全文获取类型
收费全文 | 7328篇 |
免费 | 939篇 |
国内免费 | 801篇 |
专业分类
电工技术 | 155篇 |
技术理论 | 1篇 |
综合类 | 679篇 |
化学工业 | 101篇 |
金属工艺 | 34篇 |
机械仪表 | 290篇 |
建筑科学 | 184篇 |
矿业工程 | 47篇 |
能源动力 | 26篇 |
轻工业 | 55篇 |
水利工程 | 57篇 |
石油天然气 | 45篇 |
武器工业 | 85篇 |
无线电 | 973篇 |
一般工业技术 | 394篇 |
冶金工业 | 885篇 |
原子能技术 | 16篇 |
自动化技术 | 5041篇 |
出版年
2024年 | 45篇 |
2023年 | 105篇 |
2022年 | 186篇 |
2021年 | 167篇 |
2020年 | 188篇 |
2019年 | 170篇 |
2018年 | 162篇 |
2017年 | 215篇 |
2016年 | 238篇 |
2015年 | 246篇 |
2014年 | 432篇 |
2013年 | 473篇 |
2012年 | 534篇 |
2011年 | 604篇 |
2010年 | 462篇 |
2009年 | 516篇 |
2008年 | 522篇 |
2007年 | 554篇 |
2006年 | 433篇 |
2005年 | 416篇 |
2004年 | 373篇 |
2003年 | 313篇 |
2002年 | 248篇 |
2001年 | 211篇 |
2000年 | 138篇 |
1999年 | 135篇 |
1998年 | 118篇 |
1997年 | 76篇 |
1996年 | 91篇 |
1995年 | 70篇 |
1994年 | 58篇 |
1993年 | 45篇 |
1992年 | 49篇 |
1991年 | 37篇 |
1990年 | 26篇 |
1989年 | 22篇 |
1988年 | 19篇 |
1985年 | 27篇 |
1984年 | 23篇 |
1983年 | 27篇 |
1982年 | 26篇 |
1981年 | 23篇 |
1980年 | 28篇 |
1979年 | 31篇 |
1976年 | 14篇 |
1966年 | 12篇 |
1964年 | 19篇 |
1963年 | 17篇 |
1959年 | 12篇 |
1956年 | 12篇 |
排序方式: 共有9068条查询结果,搜索用时 15 毫秒
1.
2.
Private information retrieval(PIR) is an important privacy protection issue of secure multi-party computation, but the PIR protocols based on classical cryptography are vulnerable because of new technologies,such as quantum computing and cloud computing. The quantum private queries(QPQ) protocols available, however, has a high complexity and is inefficient in the face of large database. This paper, based on the QKD technology which is mature now, proposes a novel QPQ protocol utilizing the key dilution and auxiliary parameter. Only N quits are required to be sent in the quantum channel to generate the raw key, then the straight k bits in the raw key are added bitwise to dilute the raw key, and a final key is consequently obtained to encrypt the database. By flexible adjusting of auxiliary parameters θ and k, privacy is secured and the query success ratio is improved. Feasibility and performance analyses indicate that the protocol has a high success ratio in first-trial query and is easy to implement, and that the communication complexity of O(N) is achieved. 相似文献
3.
Journal of Computer Science and Technology - DOACROSS loops are significant parts in many important scientific and engineering applications, which are generally exploited pipeline/wave-front... 相似文献
4.
The pharmacy service requires that some pharmacies are always available and shifts have to be organized: a shift corresponds to a subset of pharmacies that must be open 24 hours a day on a particular week. Under the requirement that each pharmacy belongs to exactly one shift and the assumption that users minimize the distance to the closest open pharmacy during each shift, we want to determine a partition of the pharmacies into a given number of shifts, such that the total distance covered by users is minimized. It may be also required that shift cardinalities are balanced. We discuss different versions and the related computational complexity, showing that the problem is NP-hard in general. A set packing formulation is presented and solved by branch-and-price, together with a fast solution technique based on a tabu search. They have been applied to real and random instances showing that (i) the set packing formulation is very tight and often exhibits no integrality gap; (ii) the branch-and-price solves problems of practical relevance to optimality in a reasonable amount of time (order of minutes); (iii) the tabu search finds optimal or near-optimal solutions in order of seconds. 相似文献
5.
6.
Evidence suggests that transient visual information, such as animations, may be more challenging to learn than static visualizations. However, when a procedural-manipulative task is involved, our evolved embodied cognition seems to reverse this transitory challenge. Hence, for object manipulative tasks, instructional animations may be more suitable than statics. We investigated this argument further by comparing animations with statics using a Lego task shown to university students, by examining three potential moderators of effectiveness: (a) the environment of manipulation (virtual or physical), (b) the quality of visual information (focused or unfocused), and (c) the presence of hands (no hands or with hands). In Experiment 1 we found an advantage of animation over statics, and no differences among the environments. In Experiment 2, we again observed an animation advantage, a small advantage of focused static information compared to unfocused static information, and a positive effect of not showing the hands. 相似文献
7.
The present study investigates the impact of different key solutions of mobile phones on users' effectiveness and efficiency using the devices. In the first experiment, 36 children (9 - 14 years) and in the second experiment 45 young adults (19 - 33 years) completed four common phone tasks twice consecutively on three simulated phones that had identical menus, but different key solutions. An approach was undertaken to quantify the complexity of keys in three models, incorporating different factors contributing to the keys' complexity (number of key options, number of modes and number of modes with a semantically dissimilar meaning), in order to predict users' performance decrements. As a further main factor, the degree of the users' locus of control (LOC) was measured and interactions with performance outcomes were studied. As dependent measures, the number of inefficient keystrokes, the number of tasks solved and the processing time were determined. Results showed a significant effect of control key solutions on users' efficiency and effectiveness for both children and young adults. Moreover, children's LOC values significantly interacted with performance: children with low LOC values showed the lowest performance and no learnability, especially when using keys with a high complexity. From the three factors contributing to the complexity of keys, keys exerting different functions with semantically inconsistent meanings had the worst effect on performance. It is concluded that in mobile user interface design keys with semantically inconsistent meanings should be generally avoided. 相似文献
8.
嵌入式RTOS中任务优先级反转问题研究 总被引:1,自引:0,他引:1
针对嵌入式实时系统任务调度策略的特点,任务在运行的时候可能被更高优先级的任务中断。分析了嵌入式RTOS中的最高就绪任务的查找算法,指出该调度算法存在的不同优先级的反转问题,并且针对这一问题进行研究,给出了相应的优先级继承方案。较好地解决了RTOS中任务调度中的优先级的反转问题。 相似文献
9.
Recent years have witnessed a rapid growth of interest in the study of the dynamic behavior of replenishment rules of bullwhip effect. We prove that bullwhip effect and butterfly effect share a same the self-oscillation amplifying mechanism that is the ordering decisions the supplier self-oscillation amplify the perturbations brought by the errors in the processing of retailers' demand information. This results as an explicit self-similar structure of the sensitivity of the system to the initial values duty to the nonlinear mechanism. In this paper, the causes process of the bullwhip effect is described as the internal nonlinear mechanism and study on the complexity of bullwhip effect for order-up-to policy under demand signal processing. The methodology is based on fractal and chaotic theory and allows important insights to be gained about the complexity behavior of bullwhip effect. 相似文献
10.
介绍了一种日常参数智能控制器的研制及研制过程中的几个重要问题的解决方法。特别是用于城市照明及美化城市的彩灯的开、关时间智能控制方面,给出了依据当地绝对时间、经度、纬度进行昼夜时间计算的方法,使之在不接光电传感器情况下可跟踪季节的昼夜变化。控制系统采用89C2051单片机,配有时钟日历芯片DS12887,系统体积小、功能强、可靠性高。 相似文献