全文获取类型
收费全文 | 36854篇 |
免费 | 5124篇 |
国内免费 | 2699篇 |
专业分类
电工技术 | 7053篇 |
技术理论 | 2篇 |
综合类 | 4318篇 |
化学工业 | 2598篇 |
金属工艺 | 572篇 |
机械仪表 | 1907篇 |
建筑科学 | 3075篇 |
矿业工程 | 1946篇 |
能源动力 | 1076篇 |
轻工业 | 2075篇 |
水利工程 | 1890篇 |
石油天然气 | 1591篇 |
武器工业 | 459篇 |
无线电 | 4185篇 |
一般工业技术 | 2801篇 |
冶金工业 | 1110篇 |
原子能技术 | 155篇 |
自动化技术 | 7864篇 |
出版年
2024年 | 174篇 |
2023年 | 507篇 |
2022年 | 1042篇 |
2021年 | 1203篇 |
2020年 | 1328篇 |
2019年 | 1136篇 |
2018年 | 1149篇 |
2017年 | 1473篇 |
2016年 | 1631篇 |
2015年 | 1787篇 |
2014年 | 2500篇 |
2013年 | 2520篇 |
2012年 | 2950篇 |
2011年 | 3135篇 |
2010年 | 2410篇 |
2009年 | 2320篇 |
2008年 | 2327篇 |
2007年 | 2698篇 |
2006年 | 2234篇 |
2005年 | 1851篇 |
2004年 | 1473篇 |
2003年 | 1269篇 |
2002年 | 1011篇 |
2001年 | 844篇 |
2000年 | 659篇 |
1999年 | 596篇 |
1998年 | 437篇 |
1997年 | 382篇 |
1996年 | 311篇 |
1995年 | 280篇 |
1994年 | 241篇 |
1993年 | 178篇 |
1992年 | 119篇 |
1991年 | 105篇 |
1990年 | 83篇 |
1989年 | 70篇 |
1988年 | 53篇 |
1987年 | 28篇 |
1986年 | 31篇 |
1985年 | 17篇 |
1984年 | 23篇 |
1983年 | 21篇 |
1982年 | 15篇 |
1981年 | 4篇 |
1980年 | 10篇 |
1979年 | 6篇 |
1965年 | 4篇 |
1964年 | 4篇 |
1961年 | 5篇 |
1959年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
Alexander Babich Konstantinos Mavrommatis Dieter Senk Heinrich Wilhelm Gudenau 《国际钢铁研究》2004,75(7):428-432
This contribution deals with advanced educational technologies needed to equip customers from higher education institutions, research and industry with efficient tools supporting their work and operating new skills‐training methods. The challenges are reducing the training costs, improving quality and increasing the number of graduates in engineering departments. The concept of a Virtual Lab based on the combination of various teaching methods and tools is presented. Principles of mathematisation in metallurgical education and training are discussed. An example of online course designed in the form of Virtual Lab is demonstrated. 相似文献
82.
A. Campillo J. I. Farran M. J. Pisabarro 《Applicable Algebra in Engineering, Communication and Computing》2007,18(1-2):191-203
We use the special geometry of singular points of algebraic differential equations on the affine plane over finite fields
to study the main features and parameters of error correcting codes giving by evaluating functions at sets of singular points.
In particular, one gets new methods to construct codes with designed minimum distance.
This work was partially supported by MCyT BFM2001-2251. 相似文献
83.
In this work, we co‐formulated an oil‐borne copper naphthenate/permethrin wood preservative system with synthetic polymer‐based fire‐retardant additives prior to the impregnation of Pinus radiata sapwood. We evaluated what effect, if any, the preservative had upon the fire performance properties of the fire retardants and whether the fire retardants impacted on the fungicidal and termiticidal efficacy of the preservative. The fire retardants included halogenated and phosphorus‐based systems. A mass loss calorimeter, in conjunction with a thermopile, was used to measure the time to ignition and the peak heat release rate (PHRR) from which the fire performance index (FPI) was determined. The preservative properties were evaluated using termite and soil‐block decay bioassays. In summary, we found that the rate of fire growth was reduced when the fire retardants were used in combination with the wood preservative. We also found that the PHRR was a better determinant of fire performance than the FPI. The performance of the wood preservative was enhanced against fungal decay and termite attack when used in combination with the fire retardants. The fire retardants also demonstrated some wood preservative properties of their own. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
84.
We propose subspace distance measures to analyze the similarity between intrapersonal face subspaces, which characterize the variations between face images of the same individual. We call the conventional intrapersonal subspace average intrapersonal subspace (AIS) because the image differences often come from a large number of persons. An intrapersonal subspace is referred to as specific intrapersonal subspace (SIS) if the image differences are from just one person. We demonstrate that SIS varies significantly from person to person, and most SISs are not similar to AIS. Based on these observations, we introduce the maximum a posteriori (MAP) adaptation to the problem of SIS estimation, and apply it to the Bayesian face recognition algorithm. Experimental results show that the adaptive Bayesian algorithm outperforms the non-adaptive Bayesian algorithm as well as Eigenface and Fisherface methods if a small number of adaptation images are available. 相似文献
85.
改进的GMDH方法及其在参数预报中的应用 总被引:4,自引:0,他引:4
本文在综合了GMDH方法中几种有效的改进算法的基础上,进一步研究了变量预选及部分表达式的构成问题,采用最优化方法确定变量最佳组成式并进行变量筛选,由此得到精度更高、稳定性较好的模型,将其应用于聚丙烯熔指数的预报,仿真结果令人满意。 相似文献
86.
87.
88.
杜昱 《数字社区&智能家居》2006,(8):15-15,57
文章首先概述了当前大多数的搜索引擎的主要的弊端;然后着重介绍了智能检索系统的运行基本思路和售用算法,以及该算法在检索领域中运用的优点;最后指出,神经网络运用在检索领域,可解决网络管理中的诸多难题。 相似文献
89.
“To understand and protect our home planet, to explore the universe and search for life, and to inspire the next generation of explorers” is NASA's mission. The Systems Management Office at Johnson Space Center (JSC) is searching for methods to effectively manage the Center's resources to meet NASA's mission. D-Side is a group multi-criteria decision support system (GMDSS) developed to support facility decisions at JSC. D-Side uses a series of sequential and structured processes to plot facilities in a three-dimensional (3-D) graph on the basis of each facility's alignment with NASA's mission and goals, the extent to which other facilities are dependent on the facility, and the dollar value of capital investments that have been postponed at the facility relative to the facility's replacement value. A similarity factor rank orders facilities based on their Euclidean distance from Ideal and Nadir points. These similarity factors are then used to allocate capital improvement resources across facilities. We also present a parallel model that can be used to support decisions concerning allocation of human resources investments across workforce units. Finally, we present results from a pilot study where 12 experienced facility managers from NASA used D-Side and the organization's current approach to rank order and allocate funds for capital improvement across 20 facilities. Users evaluated D-Side favorably in terms of ease of use, the quality of the decision-making process, decision quality, and overall value-added. Their evaluations of D-Side were significantly more favorable than their evaluations of the current approach. 相似文献
90.
Bar-Anan Yoav; Liberman Nira; Trope Yaacov; Algom Daniel 《Canadian Metallurgical Quarterly》2007,136(4):610
A picture-word version of the Stroop task was used to test the automatic activation of psychological distance by words carrying various senses of psychological distance: temporal (tomorrow, in a year), social (friend, enemy), and hypotheticality (sure, maybe). The pictures implied depth, with the words appearing relatively close to or distant from the observer. The participants classified the spatial distance of words faster when the word's implicit psychological distance matched its spatial distance (e.g., a geographically close word was classified faster when it was "friend" than when it was "enemy"). The findings are consistent with the idea that psychological distance is accessed automatically, even when it is not directly related to people's current goals, and suggest that psychological distance is an important dimension of meaning, common to spatial distance, temporal distance, social distance, and hypotheticality. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献