全文获取类型
收费全文 | 72996篇 |
免费 | 8398篇 |
国内免费 | 4780篇 |
专业分类
电工技术 | 9167篇 |
技术理论 | 2篇 |
综合类 | 7128篇 |
化学工业 | 5212篇 |
金属工艺 | 1792篇 |
机械仪表 | 4548篇 |
建筑科学 | 7532篇 |
矿业工程 | 3647篇 |
能源动力 | 2001篇 |
轻工业 | 2893篇 |
水利工程 | 3939篇 |
石油天然气 | 2535篇 |
武器工业 | 800篇 |
无线电 | 8265篇 |
一般工业技术 | 5382篇 |
冶金工业 | 2332篇 |
原子能技术 | 1065篇 |
自动化技术 | 17934篇 |
出版年
2024年 | 317篇 |
2023年 | 927篇 |
2022年 | 1894篇 |
2021年 | 2237篇 |
2020年 | 2591篇 |
2019年 | 2129篇 |
2018年 | 1946篇 |
2017年 | 2573篇 |
2016年 | 3008篇 |
2015年 | 3316篇 |
2014年 | 5154篇 |
2013年 | 5143篇 |
2012年 | 6069篇 |
2011年 | 6072篇 |
2010年 | 4302篇 |
2009年 | 4357篇 |
2008年 | 4119篇 |
2007年 | 4786篇 |
2006年 | 4316篇 |
2005年 | 3662篇 |
2004年 | 3032篇 |
2003年 | 2661篇 |
2002年 | 2202篇 |
2001年 | 1800篇 |
2000年 | 1563篇 |
1999年 | 1147篇 |
1998年 | 897篇 |
1997年 | 768篇 |
1996年 | 592篇 |
1995年 | 495篇 |
1994年 | 394篇 |
1993年 | 293篇 |
1992年 | 218篇 |
1991年 | 211篇 |
1990年 | 151篇 |
1989年 | 136篇 |
1988年 | 104篇 |
1987年 | 76篇 |
1986年 | 63篇 |
1985年 | 66篇 |
1984年 | 49篇 |
1983年 | 41篇 |
1982年 | 45篇 |
1981年 | 38篇 |
1980年 | 30篇 |
1979年 | 28篇 |
1978年 | 13篇 |
1977年 | 13篇 |
1964年 | 14篇 |
1956年 | 12篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Structural health monitoring system based on multi-agent coordination and fusion for large structure
In practical applications of structural health monitoring technology, a large number of distributed sensors are usually adopted to monitor the big dimension structures and different kinds of damage. The monitored structures are usually divided into different sub-structures and monitored by different sensor sets. Under this situation, how to manage the distributed sensor set and fuse different methods to obtain a fast and accurate evaluation result is an important problem to be addressed deeply. In the paper, a multi-agent fusion and coordination system is presented to deal with the damage identification for the strain distribution and joint failure in the large structure. Firstly, the monitoring system is adopted to distributedly monitor two kinds of damages, and it self-judges whether the static load happens in the monitored sub-region, and focuses on the static load on the sub-region boundary to obtain the sensor network information with blackboard model. Then, the improved contract net protocol is used to dynamically distribute the damage evaluation module for monitoring two kinds of damage uninterruptedly. Lastly, a reliable assessment for the whole structure is given by combing various heterogeneous classifiers strengths with voting-based fusion. The proposed multi-agent system is illustrated through a large aerospace aluminum plate structure experiment. The result shows that the method can significantly improve the monitoring performance for the large-scale structure. 相似文献
2.
The recent trend of integration among new network services such as the long-term evolution (LTE) based on internet protocol (IP) needs reputable analyses and prediction information on the internet traffic. The IP along with increased internet traffics due to expanding new service platforms such as smartphones will reflect policies such as network QoS according to new services. The establishment of monitoring methods and analysis plans is thus required for the development of internet traffics that will analyze their status and predict their future. The paper with the speed of Internet traffic model is developed for monitoring the state of the experiment and verified. The problem is that the proposed service Internet service provider (ISP) to resolve the conflict between the occurrences can be considerably Internet traffic and that the state of data may be helpful in understanding. The paper advancement policy to reflect the network traffic volume of Internet services and users irradiation with increased traffic due to the development and management of the analysis was carried out experimental measurements. 相似文献
3.
4.
Computer-Supported Collaborative Learning (CSCL) is concerned with how Information and Communication Technology (ICT) might facilitate learning in groups which can be co-located or distributed over a network of computers such as Internet. CSCL supports effective learning by means of communication of ideas and information among learners, collaborative access of essential documents, and feedback from instructors and peers on learning activities. As the cloud technologies are increasingly becoming popular and collaborative learning is evolving, new directions for development of collaborative learning tools deployed on cloud are proposed. Development of such learning tools requires access to substantial data stored in the cloud. Ensuring efficient access to such data is hindered by the high latencies of wide-area networks underlying the cloud infrastructures. To improve learners’ experience by accelerating data access, important files can be replicated so a group of learners can access data from nearby locations. Since a cloud environment is highly dynamic, resource availability, network latency, and learner requests may change. In this paper, we present the advantages of collaborative learning and focus on the importance of data replication in the design of such a dynamic cloud-based system that a collaborative learning portal uses. To this end, we introduce a highly distributed replication technique that determines optimal data locations to improve access performance by minimizing replication overhead (access and update). The problem is formulated using dynamic programming. Experimental results demonstrate the usefulness of the proposed collaborative learning system used by institutions in geographically distributed locations. 相似文献
5.
We study a two-agent scheduling problem in a two-machine permutation flowshop with learning effects. The objective is to minimize the total completion time of the jobs from one agent, given that the maximum tardiness of the jobs from the other agent cannot exceed a bound. We provide a branch-and-bound algorithm for the problem. In addition, we present several genetic algorithms to obtain near-optimal solutions. Computational results indicate that the algorithms perform well in either solving the problem or efficiently generating near-optimal solutions. 相似文献
7.
It is the aim of this paper to examine the effects of conditioning time on the flotation of hematite using three technical grade fatty acid reagents as providing additional evidence on their mechanism of interaction with the hematite surface. Various mechanisms have been postulated as occurring as conditioning time is increased. Both physical (e.g. conditioning time and power input) and chemical (nature, dispersion and solubility of the adsorbing species) contribute to the mechanisms of attachment of collector. In this paper, the mechanism of attachment of oleate to hematite can be readily explained by chemisorption, but the mechanism of attachment of lauric acid appears to be physical adsorption at neutral pH. The flotation of hematite with a mixture of tallow-type fatty acids (palmitic, stearic and oleic acids) is very sensitive to conditioning time, and suggests that, even though flotation is very effective at short conditioning times, it is very susceptible to the presence of fines and their associated high surface areas. It is therefore obvious that both the physical and chemical conditions contribute to the mechanisms of adsorption of fatty acids on iron-containing oxide minerals and must be understood in order to optimise the flotation of these minerals in an industrial situation. 相似文献
8.
大坝运行监测易受自然环境和监测条件影响,存在时间和空间上的变异性,监测数据具有不确定性。以云理论的随机性和不确定性分析方法为基础,并与空间数据辐射思想相结合,建立了云滴概率密度分布估计模型,然后导出云概率密度分布函数,依据样本监测数据推求母体空间数据的分布特征,并设计了基于逆向云算法云变换的计算程序。分析陆浑水库1979~1999年测压管监测数据和位移变形数据的云概率密度分布特征和云数字特征,得出了20 a来大坝的数据分布特征和运行状态。监测数据分析结果表明,云概率密度分布估计不仅能有效合理地分析大坝的运行状态,而且能够依据云数字特征来判断监测状态和监测环境的异常变化。
相似文献
9.
Many models of spoken word recognition posit the existence of lexical and sublexical representations, with excitatory and inhibitory mechanisms used to affect the activation levels of such representations. Bottom-up evidence provides excitatory input, and inhibition from phonetically similar representations leads to lexical competition. In such a system, long words should produce stronger lexical activation than short words, for 2 reasons: Long words provide more bottom-up evidence than short words, and short words are subject to greater inhibition due to the existence of more similar words. Four experiments provide evidence for this view. In addition, reaction-time-based partitioning of the data shows that long words generate greater activation that is available both earlier and for a longer time than is the case for short words. As a result, lexical influences on phoneme identification are extremely robust for long words but are quite fragile and condition-dependent for short words. Models of word recognition must consider words of all lengths to capture the true dynamics of lexical activation. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
10.
基于承包商预期收益不变的不平衡报价模型 总被引:1,自引:0,他引:1
在招标实践中,通常采用最低价中标原则,使得投标人不得不压低其投标价格。基于承包商预期收益不变的不平衡报价模型,是在“工程量清单报价”的条件下,考虑到施工中工程量的变化及施工顺序的影响,体现了资金的时间价值,在保持承包商预期收益不变的前提下,通过调整各分项工程的单价,来降低工程报价,以增加中标机会而建立的。所建立的模型简单,易于操作,并配以具体的工程实例,通过计算机求得其最优解,可供承包商投标报价时参考。 相似文献