全文获取类型
收费全文 | 5750篇 |
免费 | 230篇 |
国内免费 | 134篇 |
专业分类
电工技术 | 107篇 |
综合类 | 212篇 |
化学工业 | 696篇 |
金属工艺 | 183篇 |
机械仪表 | 381篇 |
建筑科学 | 1089篇 |
矿业工程 | 276篇 |
能源动力 | 439篇 |
轻工业 | 192篇 |
水利工程 | 136篇 |
石油天然气 | 186篇 |
武器工业 | 30篇 |
无线电 | 194篇 |
一般工业技术 | 515篇 |
冶金工业 | 220篇 |
原子能技术 | 233篇 |
自动化技术 | 1025篇 |
出版年
2024年 | 4篇 |
2023年 | 81篇 |
2022年 | 92篇 |
2021年 | 113篇 |
2020年 | 98篇 |
2019年 | 110篇 |
2018年 | 91篇 |
2017年 | 117篇 |
2016年 | 184篇 |
2015年 | 174篇 |
2014年 | 316篇 |
2013年 | 366篇 |
2012年 | 288篇 |
2011年 | 440篇 |
2010年 | 364篇 |
2009年 | 380篇 |
2008年 | 294篇 |
2007年 | 350篇 |
2006年 | 297篇 |
2005年 | 227篇 |
2004年 | 220篇 |
2003年 | 235篇 |
2002年 | 199篇 |
2001年 | 152篇 |
2000年 | 163篇 |
1999年 | 140篇 |
1998年 | 113篇 |
1997年 | 101篇 |
1996年 | 65篇 |
1995年 | 71篇 |
1994年 | 60篇 |
1993年 | 29篇 |
1992年 | 31篇 |
1991年 | 28篇 |
1990年 | 23篇 |
1989年 | 14篇 |
1988年 | 20篇 |
1987年 | 6篇 |
1986年 | 11篇 |
1985年 | 10篇 |
1984年 | 10篇 |
1983年 | 8篇 |
1982年 | 7篇 |
1981年 | 2篇 |
1980年 | 6篇 |
1979年 | 1篇 |
1978年 | 2篇 |
1977年 | 1篇 |
排序方式: 共有6114条查询结果,搜索用时 140 毫秒
141.
142.
143.
Qinjiao Gao Zongmin WuShenggang Zhang 《Computers & Mathematics with Applications》2011,62(12):4356-4361
In this paper, we propose a novel scheme for simulating geometric active contours (geometric flow) of one kind, applying multiquadric (MQ) quasi-interpolation. We first represent the geometric flow in its parametric form. Then we obtain the numerical scheme by using the derivatives of the quasi-interpolation to approximate the spatial derivative of each dependent variable and a forward difference to approximate the temporal derivative of each dependent variable. The resulting scheme is simple, efficient and easy to implement. Also images with complex boundaries can be more easily proposed on the basis of the good properties of the MQ quasi-interpolation. Several biomedical and astronomical examples of applications are shown in the paper. Comparisons with other methods are included to illustrate the validity of the method. 相似文献
144.
In this paper we present a method curve approximation from a given Lagrangian data set. An approximating problem of curves is obtained by minimizing a quadratic functional in a suitable space. This method is justified by a convergence result and an analysis of a numerical and graphical example. 相似文献
145.
Many shapes resulting from important geometric operations in industrial applications such as Minkowski sums or volume swept by a moving object can be seen as the projection of higher dimensional objects. When such a higher dimensional object is a smooth manifold, the boundary of the projected shape can be computed from the critical points of the projection. In this paper, using the notion of polyhedral chains introduced by Whitney, we introduce a new general framework to define an analogous of the set of critical points of piecewise linear maps defined over discrete objects that can be easily computed. We illustrate our results by showing how they can be used to compute Minkowski sums of polyhedra and volumes swept by moving polyhedra. 相似文献
146.
Pei-Lan Lei Gloria Yi-Ming Kao Sunny S.J. Lin Chuen-Tsai Sun 《Computers in human behavior》2009,25(6):1270-1279
Google Earth search function was used to study the impacts of small-scale spatial ability, large-scale environmental cognition, and geographical knowledge on new technology usage. The participants were 153 junior high students from central Taiwan. Geography grades served as indicators of prior knowledge, mental rotation and abstract reasoning skills as indicators of spatial ability, and sketch maps of school neighborhoods as indicators of environmental cognition (including landmark representation, intersection representation, and frame of reference). Lastly, the authors announced the landmarks searching worksheet and asked the participants to accomplish 16 familiar and unfamiliar landmark searching tasks using Google Earth with keyword search function disabled. The result showed the strongest predictor of landmark searching performance is ‘frame of reference’ in environmental cognition, followed by ‘mental rotation’ of spatial ability, ‘landmark representation’ of environmental cognition, and geographical knowledge. Google Earth landmark searches require complex cognitive processing; therefore, our conclusion is that GIS-supported image search activities give students good practice of active knowledge construction. 相似文献
147.
Muhammad F. Mysorewala Dan O. Popa Frank L. Lewis 《Journal of Intelligent and Robotic Systems》2009,54(4):535-565
The use of robotics in distributed monitoring applications requires wireless sensors that are deployed efficiently. A very
important aspect of sensor deployment includes positioning them for sampling at locations most likely to yield information
about the spatio-temporal field of interest, for instance, the spread of a forest fire. In this paper, we use mobile robots
(agents) that estimate the time-varying spread of wildfires using a distributed multi-scale adaptive sampling strategy. The
proposed parametric sampling algorithm, “EKF-NN-GAS” is based on neural networks, the extended Kalman filter (EKF), and greedy heuristics. It combines measurements arriving
at different times, taken at different scale lengths, such as from ground, airborne, and spaceborne observation platforms.
One of the advantages of our algorithm is the ability to incorporate robot localization uncertainty in addition to sensor
measurement and field parameter uncertainty into the same EKF model. We employ potential fields, generated naturally from
the estimated fire field distribution, in order to generate fire-safe trajectories that could be used to rescue vehicles and
personnel. The covariance of the EKF is used as a quantitative information measure for sampling locations most likely to yield
optimal information about the sampled field distribution. Neural net training is used infrequently to generate initial low
resolution estimates of the fire spread parameters. We present simulation and experimental results for reconstructing complex
spatio-temporal forest fire fields “truth models”, approximated by radial basis function (RBF) parameterizations. When compared
to a conventional raster scan approach, our algorithm shows a significant reduction in the time necessary to map the fire
field. 相似文献
148.
149.
150.
Marcos Sandim Douglas Cedrim Luis Gustavo Nonato Paulo Pagliosa Afonso Paiva 《Computer Graphics Forum》2016,35(2):215-224
This paper presents a novel method to detect free‐surfaces on particle‐based volume representation. In contrast to most particle‐based free‐surface detection methods, which perform the surface identification based on physical and geometrical properties derived from the underlying fluid flow simulation, the proposed approach only demands the spatial location of the particles to properly recognize surface particles, avoiding even the use of kernels. Boundary particles are identified through a Hidden Point Removal (HPR) operator used for visibility test. Our method is very simple, fast, easy to implement and robust to changes in the distribution of particles, even when facing large deformation of the free‐surface. A set of comparisons against state‐of‐the‐art boundary detection methods show the effectiveness of our approach. The good performance of our method is also attested in the context of fluid flow simulation involving free‐surface, mainly when using level‐sets for rendering purposes. 相似文献