全文获取类型
收费全文 | 6407篇 |
免费 | 787篇 |
国内免费 | 583篇 |
专业分类
电工技术 | 214篇 |
技术理论 | 1篇 |
综合类 | 767篇 |
化学工业 | 106篇 |
金属工艺 | 40篇 |
机械仪表 | 224篇 |
建筑科学 | 202篇 |
矿业工程 | 60篇 |
能源动力 | 43篇 |
轻工业 | 89篇 |
水利工程 | 65篇 |
石油天然气 | 60篇 |
武器工业 | 45篇 |
无线电 | 1158篇 |
一般工业技术 | 590篇 |
冶金工业 | 145篇 |
原子能技术 | 25篇 |
自动化技术 | 3943篇 |
出版年
2024年 | 30篇 |
2023年 | 67篇 |
2022年 | 92篇 |
2021年 | 124篇 |
2020年 | 157篇 |
2019年 | 158篇 |
2018年 | 178篇 |
2017年 | 212篇 |
2016年 | 239篇 |
2015年 | 219篇 |
2014年 | 339篇 |
2013年 | 449篇 |
2012年 | 459篇 |
2011年 | 516篇 |
2010年 | 359篇 |
2009年 | 428篇 |
2008年 | 440篇 |
2007年 | 455篇 |
2006年 | 366篇 |
2005年 | 313篇 |
2004年 | 295篇 |
2003年 | 250篇 |
2002年 | 193篇 |
2001年 | 185篇 |
2000年 | 146篇 |
1999年 | 126篇 |
1998年 | 109篇 |
1997年 | 74篇 |
1996年 | 96篇 |
1995年 | 86篇 |
1994年 | 88篇 |
1993年 | 56篇 |
1992年 | 61篇 |
1991年 | 43篇 |
1990年 | 37篇 |
1989年 | 29篇 |
1988年 | 21篇 |
1987年 | 12篇 |
1986年 | 14篇 |
1985年 | 25篇 |
1984年 | 28篇 |
1983年 | 28篇 |
1982年 | 30篇 |
1981年 | 24篇 |
1980年 | 28篇 |
1979年 | 33篇 |
1978年 | 10篇 |
1977年 | 7篇 |
1976年 | 14篇 |
1964年 | 5篇 |
排序方式: 共有7777条查询结果,搜索用时 0 毫秒
21.
求解机械装配规划的新方法 总被引:6,自引:0,他引:6
本文提出一个求解机械装配规划的算法,其计算量~O(sN~2),其中s是零件所有可能装配方向的个数,N是工件的零件数(一般s~O(N)).而现行的求机械装配规划的算法,其计算量均随N的增加按指数律增加. 相似文献
22.
奇异值分解压制随机噪声的方法及应用 总被引:9,自引:0,他引:9
针对随机噪声压制问题,通过对多项式确定的同相轴形状重新选取数据矩阵,再对新选取的数据矩阵进行SVD滤波,从而压制随机噪声。通过对矩阵奇异值分解的研究,揭示了奇异值分解的原理和SVD滤波原理,将一个多道地震记录看作一个图,它可分解为由一系列正交的子图,通过对子图适当选择并结合其它手段,从而达到提高信噪比的目的,为奇异值分解在地球物理中的进一步应用提供了理论依据。实际数据应用表明,该方法去噪手段灵活、保真性好、分辨率高,对一些突然的脉冲干扰、侧反射、以及其他的反向干扰有明显效果。 相似文献
23.
Minimizing the number of tool switches on a flexible machine 总被引:5,自引:0,他引:5
Yves Crama Antoon W. J. Kolen Alwin G. Oerlemans Frits C. R. Spieksma 《International Journal of Flexible Manufacturing Systems》1994,6(1):33-54
This article analyzes a tool switching problem arising in certain flexible manufacturing environments. A batch of jobs have to be successively processed on a single flexible machine. Each job requires a subset of tools, which have to be placed in the tool magazine of the machine before the job can be processed. The tool magazine has a limited capacity, and, in general, the number of tools needed to produce all the jobs exceeds this capacity. Hence, it is sometimes necessary to change tools between two jobs in a sequence. The problem is then to determine a job sequence and an associated sequence of loadings for the tool magazine, such that the total number of tool switches is minimized. This problem has been previously considered by several authors; it is here revisited, both from a theoretical and from a computational viewpoint. Basic results concerning the computational complexity of the problem are established. Several heuristics are proposed for its solution, and their performance is computationally assessed. 相似文献
24.
基于Legendre多项式的随机连续系统的Markov参数估计 总被引:3,自引:3,他引:0
本文在讨论连续Wisenr过程的Legendre多项式逼近值的相关性和Wiener过程扰动下连续线性系统基于该正交多项的最小二乘估计有偏性后,提出了无偏一致的且数估计误差方差最小的Markov估计(最小方差估计)算法,并给出本文方法的仿真结果。 相似文献
25.
Ilan Gronau 《Information Processing Letters》2007,104(6):205-210
In this work we consider hierarchical clustering algorithms, such as UPGMA, which follow the closest-pair joining scheme. We survey optimal O(n2)-time implementations of such algorithms which use a ‘locally closest’ joining scheme, and specify conditions under which this relaxed joining scheme is equivalent to the original one (i.e. ‘globally closest’). 相似文献
26.
Uwe Schöning 《Information Processing Letters》2006,98(4):127-129
An N-superconcentrator is a directed, acyclic graph with N input nodes and N output nodes such that every subset of the inputs and every subset of the outputs of same cardinality can be connected by node-disjoint paths. It is known that linear-size and bounded-degree superconcentrators exist. Here it is proved that such superconcentrators exist (by a random construction of certain expander graphs as building blocks) having density 28 (where the density is the number of edges divided by N). The best known density before this paper was 34.2 [U. Schöning, Construction of expanders and superconcentrators using Kolmogorov complexity, J. Random Structures Algorithms 17 (2000) 64-77] or 33 [L.A. Bassalygo, Personal communication, 2004]. 相似文献
27.
Besides equidistribution properties and statistical independence the lattice profile, a generalized version of Marsaglia's
lattice test, provides another quality measure for pseudorandom sequences over a (finite) field. It turned out that the lattice
profile is closely related with the linear complexity profile. In this article we give a survey of several features of the
linear complexity profile and the lattice profile, and we utilize relationships to completely describe the lattice profile
of a sequence over a finite field in terms of the continued fraction expansion of its generating function. Finally we describe
and construct sequences with a certain lattice profile, and introduce a further complexity measure. 相似文献
28.
Deterministic chaos theory offers useful quantitative tools to characterize the non-linear dynamic behavior of a fluidized bed and the developed complexity theory presents a new approach to evaluate finite sequences. In this paper,the non-linear,hydrodynamic behavior of the pressure flutuation signals in a reactor was discussed by chaos parameters and complexity measures.Coherent results were achieved by our multi-scale analysis,which further exposed the behavior in a gas-solid two-phase system. 相似文献
29.
Evidence from 3 experiments reveals interference effects from structural relationships that are inconsistent with any grammatical parse of the perceived input. Processing disruption was observed when items occurring between a head and a dependent overlapped with either (or both) syntactic or semantic features of the dependent. Effects of syntactic interference occur in the earliest online measures in the region where the retrieval of a long-distance dependent occurs. Semantic interference effects occur in later online measures at the end of the sentence. Both effects endure in offline comprehension measures, suggesting that interfering items participate in incorrect interpretations that resist reanalysis. The data are discussed in terms of a cue-based retrieval account of parsing, which reconciles the fact that the parser must violate the grammar in order for these interference effects to occur. Broader implications of this research indicate a need for a precise specification of the interface between the parsing mechanism and the memory system that supports language comprehension. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
30.
Eugene Fiume† 《Computer Graphics Forum》1995,14(1):47-58
The main preoccupations of research in computer-aided geometric design have been on shape-specification techniques for polynomial curves and surfaces, and on the continuity between segments or patches. When modelling with such techniques, curves and surfaces can be compressed or expanded arbitrarily. There has been relatively little work on interacting with direct spatial properties of curves and surfaces, such as their arc length or surface area. As a first step, we derive families of parametric piecewise polynomial curves that satisfy various positional and tangential constraints together with arc-length constraints. We call these curves isometric curves. A space curve is defined as a sequence of polynomial curve segments, each of which is defined by the familiar Hermite or Bézier constraints for cubic polynomials; as well, each segment is constrained to have a specified arc length. We demonstrate that this class of curves is attractive and stable. We also describe the numerical techniques used that are sufficient for achieving real time interaction with these curves on low-end workstations. 相似文献