全文获取类型
收费全文 | 2511篇 |
免费 | 281篇 |
国内免费 | 195篇 |
专业分类
电工技术 | 748篇 |
综合类 | 332篇 |
化学工业 | 245篇 |
金属工艺 | 144篇 |
机械仪表 | 186篇 |
建筑科学 | 224篇 |
矿业工程 | 85篇 |
能源动力 | 101篇 |
轻工业 | 36篇 |
水利工程 | 89篇 |
石油天然气 | 75篇 |
武器工业 | 12篇 |
无线电 | 134篇 |
一般工业技术 | 113篇 |
冶金工业 | 88篇 |
原子能技术 | 26篇 |
自动化技术 | 349篇 |
出版年
2024年 | 8篇 |
2023年 | 28篇 |
2022年 | 38篇 |
2021年 | 55篇 |
2020年 | 69篇 |
2019年 | 50篇 |
2018年 | 49篇 |
2017年 | 54篇 |
2016年 | 59篇 |
2015年 | 96篇 |
2014年 | 133篇 |
2013年 | 121篇 |
2012年 | 170篇 |
2011年 | 181篇 |
2010年 | 145篇 |
2009年 | 130篇 |
2008年 | 164篇 |
2007年 | 173篇 |
2006年 | 184篇 |
2005年 | 160篇 |
2004年 | 109篇 |
2003年 | 126篇 |
2002年 | 110篇 |
2001年 | 65篇 |
2000年 | 77篇 |
1999年 | 73篇 |
1998年 | 42篇 |
1997年 | 47篇 |
1996年 | 53篇 |
1995年 | 46篇 |
1994年 | 36篇 |
1993年 | 24篇 |
1992年 | 16篇 |
1991年 | 22篇 |
1990年 | 26篇 |
1989年 | 13篇 |
1988年 | 9篇 |
1987年 | 8篇 |
1986年 | 1篇 |
1985年 | 2篇 |
1984年 | 4篇 |
1983年 | 3篇 |
1981年 | 2篇 |
1980年 | 1篇 |
1979年 | 2篇 |
1977年 | 2篇 |
1959年 | 1篇 |
排序方式: 共有2987条查询结果,搜索用时 15 毫秒
1.
Xueye Chen Yue Tian 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2020,95(3):806-812
Since the beginning of the 21st Century, the development of microfluidic chip technology has been very rapid and has attracted the attention of more and more scholars. As an important part of the microfluidic chip, the performance of the micromixer is critical. The fractal structure in the microchannels helps to improve the mixing performance of the micromixer and improve the mixing efficiency of the micromixer. The research results of other scholars are of great significance to the research of the present paper, which mainly studies the effect of changing the baffle state on the mixing efficiency of the micromixer based on the Koch fractal principle. Through simulation analysis, it was found that the mixing efficiency of the baffles distributed on both sides of the microchannel was higher than the mixing efficiency of the baffles distributed on the microchannel side. When the distance between adjacent baffles was divided into 0.15, 0.25 and 0.35 mm, simulated data suggested that the baffle distance of 0.15 mm was best. Increasing the number of baffles from six to eight groups increased the mixing path of the fluid in the microchannel and improved mixing efficiency. A comparison of mixing efficiencies of the 0°, 15° and 30° baffle angles revealed that very significant improvement in mixing efficiency was obtained at 30°. © 2019 Society of Chemical Industry 相似文献
2.
不同折流板结构螺旋折流板换热器传热性能的比较(英文) 总被引:1,自引:0,他引:1
Numerical simulations were performed on flow and heat transfer performances of heat exchangers having six helical baffles of different baffle shapes and assembly configurations, i.e., two trisection baffle schemes, two quadrant baffle schemes, and two continuous helical baffle schemes. The temperature contour or the pressure contour and velocity contour plots with superimposed velocity vectors on meridian, transverse and unfolded concentric hexagonal slices are presented to obtain a full angular view. For the six helix baffled heat exchangers, the different patterns of the single vortex secondary flow and the shortcut leakage flow were depicted as wel as the heat transfer properties were compared. The results show that the optimum scheme among the six configurations is a circumferential overlap trisection helix baffled heat exchanger with a baffle incline angle of 20° (20°TCO) scheme with an anti-shortcut baffle structure, which exhibits the second highest pressure dropΔpo, the highest overal heat transfer coefficient K, shel-side heat transfer coefficient ho and shel-side average comprehensive index ho/Δpo. 相似文献
3.
Xuejun Xie Siying Zhang 《International Journal of Adaptive Control and Signal Processing》2002,16(1):39-59
This paper considers the adaptive pole‐placement control problem for system (1) with unmodelled dynamics ηn dominated by a small constant ε multiplied by a quantity independent of ε but tending to infinity as the past input, output, and noise grow. Using bounded external excitation and randomly varying truncation techniques, we give a design method of adaptive pole‐placement controller. It is shown that the closed‐loop system is globally stable, the estimation error for the parameter contained in the modelled part is of order ε, and the closed‐loop system under the adaptive pole‐placement control law is suboptimal in the sense of $$\mathop{\lim\sup}\limits_{{n\to\infty }}{1\over n}\mathop{\sum}\limits_{i=0}^n{\left({A^{*}(z)y_{n}‐L(z)C(z)w_{n}‐B(z)R(z)y_{n}^{*}}\right)^{2}{\leq}O({\varepsilon}^{2})+\gamma^{2}\mathop{\sum}\limits_{j=1}^q{b_{j}^{2}}}$$\nopagenumbers\end while the SPR condition used usually in other papers is replaced by a stability condition. Copyright © 2001 John Wiley & Sons, Ltd. 相似文献
4.
A Symbolic Pole/Zero Extraction Methodology Based on Analysis of Circuit Time-Constants 总被引:1,自引:0,他引:1
O. Guerra J. D. Rodríguez-García F. V. Fernández A. Rodríguez-Vázquez 《Analog Integrated Circuits and Signal Processing》2002,31(2):101-118
This paper introduces a methodology for symbolic pole/zero extraction based on the formulation of the time-constant matrix of the circuits. This methodology incorporates approximation techniques specifically devoted to achieve an optimum trade-off between accuracy and complexity of the symbolic root expressions. The capability to efficiently handle even large circuits will be demonstrated through several practical circuits. 相似文献
5.
本文提出了一种新的多变量解耦极点配置自校正前馈控制器,它具有使伺服跟踪性能和
随机调节性能两者均优的组合自校正特性.仿真例子说明了其有效性. 相似文献
6.
7.
8.
本文提出了一种新的限制输出个数减少随机多变量自适应控制中辨识参数的方法,并给出了减少辨识参数的极点配置自适应算法。虽然采用n个输入1个输出的减少辨识参数的模型来设计控制器,但所提出的控制器能够保证被控系统的几个输出跟踪参考输入信号,仿真结果表明,所提出的方法是成功的。 相似文献
9.
In this paper we have studied the control of linear systems with algebraic-equation constraint. A pole-assignment controller with two-layer structure for such constrained systems has been presented. The objective of the controller is to assign the desired poles to constrained system and simultaneously force the corresponding closed-loop system to satisfy the constraint. The conditions for the existence of pole-assignment controller are discussed in different cases. The implementation algorithm of pole-assignment controller is also presented. An example is given to illustrate the validity of the method in this paper. 相似文献
10.