全文获取类型
收费全文 | 27098篇 |
免费 | 2980篇 |
国内免费 | 2097篇 |
专业分类
电工技术 | 1677篇 |
技术理论 | 2篇 |
综合类 | 3456篇 |
化学工业 | 3317篇 |
金属工艺 | 2868篇 |
机械仪表 | 1671篇 |
建筑科学 | 1722篇 |
矿业工程 | 1203篇 |
能源动力 | 555篇 |
轻工业 | 2269篇 |
水利工程 | 485篇 |
石油天然气 | 669篇 |
武器工业 | 296篇 |
无线电 | 3012篇 |
一般工业技术 | 2906篇 |
冶金工业 | 1535篇 |
原子能技术 | 108篇 |
自动化技术 | 4424篇 |
出版年
2024年 | 112篇 |
2023年 | 382篇 |
2022年 | 710篇 |
2021年 | 886篇 |
2020年 | 936篇 |
2019年 | 733篇 |
2018年 | 663篇 |
2017年 | 902篇 |
2016年 | 948篇 |
2015年 | 1178篇 |
2014年 | 1835篇 |
2013年 | 1712篇 |
2012年 | 2235篇 |
2011年 | 2352篇 |
2010年 | 1749篇 |
2009年 | 1684篇 |
2008年 | 1491篇 |
2007年 | 1937篇 |
2006年 | 1721篇 |
2005年 | 1338篇 |
2004年 | 1052篇 |
2003年 | 898篇 |
2002年 | 715篇 |
2001年 | 641篇 |
2000年 | 561篇 |
1999年 | 424篇 |
1998年 | 359篇 |
1997年 | 355篇 |
1996年 | 272篇 |
1995年 | 268篇 |
1994年 | 257篇 |
1993年 | 150篇 |
1992年 | 156篇 |
1991年 | 137篇 |
1990年 | 117篇 |
1989年 | 112篇 |
1988年 | 68篇 |
1987年 | 30篇 |
1986年 | 14篇 |
1985年 | 17篇 |
1984年 | 13篇 |
1983年 | 11篇 |
1982年 | 10篇 |
1981年 | 11篇 |
1980年 | 8篇 |
1979年 | 5篇 |
1976年 | 2篇 |
1960年 | 1篇 |
1959年 | 2篇 |
1951年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
It is shown that the well known two-pass sequential local transformation algorithm for computing a distance transformation in rectangular domains may fail in some convex integer domains, but that a four-pass algorithm is sufficient in all two-dimensional convex domains. For non-convex domains the number of passes necessary is shown to be generally greater. Two propagation algorithms for computing the distance transformation are described and shown theoretically and experimentally to be computationally more efficient than the sequential local transformation algorithm in non-convex domains of complex shape. The relationship of the distance transformation in non-convex domains to some more general transformations is explored. 相似文献
72.
可拓市场的类型与实现方式研究 总被引:7,自引:0,他引:7
根据可拓市场的概念,探讨了在不同可拓变换下可拓市场的类型及实现可拓市场的方式。这些研究为企业开拓市场提供了有效的形式化方法。 相似文献
73.
N. C. W. Kuijpers W. H. Kool P. T. G. Koenis K. E. Nilsen I. Todd S. van der Zwaag 《Materials Characterization》2002,49(5)
During homogenisation of AA 6xxx aluminium alloys, the platelike β-AlFeSi intermetallic phase will transform to a less Si-rich and more spheroidised α-Al(FeMn)Si phase which is more favourable for extrusion. In this study, several quantitative methods, which determine the relative volume fraction of α-Al(FeMn)Si and β-AlFeSi, are compared and an assessment of each method is made. The methods used are optical microscopy, scanning electron microscopy (SEM) in combination with electron dispersive X-ray (EDX) using polished samples, and X-ray diffraction (XRD) on intermetallics, extracted through selective dissolution of the Al matrix. The highest accuracy is obtained by using SEM/EDX analysis and applying two criteria. 相似文献
74.
75.
An orthogonal basis for the hyperbolic hybrid polynomial space 总被引:1,自引:0,他引:1
Motivated by the wide usage of the Tchebyshev basis and Legendre basis in the algebra polynomial space, we construct an orthogonal basis with the properties of the H-Bézier basis in the hyperbolic hybrid polynomial space, which is similar to the Legendre basis and holds remarkable properties. Moreover, we derive the transformation matrices that map the H-Bézier basis and the orthogonal basis forms into each other. An example for approximating the degree reduction of the H- Bézier curves is sketched to illustrate the utility of the orthogonal basis. 相似文献
76.
77.
WANG Kai WANG Bei WU Rui-zhi 《国际设备工程与管理》2007,12(3):154-159
In order to reduce the vibration on a machine tool, more orthogonal experiment schemes have been designed, which are based on the steel balls vibration reducing principle. After experiments the optimal reducing vibration scheme was determined. This kind of vibration reducing scheme is used in steel balls vibration absorber, which can be used to reduce vibration magnitudes of a machine tools under the working conditions, whereby improving machining precision. The suggested experiment method is of useful reference in reducing vibrations on other machine tools too. 相似文献
78.
以有效的技改投资决策理念指导企业技改投资,加快了企业技术进步,促进了企业跨越式发展,使三钢的产能从1996年年产钢50万t钢规模发展到目前的200万t钢水平,且优化了产业结构,技术经济指标从全国同行业的中下游上升到领先水平,增强了企业实力。但是,在取得显著成绩的同时,周边民营钢铁企业异军突起,面对严峻的挑战,三钢力争两年内依靠技改使产能达到300万t钢规模,并筹谋更远大的发展。 相似文献
79.
Sánchez-Meca Julio; Marín-Martínez Fulgencio; Chacón-Moscoso Salvador 《Canadian Metallurgical Quarterly》2003,8(4):448
It is very common to find meta-analyses in which some of the studies compare 2 groups on continuous dependent variables and others compare groups on dichotomized variables. Integrating all of them in a meta-analysis requires an effect-size index in the same metric that can be applied to both types of outcomes. In this article, the performance in terms of bias and sampling variance of 7 different effect-size indices for estimating the population standardized mean difference from a 2 × 2 table is examined by Monte Carlo simulation, assuming normal and nonnormal distributions. The results show good performance for 2 indices, one based on the probit transformation and the other based on the logistic distribution. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
80.
Plasmas play a critical role in depositing thin films or etching fine patterns while manufacturing integrated circuits. A new model for plasma diagnosis is presented. This was accomplished by linking atomic force microscopy (AFM) to plasma parameters using a neural network. Experimental AFM data were collected during the etching of silicon oxynitride films in C2F6 inductively coupled plasma. Surface roughness of etched patterns was characterized by means of discrete wavelet transformation. This led to the construction of three vertical (type I), diagonal (type II), and horizontal (type III) wavelet coefficient-based models. The performance of diagnosis models was evaluated in terms of the prediction and recognition accuracies. Both accuracies were optimized as a function of the number of hidden neurons. Comparisons revealed that the type I model yielded the largest recognition and the smallest prediction error. This was demonstrated even under stricter monitoring conditions. More improved diagnosis is expected by enhancing AFM resolution. 相似文献