全文获取类型
收费全文 | 43345篇 |
免费 | 5043篇 |
国内免费 | 3589篇 |
专业分类
电工技术 | 6246篇 |
综合类 | 4361篇 |
化学工业 | 6863篇 |
金属工艺 | 1505篇 |
机械仪表 | 1600篇 |
建筑科学 | 4918篇 |
矿业工程 | 2167篇 |
能源动力 | 1517篇 |
轻工业 | 5043篇 |
水利工程 | 2387篇 |
石油天然气 | 1772篇 |
武器工业 | 386篇 |
无线电 | 2029篇 |
一般工业技术 | 3688篇 |
冶金工业 | 1038篇 |
原子能技术 | 284篇 |
自动化技术 | 6173篇 |
出版年
2024年 | 234篇 |
2023年 | 855篇 |
2022年 | 1238篇 |
2021年 | 1525篇 |
2020年 | 1656篇 |
2019年 | 1621篇 |
2018年 | 1475篇 |
2017年 | 1595篇 |
2016年 | 1721篇 |
2015年 | 1793篇 |
2014年 | 2491篇 |
2013年 | 2766篇 |
2012年 | 2975篇 |
2011年 | 3232篇 |
2010年 | 2371篇 |
2009年 | 2687篇 |
2008年 | 2401篇 |
2007年 | 2849篇 |
2006年 | 2515篇 |
2005年 | 2173篇 |
2004年 | 1864篇 |
2003年 | 1489篇 |
2002年 | 1236篇 |
2001年 | 1059篇 |
2000年 | 974篇 |
1999年 | 923篇 |
1998年 | 726篇 |
1997年 | 627篇 |
1996年 | 542篇 |
1995年 | 442篇 |
1994年 | 395篇 |
1993年 | 324篇 |
1992年 | 315篇 |
1991年 | 201篇 |
1990年 | 131篇 |
1989年 | 116篇 |
1988年 | 80篇 |
1987年 | 61篇 |
1986年 | 44篇 |
1985年 | 28篇 |
1984年 | 47篇 |
1983年 | 36篇 |
1982年 | 37篇 |
1981年 | 14篇 |
1980年 | 19篇 |
1979年 | 19篇 |
1978年 | 11篇 |
1977年 | 7篇 |
1955年 | 3篇 |
1951年 | 10篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
81.
David Angeli Author Vitae 《Automatica》2004,40(3):449-457
The problem of controlling nonlinear noisy systems affected by parametric uncertainties is approached via the introduction of a supervisor which, whenever needed, switches on, in feedback to the plant, a controller selected from a finite set of predesigned controllers. A Lyapunov-based falsification criterion allows one to ensure robust stability in the presence of uncertain constant parameters and exogenous bounded disturbances. Simulations are discussed in order to illustrate the merits of the proposed algorithms. 相似文献
82.
常压渣油热反应过程中胶体的稳定性 总被引:10,自引:0,他引:10
利用质量分数电导率方法研究了中东和克拉玛依常压渣油在热反应过程中胶体的稳定性。结果表明,随着反应时间的增长,在热反应生焦诱导期内,渣油的胶体稳定性迅速下降;开始生焦后,胶体稳定性缓慢下降。从中东常压渣油的SARA四组分的数均相对分子质量、碳氢元素组成、平均芳碳率等方面探讨了中东常压渣油在热反应过程中胶体稳定性下降的原因。结果表明,在热反应中,由于裂解和缩聚反应的共同作用,使渣油的沥青质和饱和分含量上升,芳香分含量下降,胶质含量变化不大;随着热反应的进行,四组分的数均相对分子质量均呈下降趋势,导致了渣油胶体稳定性的下降并发生生焦反应。 相似文献
83.
CHENSheng-ping LUKe-cheng LIYi-gang LIJia-fang ZHUJian-ping FENGMing LIJing 《半导体光子学与技术》2004,10(2):122-126
The effects of the variations in fiber length, fiber mirror reflectance on efficiency and output power are experimentally investigated for erbium-doped double pass backward superfluorescent fiber sources (SFSs). The influence of fiber length on mean wavelength stability (MWS) has also been demonstrated. By incorporating a short section of un-pumped erbium-doped fiber (EDF) at the output port, the pump power dependent on MWS becomes independent of pumped EDF length. This is a novel phenomenon that hasn‘t been reported up to now,and should be helpful to SFS fabrication and theory analysis. By using a fiber Michelson interferometer as spectrum slicing component,a multi-wavelength fiber source (MWFS) with ~20 channels (from 1542nm to 1559nm) is got. The MWFS has a channel spacing of ~0. 8 nm which satisfies ITUstandard. The intensity fluctuation among channels is less than 0.5dB,and the extinction ratio of all channels is above 14dB. This kind of MWFS should be useful to wavelength division multiplexing systems. 相似文献
84.
Tams Insperger Gbor Stpn 《International journal for numerical methods in engineering》2004,61(1):117-141
An updated version of the semi‐discretization method is presented for periodic systems with a single discrete time delay. The delayed term is approximated as a weighted sum of two neighbouring discrete delayed state values and the transition matrix over a single period is determined. Stability charts are constructed for the damped and delayed Mathieu equation for different time‐period/time‐delay ratios. The convergence of the method is investigated by examples. Stability charts are constructed for 1 and 2 degree of freedom milling models. The codes of the algorithm are also attached in the appendix. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
85.
In control systems, actuators often have nonlinear characteristics that can not be neglected. For linear systems driven by actuators satisfying the generalized sector condition, a robust state feedback controller synthesis method is proposed to achieve the ultimate boundedness control. The method is based on the linear matrix inequality approach and is easy to apply. As an important special case of the generalized sector condition, the saturation characteristic of actuators is discussed separately, and non‐conservative results are obtained. 相似文献
86.
87.
88.
岭澳核电重件道路施工中所遇到的38m的观景平台在大亚湾核电站占有重要地位,在工程施工中发现边坡坡体陡峭,无法达到规范规定的稳定要求,故采取了加固措施。采用抗滑稳定计算的分析方法,对边坡加固的必要性及实施加固后的稳定性进行了分析。 相似文献
89.
Global complete observability and output-to-state stability imply the existence of a globally convergent observer 总被引:1,自引:0,他引:1
Alessandro Astolfi Laurent Praly 《Mathematics of Control, Signals, and Systems (MCSS)》2006,18(1):32-65
We consider systems which are globally completely observable and output-to-state stable. The former property guarantees the
existence of coordinates such that the dynamics can be expressed in observability form. The latter property guarantees the
existence of a state norm observer and therefore the possibility of bounding any continuous state functions. Both properties
allow to conceptually build an observer from an approximation of an exponentially attractive invariant manifold in the space
of the system state and an output driven dynamic extension. The proposed observer provides convergence to zero of the estimation
error within the domain of definition of the solutions.
The work of A. Astolfi is partly supported by the Leverhulme Trust. 相似文献
90.
通过合成的一系列具有不同分子量的聚丙烯酰胺的阳离子化制得具有不同分子参数的阳离子聚丙烯酰胺(CPAM)。经评价实验就分子参数对页岩抑制性的影响进行研究 相似文献