全文获取类型
收费全文 | 17500篇 |
免费 | 599篇 |
国内免费 | 148篇 |
专业分类
电工技术 | 233篇 |
综合类 | 10篇 |
化学工业 | 2353篇 |
金属工艺 | 510篇 |
机械仪表 | 225篇 |
建筑科学 | 310篇 |
矿业工程 | 10篇 |
能源动力 | 359篇 |
轻工业 | 1377篇 |
水利工程 | 58篇 |
石油天然气 | 50篇 |
无线电 | 843篇 |
一般工业技术 | 1251篇 |
冶金工业 | 273篇 |
原子能技术 | 151篇 |
自动化技术 | 10234篇 |
出版年
2024年 | 8篇 |
2023年 | 79篇 |
2022年 | 319篇 |
2021年 | 332篇 |
2020年 | 218篇 |
2019年 | 241篇 |
2018年 | 271篇 |
2017年 | 300篇 |
2016年 | 333篇 |
2015年 | 239篇 |
2014年 | 593篇 |
2013年 | 783篇 |
2012年 | 1260篇 |
2011年 | 3648篇 |
2010年 | 1591篇 |
2009年 | 1464篇 |
2008年 | 1102篇 |
2007年 | 945篇 |
2006年 | 739篇 |
2005年 | 788篇 |
2004年 | 714篇 |
2003年 | 745篇 |
2002年 | 456篇 |
2001年 | 103篇 |
2000年 | 82篇 |
1999年 | 97篇 |
1998年 | 180篇 |
1997年 | 75篇 |
1996年 | 64篇 |
1995年 | 50篇 |
1994年 | 39篇 |
1993年 | 34篇 |
1992年 | 34篇 |
1991年 | 19篇 |
1990年 | 27篇 |
1989年 | 25篇 |
1988年 | 21篇 |
1987年 | 16篇 |
1986年 | 26篇 |
1985年 | 24篇 |
1984年 | 41篇 |
1983年 | 18篇 |
1982年 | 23篇 |
1981年 | 16篇 |
1980年 | 11篇 |
1979年 | 9篇 |
1978年 | 10篇 |
1977年 | 12篇 |
1975年 | 6篇 |
1973年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
82.
H.A. Barker Author Vitae A.H. Tan Author Vitae K.R. Godfrey Author Vitae 《Automatica》2003,39(1):127-133
Analysis of systems with direction-dependent dynamics is currently limited to cases in which the dynamics in the two directions of the output are first order; results for such systems have been published for both pseudo-random maximum-length binary (MLB) and inverse-repeat maximum-length binary (IR-MLB) inputs. These relatively limited analytical results make it useful to examine alternative ways of modelling such systems and in this paper, Wiener models are considered for this purpose. Methods for optimising the Wiener model parameters by matching the system and model cross-correlation functions, outputs, and discrete Fourier transforms of the outputs are considered, and the results are compared. These methods are also applied to a first-order direction-dependent system with a maximum-length ternary (MLT) input, for which no analytical results are currently available, and to a second-order system with an IR-MLB input. 相似文献
83.
Terry WindeattAuthor Vitae 《Pattern recognition》2003,36(12):2743-2756
Various measures, such as Margin and Bias/Variance, have been proposed with the aim of gaining a better understanding of why Multiple Classifier Systems (MCS) perform as well as they do. While these measures provide different perspectives for MCS analysis, it is not clear how to use them for MCS design. In this paper a different measure based on a spectral representation is proposed for two-class problems. It incorporates terms representing positive and negative correlation of pairs of training patterns with respect to class labels. Experiments employing MLP base classifiers, in which parameters are fixed but systematically varied, demonstrate the sensitivity of the proposed measure to base classifier complexity. 相似文献
84.
Maria E. Amato Antonio Grassi Kenny B. Lipkowitz Giuseppe M. Lombardo Giuseppe C. Pappalardo Claudia Sadun 《Journal of Inorganic and Organometallic Polymers and Materials》1996,6(3):237-253
Suitable parameter sets for the CHARMm force field were derived for the structural units in polychlorophosphazene [P=N, P N, P Cl] using the Dinur Hagler energy second derivative procedure based on quantum mechanical SCI calculations using the 6–31G* basis set. To validate the reliability of the parameter set, structural results obtained with CHARMm for the adopted model compounds (OP2NCl5 and OP3N2Cl5) were compared with those derived fromab initio quantum mechanics using the 6–31G* basis set. Application of molecular dynamics (MD) simulations in combinatioin with the available X-ray diffraction data provided structural and conformational information on the polymer. The calculation made using the periodic boundary conditions (PBC) agree well with the polychlorophosphazene ordered in a monoclinic unit cell (a=5.98,b=12.99,c=4.92 A; β=111.7). This model was stabilized mainly by the image atoms contribution to the electrostatic energy term and had aquasi-planar conformation of the backbone chain (glide symmetry). The MD calculations also provided evidence that the difference between single and double PN bonds is less marked than that measured experimentally. This result is, however, in agreement with more recent and accurate X-ray studies on poly(methylphosphazene). Validation of the polymer model provided a complete picture, otherwise experimentally inaccessible, of the internal fluctuations of the polymeric chains. 相似文献
85.
86.
The problem of the non-causal inversion of linear multivariable discrete-time systems is analyzed in the geometric approach framework and is solved through the computation of convolution profiles which guarantee perfect tracking under the assumption of infinite-length preaction and postaction time intervals. It is shown how the shape of the convolution profiles is related to both the relative degree and the invariant zeros of the plant. A computational setting for the convolution profiles is derived by means of the standard geometric approach tools. Feasibility constraints are also taken into account. A possible implementation scheme, based on a finite impulse response system acting on a stabilized control loop, is provided. 相似文献
87.
Fault-accommodation with intelligent sensors 总被引:1,自引:0,他引:1
Giacomo Tortora Author Vitae Author Vitae David Clarke Author Vitae 《Automatica》2003,39(7):1227-1233
Optimal sensor fault-accommodation is considered for faults modelled by an increase in measurement noise. This noise is taken to be bounded and its probabilistic properties unknown. It is assumed that intelligent (e.g. self-validating) instrumentation is in use and estimates of the noise bounds are available. The fault-tolerant controller is designed to optimize a noise rejection and a nominal reference tracking index and leads to a mixed norm minimization problem (l1/l2). We exploit known results and a particular feedback configuration to show that it is possible to optimize simultaneously without a trade-off the two performance indices. The results are applied to systems where the presence of auxiliary measurements allows for an optimal fault-accommodation strategy. Using properties of the optimal solution, we define a factorization for the optimal controller alternative to the Youla parametrization, leading to an algorithm which is optimal, transparent and efficient. 相似文献
88.
Wrinkling is a well known phenomenon experimented by tension membranes in Civil Engineering applications. This paper will
present an efficient numerical technique for the computational simulation of such wrinkles in a prestressed membrane. In particular,
the relaxed energy approach (Pipkin in IMA J Appl Math 36:85–99, 1986) is particularized for prestressed membranes (Gil in
Textile composites and inflatable structures, CIMNE, 2003) undergoing moderate strains. Wrinkling conditions in terms of the
Euler-Lagrange finite deformation tensor along principal directions will be obtained. This will provide a framework to describe
properly the initial instant when wrinkles start to be encountered in a prestressed Saint Venant–Kirchhoff hyperelastic membrane.
Subsequently, a modified Helmholtz’s free energy functional will be introduced with the purpose of describing the modified
constitutive behaviour of the continuum after the onset of wrinkling. Consistent derivations of the stress tensor as well
as the constitutive tensor will de depicted. The results will be particularized for membranes and cables in a Finite Element
discretization basis. Some numerical examples will prove the accuracy and robustness of the described algorithm. 相似文献
89.
The problem of tracking a periodic trajectory of the well-known cart-pendulum system is solved. After a change of coordinates and a change of feedback, the equations of this system are nonlinear but feedforward. This property is extensively used to carry out for this system the design of uniformly asymptotically stabilizing time-varying state feedbacks by using the forwarding approach. 相似文献
90.