全文获取类型
| 收费全文 | 261篇 |
| 免费 | 31篇 |
| 国内免费 | 11篇 |
专业分类
| 电工技术 | 17篇 |
| 综合类 | 27篇 |
| 化学工业 | 22篇 |
| 金属工艺 | 32篇 |
| 机械仪表 | 42篇 |
| 建筑科学 | 16篇 |
| 矿业工程 | 6篇 |
| 能源动力 | 44篇 |
| 水利工程 | 6篇 |
| 石油天然气 | 8篇 |
| 武器工业 | 3篇 |
| 无线电 | 13篇 |
| 一般工业技术 | 26篇 |
| 冶金工业 | 5篇 |
| 自动化技术 | 36篇 |
出版年
| 2025年 | 1篇 |
| 2024年 | 3篇 |
| 2023年 | 9篇 |
| 2022年 | 16篇 |
| 2021年 | 9篇 |
| 2020年 | 18篇 |
| 2019年 | 15篇 |
| 2018年 | 12篇 |
| 2017年 | 8篇 |
| 2016年 | 8篇 |
| 2015年 | 16篇 |
| 2014年 | 18篇 |
| 2013年 | 20篇 |
| 2012年 | 27篇 |
| 2011年 | 21篇 |
| 2010年 | 17篇 |
| 2009年 | 27篇 |
| 2008年 | 9篇 |
| 2007年 | 6篇 |
| 2006年 | 13篇 |
| 2005年 | 4篇 |
| 2004年 | 9篇 |
| 2002年 | 4篇 |
| 2001年 | 3篇 |
| 2000年 | 1篇 |
| 1996年 | 2篇 |
| 1993年 | 1篇 |
| 1988年 | 1篇 |
| 1972年 | 3篇 |
| 1968年 | 1篇 |
| 1960年 | 1篇 |
排序方式： 共有303条查询结果，搜索用时 15 毫秒
91.
Synthesis and catalysis of Ag nanoparticles trapped into temperature-sensitive and conductive polymers 总被引：1，自引：0，他引：1
Poly(styrene-co-N-isopropylacrylamide)/poly(N-isopropylacrylamide-co-methacrylic acid)/polypyrrole-silver [P(St-NIPAM)/P(NIPAM-co-MAA)/PPy-Ag] composite microgels were synthesized via a one-step redox polymerization of silver ammonia ions and pyrrole monomer at room temperature, using the core–shell P(St-NIPAM)/P(NIPAM-co-MAA) thermo-sensitive polymer microgels as templates. The structure, component, and properties of the as-prepared composite microgels have been characterized by transmission electron microscope, Fourier-transform infrared spectroscopy, X-ray diffraction, thermogravimetric analysis, and UV–Vis spectrophotometer. The results indicate that the size and the dispersity of the formed PPy-Ag nanocomposite particles can be regulated by adjusting the initial concentration of the precursors. The catalytic activity for the reduction of 4-nitrophenol was regulated by varying the environment temperature. Meanwhile, the higher catalytic activity is contributed to the electron transfer from the conductive polymer PPy to the Ag nanoparticles in the polymer material matrix. 相似文献
92.
煤炭营销属于工业品营销的组成部分,煤炭营销又具有其特殊性。当前煤炭市场价格也是来回拉锯。文章探讨了国内外分销模式理论,分析了当前大型煤炭集团分销存在的问题,建立了大型煤炭集团分销模式机制:提高经营管控能力、提高市场营销能力、调整产品结构和积极转变煤炭产业发展方式,针对不同客户提出了相关配套措施。 相似文献
93.
《International Journal of Hydrogen Energy》2020,45(22):12501-12513
The stoichiometric ratio and flow channel geometry play a vital role in the performance of high temperature proton exchange membrane (HT-PEM) fuel cells. Because of the high cost of experiments or simulations, most analyses and optimization of the stoichiometric ratio and flow channel geometry are limited to several points in the entire design domain. In this study, an analysis and optimization method for HT-PEM fuel cells based on the surrogate model was proposed. Surrogate models were constructed using some of the available budgets of samples to analyze and optimize the entire design domain. With this method, it was indicated that the effect of the cathode stoichiometric ratio is more significant to the cell performance than the anode stoichiometric ratio and there are significant nonlinear interactions among the flow channel geometry parameters. At the fixed operating voltage, the flow channel geometry with the maximum current density and that with the maximum real power were obtained. Compared with the base design, the designs obtained by the surrogate model improve the current density and real power by 10.54% and 3.93%, respectively. Thus, this analysis and optimization method is demonstrated to be helpful and deserves attention in future research. 相似文献
94.
《International Journal of Hydrogen Energy》2019,44(25):12842-12856
In this work, a new low-cost and high-performance system for cells voltage monitoring and degradation studies in air-cooled polymer electrolyte fuel cells has been designed, built and validated in the laboratory under experimental conditions.This system allows monitoring in real time the cells’ voltages, the stack current and temperature in fuel cells made of up to 100 cells. The developed system consists of an acquisition system, which complies with all the recommendations and features necessary to perform degradation tests. It is a scalable configuration with a low number of components and great simplicity. Additionally, the cell voltage monitoring (CVM) system offers high rate of accuracy and high reliability and low cost in comparison with other commercial systems.In the same way, looking for an \"All-in-One\" solution, the acquisition hardware is accompanied by a software tool based on the \"plug and play\" philosophy. It allows in a simple way obtaining information from the cells and performing a degradation analysis based on the study of the polarisation curve. The different options and tools included in the CVM system permit, in a very intuitive and graphical way, detecting and quantifying the cell degradation without the need of isolating the stack from the system.Experimental tests carried out on the system validate its performance and show the great applicability of the system in cases where cell faults detection and degradation analysis are required. 相似文献
95.
《International Journal of Hydrogen Energy》2019,44(38):21101-21109
The efficiency, reliability and lifespan of the fuel cell are strongly affected by the dynamic load variation of its output, which renders it desperate to investigate the influence of the power change rate on the fuel cell. In this study, three data dimensionality reduction algorithms are applied to identify the power change rate of the fuel cell in a less time-consuming way. To achieve that, the cell voltages of the stack as high-dimensional dataset is instantly projected onto the one-dimensional eigenvector space by principal component analysis (PCA), Fisher discriminant analysis (FDA) and locally linear embedding (LLE), respectively. The eigenvalue of one-dimensional eigenvector has the potential for instantly identifying the power change rate of the fuel cell and can be used as a feedback parameter in the control, which can improve the dynamic response, reliability, and lifespan of the fuel cell stack. According to the performance indicators of the algorithms including monotonicity, linearity and program execution time, the result shows that the PCA algorithm is the best-matched method for the real-time control of the fuel cell system. In the end, this study discussed some potential applications of this method in the fuel cell system, be it to be used alone or in a vehicular fuel cell hybrid system. 相似文献
96.
97.
起动电机模态特性试验分析 总被引：1，自引：0，他引：1
针对汽车厂提出的起动电机在发动机整机振动激励下不能出现共振的要求,分别利用振动台正弦激振和力锤冲击激振,对该型起动电机进行了振动模态特性试验分析,求得起动电机在安装状态下最低固有频率为528.31Hz,满足固有频率高于整机振动激励频率2.5倍的要求。起动电机在实车状态下的振动测试表明,在该发动机转速范围内,发动机的整机振动不会激起起动电机的共振。配置了上述发动机和起动电机的轿车,已大批量上市约两年,起动电机至今也未发生因异常振动导致的故障。 相似文献
98.
Crushed brick is widely known as a pozzolanic additive for composite building materials. However, crushed brick - lime composites usually show high porosity, low compressive strength and slow reaction kinetics. In this paper, we present multidisciplinary research on the amelioration of crushed brick - lime composites, using nanosilica (SiO2) and nanotitania (TiO2) as additives at 3% w/w of binder. The results suggest that despite the dominant effect of the crushed brick, nanosilica significantly improves the early-age properties of the composites, while nanotitania potentially increases their resistance against salt crystallization. Supplementary FTIR, DTA/TG and SEM analyses confirm the better hydration and carbonation evolution of lime composites with crushed brick and nano-additives. 相似文献
99.
Thiopave改性沥青路面力学响应研究 总被引：1，自引：0，他引：1
基于Thiopave改性沥青路面良好的高低温稳定性,采用有限元软件对典型半刚性基层沥青面层进行计算,得到不同沥青面层层底力学响应,并对计算结果进行对比研究,得到的主要结论如下：Thiopave沥青路面层底弯拉应力显著大于SBS沥青及基质沥青路面,路表轮隙中心处弯沉值小于SBS沥青及基质沥青路面;随着SEAM掺量的增加,Thiopave沥青路面层底弯拉应力逐渐增大,路表轮隙中心处弯沉值逐渐减小;随着沥青面层厚度的增加,沥青面层底部主拉应力减小,路表轮隙中心处弯沉值也呈现减小趋势． 相似文献
100.
基于驾驶员方向盘转动角速度与车辆低通滤波特性,对驾驶员转向意图及其紧急程度进行了表征,并以此实施了ESP系统参考模型的修正,使得ESP系统的控制介入时机更为合理,提高了车辆对驾驶员意图的响应性能,也避免了系统介入不适当对驾驶员正常行驶意图的干扰。最终通过某款轿车装备ESP后的实车场地实验,验证了修正算法的有效性。 相似文献