全文获取类型
收费全文 | 13121篇 |
免费 | 728篇 |
国内免费 | 446篇 |
专业分类
电工技术 | 511篇 |
综合类 | 850篇 |
化学工业 | 1522篇 |
金属工艺 | 208篇 |
机械仪表 | 505篇 |
建筑科学 | 802篇 |
矿业工程 | 99篇 |
能源动力 | 505篇 |
轻工业 | 383篇 |
水利工程 | 248篇 |
石油天然气 | 200篇 |
武器工业 | 46篇 |
无线电 | 608篇 |
一般工业技术 | 1474篇 |
冶金工业 | 1907篇 |
原子能技术 | 93篇 |
自动化技术 | 4334篇 |
出版年
2024年 | 24篇 |
2023年 | 155篇 |
2022年 | 215篇 |
2021年 | 272篇 |
2020年 | 265篇 |
2019年 | 279篇 |
2018年 | 247篇 |
2017年 | 342篇 |
2016年 | 384篇 |
2015年 | 397篇 |
2014年 | 538篇 |
2013年 | 977篇 |
2012年 | 566篇 |
2011年 | 880篇 |
2010年 | 643篇 |
2009年 | 766篇 |
2008年 | 751篇 |
2007年 | 814篇 |
2006年 | 723篇 |
2005年 | 682篇 |
2004年 | 560篇 |
2003年 | 500篇 |
2002年 | 436篇 |
2001年 | 341篇 |
2000年 | 264篇 |
1999年 | 288篇 |
1998年 | 379篇 |
1997年 | 218篇 |
1996年 | 166篇 |
1995年 | 136篇 |
1994年 | 129篇 |
1993年 | 120篇 |
1992年 | 114篇 |
1991年 | 112篇 |
1990年 | 101篇 |
1989年 | 51篇 |
1988年 | 60篇 |
1987年 | 47篇 |
1986年 | 58篇 |
1985年 | 73篇 |
1984年 | 48篇 |
1983年 | 47篇 |
1982年 | 31篇 |
1981年 | 16篇 |
1980年 | 18篇 |
1979年 | 12篇 |
1978年 | 11篇 |
1977年 | 8篇 |
1976年 | 4篇 |
1975年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
111.
This paper introduces a novel methodology for clustering of symbolic objects by making use of Genetic Algorithms (GAs). GAs
are a family of computational models inspired by evolution. These algorithms encode potential solutions to specific problems
on simple chromosome-like data structures and apply recombination operators to these structures so as to preserve critical
information. A new type of representation for chromosome structure is presented here along with a new method for mutation.
The efficacy of the proposed method is examined by application to numeric data of known number of classes and also to assertion
type of symbolic objects drawn from the domain of fat oil, microcomputers, microprocessors and botany. The validity of the
clusters obtained is examined. 相似文献
112.
113.
David L. Spooner 《Journal of Intelligent Manufacturing》1994,5(1):13-21
A product database for a design and manufacturing enterprise serves as a repository for the data needed to manufacture a product. This paper discusses how an object-oriented persistent object manager named ROSE, under development at Rensselaer, has been used in the Rensselaer CIM program to develop a STEP/PDES-compliant product database for its research test bed. In so doing, it provides an overview of the requirements for a product database system in an integrated design and manufacturing facility, and it discusses how the chosen system meets these requirements. 相似文献
114.
Providing definition and temporal structure for multimedia data 总被引:1,自引:0,他引:1
115.
116.
Robert L. Stevenson Susan M. Schweizer 《Journal of Mathematical Imaging and Vision》1992,2(2-3):137-154
This paper introduces a new nonlinear filtering structure for filtering image data that have been corrupted by both impulsive and nonimpulsive additive noise. Like other nonlinear filters, the proposed filtering structure uses order-statistic operations to remove the effects of the impulsive noise. Unlike other filters, however, nonimpulsive noise is smoothed by using a maximum a posteriori estimation criterion. The prior model for the image is a novel Markov random-field model that models image edges so that they are accurately estimated while additive Gaussian noise is smoothed. The Markov random-field-based prior is chosen such that the filter has desirable analytical and computational properties. The estimate of the signal value is obtained at the unique minimum of the a posteriori log likelihood function. This function is convex so that the output of the filter can be easily computed by using either digital or analog computational methods. The effects of the various parameters of the model will be discussed, and the choice of the predetection order statistic filter will also be examined. Example outputs under various noise conditions will be given. 相似文献
117.
Combined-Stage Sintering Model 总被引:8,自引:0,他引:8
James D. Hansen Richard P. Rusin Mao-Hua Teng D. Lynn Johnson 《Journal of the American Ceramic Society》1992,75(5):1129-1135
By focusing on the similarities between the three stages of sintering, a single equation is derived that quantifies sintering as a continuous process from beginning to end. The microstructure is characterized by two separate parameters representing geometry and scale. The dimensionless geometry parameter, denoted T, comprises five scaling factors that relate specific microstructural featuers (e.g., surface curvature) to the scale (grain diameter). Calculations of T from experimental data show (a) agreement with computer simulations of initial-stage sintering, (b) the effect of surface diffusion on T, and (c) changes in T with microstructural evolution during sintering. Application of the model to the design of firing schedules and the study of microstructural geometry effects on sintering is discussed. 相似文献
118.
119.
Chen-Tsung Kuo Author Vitae 《Pattern recognition》2007,40(2):742-755
Three dimensional models play an important role in many applications; the problem is how to select the appropriate models from a 3D database rapidly and accurately. In recent years, a variety of shape representations, statistical methods, and geometric algorithms have been proposed for matching 3D shapes or models. In this paper, we propose a 3D shape representation scheme based on a combination of principal plane analysis and dynamic programming. The proposed 3D shape representation scheme consists of three steps. First, a 3D model is transformed into a 2D image by projecting the vertices of the model onto its principal plane. Second, the convex hall of the 2D shape of the model is further segmented into multiple disjoint triangles using dynamic programming. Finally, for each triangle, a projection score histogram and moments are extracted as the feature vectors for similarity searching. Experimental results showed the robustness of the proposed scheme, which resists translation, rotation, scaling, noise, and destructive attacks. The proposed 3D model retrieval method performs fairly well in retrieving models having similar characteristics from a database of 3D models. 相似文献
120.
本文探讨经短时信号处理后的语音信号帧间相关信息对基于隐马尔可夫模型(HMM)的语音识别系统识虽精度的影响,鉴于HMM的输出独立假设导致语音帧间相关信息的损失,本文提出了一种描述帧间相关信息的统计模型-马尔可夫链(MCM)用来弥补HMM在这方面的缺陷;经非特定人和多话者孤立字实验表明,用MCM作为HMM的辅助模型,可将原有HMM系统的识别率提高约1~6个百分点。 相似文献