全文获取类型
收费全文 | 2598篇 |
免费 | 190篇 |
国内免费 | 80篇 |
专业分类
电工技术 | 93篇 |
综合类 | 136篇 |
化学工业 | 461篇 |
金属工艺 | 45篇 |
机械仪表 | 99篇 |
建筑科学 | 340篇 |
矿业工程 | 40篇 |
能源动力 | 51篇 |
轻工业 | 164篇 |
水利工程 | 55篇 |
石油天然气 | 61篇 |
武器工业 | 9篇 |
无线电 | 207篇 |
一般工业技术 | 444篇 |
冶金工业 | 52篇 |
原子能技术 | 102篇 |
自动化技术 | 509篇 |
出版年
2023年 | 31篇 |
2022年 | 51篇 |
2021年 | 78篇 |
2020年 | 78篇 |
2019年 | 58篇 |
2018年 | 65篇 |
2017年 | 76篇 |
2016年 | 82篇 |
2015年 | 138篇 |
2014年 | 141篇 |
2013年 | 139篇 |
2012年 | 141篇 |
2011年 | 241篇 |
2010年 | 101篇 |
2009年 | 171篇 |
2008年 | 178篇 |
2007年 | 188篇 |
2006年 | 125篇 |
2005年 | 103篇 |
2004年 | 114篇 |
2003年 | 112篇 |
2002年 | 81篇 |
2001年 | 62篇 |
2000年 | 64篇 |
1999年 | 29篇 |
1998年 | 21篇 |
1997年 | 29篇 |
1996年 | 19篇 |
1995年 | 20篇 |
1994年 | 12篇 |
1993年 | 15篇 |
1992年 | 16篇 |
1991年 | 11篇 |
1990年 | 8篇 |
1989年 | 8篇 |
1988年 | 5篇 |
1987年 | 8篇 |
1986年 | 6篇 |
1985年 | 11篇 |
1984年 | 11篇 |
1983年 | 3篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1978年 | 3篇 |
1977年 | 3篇 |
1976年 | 2篇 |
1975年 | 1篇 |
1974年 | 2篇 |
1972年 | 3篇 |
排序方式: 共有2868条查询结果,搜索用时 15 毫秒
41.
Vasile Dragan Author vitae 《Automatica》2011,47(1):122-126
In this paper, the problem of robust H∞ control is investigated for sampled-data systems with probabilistic sampling. The parameter uncertainties are time-varying norm-bounded and appear in both the state and input matrices. For the simplicity of technical development, only two different sampling periods are considered whose occurrence probabilities are given constants and satisfy Bernoulli distribution, which can be further extended to the case with multiple stochastic sampling periods. By applying an input delay approach, the probabilistic sampling system is transformed into a continuous time-delay system with stochastic parameters in the system matrices. By linear matrix inequality (LMI) approach, sufficient conditions are obtained, which guarantee the robust mean-square exponential stability of the system with an H∞ performance. Moreover, an H∞ controller design procedure is then proposed. An illustrative example is included to demonstrate the effectiveness of the proposed techniques. 相似文献
42.
Embedding a number of displacement features into a base surface is common in industrial product design and modeling, where displaced surface regions are blended with the unmodified surface region. The cubic Hermite interpolant is usually adopted for surface blending, in which tangent plane smoothness across the boundary curve is achieved. However, the polynomial degree of the tangent field curve obtained symbolically is considerably higher, and the reduction of the degree of a freeform curve is a non-trivial task. In this work, an approximation surface blending approach is proposed to achieve tangential continuity across the boundary curve. The boundary curve is first offset in the tangent field with the user-specified tolerance, after which it is refined to be compatible with the offset curve for surface blending. Since the boundary curve is offset in a three-dimensional (3D) space, the local self-intersection in the offset curve is addressed in a 2D space by approximately mapping the offset vectors in the respective tangent planes to the parameter space of the base surface. The proposed algorithm is validated using examples, and the normal vector deviation along the boundary curve is investigated. 相似文献
43.
For a positive integer d, an L(d,1)-labeling f of a graph G is an assignment of integers to the vertices of G such that |f(u)−f(v)|?d if uv∈E(G), and |f(u)−f(v)|?1 if u and u are at distance two. The span of an L(d,1)-labeling f of a graph is the absolute difference between the maximum and minimum integers used by f. The L(d,1)-labeling number of G, denoted by λd,1(G), is the minimum span over all L(d,1)-labelings of G. An L′(d,1)-labeling of a graph G is an L(d,1)-labeling of G which assigns different labels to different vertices. Denote by the L′(d,1)-labeling number of G. Georges et al. [Discrete Math. 135 (1994) 103-111] established relationship between the L(2,1)-labeling number of a graph G and the path covering number of Gc, the complement of G. In this paper we first generalize the concept of the path covering of a graph to the t-group path covering. Then we establish the relationship between the L′(d,1)-labeling number of a graph G and the (d−1)-group path covering number of Gc. Using this result, we prove that and for bipartite graphs G can be computed in polynomial time. 相似文献
44.
Jens MaßbergJan Schneider 《Theoretical computer science》2011,412(50):6948-6958
We formulate a generalization of the NP-complete rectangle packing problem by parameterizing it in terms of packing density, the ratio of rectangle areas, and the aspect ratio of individual rectangles. Then we show that almost all restrictions of this problem remain NP-complete and identify some cases where the answer to the decision problem can be found in constant time. 相似文献
45.
We show that for some special functions (called k-multigrid equidistributed functions), we can compute the limit of the frequency of patterns in the discretization of their graph, when the resolution tends to zero. This result is applied to parabolas. We deduce also that local length estimators almost never converge to the length for the parabolas. 相似文献
46.
提出了一种基于PDA的新型数据记录仪的设计方案。以 89c52单片机为核心设计了前端数据采集器 ,开发了基于PDA的数据记录应用程序。应用实验表明 ,该方案是可行的 相似文献
47.
生产管理系统的设计与实施 总被引:2,自引:0,他引:2
灵活实施是开发生产管理系统的成功关键。介绍了开发生产 管理系统软件设计方案的主要内容,并且在实践的基础上总结出若干值得参考的经验。 相似文献
48.
Eugenii Shustin Author Vitae 《Automatica》2007,43(9):1649-1655
Stability of linear systems with uncertain bounded time-varying delays is studied under the assumption that the nominal delay values are not equal to zero. An input-output approach to stability of such systems is known to be based on the bound of the L2-norm of a certain integral operator. There exists a bound on this operator norm in two cases: in the case where the delay derivative is not greater than 1 and in the case without any constraints on the delay derivative. In the present note we fill the gap between the two cases by deriving a tight operator bound which is an increasing and continuous function of the delay derivative upper bound d?1. For d→∞ the new bound corresponds to the second case and improves the existing bound. As a result, for the first time, delay-derivative-dependent frequency domain and time domain stability criteria are derived for systems with the delay derivative greater than 1. 相似文献
49.
micrOMEGAs 2.0 is a code which calculates the relic density of a stable massive particle in an arbitrary model. The underlying assumption is that there is a conservation law like R-parity in supersymmetry which guarantees the stability of the lightest odd particle. The new physics model must be incorporated in the notation of CalcHEP, a package for the automatic generation of squared matrix elements. Once this is done, all annihilation and coannihilation channels are included automatically in any model. Cross-sections at v=0, relevant for indirect detection of dark matter, are also computed automatically. The package includes three sample models: the minimal supersymmetric standard model (MSSM), the MSSM with complex phases and the NMSSM. Extension to other models, including non-supersymmetric models, is described.
Program summary
Title of program:micrOMEGAs2.0Catalogue identifier:ADQR_v2_0Program summary URL:http://cpc.cs.qub.ac.uk/summaries/ADQR_v2_0Program obtainable from: CPC Program Library, Queen's University of Belfast, N. IrelandComputers for which the program is designed and others on which it has been tested:PC, Alpha, Mac, SunOperating systems under which the program has been tested:UNIX (Linux, OSF1, SunOS, Darwin, Cygwin)Programming language used:C and FortranMemory required to execute with typical data:17 MB depending on the number of processes requiredNo. of processors used:1Has the code been vectorized or parallelized:noNo. of lines in distributed program, including test data, etc.:91 778No. of bytes in distributed program, including test data, etc.:1 306 726Distribution format:tar.gzExternal routines/libraries used:noCatalogue identifier of previous version:ADQR_v1_3Journal reference of previous version:Comput. Phys. Comm. 174 (2006) 577Does the new version supersede the previous version:yesNature of physical problem:Calculation of the relic density of the lightest stable particle in a generic new model of particle physics.Method of solution: In numerically solving the evolution equation for the density of dark matter, relativistic formulae for the thermal average are used. All tree-level processes for annihilation and coannihilation of new particles in the model are included. The cross-sections for all processes are calculated exactly with CalcHEP after definition of a model file. Higher-order QCD corrections to Higgs couplings to quark pairs are included.Reasons for the new version:There are many models of new physics that propose a candidate for dark matter besides the much studied minimal supersymmetric standard model. This new version not only incorporates extensions of the MSSM, such as the MSSM with complex phases, or the NMSSM which contains an extra singlet superfield but also gives the possibility for the user to incorporate easily a new model. For this the user only needs to redefine appropriately a new model file.Summary of revisions:- •
- Possibility to include in the package any particle physics model with a discrete symmetry that guarantees the stability of the cold dark matter candidate (LOP) and to compute the relic density of CDM.
- •
- Compute automatically the cross-sections for annihilation of the LOP at small velocities into SM final states and provide the energy spectra for final states.
- •
- For the MSSM with input parameters defined at the GUT scale, the interface with any of the spectrum calculator codes reads an input file in the SUSY Les Houches Accord format (SLHA).
- •
- Implementation of the MSSM with complex parameters (CPV-MSSM) with an interface to CPsuperH to calculate the spectrum.
- •
- Routine to calculate the electric dipole moment of the electron in the CPV-MSSM.
- •
- In the NMSSM, new interface compatible with NMHDECAY2.1.
50.
We define the notion of rational presentation of a complete metric space, in order to study metric spaces from the algorithmic complexity point of view. In this setting, we study some representations of the space C[0,1] of uniformly continuous real functions over [0,1] with the usual norm: ||f||∞ = Sup{|f(x)|; 0x1}. This allows us to have a comparison of global kind between complexity notions attached to these presentations. In particular, we get a generalization of Hoover's results concerning the Weierstrass approximation theorem in polynomial time. We get also a generalization of previous results on analytic functions which are computable in polynomial time. 相似文献