全文获取类型
收费全文 | 112127篇 |
免费 | 13271篇 |
国内免费 | 6415篇 |
专业分类
电工技术 | 17202篇 |
技术理论 | 20篇 |
综合类 | 8620篇 |
化学工业 | 11687篇 |
金属工艺 | 3854篇 |
机械仪表 | 4473篇 |
建筑科学 | 13021篇 |
矿业工程 | 2855篇 |
能源动力 | 17277篇 |
轻工业 | 7836篇 |
水利工程 | 2653篇 |
石油天然气 | 3656篇 |
武器工业 | 990篇 |
无线电 | 8079篇 |
一般工业技术 | 10929篇 |
冶金工业 | 4652篇 |
原子能技术 | 1482篇 |
自动化技术 | 12527篇 |
出版年
2024年 | 1987篇 |
2023年 | 3147篇 |
2022年 | 4414篇 |
2021年 | 4832篇 |
2020年 | 4941篇 |
2019年 | 4288篇 |
2018年 | 3652篇 |
2017年 | 4280篇 |
2016年 | 4649篇 |
2015年 | 4621篇 |
2014年 | 7897篇 |
2013年 | 7219篇 |
2012年 | 8240篇 |
2011年 | 8925篇 |
2010年 | 6772篇 |
2009年 | 6715篇 |
2008年 | 6123篇 |
2007年 | 6756篇 |
2006年 | 5692篇 |
2005年 | 4441篇 |
2004年 | 3793篇 |
2003年 | 3200篇 |
2002年 | 2711篇 |
2001年 | 2305篇 |
2000年 | 1953篇 |
1999年 | 1503篇 |
1998年 | 1195篇 |
1997年 | 909篇 |
1996年 | 837篇 |
1995年 | 639篇 |
1994年 | 577篇 |
1993年 | 443篇 |
1992年 | 367篇 |
1991年 | 300篇 |
1990年 | 245篇 |
1989年 | 203篇 |
1988年 | 167篇 |
1987年 | 136篇 |
1986年 | 102篇 |
1985年 | 136篇 |
1984年 | 109篇 |
1983年 | 71篇 |
1982年 | 85篇 |
1981年 | 44篇 |
1980年 | 50篇 |
1979年 | 30篇 |
1978年 | 17篇 |
1977年 | 20篇 |
1974年 | 13篇 |
1951年 | 14篇 |
排序方式: 共有10000条查询结果,搜索用时 10 毫秒
51.
The constrained blister test is investigated through finite element analysis to determine the applicabilities and the limitations of the new technique. Numerical results confirm that the strain energy release rate asymptotically approaches a constant value. These results also show that the test technique and the approximate solution for strain energy release rate are applicable for some practical cases. 相似文献
52.
53.
54.
通过对游戏的分类、发展历程梳理以及用户的需求分析,结合游戏产生过程给出了游戏产品有效粘合用户时间的策略,最后预测了游戏的发展趋势。 相似文献
55.
《Journal of Visual Languages and Computing》2014,25(4):363-375
Objectives: OpenMusic (OM) is a domain-specific visual programming language designed for computer-aided music composition. This language based on Common Lisp allows composers to develop functional processes generating or transforming musical data, and to execute them locally by demand-driven evaluations. As most historical computer-aided composition environments, OM relies on a transformational declarative paradigm, which is hard to conciliate with reactive data-flow (an evaluation scheme more adequate to the development of interactive systems). We propose to link these two evaluation paradigms in the same and consistent visual programming framework.Methods: We establish a denotational semantics of the visual language, which gives account for its demand-driven evaluation mechanism and the incremental construction of programs. We then extend this semantics to enable reactive computations in the functional graphs.Results: The resulting language merges data-driven executions with the existing demand-driven mechanism. A conservative implementation is proposed.Conclusions: We show that the incremental construction of programs and their data-driven and demand-driven evaluations can be smoothly integrated in the visual programming workflow. This integration allows for the propagation of changes in the programs, and the evaluation of graphically designed functional expressions as a response to external events, a first step in bridging the gap between computer-assisted composition environments and real-time musical systems. 相似文献
56.
A novel and simple growth mark method was developed to make marks during the growth process of carbon nanotube arrays. These marks can be read out under scanning electron microscope or optical microscope. Based on this method, the growth rates at different temperatures and under different acetylene partial pressures were measured, from which the activation energy and the order of reaction were determined. Based on our experimental results, the growth of carbon nanotube arrays in our experimental condition could not be diffusion-limited. The measured activation energy could possibly be attributed to the heterogeneous decomposition of acetylene over the catalyst particle. Furthermore the marked array with special segmental structure may be found some applications in the future. 相似文献
57.
The structure of benzoxazines is similar to that of phenolic resin through thermal self‐curing of the heterocyclic ring opening reaction that neither requires catalyst nor releases any condensation byproduct. These polybenzoxazine resins have several outstanding properties such as high thermal stability and high glass transition temperature. To better understand the curing kinetics of this copolybenzoxazine thermosetting resin, dynamic and isothermal differential scanning calorimetry measurements were performed. Three models, the Kissinger method, the Flynn–Wall–Osawa method, and the Kamal method, were used to describe the curing process. Dynamic kinetic activation energies based on Kissinger and Flynn–Wall–Osawa methods are 72.11 and 84.06 KJ/mol, respectively. The Kamal method based on an autocatalytic model results in a total order of reaction between 2.66 and 3.03, depending on curing temperature. Its activation energy and Arrhenius preexponential are 50.3 KJ/mol and 7959, respectively. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 95: 730–737, 2005 相似文献
58.
An optimization strategy has been applied to describe the chemical composition at the furnace bottom in the Kraft recovery boiler of a pulp production process. The concentrations of each involved chemical species were calculated through an optimization approach, minimizing the Gibbs free energy of the system. Various systems were proposed and tested, assuming different chemical species and phases number. Because serious initialization problems were found at this stage for some of the proposed systems, an optimization heuristic method (PSO) was used for the first approach to the problem. Once the appropriate phases number and chemical species in the system were determined, the initialization problems disappeared and the use of a deterministic optimization method (SQP) became viable. The proposed approach has shown to be satisfactory to reproduce industrial data and also data reported in the open scientific literature. 相似文献
59.
GAO Lin LI Sheng JIN HongGuang & LIN Hu Institute of Engineering Thermophysics Chinese Academy of Sciences Beijing China Graduate School of Chinese Academy of Sciences Beijing 《中国科学:信息科学(英文版)》2010,(1)
On basis of adopting polygeneration systems for power and alternative fuels,capturing CO2 with near zero energy penalties,and storing CO2 on sites,a new kind of Energy Network can integrate energy utilization,CO2 capture,transportation and storage synthetically.Techno-economic analysis of this solution focusing on Inner Mongolia and the Yangtze River Delta districts had been carried with comparison to the chain method for energy utilization and CO2 sequestration.This solution can save 21.5% of energy,and re... 相似文献
60.
Jianfeng Wu Jian Li Xiaohong Xu Lanfang Yang Jufang Wu Fang Zhao Chuanguo Li 《武汉理工大学学报(材料科学英文版)》2009,24(4):651-653
A new type of high temperature energy storage material was obtained through the melt infiltration method, using compounding
SiC ceramic foam as matrix and Na2SO4 as phase change material. The resulting composite material was measured by XRD, SEM, TG-DSC methods. The experimental results
indicate that the composite is composed of silicon carbide, sodium sulfate and square quartz, and no chemical reactions occurs
between Na2SO4 and SiC matrix. Na2SO4 has a good bonding with the SiC ceramic foam matrix. As the composite material is characterized by high thermal energy storage
density and high thermal conductivity, it is suit for energy storage under high temperature.
Funded by the “863” Hi-Tech Research and Development Program of China (2008AA05Z418) 相似文献