全文获取类型
收费全文 | 2406篇 |
免费 | 131篇 |
国内免费 | 5篇 |
专业分类
电工技术 | 50篇 |
综合类 | 11篇 |
化学工业 | 619篇 |
金属工艺 | 50篇 |
机械仪表 | 79篇 |
建筑科学 | 103篇 |
矿业工程 | 5篇 |
能源动力 | 85篇 |
轻工业 | 244篇 |
水利工程 | 24篇 |
石油天然气 | 6篇 |
无线电 | 196篇 |
一般工业技术 | 403篇 |
冶金工业 | 214篇 |
原子能技术 | 27篇 |
自动化技术 | 426篇 |
出版年
2023年 | 17篇 |
2022年 | 76篇 |
2021年 | 121篇 |
2020年 | 51篇 |
2019年 | 47篇 |
2018年 | 69篇 |
2017年 | 59篇 |
2016年 | 86篇 |
2015年 | 53篇 |
2014年 | 93篇 |
2013年 | 159篇 |
2012年 | 111篇 |
2011年 | 151篇 |
2010年 | 122篇 |
2009年 | 146篇 |
2008年 | 123篇 |
2007年 | 123篇 |
2006年 | 103篇 |
2005年 | 82篇 |
2004年 | 80篇 |
2003年 | 71篇 |
2002年 | 55篇 |
2001年 | 35篇 |
2000年 | 39篇 |
1999年 | 33篇 |
1998年 | 56篇 |
1997年 | 49篇 |
1996年 | 37篇 |
1995年 | 22篇 |
1994年 | 24篇 |
1993年 | 21篇 |
1992年 | 16篇 |
1991年 | 9篇 |
1990年 | 13篇 |
1989年 | 19篇 |
1988年 | 13篇 |
1987年 | 9篇 |
1986年 | 6篇 |
1985年 | 16篇 |
1984年 | 11篇 |
1983年 | 12篇 |
1982年 | 16篇 |
1981年 | 11篇 |
1980年 | 11篇 |
1979年 | 12篇 |
1978年 | 6篇 |
1977年 | 9篇 |
1976年 | 9篇 |
1975年 | 4篇 |
1973年 | 4篇 |
排序方式: 共有2542条查询结果,搜索用时 15 毫秒
61.
In this paper, we consider a neural field model comprised of two distinct populations of neurons, excitatory and inhibitory, for which both the velocities of action potential propagation and the time courses of synaptic processing are different. Using recently-developed techniques, we construct the Evans function characterising the stability of both stationary and travelling wave solutions, under the assumption that the firing rate function is the Heaviside step. We find that these differences in timing for the two populations can cause instabilities of these solutions, leading to, for example, stationary breathers. We also analyse "anti-pulses", a novel type of pattern for which all but a small interval of the domain (in moving coordinates) is active. These results extend previous work on neural fields with space-dependent delays, and demonstrate the importance of considering the effects of the different time-courses of excitatory and inhibitory neural activity. 相似文献
62.
63.
Manifold learning methods for unsupervised nonlinear dimensionality reduction have proven effective in the visualization of high dimensional data sets. When dealing with classification tasks, supervised extensions of manifold learning techniques, in which class labels are used to improve the embedding of the training points, require an appropriate method for out-of-sample mapping.In this paper we propose multi-output kernel ridge regression (KRR) for out-of-sample mapping in supervised manifold learning, in place of general regression neural networks (GRNN) that have been adopted by previous studies on the subject. Specifically, we consider a supervised agglomerative variant of Isomap and compare the performance of classification methods when the out-of-sample embedding is based on KRR and GRNN, respectively. Extensive computational experiments, using support vector machines and k-nearest neighbors as base classifiers, provide statistical evidence that out-of-sample mapping based on KRR consistently dominates its GRNN counterpart, and that supervised agglomerative Isomap with KRR achieves a higher accuracy than direct classification methods on most data sets. 相似文献
64.
The "ultra-slow" method for cholangiography in serious icterus due to chronic heptopathy is described. The results are related to different icterus stages. A comparison is drawn between this and conventional methods for examination of the bile ducts, assuming equal degrees of blood bilirubin. 相似文献
65.
Recent developments in the understanding of fretting fatigue 总被引:2,自引:0,他引:2
Considerable progress has been made in the understanding of fretting fatigue over the last decade. Experiments have become more standardised and carefully controlled and this has provided the data necessary for development of methods for predicting fretting fatigue performance. This paper reviews a number of recent developments, starting with attempts to apply multiaxial initiation criteria to the fretting problem. The importance of the size effect is highlighted and an analogy is made between fretting and notch fatigue. Methods for characterising crack initiation using asymptotic analysis are discussed, together with short crack arrest concepts which provide a means of predicting fretting fatigue limits from plain fatigue data. 相似文献
66.
Density functional numerical simulations are reported in which the non-equilibrium coherent transport properties of a coaxially gated carbon nanotube (CNT) are studied. Effects of screening properties of CNT on the channel conductance modulation are shown. Other factors which influence the CNT quantum capacitance beyond the density of states (DOS) are pointed out, first of all many-body effects which even cause the CNT to over-screen the gate field. Results stress the importance of a good electrostatic-design of the gate contact to obtain an effective field-effect current modulation, and suggest new interesting operation modes for quasi-one dimensional channel devices. 相似文献
67.
Multirobot motion coordination in space and time 总被引:5,自引:0,他引:5
Carlo Ferrari Enrico Pagello Jun Ota Tamio Arai 《Robotics and Autonomous Systems》1998,25(3-4):219-229
This paper describes a solution to the multirobot motion planning problem based on a decoupled analysis in the space domain and in the time domain. It investigates the practical use of the notion of motion plan quality and of the motion plan robustness measures for computing safe motions. The use of anytime algorithms allows one to evaluate the opportunity of looking for alternative solution paths by generating small variations of robot motions affecting both its geometrical path and its scheduled velocity. By using the concept of plan robustness, several alternative paths are generated and evaluated through various performance indices and impact factors, using heuristic rules. These indices allow one to know how much a variation affects a given plan. Finally, some recent experiments are outlined. 相似文献
68.
This paper analyzes the formulation of energy preserving/decaying schemes for dynamics problems. We argue that any energy preserving/decaying scheme can always be seen as composed of an underlying temporal discretization, that is then slightly modified in order to prove a discrete energy bound within a time step. While the details of the modified scheme depend in a critical way on the governing equations, the underlying discretization can in principle be applied to a variety of models. We review some of the temporal underlying schemes recently proposed in the literature, presenting them with a common notation. We show their similarities and highlight their differences. 相似文献
69.
The vortex reconnection rate f plays an important role in the dynamics of a tangle of quantised vortices in superfluid turbulence. The question which we address is how f depends on the vortex line density L. In the case of a homogeneous isotropic tangle of vortices we show that, besides the known regime which scales as f ~ L5/2, another regime exists which scales as f ~ L2. In the case of a polarised vortex confguration, we argue that the scaling law changes and show numerical evidence for it. Finally we construct an idealised model of turbulence decay based on vortex reconnections and discuss its implications. PACS numbers: 67.40.Vs, 67.57.Fg. 相似文献
70.
A mathematical model was developed to describe the in‐line hot rolling deformation and recrystallization behaviour of austenite after the solidification on a thin slab casting plant. The most significant features of the cast rolling process were taken into consideration: through‐thickness thermal gradients, inhomogeneous stress and strain, temperature discontinuity between the strip and the rolls. A HSLA (High Strength Low Alloy) steel has been chosen to perform the experiments of cast rolling. The characteristic constants ruling the microstructural evolution of that steel were computed and integrated into the computational module which manages the structural stress‐strain and strain rate computation. The developed approach is based on the Navier‐Stokes’ equations which were used to compute the speed field in the strip during the deformation. Then a model providing a proper constitutive equation was structured on the basis of the Yada's model based on evolution of the dislocation populations. The use of the Navier‐Stokes’ formalism allows to reach the resolution of the structural problem from the data measured easily during the industrial practice (i.e. speed of the rolled product at the entry and at the exit of a stand, the temperature of the rolled material). The validation of this computational approach was obtained by a comparison between the prior austenite grain size of the strip in different positions of the hot rolling process, as well as by a comparison between the computed deformation power and the measured one provided by the engines moving the rolls. 相似文献