全文获取类型
收费全文 | 3532篇 |
免费 | 389篇 |
国内免费 | 351篇 |
专业分类
电工技术 | 55篇 |
综合类 | 139篇 |
化学工业 | 626篇 |
金属工艺 | 102篇 |
机械仪表 | 70篇 |
建筑科学 | 62篇 |
矿业工程 | 38篇 |
能源动力 | 269篇 |
轻工业 | 176篇 |
水利工程 | 22篇 |
石油天然气 | 25篇 |
武器工业 | 4篇 |
无线电 | 545篇 |
一般工业技术 | 454篇 |
冶金工业 | 27篇 |
原子能技术 | 14篇 |
自动化技术 | 1644篇 |
出版年
2024年 | 14篇 |
2023年 | 174篇 |
2022年 | 102篇 |
2021年 | 168篇 |
2020年 | 194篇 |
2019年 | 160篇 |
2018年 | 116篇 |
2017年 | 174篇 |
2016年 | 190篇 |
2015年 | 166篇 |
2014年 | 223篇 |
2013年 | 249篇 |
2012年 | 328篇 |
2011年 | 369篇 |
2010年 | 249篇 |
2009年 | 260篇 |
2008年 | 162篇 |
2007年 | 278篇 |
2006年 | 205篇 |
2005年 | 117篇 |
2004年 | 35篇 |
2003年 | 43篇 |
2002年 | 44篇 |
2001年 | 35篇 |
2000年 | 11篇 |
1999年 | 35篇 |
1998年 | 10篇 |
1997年 | 7篇 |
1996年 | 18篇 |
1995年 | 10篇 |
1994年 | 11篇 |
1993年 | 9篇 |
1992年 | 6篇 |
1991年 | 8篇 |
1990年 | 3篇 |
1989年 | 11篇 |
1988年 | 20篇 |
1987年 | 26篇 |
1986年 | 28篇 |
1985年 | 4篇 |
排序方式: 共有4272条查询结果,搜索用时 31 毫秒
1.
Neural Processing Letters - This paper presents an approach to identify the unknown parameters of genetic regulatory network (GRN) in finite-time. The adaptive synchronization-based method is used... 相似文献
2.
《Carbon》2015
The low shear rate rheology of two phase mesophase pitches derived from coal tar pitch has been investigated. Particulate quinoline insolubles (QI) stabilised the mesophase spheres against coalescence. Viscosity measurements over the range 10–106 Pa s were made at appropriate temperature ranges. Increasing shear thinning behaviour was evident with increasing mesophase content. At low mesophase contents the dominant effect on the near Newtonian viscosity was temperature but at higher contents it was the shear rate; temperature dependence declined to near zero. The data indicated that agglomeration could be occurring at intermediate mesophase volume fractions, 0.2–0.3. The Krieger–Dougherty function and its emulsion analogue indicated that in this region the mesophase pitch emulsions actually behaved like ‘hard’ sphere systems and the effective volume fraction was estimated as a function of shear rate illustrating the change in extent of agglomeration. At the higher volume fractions approaching the maximum packing fraction, which could only be measured at higher temperatures, the shear thinning behaviour changed in character and it is considered that this is possibly due to shear induced deformation and breakup of dispersed drops in the shear field. 相似文献
3.
研究了受外场驱动的两个二能级系统分别与两个单模量子化光场相互作用模型中纠缠演化及转移问题。该工作主要是对外场驱动的Landau-Zener模型进行了研究,采用旋转波近似的方法,通过数值计算详细分析了二能级系统初始状态、能级间的耦合常数以及驱动外场的参数对子系统间纠缠和转移特性的影响。结果表明,适当调节模型中的参数,可以使系统初始纠缠完全转移为光腔场间的纠缠,实现二能级系统与光场间的最大纠缠转移。 相似文献
4.
5.
6.
The visible light driven Bi2MoO6 photocatalyst doped with different contents of Ag nanoparticles was successfully synthesized by a combination of hydrothermal and sonochemical methods. The as-synthesized samples were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning and transmission electron microscopy (SEM and TEM) and UV–visible spectroscopy to investigate crystalline structure, morphology, composition and photocatalytic properties. XRD patterns and TEM images of the samples revealed pure phase orthorhombic Bi2MoO6 nanoplates without any detection of Ag dopant due to its low concentration and very tiny particle size. TEM images showed that Ag nanoparticles with the size of 10–15 nm were dispersed randomly on the surface of Bi2MoO6. The XPS analysis of Ag/Bi2MoO6 nanocomposites revealed the presence of additional metallic Ag. Photocatalytic activities of the Ag/Bi2MoO6 nanocomposites were evaluated by determining the degradation of rhodamine B (RhB) under visible light radiation. In this research, the 10 wt% Ag/Bi2MoO6 nanocomposites showed the best photocatalytic activity. The results suggest that the dispersion of Ag nanoparticles on the surface of Bi2MoO6 significantly enhances its photocatalytic activity. 相似文献
7.
Lei He Yan Xuan Feng Zhang Xue Wang Huaqing Pan Junfeng Ren Meina Chen 《International Journal of Hydrogen Energy》2021,46(1):1096-1105
Bulk and surface properties of proton stability and transportation in Y and Nd co-doped BaCeO3 (BCYN), especially the effect of Nd segregation, were investigated by first-principles calculations. Since the structure of doped BaCeO3 at the operating temperature of proton-conducting has been unclear for a long time, we have summarized the latest experimental results and calculated the structure of the asymmetric BCYN for the first time. The results show that compared with Y, Nd doping promotes oxygen vacancy formation, however reduces proton stability. Our calculation can also provide a possible explanation for the formation of space charge layer at the grain boundary of doped BaCeO3 in experiment. Unlike the stable Y in BCYN, Nd is calculated to be easily segregated, which can facilitate both proton hydration and proton transportation near the surface. Moreover, Nd segregation at the grain boundary is predicted to be beneficial for proton transportation between grains. 相似文献
8.
9.
Process object is the instance of process. Vertexes and edges are in the graph of process object. There are different types of the object itself and the associations between object. For the large-scale data, there are many changes reflected. Recently, how to find appropriate real-time data for process object becomes a hot research topic. Data sampling is a kind of finding c hanges o f p rocess o bjects. There i s r equirements f or s ampling to be adaptive to underlying distribution of data stream. In this paper, we have proposed a adaptive data sampling mechanism to find a ppropriate d ata t o m odeling. F irst o f all, we use concept drift to make the partition of the life cycle of process object. Then, entity community detection is proposed to find changes. Finally, we propose stream-based real-time optimization of data sampling. Contributions of this paper are concept drift, community detection, and stream-based real-time computing. Experiments show the effectiveness and feasibility of our proposed adaptive data sampling mechanism for process object. 相似文献
10.
Novel core-shell-like Ni-supported hierarchical beta zeolite catalysts on bioethanol steam reforming
《International Journal of Hydrogen Energy》2020,45(33):16409-16420
Hierarchical-Beta zeolites have been hydrothermally synthesized by adding a new gemini organic surfactant. The used gemini surfactant play the role of a “pore-forming agents” on the mesoscale, on the same time, providing alkaline environment for the system. With this hierarchical Beta zeolite as the core support, we successfully prepared a shell layer of Ni-containing (22 wt%) petal-like core-shell-like catalyst and applied it to bioethanol steam reforming. At the reaction temperature of 350 °C–550 °C, the conversion rate of ethanol and the selectivity of hydrogen were always above 85% and 70%. After reaction of 100 h on stream at 400 °C, there were not obvious inactivation could be observed on NiNPs/OH-MBeta catalyst. 相似文献