全文获取类型
收费全文 | 4363篇 |
免费 | 253篇 |
国内免费 | 3篇 |
专业分类
电工技术 | 58篇 |
化学工业 | 1248篇 |
金属工艺 | 146篇 |
机械仪表 | 78篇 |
建筑科学 | 93篇 |
矿业工程 | 12篇 |
能源动力 | 134篇 |
轻工业 | 573篇 |
水利工程 | 9篇 |
石油天然气 | 9篇 |
无线电 | 95篇 |
一般工业技术 | 678篇 |
冶金工业 | 1063篇 |
原子能技术 | 23篇 |
自动化技术 | 400篇 |
出版年
2023年 | 24篇 |
2022年 | 118篇 |
2021年 | 276篇 |
2020年 | 99篇 |
2019年 | 88篇 |
2018年 | 158篇 |
2017年 | 155篇 |
2016年 | 170篇 |
2015年 | 125篇 |
2014年 | 170篇 |
2013年 | 287篇 |
2012年 | 183篇 |
2011年 | 230篇 |
2010年 | 156篇 |
2009年 | 137篇 |
2008年 | 123篇 |
2007年 | 130篇 |
2006年 | 77篇 |
2005年 | 62篇 |
2004年 | 65篇 |
2003年 | 55篇 |
2002年 | 47篇 |
2001年 | 30篇 |
2000年 | 32篇 |
1999年 | 28篇 |
1998年 | 186篇 |
1997年 | 207篇 |
1996年 | 141篇 |
1995年 | 96篇 |
1994年 | 47篇 |
1993年 | 71篇 |
1992年 | 22篇 |
1991年 | 13篇 |
1990年 | 19篇 |
1989年 | 20篇 |
1988年 | 19篇 |
1987年 | 15篇 |
1986年 | 16篇 |
1985年 | 20篇 |
1984年 | 33篇 |
1983年 | 24篇 |
1982年 | 43篇 |
1981年 | 50篇 |
1980年 | 56篇 |
1979年 | 29篇 |
1978年 | 41篇 |
1977年 | 110篇 |
1976年 | 242篇 |
1975年 | 15篇 |
1973年 | 13篇 |
排序方式: 共有4619条查询结果,搜索用时 390 毫秒
101.
Fatemeh Noroozi Tomasz Sapiński Dorota Kamińska Gholamreza Anbarjafari 《International Journal of Speech Technology》2017,20(2):239-246
This paper proposes a new vocal-based emotion recognition method using random forests, where pairs of the features on the whole speech signal, namely, pitch, intensity, the first four formants, the first four formants bandwidths, mean autocorrelation, mean noise-to-harmonics ratio and standard deviation, are used in order to recognize the emotional state of a speaker. The proposed technique adopts random forests to represent the speech signals, along with the decision-trees approach, in order to classify them into different categories. The emotions are broadly categorised into the six groups, which are happiness, fear, sadness, neutral, surprise, and disgust. The Surrey Audio-Visual Expressed Emotion database is used. According to the experimental results using leave-one-out cross-validation, by means of combining the most significant prosodic features, the proposed method has an average recognition rate of \(66.28\%\), and at the highest level, the recognition rate of \(78\%\) has been obtained, which belongs to the happiness voice signals. The proposed method has \(13.78\%\) higher average recognition rate and \(28.1\%\) higher best recognition rate compared to the linear discriminant analysis as well as \(6.58\%\) higher average recognition rate than the deep neural networks results, both of which have been implemented on the same database. 相似文献
102.
We discuss a family of states describing three-qubit systems in a context of quantum steering phenomena. We show that symmetric steering cannot appear between two qubits—only asymmetric steering can appear in such systems. The main aim of this paper is to discuss the possible relations between the entanglement measures and steering parameter for two-mode mixed state corresponding to the qubit–qubit subsystem. We have derived the conditions determining boundary values of the negativity parametrized by concurrence. We show that two-qubit mixed state cannot be steerable when the negativity of such state is smaller than, or equal to, its boundary value. Finally, we have found ranges of the values of the mixedness measure, parametrized by concurrence and negativity for steerable and unsteerable two-qubit mixed states. 相似文献
103.
104.
Mariusz Janiak Krzysztof Tchoń 《Systems & Control Letters》2011,60(8):625-631
This paper addresses the constrained motion planning problem for nonholonomic systems represented by driftless control systems with output. The problem consists in defining a control function driving the system output to a desirable point at a given time instant, whereas state and control variables remain over the control horizon within prescribed bounds. The state and control constraints are handled by extending the control system with a pair of state equations driven by the violation of constraints, and adding regularizing perturbations. For the regularized system a Jacobian motion planning algorithm is designed, called imbalanced. Solutions of example constrained motion planning problems for the rolling ball illustrate the theoretical concepts. 相似文献
105.
Michell’s problem of optimizing truss topology for stress or compliance constraints under a single load condition is solved
analytically for plane trusses having a square-shaped line support. Geometrical characteristics of the Hencky nets giving
the truss layout are expressed in terms of Lommel functions. Analytically derived truss volumes for the above problem are
compared with those of trusses supported along circles of equivalent area. Some general implications of the results are also
discussed. 相似文献
106.
Comments on the effect of yttrium on the early stages of oxidation of alumina formers 总被引:3,自引:0,他引:3
Jerzy Jedliński 《Oxidation of Metals》1993,39(1-2):55-60
107.
The precipitation process in alloys containing 4% Ti and 5 to 16% Ni was investigated using transmission electron microscopy, hardness and electrical conductivity measurements. After ageing, spherical -Ni3Ti precipitates with ordered DO22 superlattice were observed in alloys CuTiNi5 to 10 and the L12 superlattice in the CuTi4Ni16 alloy. With increasing nickel content the size of precipitates decreases; this has only a minor influence on the age hardening. The CuTiNi10 alloy has the best electrical conductivity approaching 18m–1mm–2. 相似文献
108.
Edyta Szymańska 《Information Processing Letters》2012,112(23):899-902
109.
The Parity Path problem is to decide if a given graph contains both an induced path of odd length and an induced path of even length between two specified vertices. In the related problems Odd Induced Path and Even Induced Path, the goal is to determine whether an induced path of odd, respectively even, length between two specified vertices exists. Although all three problems are NP-complete in general, we show that they can be solved in $\mathcal{O}(n^{5})$ time for the class of claw-free graphs. Two vertices s and t form an even pair in G if every induced path from s to t in G has even length. Our results imply that the problem of deciding if two specified vertices of a claw-free graph form an even pair, as well as the problem of deciding if a given claw-free graph has an even pair, can be solved in $\mathcal{O}(n^{5})$ time and $\mathcal{O}(n^{7})$ time, respectively. We also show that we can decide in $\mathcal{O}(n^{7})$ time whether a claw-free graph has an induced cycle of given parity through a specified vertex. Finally, we show that a shortest induced path of given parity between two specified vertices of a claw-free perfect graph can be found in $\mathcal {O}(n^{7})$ time. 相似文献
110.