全文获取类型
收费全文 | 7859篇 |
免费 | 1041篇 |
国内免费 | 557篇 |
专业分类
电工技术 | 708篇 |
综合类 | 1227篇 |
化学工业 | 523篇 |
金属工艺 | 180篇 |
机械仪表 | 572篇 |
建筑科学 | 432篇 |
矿业工程 | 121篇 |
能源动力 | 163篇 |
轻工业 | 183篇 |
水利工程 | 132篇 |
石油天然气 | 105篇 |
武器工业 | 73篇 |
无线电 | 1025篇 |
一般工业技术 | 1335篇 |
冶金工业 | 237篇 |
原子能技术 | 53篇 |
自动化技术 | 2388篇 |
出版年
2024年 | 23篇 |
2023年 | 95篇 |
2022年 | 112篇 |
2021年 | 193篇 |
2020年 | 285篇 |
2019年 | 274篇 |
2018年 | 297篇 |
2017年 | 324篇 |
2016年 | 381篇 |
2015年 | 333篇 |
2014年 | 437篇 |
2013年 | 543篇 |
2012年 | 549篇 |
2011年 | 550篇 |
2010年 | 398篇 |
2009年 | 442篇 |
2008年 | 435篇 |
2007年 | 499篇 |
2006年 | 425篇 |
2005年 | 348篇 |
2004年 | 321篇 |
2003年 | 347篇 |
2002年 | 276篇 |
2001年 | 241篇 |
2000年 | 225篇 |
1999年 | 157篇 |
1998年 | 145篇 |
1997年 | 149篇 |
1996年 | 103篇 |
1995年 | 78篇 |
1994年 | 80篇 |
1993年 | 58篇 |
1992年 | 62篇 |
1991年 | 41篇 |
1990年 | 37篇 |
1989年 | 27篇 |
1988年 | 26篇 |
1987年 | 14篇 |
1986年 | 14篇 |
1985年 | 10篇 |
1984年 | 9篇 |
1983年 | 4篇 |
1982年 | 10篇 |
1981年 | 15篇 |
1980年 | 8篇 |
1979年 | 6篇 |
1978年 | 7篇 |
1966年 | 5篇 |
1964年 | 13篇 |
1963年 | 6篇 |
排序方式: 共有9457条查询结果,搜索用时 0 毫秒
21.
共轭高分子三阶非线性光学材料 总被引:3,自引:0,他引:3
概述了n-共轭高分子材料的三阶非线性光学性质,着重讨论了化学结构对其光学非线性的影响,说明了n-共轭聚合物的三阶非线性极化率主要取决于共轭主链的结构,侧链取代基的变化对其非线性影响不大,文中展望了共轭高分子材料在集成光学中的应用前景。 相似文献
22.
L. FAN‡ D. PATERSON† I. McNULTY‡ M. M. J. TREACY & J. M. GIBSON‡ 《Journal of microscopy》2007,225(1):41-48
Measuring medium‐range order is a challenging and important problem in the structural study of disordered materials. We have developed a new technique, fluctuation x‐ray microscopy, that offers quantitative insight into medium‐range correlations in disordered materials at nanometre and larger length scales.In this technique, which requires a spatially coherent x‐ray beam, a series of speckle patterns are measured at a large number of locations in a sample using various illumination sizes. Examination of the speckle variance as a function of the illumination spot size allows the structural correlation length to be measured. To demonstrate this technique we have studied polystyrene latex spheres, which serve as a model for a dense random‐packed glass, and for the first time have measured the correlation length in a disordered system by fluctuation X‐ray microscopy. We discuss data analysis and procedures to correct for shot noise and detector noise. This approach could be used to explore medium‐range order and subtle spatial structural changes in a wide range of disordered materials, from soft matter to nanowire arrays, semiconductor quantum dot arrays and magnetic materials. 相似文献
23.
The static and dynamic properties of solutions of a side chain polysiloxane liquid crystal polymer have been studied in a cyanobiphenyl nematic host as a function of concentration and temperature. Refractive index measurements were carried out on aligned samples and the data used to determine the macroscopic order parameter, S, using Haller's method. Photon correlation spectroscopy has been used to measure () for the pure nematic solvent and the solutions. From these measurements it appears that the static properties vary slowly and linearly with increasing polymer concentration whilst the dynamic or viscoelastic properties change markedly. This change has been attributed to γ1, the twist viscosity, and the results have been discussed in terms of the function of the siloxane polymer backbone. 相似文献
24.
25.
This article presents a design of the internal model control(IMC)based single degree of freedom(SDF) fractional order(FO)PID controller with a desired bandwidth specification for a class of fractional order system(FOS). The drawbacks of the SDF FO-IMC are eliminated with the help of the two-degree of freedom(TDF)FO PID controller. The robust stability and robust performance of the designed controller are analyzed using an example. 相似文献
26.
陈祖龙 《电脑编程技巧与维护》2012,(6):4-5,28
伴随着科技的日益进步、控制理论的不断的研究与发展,结合当今科技的先进技术,目前传统的自动配料控制系统将面临规模化、信息化、高效化的严峻挑战。在自动配料系统生产过程中,涵盖了工业控制技术的各个领域,包括现场总线技术(ProFieldbus)、网络及通信技术、工业控制技术、数据库技术和机电技术等技术。 相似文献
27.
This study considers a flowshop type production system consisting of m machines. A material handling robot transports the parts between the machines and loads and unloads the machines. We consider the sequencing of the robot moves and determining the speeds of these moves simultaneously. These decisions affect both the robot’s energy consumption and the production speed of the system. In this study, these two objectives are considered simultaneously. We propose a second order cone programming formulation to find Pareto efficient solutions. We also develop a heuristic algorithm that finds a set of approximate Pareto efficient solutions. The conic formulation can find robot schedules for small cells with less number of machines in reasonable computation times. Our heuristic algorithm can generate a large set of approximate Pareto efficient solutions in a very short computational time. Proposed solution approaches help the decision-maker to achieve the best trade-off between the throughput of a cell and the energy efficiency of a material handling robot. 相似文献
28.
对于遵循高层体系结构(HLA)标准构建的分布式虚拟环境(DVE),时间管理服务的性能将直接影响分布式仿真的效率和正确性。目前的时间管理服务实现了两种消息排序机制:接收序和时戳序。接收序对消息按其接收顺序进行处理,实时性高,但无法正确处理接收顺序与产生顺序相违背的消息;时戳序通常指保守时戳序机制,能对消息按其产生的时间顺序进行处理,但时间开销较大,难以到达DVE的实时性要求。因此,本文以分布式中间件的方式为DVE设计实现了一种因果消息序时间管理服务,提供符合HLA标准的程序接口,使分布式仿真应用在不改变原有调用接口的情况下,能够通过中间件对消息实现因果序时间管理。实验表明,使用该中间件可以有效维护消息的处理顺序,同时时间开销小,能够较好地满足DVE的实时性要求。 相似文献
29.
The specific heat at constant pressure, C
p, of aluminum measured by Ditmars, Plint, and Shukla has been reduced to the volume V
0 appropriate for 0 K employing the Murnaghan equation. The C
v0 thus obtained is compared with the theoretical C
v0 calculated in the harmonic and the lowest-order anharmonic approximation from three different pseudopotentials (Harrison, Ashcroft, and Dagens-Rasolt-Taylor) as well as a phenomenological Morse potential. The higher-order (
4) anharmonic contributions are calculated from the same nearest-neighbor Morse potential as in the lowest-order anharmonic theory. The role of the vacancy and the higher-order anharmonic contributions to C
v0 has been examined and we conclude that the
4 contributions to C
v0 are much smaller than the vacancy contribution. After removal of the vacancy contribution, the reduced C
v0 is found to be in excellent agreement with the Ashcroft and Harrison pseudopotentials as well as the Morse potential including the
2 and
4 contributions to C
v0. 相似文献
30.