全文获取类型
收费全文 | 3627篇 |
免费 | 217篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 13篇 |
综合类 | 2篇 |
化学工业 | 1558篇 |
金属工艺 | 48篇 |
机械仪表 | 59篇 |
建筑科学 | 88篇 |
矿业工程 | 6篇 |
能源动力 | 82篇 |
轻工业 | 686篇 |
水利工程 | 17篇 |
石油天然气 | 16篇 |
无线电 | 138篇 |
一般工业技术 | 541篇 |
冶金工业 | 150篇 |
原子能技术 | 11篇 |
自动化技术 | 430篇 |
出版年
2024年 | 6篇 |
2023年 | 75篇 |
2022年 | 409篇 |
2021年 | 357篇 |
2020年 | 125篇 |
2019年 | 124篇 |
2018年 | 138篇 |
2017年 | 150篇 |
2016年 | 136篇 |
2015年 | 108篇 |
2014年 | 157篇 |
2013年 | 214篇 |
2012年 | 232篇 |
2011年 | 240篇 |
2010年 | 173篇 |
2009年 | 181篇 |
2008年 | 172篇 |
2007年 | 147篇 |
2006年 | 115篇 |
2005年 | 98篇 |
2004年 | 76篇 |
2003年 | 62篇 |
2002年 | 59篇 |
2001年 | 34篇 |
2000年 | 28篇 |
1999年 | 34篇 |
1998年 | 34篇 |
1997年 | 28篇 |
1996年 | 25篇 |
1995年 | 19篇 |
1994年 | 9篇 |
1993年 | 12篇 |
1992年 | 3篇 |
1991年 | 7篇 |
1989年 | 4篇 |
1987年 | 3篇 |
1986年 | 3篇 |
1985年 | 2篇 |
1984年 | 5篇 |
1983年 | 5篇 |
1982年 | 4篇 |
1981年 | 4篇 |
1980年 | 2篇 |
1979年 | 6篇 |
1975年 | 3篇 |
1974年 | 3篇 |
1973年 | 2篇 |
1971年 | 4篇 |
1969年 | 2篇 |
1934年 | 1篇 |
排序方式: 共有3845条查询结果,搜索用时 10 毫秒
21.
Maria Elena Bruni Francesca Guerriero 《International Transactions in Operational Research》2010,17(2):207-220
The aim of this paper is to investigate the use of heuristic information to efficiently solve to optimality the robust shortest path problem. Starting from the exact algorithm proposed by Murty and Her, we describe how this algorithm can be enhanced by using heuristic rules and evaluation functions to guide the search. The efficiency of the proposed enhanced approach is tested over a range of random generated instances. Our computational results indicate that the use of heuristic criteria is able to speed up considerably the search and that the enhanced exact solution method outperforms the state‐of‐the‐art algorithm proposed by Murty and Her in most of the instances. 相似文献
22.
23.
A synchronizing word for a given synchronizing DFA is called minimal if none of its proper factors is synchronizing. We characterize the class of synchronizing automata having only finitely many minimal synchronizing words (the class of such automata is denoted by FG). Using this characterization we prove that any such automaton possesses a synchronizing word of length at most 3n-5. We also prove that checking whether a given DFA A is in FG is co-NP-hard and provide an algorithm for this problem which is exponential in the number of states A. 相似文献
24.
Walter Lang Frank Jakobs Elena Tolstosheeva Hannes Sturm Azat Ibragimov Antonia Kesel Dirk Lehmhus Ursula DickeAuthor vitae 《Sensors and actuators. A, Physical》2011,171(1):3-11
Ubiquitous computing is about to become part of our everyday lives by integrating hundreds of “invisible” to us computing devices in our environment, so that they can unobtrusively and constantly assist us. This will imply more and smaller “invisible” sensors, homogeneously distributed and at the same time densely packed in host materials, responding to various stimuli and immediately delivering information. In order to reach this aim, the embedded sensors should be integrated within the host material, heading towards sensorial materials. The first step is to omit all parts that are not needed for the sensorial task and to find new solutions for a gentle integration. This is what we call function scale integration. The paper discusses sensor embedding in the human hand as an example of integration in nature, new technological applications and main challenges associated with this approach. 相似文献
25.
Because of their widespread use in real-world transportation situations, hub location models have been extensively studied in the last two decades. Many types of hub location problems are NP-hard and remain unmanageable when the number of nodes exceeds 200. We present a way to tackle large-sized problems using aggregation, explore the resulting error, and show how to reduce it. Furthermore, we develop a heuristic based on aggregation for k-hub center problems and present computational results. 相似文献
26.
In this paper we consider the case of nonlinear convection-diffusion problems with a dominating convection term and we propose
exponential integrators based on the composition of exact pure convection flows. These methods can be applied to the numerical
integration of the considered PDEs in a semi-Lagrangian fashion. Semi-Lagrangian methods perform well on convection dominated
problems (Pironneau in Numer. Math. 38:309–332, 1982; Hockney and Eastwood in Computer simulations using particles. McGraw-Hill, New York, 1981; Rees and Morton in SIAM J. Sci. Stat. Comput. 12(3):547–572, 1991; Baines in Moving finite elements. Monographs on numerical analysis. Clarendon Press, Oxford, 1994).
In these methods linear convective terms can be integrated exactly by first computing the characteristics corresponding to the gridpoints of the adopted discretization, and then producing
the numerical approximation via an interpolation procedure. 相似文献
27.
Ciprian Iliescu Guolin Xu Elena Barbarini Marioara Avram Andrei Avram 《Microsystem Technologies》2009,15(8):1157-1162
This paper presents a microfluidic device for magnetophoretic separation of red blood cells from blood under continuous flow.
The separation method consists of continuous flow of a blood sample (diluted in PBS) through a microfluidic channel which
presents on the bottom “dots” of ferromagnetic layer. By applying a magnetic field perpendicular on the flowing direction,
the ferromagnetic “dots” generate a gradient of magnetic field which amplifies the magnetic force. As a result, the red blood
cells are captured on the bottom of the microfluidic channel while the rest of the blood is collected at the outlet. Experimental
results show that an average of 95% of red blood cells is trapped in the device. 相似文献
28.
29.
Educational data mining (EDM) is a research area where the goal is to develop data mining methods to examine data critically from educational environments. Traditionally, EDM has addressed the following problems: clustering, classification, regression, anomaly detection and association rule mining. In this paper, the ordinal regression (OR) paradigm, is introduced in the field of EDM. The goal of OR problems is the classification of items in an ordinal scale. For instance, the prediction of students' performance in categories (where the different grades could be ordered according to A ? B ? C ? D) is a classical example of an OR problem. The EDM community has not yet explored this paradigm (despite the importance of these problems in the field of EDM). Furthermore, an amenable and interpretable OR model based on the concept of gravitation is proposed. The model is an extension of a recently proposed gravitational model that tackles imbalanced nominal classification problems. The model is carefully adapted to the ordinal scenario and validated with four EDM datasets. The results obtained were compared with state‐of‐the‐art OR algorithms and nominal classification ones. The proposed models can be used to better understand the learning–teaching process in higher education environments. 相似文献
30.
Luis Alvarez‐Icaza Oscar Rosas‐Jaimes María Elena Lárraga 《Asian journal of control》2017,19(2):494-509
A framework for stability analysis of local on‐ramp metering control strategies based on the cell transmission model is presented. Within this framework, it is possible to formulate Lyapunov and input‐state stability results for on‐ramp metering control strategies in an open section of highway with on‐ramps. Using this analysis, recommendations for the design of on‐ramp metering control laws set points are derived. Two examples on the use of such analysis are presented. One deals with the stability analysis of a local on‐ramp metering control law and the other with the design of a disturbance observer that, used in combination with the local on‐ramp metering control law, provides a more robust response to traffic regulation. Simulation results are included that confirm the possibility of using this framework to test the impact of local on‐ramp metering control strategies. 相似文献