全文获取类型
收费全文 | 15935篇 |
免费 | 2336篇 |
国内免费 | 1556篇 |
专业分类
电工技术 | 5553篇 |
综合类 | 1732篇 |
化学工业 | 313篇 |
金属工艺 | 214篇 |
机械仪表 | 1161篇 |
建筑科学 | 318篇 |
矿业工程 | 257篇 |
能源动力 | 313篇 |
轻工业 | 113篇 |
水利工程 | 173篇 |
石油天然气 | 91篇 |
武器工业 | 133篇 |
无线电 | 2543篇 |
一般工业技术 | 863篇 |
冶金工业 | 398篇 |
原子能技术 | 176篇 |
自动化技术 | 5476篇 |
出版年
2024年 | 79篇 |
2023年 | 213篇 |
2022年 | 304篇 |
2021年 | 387篇 |
2020年 | 470篇 |
2019年 | 457篇 |
2018年 | 423篇 |
2017年 | 681篇 |
2016年 | 751篇 |
2015年 | 783篇 |
2014年 | 1021篇 |
2013年 | 1206篇 |
2012年 | 1232篇 |
2011年 | 1340篇 |
2010年 | 1067篇 |
2009年 | 1130篇 |
2008年 | 1117篇 |
2007年 | 1250篇 |
2006年 | 991篇 |
2005年 | 867篇 |
2004年 | 698篇 |
2003年 | 542篇 |
2002年 | 439篇 |
2001年 | 414篇 |
2000年 | 348篇 |
1999年 | 263篇 |
1998年 | 202篇 |
1997年 | 189篇 |
1996年 | 163篇 |
1995年 | 136篇 |
1994年 | 127篇 |
1993年 | 111篇 |
1992年 | 86篇 |
1991年 | 71篇 |
1990年 | 65篇 |
1989年 | 42篇 |
1988年 | 16篇 |
1987年 | 22篇 |
1986年 | 9篇 |
1985年 | 14篇 |
1984年 | 15篇 |
1983年 | 21篇 |
1982年 | 11篇 |
1981年 | 7篇 |
1980年 | 8篇 |
1979年 | 5篇 |
1964年 | 5篇 |
1962年 | 3篇 |
1959年 | 3篇 |
1958年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
本文考虑了单输人中立型时滞系统的镇定问题。利用Byrnes等人提出的中立型时滞系统的模型,我们证明:如果系统是非奇异的,则系统可镇定的充要条件是其谱可镇定。 相似文献
62.
63.
A discrete-time, model-based output feedback control structure for nonlinear processes is developed in the present work. The structure makes use of a closed-loop observer, while at the same time it guarantees that the overall feedback controller possesses integral action. An algebraic transformation is applied on the observer states to insure that the input/output gain of the observer matches the model upon which the static state feedback control law is based. The resulting control algorithm is a two-degree-of-freedom control law, in the sense that the output and the set point are processed in different ways. The control structure is shown not only to have the same properties as the standard model-state feedback structure, but also that it emerges from a model algorithmic control framework. Finally, a simulation example using an exothermic CSTR operating at an open-loop unstable steady state is used to evaluate the closed-loop performance of the proposed method. 相似文献
64.
上海是一个经济快速发展的城市,同时也是一个资源相对匮乏的地区.文章从上海城市的总体规划出发,全面阐述坚持科学发展观,以资源节约型城市规划的理念,充分发挥城市规划的先导和调控作用,从全局和战略高度,实现能源、资源的合理节约利用,促进人与自然的和谐发展. 相似文献
65.
M. Guignard V. Nazabal F. Smektala J.‐L. Adam O. Bohnke C. Duverger A. Moréac H. Zeghlache A. Kudlinski G. Martinelli Y. Quiquempois 《Advanced functional materials》2007,17(16):3284-3294
High second‐order susceptibilities are created by thermal poling in bulk germanium disulfide based chalcogenide glasses. Experimental conditions of the poling treatment (temperature, voltage, time) were optimized for each glass composition. The second‐order nonlinear signals were recorded by using the Maker fringes experiment and a second‐order coefficient χ(2) up to 8 pm V–1 was measured in the Ge25Sb10S65 glass. This value is obtained using a simulation based on accurate knowledge of the thickness of the nonlinear layer. Two mechanisms are proposed to explain the creation of a nonlinear layer under the anode: the formation and the migration of charged defects towards the anode may mainly occur in Ge20Ga5Sb10S65 and Ge25Ga5S70 glasses, whereas the migration of Na+ ions towards the cathode may be responsible for the accumulation of negative charges under the anode in Ge33S67 and Ge25Sb10S65 glasses. Different electronic conductivity behaviors seem to be at the origin of the phenomenon. In parallel, the potential effect of the poling treatment on the structural and electronic properties is studied using Raman spectroscopy and secondary ion mass spectroscopy measurements. 相似文献
66.
Qi Gong 《Automatica》2007,43(1):184-189
In this paper we address the practical tracking problem for a class of nonlinear systems by dynamic output feedback control. Unlike most of the existing results where the unmeasurable states in the nonlinear vector field can only grow linearly, we allow higher-order growth of unmeasurable states. The proposed controller makes the tracking error arbitrarily small and demonstrates nice properties such as robustness to disturbances and universal property to reference signals. 相似文献
67.
68.
S. Bidault L. Viau O. Maury S. Brasselet J. Zyss E. Ishow K. Nakatani H. LeBozec 《Advanced functional materials》2006,16(17):2252-2262
The bottom‐up design of polymer films exhibiting quadratic nonlinear optical properties that can be tuned optically and chemically is described. The polymer matrices are doped with metal‐containing chromophores built around a ZnII core and photoisomerizable ligands with two different geometries. These molecules possess specifically designed photophysical and nonlinear optical properties to be used towards all‐optical poling, an interference process between one‐ and two‐photon excitations that locally induces macroscopic second‐order effects in polymer films. It is shown that grafting the molecules onto the polymer chains improves the stability of the macroscopic photoinduced nonlinearity in the films. 相似文献
69.
This paper considers the trajectory tracking problem for uncertain robot manipulators and proposes two adaptive controllers as solutions to this problem. The first controller is derived under the assumption that the manipulator state is measurable, while the second strategy is developed for those applications in which only position measurements are available. The adaptive schemes are very general and computationally efficient since they do not require knowledge of either the mathematical model or the parameter values of the manipulator dynamics, and are implemented without calculation of the robot inverse dynamics or inverse kinematic transformation. It is shown that the control strategies ensure uniform boundedness of all signals in the presence of bounded disturbances, and that the ultimate size of the tracking errors can be made arbitrarily small. Experimental results are presented for a PUMA 560 manipulator and demonstrate that accurate and robust trajectory tracking can be achieved by using the proposed controllers. 相似文献
70.
弹性直杆热膨胀状态下的非线性振动 总被引:30,自引:2,他引:28
以KBM法为基础,引进谐波平衡观点来研究弹性直杆热膨胀状态下的非线性振动.通过实例计算表明,弹性直杆热膨胀状态下非线性振动的频率对温度的变化非常敏感. 相似文献