全文获取类型
收费全文 | 24664篇 |
免费 | 3455篇 |
国内免费 | 2813篇 |
专业分类
电工技术 | 2872篇 |
综合类 | 3442篇 |
化学工业 | 1420篇 |
金属工艺 | 290篇 |
机械仪表 | 1671篇 |
建筑科学 | 2205篇 |
矿业工程 | 280篇 |
能源动力 | 597篇 |
轻工业 | 795篇 |
水利工程 | 670篇 |
石油天然气 | 416篇 |
武器工业 | 304篇 |
无线电 | 2836篇 |
一般工业技术 | 4128篇 |
冶金工业 | 430篇 |
原子能技术 | 271篇 |
自动化技术 | 8305篇 |
出版年
2024年 | 177篇 |
2023年 | 403篇 |
2022年 | 606篇 |
2021年 | 689篇 |
2020年 | 1066篇 |
2019年 | 975篇 |
2018年 | 931篇 |
2017年 | 1146篇 |
2016年 | 1232篇 |
2015年 | 1100篇 |
2014年 | 1425篇 |
2013年 | 2136篇 |
2012年 | 1822篇 |
2011年 | 1786篇 |
2010年 | 1323篇 |
2009年 | 1442篇 |
2008年 | 1446篇 |
2007年 | 1692篇 |
2006年 | 1422篇 |
2005年 | 1285篇 |
2004年 | 1048篇 |
2003年 | 872篇 |
2002年 | 719篇 |
2001年 | 693篇 |
2000年 | 666篇 |
1999年 | 481篇 |
1998年 | 409篇 |
1997年 | 399篇 |
1996年 | 321篇 |
1995年 | 247篇 |
1994年 | 206篇 |
1993年 | 159篇 |
1992年 | 143篇 |
1991年 | 112篇 |
1990年 | 87篇 |
1989年 | 59篇 |
1988年 | 34篇 |
1987年 | 16篇 |
1986年 | 20篇 |
1985年 | 12篇 |
1984年 | 18篇 |
1983年 | 11篇 |
1982年 | 15篇 |
1981年 | 11篇 |
1980年 | 18篇 |
1979年 | 15篇 |
1978年 | 12篇 |
1977年 | 10篇 |
1976年 | 2篇 |
1959年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
71.
针对机电作动系统在低速阶段摩擦非线性明显且同时存在其他干扰,易导致系统跟踪精度、稳定性下降这一问题,设计基于非线性观测器摩擦补偿的自适应鲁棒控制器. 针对摩擦非线性,利用LuGre摩擦模型描述系统的摩擦现象,提出非线性观测器对模型的内部摩擦状态进行观测. 针对系统摩擦系数、转动惯量及其他不确定性参数,设计参数自适应律进行估计. 利用前馈补偿的方法,对摩擦非线性和参数不确定性进行补偿,设计鲁棒项克服系统的其他扰动. 利用Lyapunov稳定性定理证明了提出的控制器在存在扰动的情况下可以实现系统的有界稳定性. 实验结果表明,提出的控制器具有较高的控制精度与较强的鲁棒性,跟踪精度较传统的PID控制器提高了一个数量级. 相似文献
72.
73.
基于优进策略的遗传算法对重油热解模型参数的估计 总被引:16,自引:1,他引:16
针对常规遗传算法全局寻优效率偏低的弱点,提出了一种优进策略,用以改进常规遗传算法。该策略将从繁衍过程中获取进化信息,自适应地改进子代分布,适时引入确定性操作,以提高全局寻优性能。提出的相关技术包括维持种群的多样性、改进交叉算子、增加Powell寻优算子等。实例测试表明这种优进策略效果良好,并已成功地应用于重油热解三集总动力学复杂数学模型的非线性参数估计。 相似文献
74.
本文应用细观力学、经典层板理论、平截面假定、FRP约束混凝土本构模型及数值积分对GFRP管混凝土组合结构压弯构件进行了非线性全过程分析。通过理论计算发现GFRP管混凝土组合结构能有效地提高构件的承载力,且构件具有良好的变形能力。FRP壳体参与承载且有效地约束混凝土的变形,显著提高核心混凝土强度和变形能力。文中讨论了轴压比、长细比、径厚比、混凝土强度等级、纵筋配筋率、铺层角变化对极限水平荷载和极限水平位移的影响,从而得到了一些有益的结论。 相似文献
75.
Berchtold von Steiger Armin Keller Rainer Schulin 《Nutrient Cycling in Agroecosystems》1998,50(1-3):303-306
Extraction of heavy metals by accumulating plants is a method which is currently in development for the "gentle" remediation of contaminated agricultural soils (phytoremediation, see [2]). Areal contaminant mass flux balances are basic criteria for the design of such remediations and their control. A framework for the integration of contaminant balances relating the field scale of remediation with the regional scale of soil monitoring networks is provided by the recently developed method PROTERRA [3]. The objective of the study presented in this paper was to test the suitability of PROTERRA for planning and monitoring gentle soil remediations. For this purpose we applied the PROTERRA method to the contaminated agricultural land in and around Dornach, Switzerland, to assess copper flux balances.The calculations showed that atmospheric deposition and the application of pesticides and manure are important pathways for the inputs of copper. The copper export with a special maize cultivar accumulating heavy metals would be about three times higher than the average metal export with crops. A moderate increase of sewage sludge application would lead to a substantial increase of the copper input. Decisions to remediate the soil should take the uncertainty of mass flux balances both on field scale as well as on regional scale into account. Therefore, an important need of further development of the PROTERRA method is the integration of uncertainty analysis on both scales. 相似文献
76.
概述了广义线性模型(含半参数广义线性模型)与非线性模型研究的新进展,着重讨论了它们参数估计的统计推断。近年来,广义线性模型与非线性模型的研究发展迅速,有着广泛的应用前景。 相似文献
77.
We note that in the literature it is often taken for granted that for fractional-order system without delays, whenever the system trajectory reaches the equilibrium, it will stay there. In fact, this is the well-known phenomenon of finite-time stability. However, in this paper, we will prove that for fractional-order nonlinear system described by Caputo’s or Riemann–Liouville’s definition, any equilibrium cannot be finite-time stable as long as the continuous solution corresponding to the initial value problem globally exists. In addition, some examples of stability analysis are revisited and linear Lyapunov function is used to prove the asymptotic stability of positive fractional-order nonlinear systems. 相似文献
78.
Halil Akçakaya 《Advanced Robotics》2014,28(9):601-611
Set point tracking control of autonomous underwater vehicle (AUV) via robust model predictive control (RMPC) is considered. Input-constrained RMPC with integral action, which has been developed in our previous work, is used to control the AUV in this study. In order to derive a RMPC control rule, non-linear dynamics of AUV with six degree of freedom is linearized at certain operating points. So, horizontal and vertical plane dynamics of system are represented by linear models which have polytopic uncertainties. Since the derived control rule will be used in real time, the computation time should be reduced. To overcome this computational time problem and get rid of trial–error step of Algorithm 1, a new algorithm is proposed here. The simulations are carried out using the control rule based on this algorithm and these results are presented. 相似文献
79.
《Journal of Process Control》2014,24(2):389-398
A hierarchical two-layer control algorithm is developed for a class of hybrid (discrete-continuous dynamic) systems to support economically optimal operation of batch or continuous processes with a predefined production schedule. For this class of hybrid systems, the optimal control moves as well as the controlled switching times between two adjacent modes are determined online. In contrast to closely related schemes for integrated scheduling and control, the sequence of modes is not optimized. On the upper layer, the economic optimal control problem is solved rigorously by a slow hybrid economic model predictive controller at a low sampling rate. On the lower layer, a fast hybrid neighboring-extremal controller is based on the same economic optimal control problem as the slow controller to ensure consistency between both layers. The fast neighboring-extremal controller updates rather than tracks the optimal trajectories from the upper layer to account for disturbances. Consequently, the fast controller steers the process to its operational bounds under disturbances and the economic potential of the process is exploited anytime. The suggested two-layer control algorithm provides fully consistent control action on the fast and slow time-scale and thus avoids performance degradation and even infeasibilities which are commonly encountered if inconsistent optimal control problems are formulated and solved. 相似文献
80.
《Journal of Process Control》2014,24(8):1260-1272
This study adapts the advanced step NMPC framework to Economic NMPC. Here, sufficient conditions for nominal stability are derived for NMPC controllers that incorporate economic stage costs with appropriate regularization. To guarantee these conditions, we derive a constructive strategy to calculate the regularization term directly. Moreover, we extend the sensitivity components in the advanced step NMPC framework to consider a rigorous path-following algorithm. This approach accounts for active set changes and allows much weaker constraint qualifications. Moreover, using an ℓ1 formulation of the NMPC problem satisfies these constraint qualifications and allows more reliable solution of the moving horizon optimization problem, even in the presence of noise. Finally, all of these concepts are demonstrated on a detailed case study with a continuously stirred tank reactor. 相似文献