全文获取类型
收费全文 | 3674篇 |
免费 | 198篇 |
国内免费 | 77篇 |
专业分类
电工技术 | 21篇 |
综合类 | 173篇 |
化学工业 | 2300篇 |
金属工艺 | 59篇 |
机械仪表 | 57篇 |
建筑科学 | 45篇 |
矿业工程 | 14篇 |
能源动力 | 125篇 |
轻工业 | 204篇 |
石油天然气 | 360篇 |
武器工业 | 10篇 |
无线电 | 59篇 |
一般工业技术 | 460篇 |
冶金工业 | 41篇 |
原子能技术 | 7篇 |
自动化技术 | 14篇 |
出版年
2024年 | 10篇 |
2023年 | 45篇 |
2022年 | 55篇 |
2021年 | 79篇 |
2020年 | 89篇 |
2019年 | 81篇 |
2018年 | 80篇 |
2017年 | 112篇 |
2016年 | 91篇 |
2015年 | 112篇 |
2014年 | 177篇 |
2013年 | 218篇 |
2012年 | 274篇 |
2011年 | 290篇 |
2010年 | 193篇 |
2009年 | 238篇 |
2008年 | 180篇 |
2007年 | 264篇 |
2006年 | 219篇 |
2005年 | 185篇 |
2004年 | 160篇 |
2003年 | 127篇 |
2002年 | 112篇 |
2001年 | 109篇 |
2000年 | 87篇 |
1999年 | 66篇 |
1998年 | 60篇 |
1997年 | 47篇 |
1996年 | 43篇 |
1995年 | 36篇 |
1994年 | 23篇 |
1993年 | 20篇 |
1992年 | 15篇 |
1991年 | 7篇 |
1990年 | 11篇 |
1989年 | 10篇 |
1988年 | 5篇 |
1987年 | 4篇 |
1986年 | 2篇 |
1985年 | 3篇 |
1984年 | 5篇 |
1983年 | 3篇 |
1982年 | 1篇 |
1979年 | 1篇 |
排序方式: 共有3949条查询结果,搜索用时 15 毫秒
1.
2.
《International Journal of Hydrogen Energy》2019,44(11):5189-5202
Independent hydrogen production from petrochemical wastewater containing mono-ethylene glycol (MEG) via anaerobic sequencing batch reactor (ASBR) was extensively assessed under psychrophilic conditions (15–25 °C). A lab-scale ASBR was operated at pH of 5.50, and different organic loading rates (OLR) of 1.00, 1.67, 2.67, and 4.00 gCOD/L/d. The hydrogen yield (HY) progressed from 134.32 ± 10.79 to 189.09 ± 22.35 mL/gMEGinitial at increasing OLR from 1.00 to 4.00 gCOD/L/d. The maximum hydrogen content of 47.44 ± 3.60% was achieved at OLR of 4.0 gCOD/L/d, while methane content remained low (17.76 ± 1.27% at OLR of 1.0 gCOD/L/d). Kinetic studies using four different mathematical models were conducted to describe the ASBR performance. Furthermore, two batch-mode experiments were performed to optimize the nitrogen supplementation as a nutrient (C/N ratio), and assess the impact of salinity (as gNaCl/L) on hydrogen production. HY substantially dropped from 62.77 ± 4.09 to 6.02 ± 0.39 mL/gMEGinitial when C/N ratio was increased from 28.5 to 114.0. Besides, the results revealed that salinity up to 10.0 gNaCl/L has a relatively low inhibitory impact on hydrogen production. Eventually, the cost/benefit analysis showed that environmental and energy recovery revenues from ASBR were optimized at OLR of 4.0 gCOD/L/d (payback period of 7.13 yrs). 相似文献
3.
4.
The Interplay of Modulus,Strength, and Ductility in Adhesive Design Using Biomimetic Polymer Chemistry
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)
High‐performance adhesives require mechanical properties tuned to demands of the surroundings. A mismatch in stiffness between substrate and adhesive leads to stress concentrations and fracture when the bonding is subjected to mechanical load. Balancing material strength versus ductility, as well as considering the relationship between adhesive modulus and substrate modulus, creates stronger joints. However, a detailed understanding of how these properties interplay is lacking. Here, a biomimetic terpolymer is altered systematically to identify regions of optimal bonding. Mechanical properties of these terpolymers are tailored by controlling the amount of a methyl methacrylate stiff monomer versus a similar monomer containing flexible poly(ethylene glycol) chains. Dopamine methacrylamide, the cross‐linking monomer, is a catechol moiety analogous to 3,4‐dihydroxyphenylalanine, a key component in the adhesive proteins of marine mussels. Bulk adhesion of this family of terpolymers is tested on metal and plastic substrates. Incorporating higher amounts of poly(ethylene glycol) into the terpolymer introduces flexibility and ductility. By taking a systematic approach to polymer design, the region in which material strength and ductility are balanced in relation to the substrate modulus is found, thereby yielding the most robust joints. 相似文献
5.
Kang Zhang Rong‐rong Wang Kai‐rui Zhang Fei Cheng Yu Tian Yi Lin Mi Zhou Pu‐xin Zhu 《Polymer International》2020,69(3):274-279
A series of hyperbranched poly(citric polyethylene glycol) (PCPEG) materials with varied polyethylene glycol (PEG) chain lengths as plasticizers were mixed with maize starch (MS) via cooking and film‐forming. The structure, pasting property, plasticization, aging property, moisture absorption and compatibility of plasticized starches were studied by means of Fourier transform infrared spectroscopy, X‐ray diffraction, rapid viscosity analysis, tension testing, moisture absorption measurements and scanning electron microscopy. Compared with PEG and citric acid, PCPEG was more effective in promoting starch chain movement and inhibiting the retrogradation of starch film. Also, PCPEG/MS had smaller moisture content. The longer the plasticizer chain, the better were the aging resistance and moisture resistance of starch. But with an increase of PEG chain length, mechanical properties of PCPEG/MS deteriorated and the compatibility between PCPEG and MS decreased. The hyperbranched derivative of PEG with longer chain exhibited improved plasticization and compatibility with starch. © 2019 Society of Chemical Industry 相似文献
6.
采用浸渍法制备了Nb2O5/α-A l2O3催化剂(简称催化剂)并用于环氧乙烷水合制乙二醇的反应,通过控制α-A l2O3载体中致孔剂的含量来调变载体的孔径、孔分布及比表面积;采用吡啶吸附红外光谱、氨程序升温脱附法研究了载体的比表面积及孔径对催化剂酸性及反应性能的影响。实验结果表明,产物的选择性受扩散因素及催化剂酸性的影响,而催化剂的酸量、酸密度可以通过载体的孔径及比表面积的变化加以调控。比表面积较小及孔径较大的载体对催化剂催化环氧乙烷水合制乙二醇的反应较为有利。当载体的比表面积小于0.80m2/g、孔径为4.00~8.00μm时,在反应温度160℃、反应压力1.5M Pa、n(H2O)∶n(EO)=22、液态空速25h-1的条件下,环氧乙烷的转化率大于99.8%,乙二醇的选择性超过89.9%。 相似文献
7.
溶剂对环氧乙烷催化水合制乙二醇的影响 总被引:1,自引:1,他引:0
研究了NY催化剂催化环氧乙烷水合制乙二醇(EG)过程中,溶剂、催化剂添加量和水与环氧乙烷的摩尔比(简称水比)对EG选择性的影响。实验结果表明,以丙三醇作为溶剂使催化剂进行循环,能提高EG的选择性,效果好于以生成的EG作为溶剂循环催化剂。催化剂添加量、水比和溶剂添加量对EG选择性具有较大影响,其中溶剂添加量对EG选择性的影响最显著。在低水比(1.0~4.0)条件下,EG质量分数小于30%、催化剂质量分数大于7.2%时,EG选择性稳定在95.63%~97.92%,平均值为96.80%,此结果对于进一步降低EG合成工艺的能耗具有指导意义。 相似文献
8.
9.
10.
Liquid viscosity and density of six binary mixtures of HFC-134a with glycols [ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol (400), and polypropylene glycol (2000)] have been measured in the temperature range from 273 to 333 K. The viscosity was measured by a rolling-ball viscometer calibrated with standard liquids of viscosities and densities (JS5, JS10, JS20, and JS50). The density was measured with a glass pycnometer. The uncertainties of the measurements were estimated to be less than 3.4 % for viscosity and 0.04 % for density, respectively. An equation is given to represent the obtained viscosity values as a function of weight fraction and temperature. 相似文献