packaging (hermetic big bags with the injection of up to 60% CO2 in a controlled atmosphere; similar bags but without the injection of CO2 in a modified atmosphere) and three sampling positions in the bags (high, medium, and low). At 3-month intervals during a 12-month period, grains were analyzed to determine their water content, color, electrical conductivity, potassium lixiviation, and content of sugars. Sensory analysis was also conducted at these sampling times. The storage of green coffee beans in hermetic big bags on a commercial scale under modified and controlled atmospheric conditions is viable over a 12-month period. The coffee packed in big bags maintained its quality and exhibited an intensification of the green coloration of the grains during storage. Sensory analysis of coffee beans stored in a controlled atmosphere showed that the medium sampling position yielded the best ratings. The results of this analysis demonstrated that this storage technique can potentially increase the effectiveness of methods used to preserve the sensory quality of coffee beans. 相似文献
167.
Arildo José Braz de Oliveira Regina Aparecida Correia Gonçalves Talita Perez Cantuaria Chierrito Marcelo Müller dos Santos Lauro Mera de Souza Philip Albert James Gorin Guilherme Lanzi Sassaki Marcello Iacomini 《Food chemistry》2011
Fructooligosaccharides have been isolated from roots and leaves of Stevia rebaudiana, by hot aqueous extraction, followed by precipitation with ethanol. Their structure has been determined using methylation and NMR analysis, MALDI-TOF, and ESI-MS. Fructooligosaccharides contained almost exclusively (2→1)-linked β-fructofuranosyl, with terminal α-glucopyranosyl and β-fructofuranosyl units. MALDI-TOF and ESI-MS analyses showed the wide range of degree of polymerisation (DP) present in various extracts. From roots and leaves, three different fractions gave profiles of homologous series, with DPs ranging up to 17 with MALDI-TOF and 19 using ESI-MS. These inulin-type fructooligosaccharides were the major component of extracts from S. rebaudiana roots and significant components from the leaves. 相似文献
168.
Influence of Alkaline Additives and Buffers on Mineral Trapping of CO2 under Mild Conditions
下载免费PDF全文
![点击此处可从《化学工程与技术》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Marta K. Schütz Natália F. Lopes Angélica Cenci João Marcelo M. Ketzer Sandra Einloft Jeane Dullius Rosane Ligabue 《化学工程与技术》2018,41(3):573-579
Carbon dioxide (CO2) gas is the main contributor to climate change. CO2 storage in underground brines and oil‐field brines by mineral trapping has been considered as a promising alternative in order to reduce CO2 emissions. However, permanent storage of CO2 in stable carbonate minerals is greatly dependent on brine pH, being favored over an alkaline pH. The effect of alkaline additives (NaOH, KOH, CaO) and buffer solutions (NaHCO3/NaOH, Na2HPO4/NaOH, NH4Cl/NH4OH) on the mineral trapping of CO2 under mild conditions using a synthetic brine is investigated. The results indicate that both NaOH+NH4Cl/NH4OH and KOH+NH4Cl/NH4OH mixtures promote precipitation mainly of calcium carbonate (CaCO3). 相似文献
169.
170.
Software for Simulation of Second‐Generation Ethanol Production by a Simultaneous Saccharification and Fermentation Process
下载免费PDF全文
![点击此处可从《化学工程与技术》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Environmental impacts associated with the consumption of fossil fuels and the need to generate power through renewable resources demands the usage of alternative materials. The objective is the production of clean energy from materials like lignocellulosic biomass to produce second‐generation (2G) ethanol. A software in the Matlab program is elaborated to simulate the simultaneous saccharification and fermentation (SSF) process of lignocellulosic biomass for the 2G ethanol production in batch reactors. Studying the effects of the process variables, it was found that the higher interference is caused by cellulose concentration. Higher concentrations of the product in batch processes are obtained with the maximum cellulose concentrations, cells, and enzyme. 相似文献