全文获取类型
收费全文 | 6375篇 |
免费 | 484篇 |
国内免费 | 394篇 |
专业分类
电工技术 | 485篇 |
综合类 | 317篇 |
化学工业 | 332篇 |
金属工艺 | 193篇 |
机械仪表 | 588篇 |
建筑科学 | 236篇 |
矿业工程 | 99篇 |
能源动力 | 309篇 |
轻工业 | 65篇 |
水利工程 | 101篇 |
石油天然气 | 63篇 |
武器工业 | 61篇 |
无线电 | 1170篇 |
一般工业技术 | 326篇 |
冶金工业 | 52篇 |
原子能技术 | 23篇 |
自动化技术 | 2833篇 |
出版年
2024年 | 17篇 |
2023年 | 80篇 |
2022年 | 130篇 |
2021年 | 180篇 |
2020年 | 196篇 |
2019年 | 163篇 |
2018年 | 162篇 |
2017年 | 221篇 |
2016年 | 284篇 |
2015年 | 288篇 |
2014年 | 429篇 |
2013年 | 444篇 |
2012年 | 420篇 |
2011年 | 558篇 |
2010年 | 343篇 |
2009年 | 369篇 |
2008年 | 393篇 |
2007年 | 319篇 |
2006年 | 339篇 |
2005年 | 312篇 |
2004年 | 218篇 |
2003年 | 202篇 |
2002年 | 183篇 |
2001年 | 111篇 |
2000年 | 111篇 |
1999年 | 121篇 |
1998年 | 85篇 |
1997年 | 67篇 |
1996年 | 71篇 |
1995年 | 64篇 |
1994年 | 70篇 |
1993年 | 48篇 |
1992年 | 38篇 |
1991年 | 39篇 |
1990年 | 37篇 |
1989年 | 33篇 |
1988年 | 18篇 |
1987年 | 8篇 |
1986年 | 13篇 |
1985年 | 7篇 |
1984年 | 15篇 |
1983年 | 11篇 |
1982年 | 11篇 |
1981年 | 6篇 |
1980年 | 2篇 |
1979年 | 3篇 |
1978年 | 6篇 |
1977年 | 3篇 |
1962年 | 1篇 |
1959年 | 2篇 |
排序方式: 共有7253条查询结果,搜索用时 15 毫秒
1.
Salehe Gomroki Zahra Yavari Ahmad Reza Abbasian Meissam Noroozifar 《International Journal of Applied Ceramic Technology》2021,18(6):2099-2110
The spongy nickel oxide (SNO) was synthesized the solution combustion method. The SNO was selected as a promoter to boost the catalytic activity of nanoraspberry-like palladium (NRPd) toward electrooxidation of five light fuels (LFs): methanol, ethanol, formaldehyde, formic acid, and ethylene glycol. The X-ray powder diffraction, Fourier-transform infrared spectroscopy (FT-IR), scanning electron microscopy, and field emission scanning electron microscope techniques were used for the materials characterization. In comparison with nonpromoted Pd, the NRPd-SNO electrocatalyst shown an excellent efficiency in parameters like the electrochemical active surface area and anti-CO poisoning behavior. The turnover data and the parameters, including reaction order, activation energy, and the coefficients of electron transfer and diffusion, were evaluated for the each process of LFs electrooxidation. The outcome for NRPd-SNO activity toward LFs electrooxidation was compared to some reported electrodes. The SNO increases the removal of intermediates created in the oxidation of LFs that can poison the surface of palladium catalyst. This is due to the presence of the lattice oxygens in SNO structure and Ni switching between its high and low valances. The compatibility of the adsorption process of LFs on the surface of the NRPd-SNO catalyst with different isotherms was determined by studying the Tafel polarization and calculating the surface coverage. 相似文献
2.
The main purpose of this paper is to survey some recent progresses on control theory for stochastic distributed parameter systems, i.e., systems governed by stochastic differential equations in infinite dimensions, typically by stochastic partial differential equations. We will explain the new phenomenon and difficulties in the study of controllability and optimal control problems for one dimensional stochastic parabolic equations and stochastic hyperbolic equations. In particular, we shall see that both the formulation of corresponding stochastic control problems and the tools to solve them may differ considerably from their deterministic/finite-dimensional counterparts. More importantly, one has to develop new tools, say, the stochastic transposition method introduced in our previous works, to solve some problems in this field. 相似文献
3.
现阶段的语义解析方法大部分都基于组合语义,这类方法的核心就是词典。词典是词汇的集合,词汇定义了自然语言句子中词语到知识库本体中谓词的映射。语义解析一直面临着词典中词汇覆盖度不够的问题。针对此问题,该文在现有工作的基础上,提出了基于桥连接的词典学习方法,该方法能够在训练中自动引入新的词汇并加以学习,为了进一步提高新学习到的词汇的准确度,该文设计了新的词语—二元谓词的特征模板,并使用基于投票机制的核心词典获取方法。该文在两个公开数据集(WebQuestions和Free917)上进行了对比实验,实验结果表明,该文方法能够学习到新的词汇,提高词汇的覆盖度,进而提升语义解析系统的性能,特别是召回率。 相似文献
4.
The paper concerns an analysis of an equilibrium problem for 2D elastic body with two semirigid inclusions. It is assumed that inclusions have a joint point, and we investigate a junction problem for these inclusions. The existence of solutions is proved, and different equivalent formulations of the problem are proposed. We investigate a convergence to infinity of a rigidity parameter of the semirigid inclusion. It is proved that in the limit, we obtain an equilibrium problem for the elastic body with a rigid inclusion and a semirigid one. A parameter identification problem is investigated. In particular, the existence of a solution to a suitable optimal control problem is proved. 相似文献
5.
This study is to evaluate the potential for development of a cellulosic ethanol facility in Vietnam. Rice straw is abundant in Vietnam and highly concentrated in the Mekong Delta, where about 26 Mt year−1 of rice straw has been yearly produced. To minimize the overall production cost (PC) of ethanol from rice straw, it is crucial to choose the optimal facility size. The delivered cost of rice straw varied from 20.5 to 65.4 $ dry t−1 depending on transportation distance. The Mekong Delta has much lower rice straw prices compared with other regions in Vietnam because of high density and quantity of rice straw supply. Thus, this region has been considered as the most suitable location for deploying ethanol production in Vietnam. The optimal plant size of ethanol production in the region was estimated up to 200 ML year−1. The improvement in solid concentration of material in the hydrothermal pre-treatment step and using residues for power generation could substantially reduce the PC in Vietnam, where energy costs account for the second largest contribution to the PC, following only enzyme costs. The potential for building larger ethanol plants with low rice straw costs can reduce ethanol production costs in Vietnam. The current estimated production cost for an optimal plant size of 200 ML year−1 was 1.19 $ L−1. For the future scenario, considering improvements in pre-treatment, enzyme hydrolysis steps, specific enzyme activity, and applying residues for energy generation, the ethanol production cost could reduce to 0.45 $ L−1 for a plant size of 200 ML year−1 in Vietnam. These data indicated that the cost-competitiveness of ethanol production could be realized in Vietnam with future improvements in production technologies. 相似文献
6.
In this paper, we proposed a robust discrete-time controller. This control system, which is derived from the idea of the normalized plant, does not include plant parameters. Thus, we obtain a control system independent of plant parameters and that has the same structure as a conventional optimal servo control system. Simulation and experimental results show that the proposed method is fairly robust to plant parameter variations and external disturbances. 相似文献
7.
8.
The problem of operating freeze drying of pharmaceutical products in vials placed in trays of a freeze dryer to remove free water (in frozen state) at a minimum time was formulated as an optimal control problem. Two different types of freeze dryer designs were considered. In type I freeze dryer design, upper and lower plate temperatures were controlled together, while in type II freeze dryer design, upper and lower plate temperatures were controlled independently. The heat input to the material being dried and the drying chamber pressure were considered as control variables. Constraints were placed on the system state variables by the melting and scorch temperatures during primary drying stage. Necessary conditions of optimality for the primary drying stage of freeze drying process in vials are derived and presented. Furthermore, an approach for constructing the optimal control policies that would minimize the drying time for the primary drying stage was given. In order to analyze optimal control policy for the primary drying stage of the freeze-drying process in vials, a rigorous multi-dimensional unsteady state mathematical model was used. The theoretical approach presented in this work was applied in the freeze drying of skim milk. Significant reductions in the drying times of primary drying stage of freeze drying process in vials were obtained, as compared to the drying times obtained from conventional operational policies. 相似文献
9.
跳出传统的设计思路,提出装多件内装物的瓦楞纸箱尺寸优化设计方法,建立优化设计模型,编写程序用于生产,节省纸用量,降低成本。 相似文献
10.
Optimal synthesis of tunable elastic wave-guides 总被引:1,自引:0,他引:1
Anton Evgrafov Cory J. Rupp 《Computer Methods in Applied Mechanics and Engineering》2008,198(2):292-301
Topology optimization, or control in the coefficients of partial differential equations, has been successfully utilized for designing wave-guides with precisely tailored functionalities. For many applications it would be desirable to have the possibility of drastically altering the wave-guiding properties of a device “on the fly,” in a controllable manner as an influence of some external input. This would enable wave-guides with highly non-linear input-output mappings, such as for example controllable wave switches.In this paper, we propose using finite elastic pre-straining for the purpose of tuning a wave-guide. In order to systematically formulate and solve the wave-guide synthesis problems we utilize mathematical programming methods in conjunction with topology optimization for parametrizing the design space. The resulting extremal problem is, from a practical point, equivalent to finding an optimal subdivision of a given control volume into two disjoint subsets occupied by two different materials, normally resulting in a highly heterogeneous elastic body with desired wave-guiding functionalities in the original and finitely deformed configurations.The proposed methodology is illustrated with numerical examples. 相似文献