全文获取类型
收费全文 | 6369篇 |
免费 | 907篇 |
国内免费 | 150篇 |
专业分类
电工技术 | 4382篇 |
综合类 | 353篇 |
化学工业 | 90篇 |
金属工艺 | 53篇 |
机械仪表 | 199篇 |
建筑科学 | 411篇 |
矿业工程 | 167篇 |
能源动力 | 130篇 |
轻工业 | 16篇 |
水利工程 | 142篇 |
石油天然气 | 37篇 |
武器工业 | 8篇 |
无线电 | 437篇 |
一般工业技术 | 67篇 |
冶金工业 | 79篇 |
原子能技术 | 10篇 |
自动化技术 | 845篇 |
出版年
2024年 | 6篇 |
2023年 | 37篇 |
2022年 | 100篇 |
2021年 | 133篇 |
2020年 | 150篇 |
2019年 | 109篇 |
2018年 | 119篇 |
2017年 | 186篇 |
2016年 | 259篇 |
2015年 | 255篇 |
2014年 | 604篇 |
2013年 | 372篇 |
2012年 | 620篇 |
2011年 | 652篇 |
2010年 | 469篇 |
2009年 | 515篇 |
2008年 | 436篇 |
2007年 | 464篇 |
2006年 | 385篇 |
2005年 | 312篇 |
2004年 | 248篇 |
2003年 | 246篇 |
2002年 | 195篇 |
2001年 | 153篇 |
2000年 | 128篇 |
1999年 | 98篇 |
1998年 | 37篇 |
1997年 | 31篇 |
1996年 | 37篇 |
1995年 | 22篇 |
1994年 | 12篇 |
1993年 | 11篇 |
1992年 | 3篇 |
1991年 | 5篇 |
1990年 | 3篇 |
1989年 | 4篇 |
1988年 | 3篇 |
1987年 | 3篇 |
1986年 | 1篇 |
1981年 | 1篇 |
1980年 | 2篇 |
排序方式: 共有7426条查询结果,搜索用时 46 毫秒
1.
Yuhang Wang Yanbin Sun Shen Su Zhihong Tian Mohan Li Jing Qiu Xianzhi Wang 《计算机、材料和连续体(英文)》2019,59(3):983-993
With the evolution of location-based services (LBS), a new type of LBS has already gain a lot of attention and implementation, we name this kind of LBS as the Device-Dependent LBS (DLBS). In DLBS, the service provider (SP) will not only send the information according to the user’s location, more significant, he also provides a service device which will be carried by the user. DLBS has been successfully practised in some of the large cities around the world, for example, the shared bicycle in Beijing and London. In this paper, we, for the first time, blow the whistle of the new location privacy challenges caused by DLBS, since the service device is enabled to perform the localization without the permission of the user. To conquer these threats, we design a service architecture along with a credit system between DLBS provider and the user. The credit system tie together the DLBS device usability with the curious behaviour upon user’s location privacy, DLBS provider has to sacrifice their revenue in order to gain extra location information of their device. We make the simulation of our proposed scheme and the result convince its effectiveness. 相似文献
2.
《International Journal of Hydrogen Energy》2020,45(39):20176-20183
Hydrogen is emerging as a zero-carbon energy source for the sustainable future. Hydrogen station plays the role of supplying hydrogen to fuel cell vehicles. However, the small number of hydrogen stations has become the biggest obstacle to the promotion of hydrogen energy. As an important infrastructure for the development of hydrogen energy industry, the hydrogen station will not be able to support the promotion and application of hydrogen fuel cell vehicles if it cannot form a large scale. In addition, the layout of the hydrogen station network should be reasonable to avoid waste of resources. The study of hydrogen station location models has significant economic, social and military implications. Considering these circumstances, this review investigates the existing research efforts and conducted a comprehensive overview of these works on hydrogen station location models. In this review, we divide the hydrogen station location models into several categories according to the spatial dimension of the facility, the structure of the planning area, and the number of objectives. We present detailed explanations, formulations and different constraints for these models. Finally, we conclude the strengths and weaknesses of these models and provide available solutions. To our best knowledge, this review might help researchers get a comprehensive understanding of related researches in the hydrogen station location. 相似文献
3.
针对阳煤五矿广场变电站的高压开关老化问题,为了保证安全性,采用了GIS气体的高压绝缘开关进行了改造。在改造后,变电站的安全性得到了显著提高,设备运行可以节省成本200多万元。 相似文献
4.
5.
Given a collection of n locations and a symmetric measure of distance (difference) between each pair of locations, we seek to identify (select) a subset of p locations so as to achieve two distinct objectives. The first objective is to use the selected locations as centers (medians) of p groups that would partition the entire collection and minimize the total distance between the locations and their respective group medians. The second objective is to maximize the minimum distance (diversity) among the selected locations themselves. We study this problem as a multi-objective optimization problem and propose an iterative algorithm to obtain its non-dominated frontier. At each iteration we construct and solve a 0–1 integer programming problem. Through a computational experiment we show that this algorithm is computationally effective for small to medium size instances of the problem. We also propose a Lagrangian heuristic algorithm for solving larger instances of this problem. 相似文献
6.
在110kV及以下电压等级变电站中,“三层一网”架构虽然简化了二次系统接线,但实时性和可靠性难以保证。针对传统拓扑结构下的实时性和可靠性无法同时达到最优效果的问题,本文采用“三层一网”架构下蛛状网拓扑结构,仿真结果表明该结构下的通信系统实时性最佳,解决了传统拓扑结构实时性差的问题,并结合算例验证了其可行性;运用故障树分析法定量分析不同结构的可靠性,结果表明蛛状网结构的可靠性更好。为解决研究复杂的通信系统可靠性时传统故障树方法有一定的局限性的问题,本文引入T-S模糊故障理论,建立T-S故障树模型,计算结果表明蛛状网结构下通信系统可靠性最好。根据本文研究可以得到蛛状网拓扑结构能同时提高通信系统实时性和可靠性的结论。 相似文献
7.
8.
为了解决基于位置的服务(LBS)和增强现实(AR)技术快速发展带来的用户位置隐私泄露的隐患,分析了现有的位置隐私保护方法的优缺点,提出基于位置安全性的位置隐私保护方法。将区域安全度和伪装区域引入该方法中,将提示某区域是否需要保护这一度量标准定义为区域安全度,非安全区域(即需要给予保护的区域)的区域安全度设置为1,安全区域(即不需要保护的区域)设置为0,通过扩大区域安全度和识别等级来计算位置安全度。实验结果表明,该方法与未引入位置安全性的方法相比降低了平均定位误差,提高了平均安全性,从而有效地保护了用户的位置隐私,提高了LBS的服务质量。 相似文献
9.
10.