全文获取类型
收费全文 | 88026篇 |
免费 | 7713篇 |
国内免费 | 4471篇 |
专业分类
电工技术 | 8667篇 |
技术理论 | 23篇 |
综合类 | 9595篇 |
化学工业 | 4227篇 |
金属工艺 | 1450篇 |
机械仪表 | 4413篇 |
建筑科学 | 13945篇 |
矿业工程 | 3253篇 |
能源动力 | 2720篇 |
轻工业 | 2209篇 |
水利工程 | 4539篇 |
石油天然气 | 1968篇 |
武器工业 | 513篇 |
无线电 | 9223篇 |
一般工业技术 | 5859篇 |
冶金工业 | 4979篇 |
原子能技术 | 597篇 |
自动化技术 | 22030篇 |
出版年
2024年 | 132篇 |
2023年 | 1031篇 |
2022年 | 1812篇 |
2021年 | 2425篇 |
2020年 | 2720篇 |
2019年 | 2032篇 |
2018年 | 1921篇 |
2017年 | 2391篇 |
2016年 | 2794篇 |
2015年 | 3171篇 |
2014年 | 7633篇 |
2013年 | 6225篇 |
2012年 | 6893篇 |
2011年 | 7090篇 |
2010年 | 5235篇 |
2009年 | 5423篇 |
2008年 | 5418篇 |
2007年 | 6482篇 |
2006年 | 5575篇 |
2005年 | 4736篇 |
2004年 | 4024篇 |
2003年 | 3503篇 |
2002年 | 2769篇 |
2001年 | 2033篇 |
2000年 | 1571篇 |
1999年 | 1187篇 |
1998年 | 791篇 |
1997年 | 608篇 |
1996年 | 493篇 |
1995年 | 424篇 |
1994年 | 323篇 |
1993年 | 245篇 |
1992年 | 160篇 |
1991年 | 136篇 |
1990年 | 86篇 |
1989年 | 113篇 |
1988年 | 81篇 |
1987年 | 40篇 |
1986年 | 72篇 |
1985年 | 75篇 |
1984年 | 77篇 |
1983年 | 86篇 |
1982年 | 28篇 |
1981年 | 21篇 |
1980年 | 18篇 |
1979年 | 15篇 |
1978年 | 8篇 |
1977年 | 15篇 |
1961年 | 7篇 |
1959年 | 10篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
In recent years, artificial intelligence (AI) is being increasingly utilised in disaster management activities. The public is engaged with AI in various ways in these activities. For instance, crowdsourcing applications developed for disaster management to handle the tasks of collecting data through social media platforms, and increasing disaster awareness through serious gaming applications. Nonetheless, there are limited empirical investigations and understanding on public perceptions concerning AI for disaster management. Bridging this knowledge gap is the justification for this paper. The methodological approach adopted involved: Initially, collecting data through an online survey from residents (n = 605) of three major Australian cities; Then, analysis of the data using statistical modelling. The analysis results revealed that: (a) Younger generations have a greater appreciation of opportunities created by AI-driven applications for disaster management; (b) People with tertiary education have a greater understanding of the benefits of AI in managing the pre- and post-disaster phases, and; (c) Public sector administrative and safety workers, who play a vital role in managing disasters, place a greater value on the contributions by AI in disaster management. The study advocates relevant authorities to consider public perceptions in their efforts in integrating AI in disaster management. 相似文献
2.
Most protons in the solar wind belong to one of two different populations,the less dense beam protons and the denser core protons.The beam protons,with a velocity of(1-2)VA(VA is the local Alfvén speed),always drift relative to the core protons;this kind of distribution is unstable and stimulates several kinds of wave mode.In this study,using a 2D hybrid simulation model,we find that the original right-handed elliptically polarized Alfvén waves become linearly polarized,and eventually become right-handed and circularly polarized.Given that linearly polarized waves are a superposition of left-handed and right-handed waves,cyclotron resonance in the right-handed/left-handed component heats beam/core protons perpendicularly.The resonance between beam protons and right-handed polarized waves is stronger when the beam relative density is lower,resulting in more dramatic perpendicular heating of beam protons,whereas the situation is reversed when the beam relative density is larger. 相似文献
3.
《International Journal of Hydrogen Energy》2022,47(17):9864-9875
Using covalent graphene derivatives in energy storage applications is promising. From this view, covalently cross-linked graphene oxide (GO) nanosheets are designed using polyoligomeric silsesquioxanes-propyl-NH2 (POPN). Then, by incorporating cobalt sulfide nanoparticles into the porous scaffold, a high-value nanocomposite is formed. In a typical three-electrode cell, this nanocomposite declared substantial specific capacity of 454 and 438 Fg-1 using cyclic voltammetry (CV) and charge-discharge (GCD) assessments. The device is assembled via two identical electrodes containing RGO-SiO3-NH2-poss-NH2-SiO3-RGO/cobalt sulfide (RGO-Si-POPN-Si-RGO/CoS2). Utilizing CV and GCD methods, specific capacitances of 328 and 315 Fg-1 are realized at a sweep rate and current density of 2 mVs?1 and 0.5 Ag-1, respectively. The device presents desirable energy density of 18.5 Whkg?1 at the power density of 325 Wkg-1. More impressively, around 97.9% of the specific capacitance is retained after 5000 charge-discharge cycles. The results confirm exceptional capacitive capabilities and super stability of the nanocomposite suitable for practical systems. 相似文献
4.
针对现有基于视频监控的人流量统计方案成本高、算法复杂且不利于个人隐私保护的局限性,利用毫米波雷达体积小、成本低、分辨率高的特点,提出了一种基于双时间点检测的人流量监测方法。该方法先获取人体目标散射点位置和多普勒频移信息来构成点云数据,然后根据多普勒频移正负来判断人体的运动方向,并筛选具有高多普勒频移值的点云数据以降低干扰点对聚类结果的影响;在双时间点对特定区域内人员数量进行统计,并根据双时间点之间所获取的点云数据聚类结果对所统计人员数据进行修正。实验结果表明,该方法能够用匿名的方式以较高的正确率统计人员进出。 相似文献
6.
《Contact lens & anterior eye》2022,45(3):101538
The disease of myopia has come into focus as a worldwide public health concern. Myopia has shown increasing prevalence, incidence at earlier age and progression to a higher degree. Progressive increase in degree of myopia is strongly associated with increase in axial length of the eye. Various interventions have been shown to slow axial elongation in children. These interventions have been studied to assess efficacy in slowing axial elongation and correction of vision. In addition, research into quality of vision, risk of adverse events, overall safety and impact on vision-related quality (VR-QoL) of life has been pursued. In contrast, studies have been published to demonstrate the risks of myopia, high myopia and increased axial length. This review will discuss VR-QoL assessment on the most effective and most commonly prescribed interventions to slow axial elongation and myopia progression. The patient attributes considered are VR-QoL scores from validated instruments. The development and use of validated survey instruments to assess the patient-reported outcomes is discussed. The review demonstrates that there are numerous factors that may impact VR-QoL to evaluate in the decision-making process when eye care providers consider when, how and if to prescribe myopia management (MM) for children with myopia. 相似文献
7.
“十四五”期间,通过强化供水工程运行管理,巩固维护好已建农村供水工程成果,是水利部门实施乡村振兴的基本任务。2021年4月,《安徽省农村供水工程运行管理指南(试行)》正式印发实施。《指南》是在安徽省农村供水工作重点由工程建设转入运行管理的背景下,指导推进农村供水工程规范化管理的重要文件。通过介绍《指南》编制的有关背景、编制目标和特点,解析《指南》的主要内容和条款,可帮助供水管理人员快速掌握《指南》要点,助力《指南》在安徽省内贯彻和实施。 相似文献
8.
9.
《International Journal of Hydrogen Energy》2022,47(92):39239-39254
The energy management and trajectory tracking control are crucial to realize long-endurance autonomous flight for hybrid electric UAVs. This study aims to comprehensively consider energy management and trajectory tracking for hybrid electric fixed wing UAVs with photovoltaic panel/fuel cell/battery. A double-layer fuzzy adaptive nonlinear model predictive control method (DFNMPC) is proposed. Separated by the surplus demand power, energy management and trajectory tracking problem are decoupled into the high-layer fuzzy adaptive nonlinear model predictive controll problem (H-FNMPC) and low-layer fuzzy adaptive nonlinear model predictive controll problem (L-FNMPC). H-FNMPC solves the trajectory tracking and navigation control probelm for the greatest benefit of solar energy. L-FNMPC solves the power allocation problem of hybrid energy system for minimum equivalent hydrogen consumption. A fuzzy adaptive prediction horizon adjustment method based on UAV maneuvering degree is proposed to effectively improve proposed method adaptability to different mission profiles. Analogously, a fuzzy adaptive equivalent hydrogen consumption factor adjustment method in L-FNMPC is proposed to ensure the flexible utilization of battery. In addition, an equivalent hydrogen flow rate calculation method based on the real-time current ratio is proposed for PV/FC/Battery hybrid energy system. Numerical simulation results including a spiral trajectory tracking and a quadrilateral trajectory tracking, demonstrate that DFNMPC can simultaneously handle energy management and trajectory tracking problem for hybrid electric UAVs. Compared to hierarchical fuzzy state machine strategy, DFNMPC can save 13.3% hydrogen for the spiral trajectory tracking, and 56.9% for the quadrilateral trajectory tracking. It indicates that the energy efficiency can be improved from both levels of energy management and flight motion. The proposed method prospected for exploring high-energy-efficiency autonomous flight of hybrid electric UAVs in the future. 相似文献
10.