全文获取类型
收费全文 | 2091篇 |
免费 | 30篇 |
国内免费 | 4篇 |
专业分类
电工技术 | 22篇 |
综合类 | 5篇 |
化学工业 | 311篇 |
金属工艺 | 105篇 |
机械仪表 | 27篇 |
建筑科学 | 88篇 |
矿业工程 | 4篇 |
能源动力 | 66篇 |
轻工业 | 153篇 |
水利工程 | 29篇 |
石油天然气 | 5篇 |
无线电 | 184篇 |
一般工业技术 | 413篇 |
冶金工业 | 462篇 |
原子能技术 | 15篇 |
自动化技术 | 236篇 |
出版年
2023年 | 7篇 |
2022年 | 9篇 |
2021年 | 26篇 |
2020年 | 15篇 |
2019年 | 17篇 |
2018年 | 21篇 |
2017年 | 29篇 |
2016年 | 26篇 |
2015年 | 38篇 |
2014年 | 39篇 |
2013年 | 91篇 |
2012年 | 69篇 |
2011年 | 100篇 |
2010年 | 91篇 |
2009年 | 86篇 |
2008年 | 84篇 |
2007年 | 101篇 |
2006年 | 75篇 |
2005年 | 76篇 |
2004年 | 58篇 |
2003年 | 69篇 |
2002年 | 70篇 |
2001年 | 41篇 |
2000年 | 44篇 |
1999年 | 60篇 |
1998年 | 116篇 |
1997年 | 72篇 |
1996年 | 69篇 |
1995年 | 65篇 |
1994年 | 69篇 |
1993年 | 53篇 |
1992年 | 25篇 |
1991年 | 16篇 |
1990年 | 27篇 |
1989年 | 30篇 |
1988年 | 18篇 |
1987年 | 20篇 |
1986年 | 17篇 |
1985年 | 21篇 |
1984年 | 26篇 |
1983年 | 14篇 |
1982年 | 13篇 |
1981年 | 13篇 |
1980年 | 10篇 |
1979年 | 11篇 |
1978年 | 10篇 |
1977年 | 10篇 |
1976年 | 24篇 |
1975年 | 8篇 |
1974年 | 7篇 |
排序方式: 共有2125条查询结果,搜索用时 0 毫秒
31.
Calculating and categorizing the similarity of curves is a fundamental problem which has generated much recent interest. However, to date there are no implementations of these algorithms for curves on surfaces with provable guarantees on the quality of the measure. In this paper, we present a similarity measure for any two cycles that are homologous, where we calculate the minimum area of any homology (or connected bounding chain) between the two cycles. The minimum area homology exists for broader classes of cycles than previous measures which are based on homotopy. It is also much easier to compute than previously defined measures, yielding an efficient implementation that is based on linear algebra tools. We demonstrate our algorithm on a range of inputs, showing examples which highlight the feasibility of this similarity measure. 相似文献
32.
In this paper, a non-cooperative distributed MPC algorithm based on reduced order model is proposed to stabilize large-scale systems. The large-scale system consists of a group of interconnected subsystems. Each subsystem can be partitioned into two parts: measurable part, whose states can be directly measured by sensors, and the unmeasurable part. In the online computation phase, only the measurable dynamics of the corresponding subsystem and neighbour-to-neighbour communication are necessary for the local controller design. Satisfaction of the state constraints and the practical stability are guaranteed while the complexity of the optimization problem is reduced. Numerical examples are given to show the effectiveness of this algorithm. 相似文献
33.
Ted C. Eckmann Dar A. Roberts Christopher J. Still 《Remote sensing of environment》2008,112(10):3773-3783
The Moderate-Resolution Imaging Spectroradiometer (MODIS) sensors on NASA's Terra and Aqua satellites image most of the Earth multiple times each day, providing useful data on fires that cannot be practically acquired using other means. Unfortunately, current fire products from MODIS and other sensors leave large uncertainties in measurements of fire sizes and temperatures, which strongly influence how fires spread, the amount and chemistry of their gas and aerosol emissions, and their impacts on ecosystems. In this study, we use multiple endmember spectral mixture analysis (MESMA) to retrieve subpixel fire sizes and temperatures from MODIS, possibly overcoming some limitations of existing methods for characterizing fire intensities such as estimating the fire radiative power (FRP). MESMA is evaluated using data from the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) to assess the performance of FRP and MESMA retrievals of fire properties from a simultaneously acquired MODIS image, for a complex of fires in Ukraine from August 21, 2002. The MESMA retrievals of fire size described in this paper show a slightly stronger correlation than FRP does to fire pixel counts from the coincident ASTER image. Prior to this work, few studies, if any, had used MESMA for retrieving fire properties from a broad-band sensor like MODIS, or compared MESMA to higher-resolution fire data or other measures of fire properties like FRP. In the future, MESMA retrievals could be useful for fire spread modeling and forecasting, reducing hazards that fires pose to property and health, and enhancing scientific understanding of fires and their effects on ecosystems and atmospheric composition. 相似文献
34.
35.
Cecilia Laschi Gioel Asuni Eugenio Guglielmelli Giancarlo Teti Roland Johansson Hitoshi Konosu Zbigniew Wasik Maria Chiara Carrozza Paolo Dario 《Autonomous Robots》2008,25(1-2):85-101
This paper presents a sensory-motor coordination scheme for a robot hand-arm-head system that provides the robot with the capability to reach an object while pre-shaping the fingers to the required grasp configuration and while predicting the tactile image that will be perceived after grasping. A model for sensory-motor coordination derived from studies in humans inspired the development of this scheme. A peculiar feature of this model is the prediction of the tactile image. The implementation of the proposed scheme is based on a neuro-fuzzy module that, after a learning phase, starting from visual data, calculates the position and orientation of the hand for reaching, selects the best-suited hand configuration, and predicts the tactile feedback. The implementation of the scheme on a humanoid robot allowed experimental validation of its effectiveness in robotics and provided perspectives on applications of sensory predictions in robot motor control. 相似文献
36.
Leonid B. Freidovich Pedro La Hera Uwe Mettin Anders Robertsson Anton S. Shiriaev Rolf Johansson 《Asian journal of control》2009,11(5):548-556
We consider an underactuated two‐link robot called the inertia wheel pendulum. The system consists of a free planar rotational pendulum and a symmetric disk attached to its end, which is directly controlled by a DC‐motor. The goal is to create stable oscillations of the pendulum, which is not directly actuated. We exploit a recently proposed feedback‐control design strategy based on motion planning via virtual holonomic constraints. This strategy is shown to be useful for design of regulators for achieving orbitally exponentially stable oscillatory motions. The main contribution is a step‐by‐step procedure on how to achieve oscillations with pre‐specified amplitude from a given range and an arbitrary independently chosen period. The theoretical results are verified via experiments with a real hardware setup. Copyright © 2009 John Wiley and Sons Asia Pte Ltd and Chinese Automatic Control Society 相似文献
37.
A. P. Litvinchuk C. Thomsen M. Cardona L. Börjesson M. Käll P. Berastegui L. -G. Johansson 《Journal of Superconductivity》1994,7(1):113-116
We report a reflectivity study of thez-polarized TO-phonons of Pr
x
Y1–x
Ba2Cu4O8 and YBa2–y
Sr
y
Cu4O8 alloys in the temperature range 10–300 K. Anomalies of the frequency and linewidth of the plane-oxygen vibration at300 cm–1 due to the opening of the superconducting gap are found to occur upon crossing the superconducting transition temperatureT
c
. Phonon self-energy effects are strongly dependent onT
c
, providing evidence for a relative shift of the gap with respect to the energy of phonon.On leave from the Institute for Semiconductor Physics, Ukrainian Academy of Sciences, 252650 Kiev-28, Ukraine. 相似文献
38.
L. Marin A. Karageorghis D. Lesnic B. T. Johansson 《Inverse Problems in Science & Engineering》2017,25(5):652-673
An inverse problem in static thermo-elasticity is investigated. The aim is to reconstruct the unspecified boundary data, as well as the temperature and displacement inside a body from over-specified boundary data measured on an accessible portion of its boundary. The problem is linear but ill-posed. The uniqueness of the solution is established but the continuous dependence on the input data is violated. In order to reconstruct a stable and accurate solution, the method of fundamental solutions is combined with Tikhonov regularization where the regularization parameter is selected based on the L-curve criterion. Numerical results are presented in both two and three dimensions showing the feasibility and ease of implementation of the proposed technique. 相似文献
39.
Hongche Liu Tsai-Hong Hong Martin Herman Ted Camus Rama Chellappa 《Computer Vision and Image Understanding》1998,72(3):271-286
There have been two thrusts in the development of optical flow algorithms. One has emphasized higher accuracy; the other faster implementation. These two thrusts, however, have been independently pursued, without addressing the accuracy vs efficiency trade-offs. Although the accuracy–efficiency characteristic is algorithm dependent, an understanding of a general pattern is crucial in evaluating an algorithm as far as real-world tasks are concerned, which often pose various performance requirements. This paper addresses many implementation issues that have often been neglected in previous research, including temporal filtering of the output stream, algorithms' flexibility, and robustness to noise, subsampling, etc. Their impacts on accuracy and/or efficiency are emphasized. We present a survey of different approaches toward the goal of higher performance and present experimental studies on accuracy vs efficiency trade-offs. A detailed analysis of how this trade-off affects algorithm design is manifested in a case study involving two state-of-the-art optical flow algorithms: a gradient and a correlation-based method. The goal of this paper is to bridge the gap between the accuracy- and the efficiency-oriented approaches. 相似文献