全文获取类型
收费全文 | 286287篇 |
免费 | 18414篇 |
国内免费 | 7943篇 |
专业分类
电工技术 | 12395篇 |
技术理论 | 23篇 |
综合类 | 13265篇 |
化学工业 | 46637篇 |
金属工艺 | 15261篇 |
机械仪表 | 15355篇 |
建筑科学 | 18549篇 |
矿业工程 | 5524篇 |
能源动力 | 7089篇 |
轻工业 | 16246篇 |
水利工程 | 4459篇 |
石油天然气 | 11467篇 |
武器工业 | 1353篇 |
无线电 | 34711篇 |
一般工业技术 | 42361篇 |
冶金工业 | 13476篇 |
原子能技术 | 2524篇 |
自动化技术 | 51949篇 |
出版年
2024年 | 2156篇 |
2023年 | 3609篇 |
2022年 | 6068篇 |
2021年 | 8079篇 |
2020年 | 6043篇 |
2019年 | 5151篇 |
2018年 | 19124篇 |
2017年 | 18977篇 |
2016年 | 15223篇 |
2015年 | 7961篇 |
2014年 | 9862篇 |
2013年 | 12532篇 |
2012年 | 15216篇 |
2011年 | 22794篇 |
2010年 | 19470篇 |
2009年 | 16690篇 |
2008年 | 17315篇 |
2007年 | 17926篇 |
2006年 | 10971篇 |
2005年 | 10782篇 |
2004年 | 7630篇 |
2003年 | 6876篇 |
2002年 | 5771篇 |
2001年 | 4819篇 |
2000年 | 5039篇 |
1999年 | 5700篇 |
1998年 | 5340篇 |
1997年 | 4385篇 |
1996年 | 4005篇 |
1995年 | 3322篇 |
1994年 | 2780篇 |
1993年 | 2195篇 |
1992年 | 1712篇 |
1991年 | 1303篇 |
1990年 | 1018篇 |
1989年 | 880篇 |
1988年 | 694篇 |
1987年 | 501篇 |
1986年 | 400篇 |
1985年 | 339篇 |
1984年 | 214篇 |
1983年 | 201篇 |
1982年 | 165篇 |
1981年 | 145篇 |
1980年 | 131篇 |
1979年 | 97篇 |
1977年 | 63篇 |
1976年 | 77篇 |
1955年 | 63篇 |
1954年 | 68篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Background The accelerator-driven subcritical transmuta-tion system(ADS)is an advanced technology for the harmless disposal of nuclear waste.A theoretical analy... 相似文献
992.
993.
受小煤窑开采的破坏,在露天煤矿的开采中,对采空区探查的安全技术管理非常重要并直接影响到安全生产。根据采空区破坏范围和形态,采用科学、合理的探查手段和方法探查采空区,能取得较好的爆破效果。 相似文献
994.
The polynomial-time solvable k-hurdle problem is a natural generalization of the classical s-t minimum cut problem where we must select a minimum-cost subset S of the edges of a graph such that |p∩S|≥k for every s-t path p. In this paper, we describe a set of approximation algorithms for “k-hurdle” variants of the NP-hard multiway cut and multicut problems. For the k-hurdle multiway cut problem with r terminals, we give two results, the first being a pseudo-approximation algorithm that outputs a (k−1)-hurdle solution whose cost is at most that of an optimal solution for k hurdles. Secondly, we provide a
2(1-\frac1r)2(1-\frac{1}{r})-approximation algorithm based on rounding the solution of a linear program, for which we give a simple randomized half-integrality
proof that works for both edge and vertex k-hurdle multiway cuts that generalizes the half-integrality results of Garg et al. for the vertex multiway cut problem. We
also describe an approximation-preserving reduction from vertex cover as evidence that it may be difficult to achieve a better
approximation ratio than
2(1-\frac1r)2(1-\frac{1}{r}). For the k-hurdle multicut problem in an n-vertex graph, we provide an algorithm that, for any constant ε>0, outputs a ⌈(1−ε)k⌉-hurdle solution of cost at most O(log n) times that of an optimal k-hurdle solution, and we obtain a 2-approximation algorithm for trees. 相似文献
995.
Bankruptcy prediction has long time been an active research field in finance. One of the main approaches to this issue is
dealing with it as a classification problem. Among the range of instruments available, we focus our attention on the Evolutionary
Nearest Neighbor Classifier (ENPC). In this work we assess the performance of the ENPC comparing it to six alternatives. The
results suggest that this algorithm might be considered a good choice. 相似文献
996.
This study investigated the effects of screen layout on the usability of a large number of color combination options for customized product. Using an L18 orthogonal array, 18 interfaces were designed around four factors: color display, color name, color formation and alignment. Participants completed a color combination search task and a questionnaire concerning their satisfaction with the interfaces.Based on the search time and user satisfaction, the display of color samples by modular sections (itemized color chips) was found to be the optimal method of color selection. This arrangement reduced the number of combinations of color samples displayed on the screen and allowed efficient navigation of a large palette of color combinations. Vertical alignment aided the product color discrimination and reduced the search time. Users viewed various product color combinations directly with or without the aid of color names.
Relevance to industry
Because of the considerable observed reductions in search time and the superior reported degrees of satisfaction associated with the tested configurations for customized product color combination, the findings of this study have important ramifications for consumers and manufacturers of products as diverse as sofas, curtains, clothing, athletic shoes, cars, mobile phones and the other customized products. 相似文献997.
Image coding quality assessment using fuzzy integrals with a three-component image model 总被引:2,自引:0,他引:2
Based on importance measures and fuzzy integrals, a new assessment method for image coding quality is presented in this paper. The proposed assessment is based on two subevaluations. In the first subevaluation, errors on edges, textures, and flat regions are computed individually. The errors are then assessed using an assessment function. A global evaluation with Sugeno fuzzy integral is then obtained based on the importance measure of edge, texture, and flat region. In the second subevaluation, an importance measure is first established depending on the types of regions where errors occur, a subtle evaluation is then obtained using Sugeno fuzzy integral on all pixels of the image. A final evaluation is obtained based on the two subevaluations. Experimental results show that this new image quality assessment closely approximates human subjective tests such as mean opinion score with a high correlation coefficient of 0.963, which is a significant improvement over peak signal-to-noise ratio, picture quality scale, and weighted mean square error, three other image coding quality assessment methods, which have the correlation coefficients of 0.821, 0.875, and 0.716, respectively. 相似文献
998.
脊波导在传播电磁波的过程中伴随有能量损耗,为了研究填充介质脊波导的衰减特性,本文采用有限元法借助Matlab软件计算了TE模式下部分填充介质倒梯形对称双脊波导的衰减常数和功率容量.分析了脊波导衰减常数和功率容量与脊波导尺寸、工作频率、填充介质相对介电常数之间的关系,给出关系曲线图.这些结果将丰富现有的填充非均匀介质脊波导的数据,为填充介质脊波导的设计和优化提供有价值的依据. 相似文献
999.
In this paper, the finite‐time agreement problem of continuous‐time multi‐agent systems with communication delays is considered. First, the multi‐agent system researched in the paper is described. Second, some notations and lemmas used in the paper are given. Then, agreement protocols for continuous (but non‐smooth) multi‐agent systems are proposed, which ensure that the states of agents reach agreement in finite time. The stability analysis and simulations are presented to show the effectiveness of the method. Copyright © 2009 John Wiley and Sons Asia Pte Ltd and Chinese Automatic Control Society 相似文献
1000.
针对目前纯软件实现的IP电话存在的使用不方便等缺陷,设计并实现了一种局域网IP电话系统。文章详细描述了该系统中下位机软件的设计及实现方法,并说明了软件设计中应注意的事项。 相似文献