全文获取类型
收费全文 | 97589篇 |
免费 | 12454篇 |
国内免费 | 4521篇 |
专业分类
电工技术 | 49448篇 |
技术理论 | 3篇 |
综合类 | 7567篇 |
化学工业 | 4651篇 |
金属工艺 | 2099篇 |
机械仪表 | 3800篇 |
建筑科学 | 3097篇 |
矿业工程 | 2005篇 |
能源动力 | 7883篇 |
轻工业 | 2206篇 |
水利工程 | 2526篇 |
石油天然气 | 858篇 |
武器工业 | 666篇 |
无线电 | 12648篇 |
一般工业技术 | 3570篇 |
冶金工业 | 1742篇 |
原子能技术 | 2151篇 |
自动化技术 | 7644篇 |
出版年
2024年 | 187篇 |
2023年 | 1249篇 |
2022年 | 2344篇 |
2021年 | 2878篇 |
2020年 | 3207篇 |
2019年 | 2640篇 |
2018年 | 2368篇 |
2017年 | 3425篇 |
2016年 | 3681篇 |
2015年 | 4184篇 |
2014年 | 7028篇 |
2013年 | 5803篇 |
2012年 | 8011篇 |
2011年 | 8620篇 |
2010年 | 6260篇 |
2009年 | 6352篇 |
2008年 | 6223篇 |
2007年 | 7426篇 |
2006年 | 6610篇 |
2005年 | 5346篇 |
2004年 | 4352篇 |
2003年 | 3484篇 |
2002年 | 2654篇 |
2001年 | 2312篇 |
2000年 | 1844篇 |
1999年 | 1326篇 |
1998年 | 869篇 |
1997年 | 668篇 |
1996年 | 683篇 |
1995年 | 542篇 |
1994年 | 486篇 |
1993年 | 301篇 |
1992年 | 264篇 |
1991年 | 165篇 |
1990年 | 136篇 |
1989年 | 111篇 |
1988年 | 83篇 |
1987年 | 62篇 |
1986年 | 40篇 |
1985年 | 39篇 |
1984年 | 63篇 |
1983年 | 51篇 |
1982年 | 54篇 |
1981年 | 23篇 |
1980年 | 14篇 |
1979年 | 12篇 |
1978年 | 15篇 |
1977年 | 8篇 |
1959年 | 15篇 |
1951年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
Yi-Ming Zhao Shikha Ojha Catherine M. Burgess Da-Wen Sun Brijesh K. Tiwari 《International Journal of Food Science & Technology》2021,56(2):721-732
This study aimed to evaluate the influence of plasma treatment time, bacterial exposure time to PAW and bacterial species on the inactivation efficacy of plasma-activated water (PAW), with additional investigation of the inactivation mechanisms of PAW. Six bacterial species, including Listeria innocua, Staphyloccus aureus, Escherichia coli, Pseudomonas fluorescens, Shewanella putrefaciens and Aeromonas hydrophila were selected as the representative bacteria. The initial bacterial concentration was around 7 log CFU ml−1 after mixing with PAW, and the inactivation efficacy was measured after different exposure times during the 4 °C storage. Scanning electron microscopy (SEM) images of the bacteria after PAW treatment were carried out to inspect the cell structure damage, and physicochemical properties of PAW, including pH, conductivity and long-living reactive species of H2O2, , and , were examined. The results showed that the inactivation efficacy of PAW was positively correlated with plasma treatment time and bacterial exposure time, and for the species examined in this study, the Gram-negative species were more sensitive to PAW than the Gram-positive species. Cell structure damage, including shrinkage, distortion, or holes, was observed after PAW treatment. The pH of PAW was acidified to 2.5–2.9, and conductivity was significantly increased to 518.0 μs cm−1. and H2O2 were reduced during the 48 h storage, while an increased concentration was observed for . This study demonstrated that the processing parameters of plasma treatment time, exposure time and characteristics of bacteria can significantly affect the inactivation efficacy of PAW. 相似文献
72.
Jiming Xu Howard M. Heys 《International Journal of Circuit Theory and Applications》2019,47(6):971-990
Side-channel attacks have shown to be efficient tools in breaking cryptographic hardware. Many conventional algorithms have been proposed to perform side-channel attacks exploiting the dynamic power leakage. In recent years, with the development of processing technology, static power has emerged as a new potential source for side-channel leakage. Both types of power leakage have their advantages and disadvantages. In this work, we propose to use the deep neural network technique to combine the benefits of both static and dynamic power. This approach replaces the classifier in template attacks with our proposed long short-term memory network schemes. Hence, instead of deriving a specific probability density model for one particular type of power leakage, we gain the ability of combining different leakage sources using a structural algorithm. In this paper, we propose three schemes to combine the static and dynamic power leakage. The performance of these schemes is compared using simulated test circuits designed with a 45-nm library. 相似文献
73.
为研究熔盐堆系统在商业应用中的价值,分析其是否满足电网负荷的变化需求和安全运行的能力,本文以1 GWt球床式氟盐冷却高温堆(PB-FHR)为研究对象,仿真计算其在负荷跟踪模式下的瞬态行为和运行特性。以RELAP5/MOD4.0程序为研究工具,并植入相关的熔盐物性与计算关系式,建立氟盐冷却高温堆的热工水力系统与功率控制系统的仿真模型,对典型负荷工况参数变化情况下控制系统的响应特性进行仿真分析。结果表明:该氟盐冷却高温堆系统在设计的控制逻辑的调控下,展示出良好的负荷跟踪运行能力,堆芯功率能迅速响应负荷变化,功率超调和温度超调小,反应堆的运行参数始终处于合理的运行范围内。 相似文献
74.
隔震技术能有效减小核电厂上部结构的加速度响应,但强地震作用下隔震层位移过大会导致管道断裂。本文基于曲面运动原理及预压弹簧伸缩特性提出了一种负刚度阻尼系统,通过球铰在拱球面曲线运动实现负刚度特性,并在弹簧压缩方向提供黏滞阻尼性能。提出了负刚度系统的理论恢复力模型并进行了力学特性分析,设计了负刚度装置并完成了静力试验,结果显示理论恢复力模型与试验结果的一致性较理想。将核电厂负刚度阻尼隔震结构与核电厂隔震结构进行了地震响应对比分析,比较了不同地震波输入下的地震响应。结果表明负刚度阻尼系统可有效同时减小核电厂上部加速度响应和隔震层位移响应。 相似文献
75.
76.
Presently, many wind turbine generators (WTGs) are connected to the power grid. While the penetration of wind power to the power system is increasing, FIT price is decreasing. Therefore, wind generation companies want to increase the electric power output from wind farms (WFs). In this article, we propose a control technique to reduce the influence of the wake by changing a power coefficient of each WTG in a WF for the purpose of improving electric power output of WFs. We showed the optimization technique of a power coefficient of each WTG and the effect of reducing the influence of the wake using measurement data from WFs. In addition, we formulated the wake effect as a function of distance between WTGs. We verified 1% improvement of generated energy in a year compared to the conventional control method by simulation. Furthermore, we quantified the improvement of generated energy output, using the distance between WTGs and the occurrence rate of the direction of the wind as a variable. 相似文献
77.
78.
79.
Dr. Aimee J. Marko Mykhaylo Dukh Dr. Nayan J. Patel Joseph R. Missert Prof. Dr. Tymish Ohulchanskyy Walter A. Tabaczynski Dr. Kei Ohkubo Prof. Dr. Shunichi Fukuzumi Prof. Dr. Rutao Yao Prof. Dr. Munawwar Sajjad Prof. Dr. Ravindra K. Pandey 《ChemMedChem》2019,14(16):1503-1513
Herein we report the synthesis, photophysical properties, positron emission tomography (PET) imaging and photodynamic therapy (PDT) efficacy of methyl 3-(1′-m-iodobenzyloxy)ethyl-3-devinyl-verdin 4 (with or without the 124I isotope). The PET imaging ability and ex vivo biodistribution of [124I] 4 were compared with the well-studied methyl [3-(1241′-m-iodobenzyloxy)ethyl]-3-devinyl-pyropheophorbide-a methyl ester (PET-ONCO or [124I] 2 ) and [18F]fluorodeoxyglucose ([18F]FDG) in BALB/c mice bearing colon-26 tumors. Whole-body PET images of [124I] 4 containing a fused methoxy cyclohexenone ring system showed excellent tumor contrast with time (72>48>24 h post-injection). Ex vivo biodistribution results indicate that relative to the current clinical standard [18F]FDG and [124I] 2 in 2 % ethanol formulation, [124I] 4 , at the same radioactive dose (25 μCi per mouse), showed higher tumor uptake at 24 h post-injection and longer tumor retention. In biological environments, compound 4 showed lower fluorescence and lower singlet oxygen yield than 2 , which is possibly due to higher aggregation caused by the presence of a fused cyclohexenone ring system, resulting in limited in vitro/in vivo PDT efficacy. Therefore, the chlorophyll-a analogue [124I] 4 provides easy access to a novel PET imaging agent (with no skin phototoxicity) to image cancer types—brain, renal carcinomas, pancreas—in which [18F]FDG shows limitations. 相似文献
80.
The enormous magnitude and variety of microwave applications in household, commercial and industrial food processing creates a strong motivation for improving the energy efficiency and hence, sustainability of the process. This review critically assesses key energy issues associated with microwave food processing, focusing on previous energy performance studies, energy performance metrics, standards and regulations. Factors affecting energy-efficiency are categorised into source, load and source-load matching factors. This highlights the need for highly-flexible and controllable power sources capable of receiving real-time feedback on load properties, and effecting rapid control actions to minimise reflections, heating non-uniformities and other imperfections that lead to energy losses. A case is made for the use of solid-state amplifiers as alternatives to conventional power sources, magnetrons. By a full-scale techno-economic analysis, including energy aspects, it is shown that the use of solid-state amplifiers as replacements to magnetrons is promising, not only from an energy and overall technical perspective, but also in terms of economics. 相似文献