全文获取类型
收费全文 | 26633篇 |
免费 | 2115篇 |
国内免费 | 25篇 |
专业分类
电工技术 | 177篇 |
综合类 | 12篇 |
化学工业 | 5641篇 |
金属工艺 | 432篇 |
机械仪表 | 564篇 |
建筑科学 | 837篇 |
矿业工程 | 54篇 |
能源动力 | 518篇 |
轻工业 | 5505篇 |
水利工程 | 305篇 |
石油天然气 | 119篇 |
武器工业 | 1篇 |
无线电 | 1088篇 |
一般工业技术 | 4378篇 |
冶金工业 | 5410篇 |
原子能技术 | 70篇 |
自动化技术 | 3662篇 |
出版年
2024年 | 53篇 |
2023年 | 285篇 |
2022年 | 282篇 |
2021年 | 727篇 |
2020年 | 669篇 |
2019年 | 681篇 |
2018年 | 1247篇 |
2017年 | 1218篇 |
2016年 | 1277篇 |
2015年 | 976篇 |
2014年 | 1123篇 |
2013年 | 2323篇 |
2012年 | 1767篇 |
2011年 | 1570篇 |
2010年 | 1299篇 |
2009年 | 1110篇 |
2008年 | 1171篇 |
2007年 | 1073篇 |
2006年 | 687篇 |
2005年 | 568篇 |
2004年 | 547篇 |
2003年 | 509篇 |
2002年 | 439篇 |
2001年 | 332篇 |
2000年 | 263篇 |
1999年 | 314篇 |
1998年 | 1895篇 |
1997年 | 1194篇 |
1996年 | 730篇 |
1995年 | 398篇 |
1994年 | 304篇 |
1993年 | 322篇 |
1992年 | 89篇 |
1991年 | 74篇 |
1990年 | 62篇 |
1989年 | 59篇 |
1988年 | 81篇 |
1987年 | 75篇 |
1986年 | 61篇 |
1985年 | 75篇 |
1984年 | 64篇 |
1983年 | 38篇 |
1982年 | 38篇 |
1981年 | 62篇 |
1980年 | 62篇 |
1978年 | 31篇 |
1977年 | 105篇 |
1976年 | 208篇 |
1975年 | 34篇 |
1973年 | 39篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
E. J. Martínez-Conesa M. J. Salar-García A. P. De Los Ríos F. J. Hernández-Fernández L. J. Lozano 《Chemical Engineering Communications》2017,204(1):97-104
Although modeling is regarded as a useful tool to understand the performance of microbial fuel cells (MFCs), the number of MFC models remains very low compared with the number of experimental works available in the literature. Moreover, there are very few MFC modeling attempts dealing with the use of wastewater as fuel in these devices, which is essential for the practical implementation of MFCs since the potential of this technology lies in the two-fold benefit of wastewater treatment and bioenergy generation. In this work, a four-factor three-level Box–Behnken design was developed to model the electrochemical power generation in two-chamber MFCs using wastewater as fuel. The optimum values of temperature, external resistance, feed concentration and anodic pH that maximized power output were investigated. Optimum conditions were found at T = 35°C and R = 1 kΩ, corresponding to a maximum power density of 0.88 W·m?3, while feed concentration and pH did not show statistical significance in the ranges studied. Thus, a Box–Behnken design-based model as empirical approach could provide an effective tool for the optimization study of MFC systems. 相似文献
992.
993.
Ionene Hydrogels: Synergistic Computational‐Experimental Approach to Improve Ionene Polymer‐Based Functional Hydrogels (Adv. Funct. Mater. 31/2014)
下载免费PDF全文
![点击此处可从《Advanced functional materials》网站下载免费的PDF全文](/ch/ext_images/free.gif)
994.
Víctor Otero-Tuárez Ximena Carrión-Granda Idoya Fernández-Pan Teresa Fernández Juan I. Maté 《International Journal of Food Science & Technology》2019,54(3):835-843
Two distinct strategies were combined to preserve fresh fish (Merluccius merluccius) under refrigeration at 4 °C for 12 days: (i) the application of an antimicrobial edible coating enriched with oregano essential oil (OEO) or carvacrol (CV) and (ii) the reduction of initial microbial load by good handling practise and the use of sodium hypochlorite (NaOCl). The action of antimicrobial coatings alone retarded the growth of Enterobacteriaceae, lactic acid bacteria (LAB) and H2S producing bacteria on fish samples. The reduction of initial microbial load by itself only affected the evolution of LAB, but not the rest of the bacterial groups. When using both techniques combined, edible antimicrobial coatings were significantly more effective with additional and significant delays in the growth of mesophilic, psychrotrophic and Pseudomonas bacteria. Thus, the use of both strategies combined resulted in a reduction of the counts of all bacterial groups after 12 days of storage which ranged from 1.5 log and 8 log, in Pseudomonas and H2S producing bacteria, respectively. Moreover, no significant differences were observed when comparing the microbiological evolution of samples treated with OEO compared to those only treated with CV. 相似文献
995.
Modeling and performance analysis of an absorption chiller with a microchannel membrane‐based absorber using LiBr‐H2O,LiCl‐H2O,and LiNO3‐NH3
下载免费PDF全文
![点击此处可从《国际能源研究杂志》网站下载免费的PDF全文](/ch/ext_images/free.gif)
In order to develop compact absorption refrigeration cycles driven by low heat sources, the simulated performance of a microchannel absorber of 5‐cm length and 9.5 cm3 in volume provided with a porous membrane is presented for 3 different solution‐refrigerant pairs: LiBr‐H2O, LiCl‐H2O, and LiNO3‐NH3. The high absorption rates calculated for the 3 solutions lead to large cooling effect to absorber volume ratios: 625 kW/m3 for the LiNO3‐NH3, 552 kW/m3 for the LiBr‐H2O, and 318 kW/m3 for the LiCl‐H2O solutions given the studied geometry. The performance of a complete absorption system is also analyzed varying the solution concentration, condensation temperature, and desorption temperature. The LiNO3‐NH3 and the LiBr‐H2O solutions provide the largest cooling effects. The LiNO3‐NH3 can work at a lower temperature of the heating source, in comparison with the one needed in a LiBr‐H2O system. The lowest cooling effect and coefficient of performance are found for the LiCl‐H2O solution, but this mixture allows the use of lower temperature heating sources (below 70°C). These results can be used for the selection of the most suitable solution for a given cooling duty, depending on the available heat source and condensation temperature. 相似文献
996.
Ana M. Herrera-González Martín Caldera-Villalobos Jesús García-Serrano Marissa Vargas Ramírez Azdrubal Lobo Guerrero-Serrano 《Designed Monomers and Polymers》2018,21(1):137-144
In this paper we report the synthesis of a new polyacrylate named poly(1,1?-BP4MA) which is a derivate from 4-biphenylmethanol monomer. Poly(1,1?-BP4MA) was obtained by solution and bulk polymerization techniques to yield polymers with high molecular weight and high solubility. The study of the optical properties showed that poly(1,1?-BP4MA) is a fluorescent material with emission in the UV-green region and it has similar quantum yield to tryptophan. 相似文献
997.
Metallurgical and Materials Transactions A - The interface structure of semicoherent titanium carbide (TiC) nanoparticles and incoherent micron-sized TiC precipitates in Fe–C–Ti alloy... 相似文献
998.
999.
Combination of Reaction and Separation in Heterogeneous Catalytic Hydrogenation of Ethylformate
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)
Gerson Martin Carla Pereira Frank Pettersson Henrik Saxén Dmitry Y. Murzin Alírio Rodrigues Tapio Salmi 《化学工程与技术》2015,38(5):804-812
Continuous hydrogenation reaction of ethyl benzoylformate was studied over a (–)‐cinchonidine (CD)‐modified Pt/Al2O3 catalyst. The catalyst showed a good stability, and high enantioselectivity was achieved in the fixed‐bed reactor. Chromatographic separation of (R)‐ and (S)‐ethyl mandelate originating from a post‐continuous hydrogenation reaction of ethyl benzoylformate over the (–)‐CD‐modified Pt/Al2O3 catalyst was investigated in the same reaction mixture. A commercial column filled with a chiral selector resin was chosen as a perspective preparative‐scale adsorbent. Since adsorption equilibrium isotherms were linear within the entire investigated range of concentrations, they were determined by pulse experiments for the isomers present in a post‐reaction mixture. Breakthrough curves were measured and described successfully by the dispersive plug‐flow model with linear driving force approximation. 相似文献
1000.
Carmen G. Manzanarez-Quín Lilia M. Beltrán-Barrientos Adrián Hernández-Mendoza Aarón F. González-Córdova Belinda Vallejo-Cordoba 《Journal of dairy science》2021,104(4):3766-3778
The growing prevalence of obesity affects millions of people around the world and has gained increased attention over the years because it is associated with the development of other chronic degenerative diseases. Different organizations recommend lifestyle changes to treat obesity; nevertheless, other strategies in addition to lifestyle changes have recently been suggested. One of these strategies is the use of probiotics in fermented dairy products; however, a need exists to review the different studies available related to the potential antiobesity effect of these products. Because probiotic fermented dairy products that support weight management are not available in the market, there is a great opportunity for the development of functional dairy products with new lactic acid bacteria that may present this added health benefit. Thus, the purpose of this overview is to highlight the importance of probiotic fermented dairy products as potential antiobesogenic functional foods and present in vitro and in vivo studies required before this kind of product may be introduced to the market. Overall, most studies attributed the antiobesity effect of fermented dairy foods to the probiotic strains present; however, bioactive peptides released during milk fermentation may also be responsible for this effect. 相似文献