全文获取类型
收费全文 | 446138篇 |
免费 | 38088篇 |
国内免费 | 23341篇 |
专业分类
电工技术 | 29036篇 |
技术理论 | 45篇 |
综合类 | 35599篇 |
化学工业 | 70628篇 |
金属工艺 | 27062篇 |
机械仪表 | 28833篇 |
建筑科学 | 34053篇 |
矿业工程 | 14977篇 |
能源动力 | 12098篇 |
轻工业 | 34330篇 |
水利工程 | 9567篇 |
石油天然气 | 26132篇 |
武器工业 | 4096篇 |
无线电 | 47890篇 |
一般工业技术 | 46629篇 |
冶金工业 | 22060篇 |
原子能技术 | 5348篇 |
自动化技术 | 59184篇 |
出版年
2024年 | 2021篇 |
2023年 | 6978篇 |
2022年 | 13324篇 |
2021年 | 18222篇 |
2020年 | 13589篇 |
2019年 | 10642篇 |
2018年 | 12150篇 |
2017年 | 13737篇 |
2016年 | 12539篇 |
2015年 | 17526篇 |
2014年 | 22257篇 |
2013年 | 26767篇 |
2012年 | 29822篇 |
2011年 | 32631篇 |
2010年 | 29514篇 |
2009年 | 28040篇 |
2008年 | 28297篇 |
2007年 | 26972篇 |
2006年 | 26421篇 |
2005年 | 22869篇 |
2004年 | 15724篇 |
2003年 | 13242篇 |
2002年 | 12312篇 |
2001年 | 11095篇 |
2000年 | 10538篇 |
1999年 | 10047篇 |
1998年 | 7349篇 |
1997年 | 6260篇 |
1996年 | 5915篇 |
1995年 | 4861篇 |
1994年 | 3942篇 |
1993年 | 2701篇 |
1992年 | 2125篇 |
1991年 | 1621篇 |
1990年 | 1290篇 |
1989年 | 1055篇 |
1988年 | 870篇 |
1987年 | 553篇 |
1986年 | 433篇 |
1985年 | 279篇 |
1984年 | 228篇 |
1983年 | 183篇 |
1982年 | 142篇 |
1981年 | 96篇 |
1980年 | 122篇 |
1979年 | 59篇 |
1977年 | 23篇 |
1976年 | 32篇 |
1959年 | 31篇 |
1951年 | 21篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
161.
Wai-Chuen Gan Li Qiu 《Industrial Electronics, IEEE Transactions on》2003,50(2):272-282
It is well known that the system performance for an indirect-field-oriented-control induction motor drive degrades under the variation of rotor resistance and in the presence of external load torque. In this paper, a plug-in robust compensator for speed and position control enhancement of an indirect-field-oriented-control induction machine drive is developed. In the case where a controller for the induction machine already exists or is in operation with satisfactory nominal tracking performance, this plug-in compensator, designed using the H/sub /spl infin// loop-shaping techniques, can be plugged into the existing controller without affecting the already satisfactory nominal tracking performance of the existing closed-loop system but with the capability to improve the system performance under plant parameter variations and in the presence of external disturbances. Simulation and experimental results are given to validate the proposed plug-in robust compensator. 相似文献
162.
Vacuum treatment and ion-beam bombardment are two major processes in the low energy ion-beam implantation. To accurately study the contributions of these two major factors to the bioeffects separately, the M1 generation variation of Arabidopsis thaliana with ion-beam implantation and vacuum treatment were compared through a series of key plant development parameters including morphological observation, biochemical assay and RAPD (random amplified polymorphic DNA) analysis. The results showed that ion-beam implantation had obvious effect on almost all of these parameters, and the vacuum treatment had some impacts on several morphological parameters such as the bolting time and the length of the primary stem. Taking the results together, the indication is that vacuum treatment has some slight contributions to the bioeffects of ion-beam implantation while ion-beam bombardment itself is the major creator of the bioeffects. 相似文献
163.
A ternary blend system comprising poly(cyclohexyl methacrylate) (PCHMA), poly(α‐methyl styrene) (PαMS) and poly(4‐methyl styrene) (P4MS) was investigated by thermal analysis, optical and scanning electron microscopy. Ternary phase behaviour was compared with the behaviour for the three constituent binary pairs. This study showed that the ternary blends of PCHMA/PαMS/P4MS in most compositions were miscible, with an apparent glass transition temperature (Tg) and distinct cloud‐point transitions, which were located at lower temperatures than their binary counterparts. However, in a closed‐loop range of compositions roughly near the centre of the triangular phase diagram, some ternary blends displayed phase separation with heterogeneity domains of about 1 µm. Therefore, it is properly concluded that ternary PCHMA/PαMS/P4M is partially miscible with a small closed‐loop immisciblity range, even though all the constituent binary pairs are fully miscible. Thermodynamic backgrounds leading to decreased miscibility and greater heterogeneity in a ternary polymer system in comparison with the binary counterparts are discussed. © 2003 Society of Chemical Industry 相似文献
164.
Stabilization of singularly perturbed fuzzy systems 总被引:6,自引:0,他引:6
This paper presents some novel results for stabilizing singularly perturbed (SP) nonlinear systems with guaranteed control performance. By using Takagi-Sugeno fuzzy model, we construct the SP fuzzy (SPF) systems. The corresponding fuzzy slow and fast subsystems of the original SPF system are also obtained. Two fuzzy control designs are explored. In the first design method, we propose the composite fuzzy control to stabilize the SPF subsystem with H/sup /spl infin// control performance. Based on the Lyapunov stability theorem, the stability conditions are reduced to the linear matrix inequality (LMI) problem. The composite fuzzy control will stabilize the original SP nonlinear systems for all /spl epsiv//spl isin/(0,/spl epsiv//sup */) and the upper bound /spl epsiv//sup */ can be determined. For the second design method, we present a direct fuzzy control scheme to stabilize the SP nonlinear system with H/sup /spl infin// control performance. By utilizing the Lyapunov stability theorem, the direct fuzzy control can guarantee the stability of the original SP nonlinear systems for a given interval /spl epsiv//spl isin/[/spl epsiv/_,/spl epsiv/~]. The stability conditions are also expressed in the LMIs. Two SP nonlinear systems are adopted to demonstrate the feasibility and effectiveness of the proposed control schemes. 相似文献
165.
166.
167.
研制了一种新型的结构化钢毛——胶结钢毛。和传统的普通钢毛相比,胶结钢毛具有很强的结构刚度和很低的钢毛流失量;同时,对高岭土有较高的除铁效率。 相似文献
168.
预应力钢-混凝土组合梁的应用与研究 总被引:1,自引:0,他引:1
回顾了预应力钢 混凝土组合梁国内外应用与研究历史 ,分析了现有规范及理论的不足 ,并指出了有待解决的问题。 相似文献
169.