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31.
本文针对网络化数字媒体的版权保护提出了一种新的灰度水印图像嵌入到RGB彩色图像中的方法。首先将灰度水印图像进行置乱变换,再将置乱后的图像转换成二值序列,并将二值序列进一步分解成三个二值序列;然后将待嵌入水印的彩色图像分解成R、G、B三个分量,对每个分量分别作二级小波变换,得到小波变换的子带系数,再用奇偶判断法把三个二值序列的值分别嵌入各分量子带;最后用小波逆变换,恢复图像,合并三个分量,得到嵌入水印后的图像。仿真结果表明,本文方法有很好的透明性,且能有效的抵抗剪切、灰度调整、有损压缩等攻击。 相似文献
32.
Floodplain roughness parameterization using airborne laser scanning and spectral remote sensing 总被引:1,自引:0,他引:1
Floodplain roughness parameterization is one of the key elements of hydrodynamic modeling of river flow, which is directly linked to exceedance levels of the embankments of lowland fluvial areas. The present way of roughness mapping is based on manually delineated floodplain vegetation types, schematized as cylindrical elements of which the height (m) and the vertical density (the projected plant area in the direction of the flow per unit volume, m− 1) have to be assigned using a lookup table. This paper presents a novel method of automated roughness parameterization. It delivers a spatially distributed roughness parameterization in an entire floodplain by fusion of CASI multispectral data with airborne laser scanning (ALS) data. The method consists of three stages: (1) pre-processing of the raw data, (2) image segmentation of the fused data set and classification into the dominant land cover classes (KHAT = 0.78), (3) determination of hydrodynamic roughness characteristics for each land cover class separately. In stage three, a lookup table provides numerical values that enable roughness calculation for the classes water, sand, paved area, meadows and built-up area. For forest and herbaceous vegetation, ALS data enable spatially detailed analysis of vegetation height and density. The hydrodynamic vegetation density of forest is mapped using a calibrated regression model. Herbaceous vegetation cover is further subdivided in single trees and non-woody vegetation. Single trees were delineated using a novel iterative cluster merging method, and their height is predicted (R2 = 0.41, rse = 0.84 m). The vegetation density of single trees was determined in an identical way as for forest. Vegetation height and density of non-woody herbaceous vegetation were also determined using calibrated regression models. A 2D hydrodynamic model was applied with the results of this novel method, and compared with a traditional roughness parameterization approach. The modeling results showed that the new method is well able to provide accurate output data. The new method provides a faster, repeatable, and more accurate way of obtaining floodplain roughness, which enables regular updating of river flow models. 相似文献
33.
An instance of the path hitting problem consists of two families of paths,
and ℋ, in a common undirected graph, where each path in ℋ is associated with a non-negative cost. We refer to
and ℋ as the sets of demand and hitting paths, respectively. When p∈ℋ and
share at least one mutual edge, we say that p
hits q. The objective is to find a minimum cost subset of ℋ whose members collectively hit those of
. In this paper we provide constant factor approximation algorithms for path hitting, confined to instances in which the underlying
graph is a tree, a spider, or a star. Although such restricted settings may appear to be very simple, we demonstrate that
they still capture some of the most basic covering problems in graphs. Our approach combines several novel ideas: We extend
the algorithm of Garg, Vazirani and Yannakakis (Algorithmica, 18:3–20, 1997) for approximate multicuts and multicommodity flows in trees to prove new integrality properties; we present a reduction
that involves multiple calls to this extended algorithm; and we introduce a polynomial-time solvable variant of the edge cover
problem, which may be of independent interest.
An extended abstract of this paper appeared in Proceedings of the 14th Annual European Symposium on Algorithms, 2006.
This work is part of D. Segev’s Ph.D. thesis prepared at Tel-Aviv University under the supervision of Prof. Refael Hassin. 相似文献
34.
We study the problem of segmenting a sequence into k pieces so that the resulting segmentation satisfies monotonicity or unimodality constraints. Unimodal functions can be used
to model phenomena in which a measured variable first increases to a certain level and then decreases. We combine a well-known
unimodal regression algorithm with a simple dynamic-programming approach to obtain an optimal quadratic-time algorithm for
the problem of unimodal k-segmentation. In addition, we describe a more efficient greedy-merging heuristic that is experimentally shown to give solutions
very close to the optimal. As a concrete application of our algorithms, we describe methods for testing if a sequence behaves
unimodally or not. The methods include segmentation error comparisons, permutation testing, and a BIC-based scoring scheme.
Our experimental evaluation shows that our algorithms and the proposed unimodality tests give very intuitive results, for
both real-valued and binary data.
Niina Haiminen received the M.Sc. degree from the University of Helsinki in 2004. She is currently a Graduate Student at the Department
of Computer Science of University of Helsinki, and a Researcher at the Basic Research Unit of Helsinki Institute for Information
Technology. Her research interests include algorithms, bioinformatics, and data mining.
Aristides Gionis received the Ph.D. degree from Stanford University in 2003, and he is currently a Senior Researcher at the Basic Research
Unit of Helsinki Institute for Information Technology. His research experience includes summer internship positions at Bell
Labs, AT&T Labs, and Microsoft Research. His research areas are data mining, algorithms, and databases.
Kari Laasonen received the M.Sc. degree in Theoretical Physics in 1995 from the University of Helsinki. He is currently a Graduate Student
in Computer Science at the University of Helsinki and a Researcher at the Basic Research Unit of Helsinki Institute for Information
Technology. His research is focused on algorithms and data analysis methods for pervasive computing. 相似文献
35.
左旭辉 《数字社区&智能家居》2009,5(9):7073-7074
为解决行为识别中运动特征提取的问题,该文提出了一种基于三阶帧差的运动特征提取方案,用于提取运动特征中的变化大小、运动变化的一致性、运动方向的一致性等。实验证明,新方法速度快,准确度高。 相似文献
36.
定义八近邻图像的边界跟踪自动机,利用自动机跟踪图像所有区域边界,自动机的输出为边界的顶点链码,在自动机跟踪所有边界的同时生成围线的树结构.跟踪算法复杂度是线性的,能跟踪任意复杂图像区域. 相似文献
37.
个性化、高性能的树形菜单有着广泛的应用。在分析.NET框架的TreeView控件的基础上,总结了基于.NET平台实现个性化树形菜单的基本方法,给出了优化树形菜单数据处理性能的基本策略。 相似文献
38.
定义了各种类型的经典二元关系和模糊二元关系,讨论了二元关系的合成及其性质.给出了两个近似空间合成的概念,并讨论合成前的近似空间所导出的近似算子与合成后的近似空间所导出的近似算子之间的关系.证明了合成后的近似空间所导出的近似算子恰好是两个近似空间所导出的近似算子的合成. 相似文献
39.
为了增强模型检测工具的检测能力,拓宽模型检测技术的应用范围,对基于时间自动机的LTL性质模型检测进行了研究,对自动机的状态空间的存储方式和状态空间的展开过程进行了分析,讨论了LTL性质模型检测工具的检测流程和检测算法的实现策略对工具检测性能的影响,针对制约模型工具的检测能力和检测效率的因素,采取了一些相应的优化改进策略.采用了BDD(二叉决策图)共享存储技术和位编码压缩存储,较有效地减小了空间消耗,缓解了模型检测中状态爆炸引起的内存空间不足问题.与DTSpin等著名的模型检测工具进行了实验比较,取得了较好的实验结果. 相似文献
40.
Hrmel Nestra 《The Journal of Logic and Algebraic Programming》2009,78(7):573-592
Transfinite semantics is a semantics according to which program executions can continue working after an infinite number of steps. Such a view of programs can be useful in the theory of program transformations.So far, transfinite semantics have been succesfully defined for iterative loops. This paper provides an exhaustive definition for semantics that enable also infinitely deep recursion.The definition is actually a parametric schema that defines a family of different transfinite semantics. As standard semantics also match the same schema, our framework describes both standard and transfinite semantics in a uniform way.All semantics are expressed as greatest fixpoints of monotone operators on some complete lattices. It turns out that, for transfinite semantics, the corresponding lattice operators are cocontinuous. According to Kleene’s theorem, this shows that transfinite semantics can be expressed as a limit of iteration which is not transfinite. 相似文献