全文获取类型
收费全文 | 269278篇 |
免费 | 27698篇 |
国内免费 | 16969篇 |
专业分类
电工技术 | 38531篇 |
技术理论 | 24篇 |
综合类 | 29804篇 |
化学工业 | 11820篇 |
金属工艺 | 8467篇 |
机械仪表 | 22210篇 |
建筑科学 | 20530篇 |
矿业工程 | 9815篇 |
能源动力 | 8456篇 |
轻工业 | 8654篇 |
水利工程 | 6943篇 |
石油天然气 | 7560篇 |
武器工业 | 5073篇 |
无线电 | 37526篇 |
一般工业技术 | 14417篇 |
冶金工业 | 7295篇 |
原子能技术 | 2737篇 |
自动化技术 | 74083篇 |
出版年
2024年 | 514篇 |
2023年 | 3216篇 |
2022年 | 5883篇 |
2021年 | 7325篇 |
2020年 | 7623篇 |
2019年 | 5761篇 |
2018年 | 5165篇 |
2017年 | 7186篇 |
2016年 | 8373篇 |
2015年 | 9858篇 |
2014年 | 17851篇 |
2013年 | 15177篇 |
2012年 | 20751篇 |
2011年 | 21940篇 |
2010年 | 16611篇 |
2009年 | 16607篇 |
2008年 | 16879篇 |
2007年 | 21019篇 |
2006年 | 18545篇 |
2005年 | 16447篇 |
2004年 | 13252篇 |
2003年 | 11844篇 |
2002年 | 8934篇 |
2001年 | 7387篇 |
2000年 | 6049篇 |
1999年 | 4814篇 |
1998年 | 3642篇 |
1997年 | 2875篇 |
1996年 | 2610篇 |
1995年 | 2189篇 |
1994年 | 1801篇 |
1993年 | 1232篇 |
1992年 | 1045篇 |
1991年 | 762篇 |
1990年 | 625篇 |
1989年 | 502篇 |
1988年 | 368篇 |
1987年 | 210篇 |
1986年 | 142篇 |
1985年 | 145篇 |
1984年 | 125篇 |
1983年 | 114篇 |
1982年 | 91篇 |
1981年 | 83篇 |
1980年 | 68篇 |
1979年 | 52篇 |
1978年 | 40篇 |
1977年 | 31篇 |
1976年 | 27篇 |
1959年 | 23篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
在单光子计数激光雷达检测领域,目前的检测方法在低信噪比情况下虚警概率会增加,同时也无法适应噪声变化的问题。针对这些问题,提出了一种基于Bayesian的检测方法,该方法首先通过雷达方程估计回波信号光子数的范围,将其作为先验信息,而后结合二项分布建立了累计概率模型,基于Bayesian判决准则计算得到检测阈值,此阈值能够在检测概率与虚警概率中间择其平衡。这种方法不仅克服了低信噪比检测困难的情况,还减少了先验信息的获取难度。实验结果表明,对比固定阈值其虚警概率降低了10倍。对比“恒虚警”其检测概率提高了约20。验证了方法具有良好的检测效果,具备一定的可操作性。 相似文献
2.
提出了一种基于FCOS神经网络的小建筑物目标检测算法,针对FCOS模型在特征提取阶段提取到的小建筑物目标特征较少问题,引入多尺度检测和可变形卷积方式,加强网络对小建筑物目标的特征提取能力,并通过改进后的SGE注意力机制降低特征图中的干扰噪声权重。改进后的网络可以提取到更多的小建筑物目标特征,对环境干扰噪声的鲁棒性更强。在自己搭建的数据集上进行了实验测试,结果表明,在相同环境下网络改进后建筑物的整体检测准确率提升了1.7%,其中对小建筑物目标提升了3.6%,减少了小建筑物目标漏检、误检的问题。 相似文献
3.
4.
5.
6.
《International Journal of Hydrogen Energy》2022,47(62):26435-26457
In this study, some locations with different climates, off-grid zero energy buildings with hydrogen energy storage systems are designed, and transient analysis is conducted. These considered buildings supply their electricity consumption without using the electrical grid and PV panels or wind turbines. Also, they supply thermal comfort to occupants by using a vapor compression chiller and humidifier. Domestic hot water of occupants is supplied using solar collectors. For analyzing building's performance and objectives achievement, TRNSYS software is used. Also, for evaluating occupant thermal comfort, the Fanger model is used. The considered building is a one-story building with a 150 m2 area. Four occupants are considered. Both of them are seated at rest, and another is seated with light working such as typing. Using the Fanger model equation and MATLAB software, the thermal comfort of occupants is determined. For domestic hot water consumption, verified profiles that vary during 24 h of the day are considered. Achieved results show that for humid and cold cities, PV panels with an area of 73 and 76 m2 can be supplied the required electricity of considered building with four occupants and battery state of charge is higher than 50% and 10%, respectively. Moreover, with a suitable air conditioner system, the predicted percentage of dissatisfied (PPD) can be lower than 12% and 8% for humid and cold cities. Therefore, the building can be converted to a zero-energy building using its rooftop area. 相似文献
7.
《International Journal of Hydrogen Energy》2022,47(67):29172-29183
To improve the safety of wet dust removal systems for processing magnesium-based alloys, a new method is proposed for preventing hydrogen generation. In this paper, hydrogen generation by Mg–Zn alloy dust was inhibited with six common metal corrosion inhibitors. The results showed that sodium dodecylbenzene sulfonate was the best hydrogen inhibitor, while CeCl3 enhanced hydrogen precipitation. The film-forming stability of sodium dodecylbenzene sulfonate was tested with different contents, temperatures, Cl? concentrations and perturbation rates. The results showed that this inhibitor formed stable protective films on the surfaces of Mg–Zn alloy particles, and adsorption followed the Langmuir adsorption model. 相似文献
8.
《International Journal of Hydrogen Energy》2022,47(94):39931-39942
A dual-coolant integrated experimental facility named DRAGON-V has been developed at the Institute of Nuclear Energy Safety Technology, Hefei Institute of Physical Science, Chinese Academy of Sciences, for the key technology research and performance evaluation of candidate liquid lithium-lead (PbLi) blanket of hydrogen fusion reactors. The loop is composed of a material test sub-loop and thermal-hydraulic test sub-loop, the design parameters are PbLi inventory 20 tons, PbLi temperature up to 550 °C, the maximum PbLi flow rate up to 40 kg/s. A novel cold trap system is designed to remove the suspended and crystalized impurities in PbLi fluid with three cooling zones and cross row arrangement of rod bundle filter elements. The paper describes the loop itself and its major components, initial loop testing, flow and measurement diagnostics and current experiments. The obtained test results of the loop and its components have demonstrated that the new facility is fully functioning and ready for experimental studies of material corrosion with/without a magnetic field, magnetohydrodynamic (MHD) effect, purification, heat and mass transfer phenomena in PbLi flows and can also be used in mock-up testing in conditions relevant to fusion applications. 相似文献
9.
In the present work, the heating performance of a new system combined with a new modified baseboard radiator and fan coil is investigated. Using longitudinal fins with special geometry and also forced airflow at the end of the system causes that at the lower inlet water temperature compared with the conventional models, higher heat output rate be obtained. The heat output rate of the new modified system is obtained by experimental metrology based on the European Standard No. EN-442. Temperature and velocity distribution in the room space is done by simulation of the modified system in the Flovent software. Computational fluid dynamics (CFD) results are validated against experimental results and there is a good agreement between them. Also, the energy consumption of the system during the winter season is calculated in TRANSYS software. Experimental results show that the heat output rate of a new modified heating system with inlet water temperature in the range of 45–55°C is on average 4.17 times higher compared with the conventional model. CFD simulation also showed that the combined system provides good thermal comfort conditions. Energy consumption of the new system reduced about 13% compared with conventional models. 相似文献
10.