全文获取类型
收费全文 | 320658篇 |
免费 | 25989篇 |
国内免费 | 19000篇 |
专业分类
电工技术 | 47697篇 |
技术理论 | 24篇 |
综合类 | 31722篇 |
化学工业 | 30733篇 |
金属工艺 | 14133篇 |
机械仪表 | 26250篇 |
建筑科学 | 22268篇 |
矿业工程 | 10394篇 |
能源动力 | 11730篇 |
轻工业 | 11099篇 |
水利工程 | 7082篇 |
石油天然气 | 10854篇 |
武器工业 | 4684篇 |
无线电 | 33852篇 |
一般工业技术 | 22049篇 |
冶金工业 | 9141篇 |
原子能技术 | 3433篇 |
自动化技术 | 68502篇 |
出版年
2024年 | 902篇 |
2023年 | 3183篇 |
2022年 | 5924篇 |
2021年 | 7809篇 |
2020年 | 7771篇 |
2019年 | 6262篇 |
2018年 | 5805篇 |
2017年 | 8063篇 |
2016年 | 9272篇 |
2015年 | 10566篇 |
2014年 | 18505篇 |
2013年 | 17202篇 |
2012年 | 22303篇 |
2011年 | 24516篇 |
2010年 | 19068篇 |
2009年 | 19845篇 |
2008年 | 19852篇 |
2007年 | 24296篇 |
2006年 | 22298篇 |
2005年 | 19407篇 |
2004年 | 16162篇 |
2003年 | 14830篇 |
2002年 | 11551篇 |
2001年 | 9599篇 |
2000年 | 8062篇 |
1999年 | 6515篇 |
1998年 | 4808篇 |
1997年 | 3859篇 |
1996年 | 3484篇 |
1995年 | 3083篇 |
1994年 | 2573篇 |
1993年 | 1890篇 |
1992年 | 1562篇 |
1991年 | 1068篇 |
1990年 | 789篇 |
1989年 | 709篇 |
1988年 | 486篇 |
1987年 | 304篇 |
1986年 | 220篇 |
1985年 | 204篇 |
1984年 | 174篇 |
1983年 | 137篇 |
1982年 | 122篇 |
1981年 | 121篇 |
1980年 | 76篇 |
1979年 | 65篇 |
1978年 | 55篇 |
1977年 | 48篇 |
1976年 | 47篇 |
1975年 | 25篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
151.
Zhen Wu Jing Yao Pengfei Zhu Fusheng Yang Xiangyu Meng Sandra Kurko Zaoxiao Zhang 《International Journal of Hydrogen Energy》2021,46(19):11183-11198
Advanced biogas power generation technology has been attracting attentions, which contributes to the waste disposal and the mitigation of greenhouse gas emissions. This work proposes and models a novel biogas-fed hybrid power generation system consisting of solid oxide fuel cell, water gas shift reaction, thermal swing adsorption and proton exchange membrane fuel cell (SOFC-WGS-TSA-PEMFC). The thermodynamic, exergetic, and thermo-economic analyses of this hybrid system for power generation were conducted to comprehensively evaluate its performance. It was found that the novel biogas-fed hybrid system has a gross energy conversion efficiency of 68.63% and exergy efficiency of 65.36%, indicating high efficiency for this kind of hybrid power technology. The market sensitivity analysis showed that the hybrid system also has a low sensitivity to market price fluctuation. Under the current subsidy level for the distributed biogas power plant, the levelized cost of energy can be lowered to 0.02942 $/kWh for a 1 MW scale system. Accordingly, the payback period and annual return on investment can reach 1.4 year and about 20%, respectively. These results reveal that the proposed hybrid system is promising and economically feasible as a distributed power plant, especially for the small power scale (no more than 2 MW). 相似文献
152.
Catalytic Hydrocracking of a Bitumen‐Derived Asphaltene over NiMo/γ‐Al2O3 at Various Temperatures
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)
Hydrocracking of a bitumen‐derived asphaltene over NiMo/γ‐Al2O3 was investigated in a microbatch reactor at varying temperatures. The molar kinetics of asphaltene cracking reaction was examined by fitting the experimental data. Below a defined temperature, the molar reaction showed the first‐order kinetic feature while at higher temperatures secondary reactions such as coke formation became significant, causing deviation of the reaction behavior from the proposed first‐order kinetic model. Selectivity analysis proved that dominant products varied from gases to liquids to gases with increasing temperature, shifting the dominant reaction from C–S bonds cleavage to C–C bonds cleavage. 相似文献
153.
The network reconfiguration is an important stage of restoring a power system after a complete blackout or a local outage. Reasonable planning of the network reconfiguration procedure is essential for rapidly restoring the power system concerned. An approach for evaluating the importance of a line is first proposed based on the line contraction concept. Then, the interpretative structural modeling (ISM) is employed to analyze the relationship among the factors having impacts on the network reconfiguration. The security and speediness of restoring generating units are considered with priority, and a method is next proposed to select the generating unit to be restored by maximizing the restoration benefit with both the generation capacity of the restored generating unit and the importance of the line in the restoration path considered. Both the start-up sequence of generating units and the related restoration paths are optimized together in the proposed method, and in this way the shortcomings of separately solving these two issues in the existing methods are avoided. Finally, the New England 10-unit 39-bus power system and the Guangdong power system in South China are employed to demonstrate the basic features of the proposed method. 相似文献
154.
心理测试的根本目的是为了让人们在测试过程中,产生某些特定行为,即个体对测试题目的反应,并根据这些行为反应来推论其相应的心理特性。在一定程度上帮助我们了解人类的心理活动,并从中得到帮助。因此,本文对基于学生群体心理测试系统的设计进行深入研究。 相似文献
155.
156.
The eutectic 80Au/20Sn solder alloy is widely used in high power electronics and optoelectronics packaging. In this study, low cycle fatigue behavior of a eutectic 80Au/20Sn solder alloy is reported. The 80Au/20Sn solder shows a quasi-static fracture characteristic at high strain rates, and then gradually transforms from a transgranular fracture (dominated by fatigue damage) to intergranular fracture (dominated by creep damage) at low strain rates with increasing temperature. Coffin-Manson and Morrow models are proposed to evaluate the low cycle fatigue behavior of the 80Au/20Sn solder. Besides, the 80Au/20Sn solder has enhanced fatigue resistance compared to the 63Sn/37Pb solder. 相似文献
157.
Application of chitosan–alginate microspheres for the sustained release of bacteriophage in simulated gastrointestinal conditions
下载免费PDF全文
![点击此处可从《International Journal of Food Science & Technology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
This study was designed to evaluate the acid stability, release property and antimicrobial efficacy of Escherichia coli O157:H7 bacteriophages encapsulated in chitosan–alginate microspheres under the simulated gastrointestinal conditions. The bacteriophages belonging to Myoviridae family were stable at the pH above 4 in trypticase soy broth. The chitosan–alginate microspheres exhibited protective effect on the viability of bacteriophages in the simulated gastric conditions at pH 2.0 and pH 2.5, showing 4.8 and 5.6 log PFU mL‐1, respectively, after 1 h of incubation at 37 °C. The release per cent of bacteriophages from microspheres gradually increased up to 65% in the simulated intestinal condition (pH 7.5) at 37 °C for 6 h. The lytic efficacy of chitosan‐ and alginate‐encapsulated bacteriophages against E. coli O157:H7 was significantly maintained in the simulated intestinal conditions to 10 h of incubation (1.3 log reduction). The results suggest that the chitosan–alginate microspheres can be used as a reliable delivery system for bacteriophages. 相似文献
158.
张居晓 《计算机技术与发展》2015,(1)
计算机录入编辑盲文是信息处理的特殊应用领域,是特殊教育中的重要研究课题。文中将盲文制作为特殊符号,通过制作字库,编写个性化码表,然后嵌入到主流输入法,从而实现盲文与汉字混排以及实现单手盲文输入。该系统具有易学易记性、盲文编码多样性、嵌入性强等优点,并通过实验证明输入盲文效率能提高5~6倍,在盲文出版、盲文印刷、盲文教学等领域有重要的应用价值。但盲文字符在不同平台(如智能手机)与不同操作系统兼容性问题还有待进一步研究开发。 相似文献
159.