全文获取类型
收费全文 | 301645篇 |
免费 | 27437篇 |
国内免费 | 17048篇 |
专业分类
电工技术 | 71512篇 |
技术理论 | 35篇 |
综合类 | 31779篇 |
化学工业 | 13540篇 |
金属工艺 | 9343篇 |
机械仪表 | 21778篇 |
建筑科学 | 22484篇 |
矿业工程 | 10930篇 |
能源动力 | 15323篇 |
轻工业 | 6338篇 |
水利工程 | 9010篇 |
石油天然气 | 8729篇 |
武器工业 | 4317篇 |
无线电 | 33435篇 |
一般工业技术 | 14482篇 |
冶金工业 | 8833篇 |
原子能技术 | 4296篇 |
自动化技术 | 59966篇 |
出版年
2024年 | 1104篇 |
2023年 | 3007篇 |
2022年 | 5926篇 |
2021年 | 7284篇 |
2020年 | 8134篇 |
2019年 | 6262篇 |
2018年 | 5652篇 |
2017年 | 7929篇 |
2016年 | 9169篇 |
2015年 | 10675篇 |
2014年 | 19566篇 |
2013年 | 16506篇 |
2012年 | 22828篇 |
2011年 | 24398篇 |
2010年 | 18396篇 |
2009年 | 18305篇 |
2008年 | 18621篇 |
2007年 | 23116篇 |
2006年 | 20718篇 |
2005年 | 18230篇 |
2004年 | 14948篇 |
2003年 | 13147篇 |
2002年 | 10044篇 |
2001年 | 8499篇 |
2000年 | 7046篇 |
1999年 | 5537篇 |
1998年 | 4043篇 |
1997年 | 3288篇 |
1996年 | 2901篇 |
1995年 | 2422篇 |
1994年 | 2052篇 |
1993年 | 1372篇 |
1992年 | 1167篇 |
1991年 | 824篇 |
1990年 | 663篇 |
1989年 | 563篇 |
1988年 | 395篇 |
1987年 | 234篇 |
1986年 | 146篇 |
1985年 | 147篇 |
1984年 | 147篇 |
1983年 | 133篇 |
1982年 | 116篇 |
1981年 | 84篇 |
1980年 | 62篇 |
1979年 | 57篇 |
1978年 | 45篇 |
1977年 | 34篇 |
1976年 | 26篇 |
1959年 | 35篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
对1600圆盘式高速金属冷锯机进行了锯切功率的实验研究。对某厂四种有代表性的产品,用不同的进锯速度,实测每种条件下的锯切功率变化,和最大瞬时锯切功率与平均锯切功率之比。并以实测数据为基础,得出每种产品以进锯速度为自变量的平均锯切功率回归公式。这些工作,不仅可以为这种冷锯机锯切功率的理论研究提供依据,还可直接为使用和设计这种冷锯机给出具体参考数据。 相似文献
92.
Kosuke Kurokawa 《Electrical Engineering in Japan》1993,113(4):54-65
Solar radiation has an irregularly varying factor due to a basic day and night cycle and climatic conditions. For such conditions a data sampling interval is important to ensure the accuracy of energy monitoring in a photovoltaic system. While treating a system monitoring equipment as a black box. the author has developed the method of calibrating an energy-integrating function. At first for various input waveforms, the relationship between sampling intervals and quasi-integration outputs have been examined by trapezoidal rule. In the numerical simulation the phases of the sampling clock also are considered Then it is concluded that a sampling interval can be inspected through outside observation only by using a rectangular single pulse. By applying the pulse to the energy-integrating process, two kinds of integrated outputs can be obtained for different sampling phases. The calculated difference between both outputs can uniquely give the sampling interval being inspected. Conditions to ensure measuring accuracy are discussed and the validity of this method has been demonstrated experimentally. Practical calibrating procedures also are proposed for the integrating function of PV system monitoring. 相似文献
93.
This paper describes a database model based on the original rough sets theory. Its rough relations permit the representation of a rough set of tuples not definable in terms of the elementary classes, except through use of lower and upper approximations. The rough relational database model also incorporates indiscernibility in the representation and in all the operators of the rough relational algebra. This indiscernibility is based strictly on equivalence classes which must be defined for every attribute domain. There are several obvious applications for which the rough relational database model can more accurately model an enterprise than does the standard relational model. These include systems involving ambiguous, imprecise, or uncertain data. Retrieval over mismatched domains caused by the merging of one or more applications can be facilitated by the use of indiscernibility, and naive system users can achieve greater recall with the rough relational database. In addition, applications inherently “rough” could be more easily implemented and maintained in the rough relational database. 相似文献
95.
基于物联网技术的监狱人员定位可视化管理系统 总被引:1,自引:0,他引:1
提出了一种监狱人员定位可视化管理系统的设计和实现方法。该系统基于WLAN的RTLS定位技术,实现对服刑人员、干警、访客等人群的可视化定位管理。文章结合监狱的应用需求,首先给出了系统的总体设计原则;同时在总体原则约束下,对系统功能、总体实现方案、实现框图、应用流程、网络安全等部分进行阐述,给出了标签软硬件设计、定位管理系统的平台选型和软件架构;最后对设计的系统进行了测试。测试结果显示,该可视化定位管理系统的定位精度达到了预期效果。在进一步优化和完善后,即可大规模推广使用。 相似文献
96.
In group assessment, the focus is on finding high‐authority experts to improve the reliability of assessment results. In this study, we propose an authority updating algorithm while considering the power and judgement reliability of an expert on the basis of social networks and post‐evaluations. A network power index is established and used to reflect the power of an expert while considering social networks. The measurement of the judgement reliability of an expert considers the post‐evaluation of the objects selected by experts, thereby more scientifically reflecting the reliability of experts. The analysis shows the following: although the social‐network structure influences the authority of experts, the influence weakens when the assessment group is a highly or even fully connected group; the network effect may increase the authority of some experts and reduce that of others, and it will weaken as the network connectivity increases; moreover, the judgement reliability and authority of an expert while considering post‐evaluation can encourage him/her to make fair assessments and strive to reduce his/her motivation and cognitive biases. 相似文献
97.
Scheduling semiconductor wafer manufacturing systems has been viewed as one of the most challenging optimization problems owing to the complicated constraints, and dynamic system environment. This paper proposes a fuzzy hierarchical reinforcement learning (FHRL) approach to schedule a SWFS, which controls the cycle time (CT) of each wafer lot to improve on-time delivery by adjusting the priority of each wafer lot. To cope with the layer correlation and wafer correlation of CT due to the re-entrant process constraint, a hierarchical model is presented with a recurrent reinforcement learning (RL) unit in each layer to control the corresponding sub-CT of each integrated circuit layer. In each RL unit, a fuzzy reward calculator is designed to reduce the impact of uncertainty of expected finishing time caused by the rematching of a lot to a delivery batch. The results demonstrate that the mean deviation (MD) between the actual and expected completion time of wafer lots under the scheduling of the FHRL approach is only about 30 % of the compared methods in the whole SWFS. 相似文献
98.
In recent years, the concept of digital twin (DT) is attracting more and more attention from researchers and engineers. But there is still no consensus on what a right DT is. On one hand, some common models are renamed as DTs. On the other hand, some DTs extremely pursue ‘the same’ as physical objects, which bring unnecessary complexities to them. In this paper, we try to answer two questions from the point of view of model engineering: how to define a right digital twin, and how to build a right digital twin. The concept and related technologies of model engineering are introduced. Some basic principles and a set of metrics for a right DT are given. An evolutionary concurrent modeling method for DT (ECoM4DT) is proposed not only inheriting the theory from classic M&S methods but also highlighting the characteristics of DT compared with traditional models to systemically guide the DT modeling process. 相似文献
99.
《Calphad》2021
Accurate Young's modulus is the necessity for the design of biomedical Ti alloys. A combinatorial method of the diffusion couple, nanoindentation, electron probe microanalysis (EPMA), and CALculation of PHAse Diagrams (CALPHAD) techniques has been utilized to construct the Young's modulus database of Ti alloys with various compositions in the present work. Two groups of body-centered cubic (bcc) Ti–Nb–Zr–Mo quaternary diffusion couples annealed at 1273 K for 25 h were experimentally prepared. Subsequently, the composition-dependent mechanical properties in the wide compositional range of Ti-based alloys were obtained by using EPMA and nanoindentation probes. Finally, on the basis of the measured Young's moduli in the present and previous work and the modeling parameters of Young's modulus of Ti–Nb–Zr system, the Young's modulus database of bcc Ti–Nb–Zr–Mo system was established through the CALPHAD approach. The CALPHAD-type database of bcc Ti–Nb–Zr–Mo system can provide the accurate Young's moduli of Ti alloys with wide compositions. 相似文献
100.
针对以前的发电管理系统或只是数据呈现,提供市电及发电相关数据信息,或只是提供出车轨迹,主要实现对出车的管理,不能全面反应发电全过程且不便于对发电事件进行分析的情况,提出可视化发电管理系统的概念。在简要介绍了LBS系统、动力环境监控系统后,讲述了可视化基站发电管理系统的组成以及通过LBS定位管理、短信互动、实时监测数据等进行系统实现。可视化发电管理系统通过可视化的界面帮助发电管理人员进行管理,直观、便捷。 相似文献