全文获取类型
收费全文 | 25368篇 |
免费 | 3723篇 |
国内免费 | 3033篇 |
专业分类
电工技术 | 2904篇 |
综合类 | 3381篇 |
化学工业 | 848篇 |
金属工艺 | 377篇 |
机械仪表 | 1728篇 |
建筑科学 | 1128篇 |
矿业工程 | 428篇 |
能源动力 | 560篇 |
轻工业 | 465篇 |
水利工程 | 618篇 |
石油天然气 | 424篇 |
武器工业 | 297篇 |
无线电 | 3236篇 |
一般工业技术 | 1422篇 |
冶金工业 | 610篇 |
原子能技术 | 217篇 |
自动化技术 | 13481篇 |
出版年
2024年 | 116篇 |
2023年 | 313篇 |
2022年 | 457篇 |
2021年 | 591篇 |
2020年 | 782篇 |
2019年 | 774篇 |
2018年 | 724篇 |
2017年 | 934篇 |
2016年 | 1107篇 |
2015年 | 1177篇 |
2014年 | 1624篇 |
2013年 | 1891篇 |
2012年 | 1971篇 |
2011年 | 2119篇 |
2010年 | 1683篇 |
2009年 | 1812篇 |
2008年 | 1896篇 |
2007年 | 1983篇 |
2006年 | 1699篇 |
2005年 | 1479篇 |
2004年 | 1173篇 |
2003年 | 1015篇 |
2002年 | 740篇 |
2001年 | 667篇 |
2000年 | 578篇 |
1999年 | 431篇 |
1998年 | 335篇 |
1997年 | 311篇 |
1996年 | 275篇 |
1995年 | 255篇 |
1994年 | 205篇 |
1993年 | 171篇 |
1992年 | 151篇 |
1991年 | 133篇 |
1990年 | 120篇 |
1989年 | 89篇 |
1988年 | 54篇 |
1987年 | 39篇 |
1986年 | 17篇 |
1985年 | 28篇 |
1984年 | 29篇 |
1983年 | 35篇 |
1982年 | 16篇 |
1981年 | 15篇 |
1980年 | 13篇 |
1979年 | 10篇 |
1976年 | 9篇 |
1964年 | 7篇 |
1963年 | 8篇 |
1961年 | 10篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
A knowledge-based system (KBS) for diagnosis of multiple defects in injection molding is presented. The general scheme for knowledge representation based on fuzzy set theory has been shown useful in representing inexact and incomplete information for developing the KBS. An optimality criterion is created for selecting a simple and best cover to explain the given problem. An efficient search algorithm for finding such cover is also discussed. 相似文献
72.
A robustness analysis and synthesis for incomplete nonlinear decoupling for a class of nonlinear systems is discussed. Rigid and elastic-joint robot models belong to this class. For the elastic case, a transformation facilitates the robustness analysis under a weak assumption. Charts with H
1- and H
- norms of closed-loop disturbance transfer functions of the nonlinear-decoupled system are presented for a robust pole assignment. 相似文献
73.
74.
针对一类由局部状态空间(LSS)Fornasini-Marchesini(FM)第二模型描述的,具有时变状态滞后的2-D离散系统,其中时变滞后项的上、下界均为正实数,研究了其稳定性和控制综合问题。首先,利用Lyapunov-Krasovski泛函方法,提出了系统的稳定性准则。再根据这一准则,分别设计状态反馈和动态输出反馈控制器保证系统的稳定性。状态反馈控制律和输出反馈矩阵可由线性矩阵不等式(LMI)求得。最后,通过数值算例说明所得结果的有效性。 相似文献
75.
J. De Caigny J. F. Camino R. C. L. F. Oliveira P. L. D. Peres J. Swevers 《国际强度与非线性控制杂志
》2012,22(5):535-558
》2012,22(5):535-558
This paper presents synthesis conditions for the design of gain‐scheduled dynamic output feedback controllers for discrete‐time linear parameter‐varying systems. The state‐space matrix representation of the plant and of the controller can have a homogeneous polynomial dependency of arbitrary degree on the scheduling parameter. As an immediate extension, conditions for the synthesis of a multiobjective ??∞ and ??2 gain‐scheduled dynamic feedback controller are also provided. The scheduling parameters vary inside a polytope and are assumed to be a priori unknown, but measured in real‐time. If bounds on the rate of parameter variation are known, they can be taken into account, providing less conservative results. The geometric properties of the uncertainty domain are exploited to derive finite sets of linear matrix inequalities based on the existence of a homogeneous polynomially parameter‐dependent Lyapunov function. An application of the control design to a realistic engineering problem illustrates the benefits of the proposed approach. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
76.
This paper addresses the problem of semi‐global stabilization by output feedback for a class of nonlinear systems whose output gains are unknown. For each subsystem, we first design a state compensator and use the compensator states to construct a control law to stabilize the nominal linear system without the perturbing nonlinearities. Then, combining the output feedback domination approach with block‐backstepping scheme, a series of homogeneous output feedback controllers are constructed recursively for each subsystem and the closed‐loop system is rendered semi‐globally asymptotically stable. 相似文献
77.
In this paper, the authors address the problem of edge-perception for its applications to vision-feedback control in robotic systems.In natural vision, the recognition of objects takes place through the process consisting of eye system, neural networks and cognition. The cognitive process, in turn yields a phenomenon known as perception. This is the phenomenon of perception of physical attributes, such as edges, color and texture, etc., which is responsible for the recognition of objects through the natural vision processes.In this paper, we make an attempt to postulate the theory of perception for gray-level images. The gray-level images, when going through the cognitive and perception processes, are contaminated by the uncertainty; here we call it cognitive uncertainty.The studies in this paper are confined to the phenomenon of edge-perception for two-dimensional gray-level images, however, these studies can be extended to other types of visual attributes both in two-dimensional and three-dimensional spaces. Indeed, the perception of these attributes, which attempts to emulate the human vision system, may help in the design of a truly robust computer vision-feedback control system for robotic applications. 相似文献
78.
The minimum flow requirements in the Svartå River in Sweden are directed at maintaining fishlife and providing suitable dilution for waste flows. The implications of varying the minimum flow requirements in the river are examined using a mixed integer optimisation model. The model is formulated as a modified method-of-weights technique with the economic issues of hydro-electricity generation, irrigation and urban water supply placed in the objective function and the minimum flows specified within the constraint set. The integer component of the model is required to model the operating policy at the major flow regulation facility in the system and the restricted validity of the irrigation permits. Application of the model shows that in dry years where competition between minimum flow levels and the other economic uses, is most intense, the levels achieved by the various economic objectives are only slightly reduced even with significant increases in the minimum flow requirements. Variations in minimum flow requirements of up to 45% only produce changes of 10% or less in the economic objectives. The lack of sensitivity of the objective levels is due primarily to the level of control exerted indirectly on the whole system in dry years by the release regulation policy and the restricted validity of the irrigation permits. In normal to wet years these policies are not as restrictive and more choice is available. In such years, however, there is generally sufficient water to satisfy all requirements and allocation is not a critical issue. The model itself is formulated generally so that a range of scenarios beyond those examined specifically in the paper can be considered. 相似文献
79.
为了进一步研究旋转对固体火箭发动机工作的影响,采用RSM湍流模型对内孔燃烧、内孔与端面同时燃烧管状装药旋转固体火箭发动机统一流场进行了仿真。采用UDF编程给出质量入口边界,获得了旋转条件下发动机内流场结构参数特点,并给予理论说明。计算结果表明,内孔燃烧装药发动机切向速度流场类似于典型的Rankine涡,端面和内孔同时燃烧装药发动机切向速度流场呈现出Rankine涡和由端面燃烧引起的强迫涡的复杂组合涡;在发动机前封头和喷管喉部涡核切向速度峰值非常大,使燃烧室前封头和喷管喉部工作环境显著恶化;旋转使发动机燃烧室压力沿径向逐渐增大,强迫涡附近的压力梯度远大于推进剂表面的压力梯度。 相似文献
80.