全文获取类型
收费全文 | 306356篇 |
免费 | 33866篇 |
国内免费 | 19555篇 |
专业分类
电工技术 | 52224篇 |
技术理论 | 8篇 |
综合类 | 26993篇 |
化学工业 | 29860篇 |
金属工艺 | 12487篇 |
机械仪表 | 25580篇 |
建筑科学 | 25770篇 |
矿业工程 | 11220篇 |
能源动力 | 9050篇 |
轻工业 | 12850篇 |
水利工程 | 8662篇 |
石油天然气 | 9979篇 |
武器工业 | 4076篇 |
无线电 | 26781篇 |
一般工业技术 | 21168篇 |
冶金工业 | 12150篇 |
原子能技术 | 2216篇 |
自动化技术 | 68703篇 |
出版年
2024年 | 548篇 |
2023年 | 4000篇 |
2022年 | 7074篇 |
2021年 | 10079篇 |
2020年 | 9153篇 |
2019年 | 7694篇 |
2018年 | 7504篇 |
2017年 | 10371篇 |
2016年 | 12550篇 |
2015年 | 13972篇 |
2014年 | 21318篇 |
2013年 | 19290篇 |
2012年 | 22354篇 |
2011年 | 23287篇 |
2010年 | 17627篇 |
2009年 | 18169篇 |
2008年 | 17930篇 |
2007年 | 22314篇 |
2006年 | 20324篇 |
2005年 | 17342篇 |
2004年 | 13766篇 |
2003年 | 12233篇 |
2002年 | 9646篇 |
2001年 | 7941篇 |
2000年 | 6897篇 |
1999年 | 5009篇 |
1998年 | 3715篇 |
1997年 | 3191篇 |
1996年 | 2675篇 |
1995年 | 2277篇 |
1994年 | 1951篇 |
1993年 | 1445篇 |
1992年 | 1147篇 |
1991年 | 912篇 |
1990年 | 748篇 |
1989年 | 660篇 |
1988年 | 439篇 |
1987年 | 281篇 |
1986年 | 210篇 |
1985年 | 205篇 |
1984年 | 268篇 |
1983年 | 184篇 |
1982年 | 179篇 |
1981年 | 125篇 |
1980年 | 115篇 |
1979年 | 95篇 |
1978年 | 58篇 |
1977年 | 66篇 |
1964年 | 48篇 |
1962年 | 72篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
1.
《International Journal of Hydrogen Energy》2022,47(85):36216-36231
The fuel cell/battery durability and hybrid system stability are major considerations for the power management of fuel cell hybrid electric bus (FCHEB) operating on complicated driving conditions. In this paper, a real time nonlinear adaptive control (NAC) with stability analyze is formulated for power management of FCHEB. Firstly, the mathematical model of hybrid power system is analyzed, which is established for control-oriented design. Furthermore, the NAC-based strategy with quadratic Lyapunov function is set up to guarantee the stability of closed-loop power system, and the power split between fuel cell and battery is controlled with the durability consideration. Finally, two real-time power management strategies, state machine control (SMC) and fuzzy logic control (FLC), are implemented to evaluate the performance of NAC-based strategy, and the simulation results suggest that the guaranteed stability of NAC-based strategy can efficiently prolong fuel cell/battery lifespan and provide better fuel consumption economy for FCHEB. 相似文献
2.
高面板坝的变形对面板的安全运行有着特别重要的影响,国内外已建的高面板坝工程中,因坝体变形大导致防渗面板挤压破损,坝体渗漏量大的实例较多,不得不降低水库水位进行修复处理,造成较大的经济损失乃至给大坝的长期运行留下安全隐患。通过发生挤压破损的实例分析,发现变形控制缺乏系统性是发生面板挤压破损的主要因素,为预防面板破损,系统提出了“控制坝体总变形,转化有害变形,适应纵向变形”的坝体变形控制方法,并在使用软硬岩混合料筑坝的董箐面板堆石坝中得到的应用,取得了良好效果,该工程运行至今达十余年,未见面板有挤压破损迹象,该方法对建设200 m以上乃至300 m级超高面板坝具有重要借鉴意义。 相似文献
3.
Sk Tanbir Islam Sudip K. Samanta Santanu Das Himadri Chattopadhyay 《Journal of the American Ceramic Society》2022,105(7):4608-4620
The micro-powder injection molding (micro-PIM) process has the potential to bridge the gap between the design and manufacturing of micro-components that are often used in small and handy devices. Numerical modeling helps to analyze and overcome various difficulties of micro-PIM. In the present work, a numerical model is developed to predict the powder–binder separation (a common defect in PIM and especially severe in micro-PIM) during the injection of an alumina feedstock. A powder–binder separation criterion is proposed dealing with applied injection pressure and friction force between the powder and binder. An indirect comparison of feedstock travel time between two locations is used to validate the model. The predicted segregation from the simulated result is supported by a qualitative experimental measurement. The developed model can be used to optimize injection parameters to get a defect-free product. 相似文献
4.
5.
6.
《Ceramics International》2022,48(1):754-759
Thermal control coatings (TCCs) are an essential part of the thermal control systems in the spacecraft. Solar absorptance and emittance are the key performance parameters of TCCs. To develop an ultra-low solar absorption and stable inorganic TCCs for surface radiator, different TCCs were prepared by co-sintering ZnO and SiO2 nanoparticles to form Zn2SiO4/SiO2 pigment in this work, and the optical properties and radiation stability were systematically studied. It is found that the coating based on composite pigment has high reflectivity in the ultraviolet band and excellent optical performance possessing the low solar absorption of 0.06. In addition, the Zn2SiO4/SiO2 coating demonstrates the highest proton and electron radiation stability because that SiO2 between Zn2SiO4 particles acts as the relaxation center of the defects caused by radiation. 相似文献
7.
益生菌可在肠道定植从而发挥抗炎或抗氧化活性,有利于宿主肠道健康。本实验研究了从新疆传统发酵乳制品中分离得到的8?株植物乳杆菌对大肠杆菌侵袭和过氧化氢刺激肠上皮细胞HT-29的保护作用。结果表明:在8?株植物乳杆菌中,植物乳杆菌35具有最高的黏附能力。植物乳杆菌35可通过取代、竞争、排阻的方式抑制大肠杆菌对HT-29细胞的黏附,抑制率分别为42.60%、59.17%、60.19%。植物乳杆菌35及其多糖可抑制大肠杆菌刺激HT-29细胞产生白细胞介素-8;同时保护HT-29细胞免受过氧化氢的损伤,增加超氧化物歧化酶、谷胱甘肽过氧化物酶活力水平并降低丙二醛含量。结论:植物乳杆菌35及其粗胞外多糖具有抑制大肠杆菌O157诱导的炎症性肠病的潜力。 相似文献
8.
9.
《International Journal of Hydrogen Energy》2022,47(77):33014-33026
The present study investigates the combined influence of Channel to Rib Width (CRW) ratio and clamping pressure on the structure and performance of High Temperature-Polymer Electrolyte Membrane Fuel Cell (HT-PEMFC) using a three-dimensional numerical model developed previously. It also considers the impact of interfacial contact resistance between the Gas Diffusion Layer (GDL) and Bipolar Plate (BPP). The structural analysis of the single straight channel HT-PEMFC geometry shows that the von-Mises stress greatly increases in the GDL under the ribs as the CRW ratio increases resulting in considerably high deformation. The cell performance analysis depicts the significance of ohmic resistance and concentration polarization for different CRW ratios, particularly at higher operating current densities. However, in low to medium current density regions, the CRW ratio has little influence on cell performance. A substantial impact on the species, overpotential, and current distributions is observed. The findings also reveal that the CRW ratio significantly affects the temperature distribution in the cell. 相似文献
10.
随着社会的进步和发展,计算机网络通信技术已被应用到实际生活、生产的各个方面,对人们的生活、生产等产生了深刻的影响。为此,文章就计算机通信及网络远程控制技术在实际生活中的应用问题进行了探究,旨在借助先进科技促进社会实现更优质发展。 相似文献