全文获取类型
收费全文 | 3558篇 |
免费 | 499篇 |
国内免费 | 163篇 |
专业分类
电工技术 | 113篇 |
综合类 | 467篇 |
化学工业 | 122篇 |
金属工艺 | 125篇 |
机械仪表 | 632篇 |
建筑科学 | 294篇 |
矿业工程 | 130篇 |
能源动力 | 73篇 |
轻工业 | 47篇 |
水利工程 | 73篇 |
石油天然气 | 43篇 |
武器工业 | 106篇 |
无线电 | 450篇 |
一般工业技术 | 663篇 |
冶金工业 | 35篇 |
原子能技术 | 17篇 |
自动化技术 | 830篇 |
出版年
2024年 | 4篇 |
2023年 | 50篇 |
2022年 | 72篇 |
2021年 | 94篇 |
2020年 | 92篇 |
2019年 | 80篇 |
2018年 | 82篇 |
2017年 | 126篇 |
2016年 | 122篇 |
2015年 | 136篇 |
2014年 | 232篇 |
2013年 | 239篇 |
2012年 | 325篇 |
2011年 | 348篇 |
2010年 | 215篇 |
2009年 | 192篇 |
2008年 | 222篇 |
2007年 | 250篇 |
2006年 | 203篇 |
2005年 | 179篇 |
2004年 | 153篇 |
2003年 | 184篇 |
2002年 | 106篇 |
2001年 | 88篇 |
2000年 | 83篇 |
1999年 | 61篇 |
1998年 | 44篇 |
1997年 | 47篇 |
1996年 | 41篇 |
1995年 | 29篇 |
1994年 | 27篇 |
1993年 | 23篇 |
1992年 | 18篇 |
1991年 | 8篇 |
1990年 | 9篇 |
1989年 | 5篇 |
1988年 | 6篇 |
1987年 | 7篇 |
1986年 | 3篇 |
1985年 | 2篇 |
1983年 | 5篇 |
1982年 | 2篇 |
1979年 | 1篇 |
1972年 | 1篇 |
1961年 | 2篇 |
1960年 | 1篇 |
1955年 | 1篇 |
排序方式: 共有4220条查询结果,搜索用时 15 毫秒
1.
2.
We have developed, based on the oscillating-center transformation, a general theoretical approach for self-consistent plasma dynamics including, explicitly, effects of nonlinear(higherorder) wave-particle resonances. A specific example is then given for low-frequency responses of trapped particles in axisymmetric tokamaks. Possible applications to transport as well as nonlinear wave growth/damping are also briefly discussed. 相似文献
3.
4.
In the early design stage, automotive modeling should both meet the requirements of aesthetics and engineering. Therefore, a vehicle CAD (computer aided design) model that can be easily adjusted by feedbacks is necessary. Based on CE-Bézier surface, this paper presents a set of algorithms for parametric segmentation and fairing surface generation in a car model. This model is defined by a simplified automotive template and relevant control points, shape parameters and segmentation parameters, which can be modified to alter the car form efficiently. With this model and the corresponding adjustment method, more than fifty various vehicle models are established in this research according to different parameters. And two methods for calculating similarity index between car models are constructed, which are suitable for brand design trend analysis and modelling design decisionmaking. 相似文献
5.
《Mechatronics》2015
In this paper, adaptive robust control (ARC) of fully-constrained cable driven parallel robots is studied in detail. Since kinematic and dynamic models of the robot are partly structurally unknown in practice, in this paper an adaptive robust sliding mode controller is proposed based on the adaptation of the upper bound of the uncertainties. This approach does not require pre-knowledge of the uncertainties upper bounds and linear regression form of kinematic and dynamic models. Moreover, to ensure that all cables remain in tension, proposed control algorithm benefit the internal force concept in its structure. The proposed controller not only keeps all cables under tension for the whole workspace of the robot, it is chattering-free, computationally simple and it does not require measurement of the end-effector acceleration. The stability of the closed-loop system with proposed control algorithm is analyzed through Lyapunov second method and it is shown that the tracking error will remain uniformly ultimately bounded (UUB). Finally, the effectiveness of the proposed control algorithm is examined through some experiments on a planar cable driven parallel robot and it is shown that the proposed controller is able to provide suitable tracking performance in practice. 相似文献
6.
Output feedback controller for polytopic systems exploiting the direct searching of the design space
This paper deals with the problem of designing a robust static output feedback controller for polytopic systems. The current research that tackled this problem is mainly based on LMI method, which is conservative by nature. In this paper, a novel approach is proposed, which considers the design space of the controller parameters and iteratively partitions the space to small simplexes. Then, by assessing the stability in each simplex, the solution space for design parameters is directly determined. It has been theoretically proved that, if there exists a feasible solution in the design space, the algorithm can find it. To validate the result of the proposed approach, comparative simulation examples are given to illustrate the performance of the design methodology as compared to those of previous approaches. 相似文献
7.
主动声呐信号处理中一般采用匹配滤波和背景均衡等算法检测回波信号,为提高信号的检测性能,还需利用信号与混响和环境噪声在时间、空间上的统计特征差异。文章在对信号的时、空特征算法进行简单描述的基础上,提出了频率能量统计特征和方位能量统计特征,将两种特征检测器的输出进行融合处理构成时、空联合检测器。仿真和试验数据处理结果证明,此方法可有效提高机动小目标在混响及环境噪声中的检测性能。 相似文献
8.
9.
The Wigner representation of parametric down conversion in the Heisenberg picture is applied to the study of the Rome teleportation experiment. We investigate the physical meaning of the zeropoint inputs at the different areas of the experimental set-up. In particular, we establish a quantitative relationship between the zeropoint sets of modes that are needed for the preparation of the quantum state to be teleported, the idle channels inside the one-photon polarization-momentum Bell-state analyser, and the possibility of performing teleportation of a polarization state with certainty. 相似文献
10.
Parametric study on the thermoelectric conversion performance of a concentrated solar‐driven thermionic‐thermoelectric hybrid generator 下载免费PDF全文
A concentrated solar‐driven thermionic‐thermoelectric hybrid generator composed of solar heat collector, thermionic generator (TIG), thermoelectric generator (TEG), and radiator is introduced in this paper. A theoretical model of thermoelectric conversion performance for the hybrid generator is built up based on the heat source of the concentrated solar radiation rather than isothermal heat source. Based on the model, the impacts of related parameters on the internal temperature distributions, output power, and efficiency have been discussed. Moreover, the optimal operating conditions of the TIG‐TEG hybrid device at its maximum output power and efficiency have been determined. Results show that when cascading the TEG with the TIG, there is very little change of the TIG cathode temperature in most conditions, namely, TC ≈ TC′. Meanwhile, the anode temperature becomes higher, and the TEG cold end temperature T2 is close to the anode temperature TA′ for the single TIG system, ie, TA > TA′ ≈ T2. In theory, the optimal concentrated solar radiation I0 for the maximum output power Pmax and the maximum efficiency ηmax differs, which are I0,P = 2.5 × 106 W/m2 and I0,η = 2 × 106 W/m2, respectively, whereas the output power and efficiency of the TIG‐TEG hybrid system simultaneously reach their maximum values when the optimal TIG anode temperature TA,opt = 1025 K, the optimal TIG output voltage Vopt = 2 V, and the optimal ratio of load resistance to internal resistance (R2/R)opt = 2. However, in practice, the parameter values of I0, ΦA, and TA should be strictly controlled under 1.8 × 106 W/m2, 1.4 eV, and 660 K, respectively. Generally, the maximum output power and efficiency of the hybrid TIG‐TEG system are, respectively, 35% and 4% higher than that of the single TIG. 相似文献