全文获取类型
收费全文 | 32091篇 |
免费 | 3956篇 |
国内免费 | 2183篇 |
专业分类
电工技术 | 5234篇 |
技术理论 | 4篇 |
综合类 | 3949篇 |
化学工业 | 1804篇 |
金属工艺 | 940篇 |
机械仪表 | 2455篇 |
建筑科学 | 3774篇 |
矿业工程 | 1080篇 |
能源动力 | 1069篇 |
轻工业 | 583篇 |
水利工程 | 1073篇 |
石油天然气 | 1408篇 |
武器工业 | 430篇 |
无线电 | 4737篇 |
一般工业技术 | 2589篇 |
冶金工业 | 777篇 |
原子能技术 | 610篇 |
自动化技术 | 5714篇 |
出版年
2024年 | 125篇 |
2023年 | 486篇 |
2022年 | 936篇 |
2021年 | 1077篇 |
2020年 | 1280篇 |
2019年 | 1052篇 |
2018年 | 851篇 |
2017年 | 1194篇 |
2016年 | 1336篇 |
2015年 | 1405篇 |
2014年 | 2402篇 |
2013年 | 1942篇 |
2012年 | 2609篇 |
2011年 | 2797篇 |
2010年 | 2014篇 |
2009年 | 2079篇 |
2008年 | 1932篇 |
2007年 | 2263篇 |
2006年 | 1860篇 |
2005年 | 1649篇 |
2004年 | 1345篇 |
2003年 | 1103篇 |
2002年 | 909篇 |
2001年 | 776篇 |
2000年 | 600篇 |
1999年 | 477篇 |
1998年 | 346篇 |
1997年 | 292篇 |
1996年 | 231篇 |
1995年 | 208篇 |
1994年 | 143篇 |
1993年 | 100篇 |
1992年 | 98篇 |
1991年 | 74篇 |
1990年 | 56篇 |
1989年 | 61篇 |
1988年 | 46篇 |
1987年 | 14篇 |
1986年 | 4篇 |
1985年 | 8篇 |
1984年 | 8篇 |
1983年 | 4篇 |
1982年 | 6篇 |
1981年 | 7篇 |
1980年 | 6篇 |
1979年 | 8篇 |
1975年 | 2篇 |
1969年 | 1篇 |
1959年 | 4篇 |
1951年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 659 毫秒
971.
The stabilization problem of polytopic differential inclusion (PDI) systems is investigated by using sliding mode control. Sliding surface is designed and sufficient conditions for asymptotic stability of sliding mode dynamics are derived. A novel feedback law is established to make the state of system reach the sliding surface in a finite time. Finally, an example is given to illustrate the validity of the proposed design. 相似文献
972.
Time-varying sliding mode control for a class of uncertain MIMO nonlinear system subject to control input constraint 总被引:1,自引:0,他引:1
To solve the regulator problem of a class of uncertain MIMO nonlinear systems subject to control input constraint, three types of time-varying sliding mode control laws are proposed. The sliding surfaces pass the initial value of the system at the initial time, and are shifted/rotated towards the predetermined ones. The controller parameters are optimized by genetic algorithm (GA). Lyapunov method is adopted to prove the stability and robustness to the parameter uncertainties and external disturbance. By me... 相似文献
973.
随着网络的普及和发展,信息的安全问题日益突出,使得加强信息安全学科、专业和培训机构体系化建设刻不容缓。信息安全人才的培养需要从培养目标、专业定位、理论教学、实践教学和实验室建设等各个方面综合考虑,制定合理可行的信息安全人才培养模式。 相似文献
974.
Oscillations and transfer properties of relay feedback systems with time-delay linear plants 总被引:1,自引:0,他引:1
Igor Boiko Author vitae 《Automatica》2009,45(12):2897-2902
Oscillations and transfer properties of relay feedback systems with linear plants having a dead time (time delay) are considered. Poincare maps are found explicitly in terms of the system parameters. The oscillatory and transfer properties are presented in the format of the locus of a perturbed relay system (LPRS), which represents the continuum of all possible periodic solutions and transfer properties of the system with a given linear plant. Conditions of local orbital asymptotic stability are found in terms of the system parameters. The proposed approach is illustrated by examples. 相似文献
975.
The paper presents an approach to characterizing a “stop–flow” mode of sensor array operation. The considered operation mode involves three successive phases of sensors exposure: flow (in a stream of measured gas), stop (in zero flow conditions) and recovery (in a stream of pure air). The mode was characterized by describing the distribution of information, which is relevant for classification of measured gases in the response of sensor array. The input data for classifier were the sets of sensors output values, acquired in discrete time moments of the measurement. Discriminant Function Analysis was used for data analysis. Organic vapours of ethanol, acetic acid and ethyl acetate in air were measured and classified. Our attention was focused on data sets which allowed for 100% efficient recognition of analytes. The number, size and composition of those data sets were examined versus time of sensor array response. This methodology allowed to observe the distribution of classification-relevant information in the response of sensor array obtained in “stop–flow” mode. Hence, it provided for the characterization of this mode. 相似文献
976.
The conductance of several tin oxide gas sensitive layers was simultaneously measured in thermo-cyclic and isothermal operation mode at various concentrations of CO and propene in air, respectively. Different measurement conditions were set by the cycle time, the gas flow rate, the humidity and the thickness of the sensitive layer. The sensor response is expressed by the conductance-over-time profiles (CTPs), the gas sensitivity or by the sum of the CTP sampling points. The resultant sensitivities from the CTPs were found to be higher than those of the isothermal measurements. The CTPs considerably change with the kind of gas as well as with the variation of the measurement conditions. This is discussed for both types of target gases with respect to the temperature, the adsorbates assumed and the reaction kinetics in relation to the gas transport conditions in the porous gas sensitive layer. 相似文献
977.
978.
为了在B/S下实现即时通信,提出一个适合于B/S和C/S的即时通信框架,选择Aiax,Flash作为客户端技术,实现一套即时通信系统。该系统克服以往C/S即时通信软件无法在B/S系统中应用的缺点,在基于B/S,C/S的系统间实现统一通信。 相似文献
979.
结合中国电信行业信息化建设的实际需求,引入JavaEE架构体系,提出一种在JavaEE平台上开发大型电信客户关系管理数据持久层的方法。通过门面模式、VO模式和DAO模式在SpringJDBC架构中的应用,实现持久层之间的松散耦合,使整个系统具备良好的稳定性、可伸缩性和可扩展性。 相似文献
980.
为研究采煤机滚筒在煤岩混合复杂工况下的调高连续性,依据液压机构的工作原理建立了滚筒调高机构的动力学模型.基于自适应模糊微分积分滑模(AFDI-SMC)鲁棒性强的优点,采用了萤火虫-细菌觅食(GSO-BFA)算法优化滑模控制器参数条件下的滚筒调高控制方案.为保证双滚筒工作时举升高度的一致性,引入偏差-环形耦合同步控制策略补偿位置偏差,同时采用融合算法(GSO-BFA)对外闭环(滚筒高度-电压)控制器参数进行优化,并分析了双滚筒同步调高性能,且与采用遗传算法(GA)优化的系统同步调高精度相比较.仿真结果表明,采用融合算法优化且结合自适应模糊微分积分滑模的滚筒同步调高系统具有良好的鲁棒性及较高的同步精度. 相似文献