全文获取类型
收费全文 | 83536篇 |
免费 | 954篇 |
国内免费 | 406篇 |
专业分类
电工技术 | 770篇 |
综合类 | 2316篇 |
化学工业 | 11382篇 |
金属工艺 | 4779篇 |
机械仪表 | 3012篇 |
建筑科学 | 2151篇 |
矿业工程 | 562篇 |
能源动力 | 1096篇 |
轻工业 | 3567篇 |
水利工程 | 1270篇 |
石油天然气 | 341篇 |
无线电 | 9222篇 |
一般工业技术 | 16265篇 |
冶金工业 | 2618篇 |
原子能技术 | 253篇 |
自动化技术 | 25292篇 |
出版年
2019年 | 8篇 |
2018年 | 14453篇 |
2017年 | 13378篇 |
2016年 | 9958篇 |
2015年 | 606篇 |
2014年 | 224篇 |
2013年 | 185篇 |
2012年 | 3132篇 |
2011年 | 9390篇 |
2010年 | 8268篇 |
2009年 | 5530篇 |
2008年 | 6762篇 |
2007年 | 7767篇 |
2006年 | 106篇 |
2005年 | 1201篇 |
2004年 | 1120篇 |
2003年 | 1165篇 |
2002年 | 531篇 |
2001年 | 93篇 |
2000年 | 174篇 |
1999年 | 54篇 |
1998年 | 49篇 |
1997年 | 27篇 |
1996年 | 43篇 |
1995年 | 8篇 |
1994年 | 11篇 |
1993年 | 8篇 |
1992年 | 11篇 |
1991年 | 22篇 |
1988年 | 9篇 |
1969年 | 24篇 |
1968年 | 43篇 |
1967年 | 33篇 |
1966年 | 42篇 |
1965年 | 44篇 |
1964年 | 11篇 |
1963年 | 28篇 |
1962年 | 22篇 |
1961年 | 18篇 |
1960年 | 30篇 |
1959年 | 35篇 |
1958年 | 37篇 |
1957年 | 36篇 |
1956年 | 34篇 |
1955年 | 63篇 |
1954年 | 68篇 |
1953年 | 5篇 |
1952年 | 6篇 |
1950年 | 6篇 |
1949年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
This paper presents an approach in designing a robust controller for vehicle suspensions considering changes in vehicle inertial properties. A four-degree-of-freedom half-car model with active suspension is studied in this paper, and three main performance requirements are considered. Among these requirements, the ride comfort performance is optimized by minimizing the H∞ norm of the transfer function from the road disturbance to the sprung mass acceleration, while the road holding performance and the suspension deflection limitation are guaranteed by constraining the generalized H2 (GH2) norms of the transfer functions from the road disturbance to the dynamic tyre load and the suspension deflection to be less than their hard limits, respectively. At the same time, the controller saturation problem is considered by constraining its peak response output to be less than a given limit using the GH2 norm as well. By solving the finite number of linear matrix inequalities (LMIs) with the minimization optimization procedure, the controller gains, which are dependent on the time-varying inertial parameters, can be obtained. Numerical simulations on both frequency and bump responses show that the designed parameter-dependent controller can achieve better active suspension performance compared with the passive suspension in spite of the variations of inertial parameters. 相似文献
992.
Two model reference adaptive system (MRAS) estimators are developed for identifying the parameters of permanent magnet synchronous motors (PMSM) based on the Lyapunov stability theorem and the Popov stability criterion, respectively. The proposed estimators only need online measurement of currents, voltages, and rotor speed to effectively estimate stator resistance, inductance, and rotor flux-linkage simultaneously. The performance of the estimators is compared and verified through simulations and experiments, which show that the two estimators are simple, have good robustness against parameter variation, and are accurate in parameter tracking. However, the estimator based on the Popov stability criterion, which can overcome parameter variation in a practical system, is superior in terms of response speed and convergence speed since there are both proportional and integral units in the estimator, in contrast to only one integral unit in the estimator based on the Lyapunov stability theorem. In addition, the estimator based on the Popov stability criterion does not need the expertise that is required in designing a Lyapunov function. 相似文献
993.
Direct piezoelectricity of electro-active papers(EAPap)is analysed in this paper. The test setups for direct effect are designed and determined. Different ambient factors impacting the piezoelectricity of EAPap, such as temperature, humidity, and strain rate, are applied and analyzed. Strong piezoelectricity of EAPap is found on the basis of the test results and in comparison with polyvinylidene fluoride(PVDF)and lead zirconate titanate(PZT)-5H. The maximum piezoelectric constant is achieved to be 504 pC/N. The reason of strong piezoelectricity of EAPap is discussed in this paper. The potential of EAPap as a biomimetic actuator and sensor is also investigated. 相似文献
994.
Chun-Chieh Wang Kuo-Hsien Hsia Kuo-Lan Su Yi-Chun Hsieh Chyun-Luen Lin 《Artificial Life and Robotics》2010,15(3):284-290
As one of the major steps toward a fully intelligent autonomous robotic weapon, we have made progress in three major areas,
(1) design of the surveillance system by an AVR microcontroller, (2) implementation of the design mechanism, and (3) performance
of the human- machine interface surveillance system via the LabVIEW graphical programming environment, so that the supervisor
can control the vehicle with a keyboard or a specially adapted mouse. In order to accomplish all these achievements, there
have been major additions and overhauls in both system software codes and system circuit board developments. All these developments,
including a new algorithm and hardware implementation, are described in this article. The experimental results have shown
the practicality of the AVR microcontroller, the LabVIEW graphical programming environment, and ZigBee wireless technology
applied to a robotic weapon. 相似文献
995.
996.
In this paper, we search for theoretical limitations of the Tile Assembly Model (TAM), along with techniques to work around such limitations. Specifically, we investigate
the self-assembly of fractal shapes in the TAM. We prove that no self-similar fractal weakly self-assembles at temperature
1 in a locally deterministic tile assembly system, and that certain kinds of discrete self-similar fractals do not strictly
self-assemble at any temperature. Additionally, we extend the fiber construction of Lathrop et al. (2009) to show that any discrete self-similar fractal belonging to a particular class of “nice” discrete self-similar fractals
has a fibered version that strictly self-assembles in the TAM. 相似文献
997.
Lev Goldfarb 《Natural computing》2010,9(2):365-379
My main objective is to point out a fundamental weakness in the conventional conception of computation and suggest a promising way out. This weakness is directly related
to a gross underestimation of the role of object representation in a computational model, hence confining such models to an
unrealistic (input) environment, which, in turn, leads to “unnatural” computational models. This lack of appreciation of the
role of structural object representation has been inherited from logic and partly from mathematics, where, in the latter, the centuries-old tradition is to represent
objects as unstructured “points”. I also discuss why the appropriate fundamental reorientation in the conception of computational
models will bring the resulting study of computation closer to the “natural” computational constrains. An example of the pertinent,
class-oriented, representational formalism developed by our group over many years—Evolving Transformation System (ETS)—is
briefly outlined here, and several related general lines of research are suggested. 相似文献
998.
This article proposes an optimization–simulation model for planning the transport of supplies to large public infrastructure
works located in congested urban areas. The purpose is to minimize their impact on the environment and on private transportation
users on the local road network. To achieve this goal, the authors propose and solve an optimization problem for minimizing
the total system cost made up of operating costs for various alternatives for taking supplies to the worksite and the costs
supported by private vehicle users as a result of increased congestion due to the movement of heavy goods vehicles transporting
material to the worksite. The proposed optimization problem is a bi-level Math Program model. The upper level defines the
total cost of the system, which is minimized taking into account environmental constraints on atmospheric and noise pollution.
The lower level defines the optimization problem representing the private transportation user behavior, assuming they choose
the route that minimizes their total individual journey costs. Given the special characteristics of the problem, a heuristic
algorithm is proposed for finding optimum solutions. Both the model developed and the specific solution algorithm are applied
to the real case of building a new port at Laredo (Northern Spain). A series of interesting conclusions are obtained from
the corresponding sensitivity analysis. 相似文献
999.
This research focuses on pre-disaster transportation network protection against uncertain future disasters. Given limited
resources, the goal of the central planner is to choose the best set of network components to protect while allowing the network
users to follow their own best-perceived routes in any resultant network configuration. This problem is formulated as a two-stage
stochastic programming problem with equilibrium constraints, where the objective is to minimize the total expected physical
and social losses caused by potential disasters. Developing efficient solution methods for such a problem can be challenging.
In this work, we will demonstrate the applicability of progressive hedging-based method for solving large scale stochastic
network optimization problems with equilibrium constraints. In the proposed solution procedure, we solve each modified scenario
sub-problem as a mathematical program with complementary constraints and then gradually aggregate scenario-dependent solutions
to the final optimal solution. 相似文献
1000.