全文获取类型
收费全文 | 186866篇 |
免费 | 17758篇 |
国内免费 | 13456篇 |
专业分类
电工技术 | 31330篇 |
技术理论 | 9篇 |
综合类 | 18257篇 |
化学工业 | 9342篇 |
金属工艺 | 6753篇 |
机械仪表 | 16888篇 |
建筑科学 | 15286篇 |
矿业工程 | 7131篇 |
能源动力 | 4862篇 |
轻工业 | 4725篇 |
水利工程 | 5602篇 |
石油天然气 | 5742篇 |
武器工业 | 2958篇 |
无线电 | 17394篇 |
一般工业技术 | 9037篇 |
冶金工业 | 7988篇 |
原子能技术 | 1211篇 |
自动化技术 | 53565篇 |
出版年
2024年 | 863篇 |
2023年 | 2316篇 |
2022年 | 3670篇 |
2021年 | 4481篇 |
2020年 | 5413篇 |
2019年 | 4357篇 |
2018年 | 3869篇 |
2017年 | 5523篇 |
2016年 | 6110篇 |
2015年 | 6829篇 |
2014年 | 12601篇 |
2013年 | 11000篇 |
2012年 | 13807篇 |
2011年 | 14832篇 |
2010年 | 11246篇 |
2009年 | 11482篇 |
2008年 | 11454篇 |
2007年 | 13885篇 |
2006年 | 12413篇 |
2005年 | 10806篇 |
2004年 | 8944篇 |
2003年 | 7879篇 |
2002年 | 6271篇 |
2001年 | 5219篇 |
2000年 | 4493篇 |
1999年 | 3613篇 |
1998年 | 2775篇 |
1997年 | 2428篇 |
1996年 | 1950篇 |
1995年 | 1573篇 |
1994年 | 1335篇 |
1993年 | 974篇 |
1992年 | 779篇 |
1991年 | 578篇 |
1990年 | 444篇 |
1989年 | 382篇 |
1988年 | 273篇 |
1987年 | 161篇 |
1986年 | 115篇 |
1985年 | 112篇 |
1984年 | 160篇 |
1983年 | 123篇 |
1982年 | 120篇 |
1981年 | 81篇 |
1980年 | 57篇 |
1979年 | 66篇 |
1978年 | 49篇 |
1977年 | 49篇 |
1964年 | 14篇 |
1959年 | 15篇 |
排序方式: 共有10000条查询结果,搜索用时 8 毫秒
71.
给水流量控制系统仿真辅助设计 总被引:2,自引:1,他引:1
本文将给水流量系统规范化,给出静、动态数学模型,通过计算机仿真计算建立起设计参数S与系统特性间关系数据库,这些数据可用于控制系统辅助设计。本文还介绍了在S较小时自动补偿系统增益和时间常数的自适应控制方法并给出仿真结果。 相似文献
72.
This paper addresses the existence of loop gain-phase shaping (LGPS) solutions for the design of robust digital control systems for SISO, minimum-phase, continuous-time processes with parametric uncertainty. We develop the frequency response properties of LGPS for discrete-time systems using the Δ-transform, a transform method that applies to both continuous-time and discrete-time systems. A theorem is presented which demonstrates that for reasonable specifications there always exists a sampling period such that the robust digital control problem has a solution. Finally, we offer a procedure for estimating the maximum feasible sampling period for LGPS solutions to robust digital control problems. 相似文献
73.
Anthony E. Bentley 《国际强度与非线性控制杂志
》1994,4(1):119-160
》1994,4(1):119-160
Two different control systems were developed using quantitative feedback theory for weld quality improvement. The first application to be discussed was designed for the resistance pinch welding process and uses electrode displacement and force as feedback parameters. A correlation between weld quality and electrode displacement is established for constant electrode force. The system is capable of producing repeatable welds of consistent quality, with wide variations in weld parameters. This is the first time feedback control has been successfully applied to pinch welding. The second example presented in this paper was developed for penetration control of the gas-tungsten-arc welding process. The feedback signal is obtained by measuring the amount of light emitted from the back side of the weld. Welds of constant penetration have been demonstrated in tests with travel speeds varying from 1.5 to 6 inches per minute and with 200 per cent changes in part thickness. 相似文献
74.
Control law design for rotorcraft fly-by-wire systems normally attempts to decouple the angular responses using fixed-gain crossfeeds. This approach can lead to poor decoupling over the frequency range of pilot inputs and increase the load on the feedback loops. In order to improve the decoupling performance, dynamic crossfeeds should be adopted. Moreover, because of the large changes that occur in the aircraft dynamics due to small changes about the nominal design condition, especially for near-hovering flight, the crossfeed design must be ‘robust’. A new low-order matching method is presented here to design robust crossfeed compensators for multi-input, multi-output (MIMO) systems. The technique minimizes cross-coupling given an anticipated set of parameter variations for the range of flight conditions of concern. Results are presented in this paper of an analysis of the pitch/roll coupling of the UH-60 Black Hawk helicopter in near-hovering flight. A robust crossfeed is designed that shows significant improvement in decoupling perfomance and robustness over the fixed-gain or single point dynamic compensators. The design method and results are presented in an easily used graphical format that lends significant physical insight to the design procedure. This plant precompensation technique is an appropriate preliminary step to the design of robust feedback control laws for rotorcraft. 相似文献
75.
Russel B. Miller Isaac M. Horowitz Constantine H. Houpis A. Finley Barfield 《国际强度与非线性控制杂志
》1994,4(1):211-230
》1994,4(1):211-230
Nonlinear quantitative feedback theory (QFT) and pilot compensation techniques are used to design a 2 × 2 flight control system for the YF-16 aircraft over a large range of plant uncertainty. The design is based on numerical input-output time histories generated with a FORTRAN implemented nonlinear simulation of the YF-16. The first step of the design process is the generation of a set of equivalent linear time-invariant (LTI) plant models to represent the actual nonlinear plant. It has been proven that the solution to the equivalent plant problem is guaranteed to solve the original nonlinear problem. Standard QFT techniques are then used in the design synthesis based on the equivalent plant models. A detailed mathematical development of the method used to develop these equivalent LTI plant models is provided. After this inner-loop design, pilot compensation is developed to reduce the pilot's workload. This outer-loop design is also based on a set of equivalent LTI plant models. This is accomplished by modelling the pilot with parameters that result in good handling qualities ratings, and developing the necessary compensation to force the desired system responses. 相似文献
76.
Matthew R. James 《国际强度与非线性控制杂志
》1994,4(6):791-806
》1994,4(6):791-806
In this paper we present a numerical method for estimating the current state of a nonlinear control system. We use finite differences to discretize a modified version of the finite-time observer equations in James. The discretized equations are simple and easily programmed. The convergence and accuracy of the scheme is proved, and the scheme enjoys a number of important properties: availability of rate of convergence estimates, good robustness characteristics, and the ability to handle certain types of discontinuities in the observations. The major disadvantage is that the number of grid points required increases exponentially with the number of state dimensions. 相似文献
77.
三峡水库减淤增容调度方式研究——多汛限水位调度方案 总被引:8,自引:0,他引:8
本文建议在汛期中小流量时(Q<35000m3/s),将坝前水位维持在148~151m;出现汛情且流量更较大后,将坝前水位降低到143m;入库流量大于35000m3/s且短期预报将出现大于十年一遇洪水时,预泄洪水到135m.按这一调度,汛期约80%时间可以维持在较高水位,一般洪水期。汛限水位143m不影响坝区通航,135m水位迎洪可大量增加防洪库客。到100年后可减淤30亿m3,增加防洪库容约40亿m3.变动回水区减淤40%,优化了坝区水沙搭配,可改善通航条件。降低库区洪水位,缓解防洪与移民的矛盾。可对发电带来较大好处:提高发电效益,减少粗沙过机。初期水库排沙比大于原方案,可减轻下游冲刷。同时,可减小三峡汛初泄水与鄱阳湖防洪的矛盾。 相似文献
78.
A Linear Cross-Coupled Control System for High-Speed Machining 总被引:4,自引:0,他引:4
Q. Zhong Y. Shi J. Mo S. Huang 《The International Journal of Advanced Manufacturing Technology》2002,19(8):558-563
We present a linear cross-coupled controller to improve highspeed contouring accuracy independently of tracking accuracy in
a biaxial machine tool feed drive servomechanism. Unlike conventional cross-coupled controllers, the cross-coupled controller
presented here is a linear system, so it is very easy to perform the stability and steady-state error analysis, and to optimise
the controller parameters. The proposed controller is evaluated experimentally on a CNC LOM machine and compared to an uncoupled
controller and a conventional cross-coupled controller. Controller performance is evaluated for a circular contour at a feedrate
of 30 m min _1 . The experimental results show that the proposed controller can greatly reduce the contour error at large feedrates. The
linear cross-coupled controller is simple to implement and is practical. 相似文献
79.
Freelance 2000 DCS在轴流机上的应用 总被引:1,自引:1,他引:0
简要介绍了Freelance 2000 DCS的功能特点以及轴流机的控制要求.结合轴流机的控制特点,用Freelance 2000 DCS对原模拟电子系统进行改造,实现并改进了轴流机流量-静叶位置调节、防喘振控制、逻辑控制、状态监测、信息管理等功能。改造后的系统可靠性高、技术先进、信息管理功能强,其设计思想和方法均可供石化企业大型压缩机控制系统的设计和改造借鉴。 相似文献
80.