全文获取类型
收费全文 | 13330篇 |
免费 | 223篇 |
国内免费 | 154篇 |
专业分类
电工技术 | 189篇 |
综合类 | 8篇 |
化学工业 | 940篇 |
金属工艺 | 504篇 |
机械仪表 | 126篇 |
建筑科学 | 163篇 |
矿业工程 | 3篇 |
能源动力 | 242篇 |
轻工业 | 303篇 |
水利工程 | 55篇 |
石油天然气 | 87篇 |
无线电 | 729篇 |
一般工业技术 | 730篇 |
冶金工业 | 164篇 |
原子能技术 | 102篇 |
自动化技术 | 9362篇 |
出版年
2024年 | 12篇 |
2023年 | 118篇 |
2022年 | 207篇 |
2021年 | 273篇 |
2020年 | 182篇 |
2019年 | 192篇 |
2018年 | 229篇 |
2017年 | 168篇 |
2016年 | 177篇 |
2015年 | 112篇 |
2014年 | 347篇 |
2013年 | 441篇 |
2012年 | 932篇 |
2011年 | 3247篇 |
2010年 | 1260篇 |
2009年 | 1134篇 |
2008年 | 764篇 |
2007年 | 641篇 |
2006年 | 517篇 |
2005年 | 633篇 |
2004年 | 569篇 |
2003年 | 611篇 |
2002年 | 306篇 |
2001年 | 35篇 |
2000年 | 28篇 |
1999年 | 50篇 |
1998年 | 117篇 |
1997年 | 43篇 |
1996年 | 37篇 |
1995年 | 16篇 |
1994年 | 21篇 |
1993年 | 24篇 |
1992年 | 26篇 |
1991年 | 13篇 |
1990年 | 17篇 |
1989年 | 21篇 |
1988年 | 24篇 |
1987年 | 11篇 |
1986年 | 22篇 |
1985年 | 17篇 |
1984年 | 30篇 |
1983年 | 19篇 |
1982年 | 11篇 |
1981年 | 13篇 |
1980年 | 6篇 |
1979年 | 5篇 |
1978年 | 8篇 |
1977年 | 4篇 |
1976年 | 7篇 |
1974年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
121.
Generalized adaptive notch filters with frequency debiasing for tracking of polynomial phase systems
Generalized adaptive notch filters are used for identification/tracking of quasi-periodically varying dynamic systems and can be considered an extension, to the system case, of classical adaptive notch filters. For general patterns of frequency variation the generalized adaptive notch filtering algorithms yield biased frequency estimates. We show that when system frequencies change slowly in a smooth way, the estimation bias can be substantially reduced by means of post-filtering of the frequency estimates. The modified (debiased) algorithm has better tracking capabilities than the original algorithm. 相似文献
122.
In this paper we introduce a new symmetry feature named “symmetry kernel” (SK) to support a measure of symmetry. Given any symmetry transform S, SK of a pattern P is the maximal included symmetric sub-set of P for all directions and shifts. We provide a first algorithm to exhibit this kernel where the centre of symmetry is assumed to be the centre of mass. Then we prove that, in any direction, the optimal axis corresponds to the maximal correlation of a pattern with its symmetric version. That leads to a second algorithm. The associated symmetry measure is a modified difference between the respective surfaces of a pattern and its kernel. A series of experiments supports the actual algorithm validation. 相似文献
123.
Alireza Karimi Author VitaeAuthor Vitae 《Automatica》2007,43(8):1395-1402
Robust control synthesis of linear time-invariant SISO polytopic systems is investigated using the polynomial approach. A convex set of all stabilizing controllers for a polytopic system is given over an infinite-dimensional space. A finite-dimensional approximation of this set is obtained using the orthonormal basis functions and represented by a set of LMIs thanks to the KYP lemma. Then, an LMI based convex optimization problem for robust pole placement with sensitivity function shaping in two- and infinity-norm is proposed. The simulation results show the effectiveness of the proposed method. 相似文献
124.
Robert Jenssen Author Vitae Deniz Erdogmus Author Vitae Author Vitae Jose C. Principe Author Vitae Author Vitae 《Pattern recognition》2007,40(3):796-806
We introduce a new graph cut for clustering which we call the Information Cut. It is derived using Parzen windowing to estimate an information theoretic distance measure between probability density functions. We propose to optimize the Information Cut using a gradient descent-based approach. Our algorithm has several advantages compared to many other graph-based methods in terms of determining an appropriate affinity measure, computational complexity, memory requirements and coping with different data scales. We show that our method may produce clustering and image segmentation results comparable or better than the state-of-the art graph-based methods. 相似文献
125.
Mohamed Abid Author Vitae 《Computers & Electrical Engineering》2007,33(4):231-232
126.
127.
128.
Chen-Tsung Kuo Author Vitae 《Pattern recognition》2007,40(2):742-755
Three dimensional models play an important role in many applications; the problem is how to select the appropriate models from a 3D database rapidly and accurately. In recent years, a variety of shape representations, statistical methods, and geometric algorithms have been proposed for matching 3D shapes or models. In this paper, we propose a 3D shape representation scheme based on a combination of principal plane analysis and dynamic programming. The proposed 3D shape representation scheme consists of three steps. First, a 3D model is transformed into a 2D image by projecting the vertices of the model onto its principal plane. Second, the convex hall of the 2D shape of the model is further segmented into multiple disjoint triangles using dynamic programming. Finally, for each triangle, a projection score histogram and moments are extracted as the feature vectors for similarity searching. Experimental results showed the robustness of the proposed scheme, which resists translation, rotation, scaling, noise, and destructive attacks. The proposed 3D model retrieval method performs fairly well in retrieving models having similar characteristics from a database of 3D models. 相似文献
129.
The electrical properties of CdTe thin film have been studied and discussed, including, the conduction mechanism, and the effect of temperature and indium doping on the current passing through the CdTe film and hence on the film conductivity. It is observed that the CdTe film is of the modified Poole–Frenkel conduction mechanism and the resistivity of the film can be lowered by more than one order of magnitude due to indium doping. 相似文献
130.
Sheng-Guo Wang Author Vitae 《Automatica》2003,39(3):525-532
This paper presents a general analysis of robust pole clustering in a good ride quality region (GRQR) of aircraft for matrices with structured uncertainties. This region is an intersection of a ring and a horizontal strip, located in the left half-plane, which is a specific non-Ω-transformable region providing good ride quality of aircraft. The paper applies the Rayleigh principle along the norm theory to analyze robust pole clustering within this region since the generalized Lyapunov theory is not valid for non-Ω-transformable regions. Concerned uncertainties are structured/parametric uncertainties, including interval matrices. The results are useful for robust control analysis and design, especially, of robust good ride quality of aircraft, shuttles, vehicles and space station, as well as some industrial systems. An example of the F-16 dynamics for which GRQR is suitable is included to illustrate the results. 相似文献