全文获取类型
收费全文 | 3762篇 |
免费 | 140篇 |
国内免费 | 96篇 |
专业分类
电工技术 | 422篇 |
综合类 | 215篇 |
化学工业 | 409篇 |
金属工艺 | 79篇 |
机械仪表 | 226篇 |
建筑科学 | 982篇 |
矿业工程 | 57篇 |
能源动力 | 309篇 |
轻工业 | 128篇 |
水利工程 | 151篇 |
石油天然气 | 141篇 |
武器工业 | 16篇 |
无线电 | 250篇 |
一般工业技术 | 339篇 |
冶金工业 | 149篇 |
原子能技术 | 24篇 |
自动化技术 | 101篇 |
出版年
2024年 | 27篇 |
2023年 | 100篇 |
2022年 | 110篇 |
2021年 | 109篇 |
2020年 | 111篇 |
2019年 | 110篇 |
2018年 | 39篇 |
2017年 | 75篇 |
2016年 | 87篇 |
2015年 | 110篇 |
2014年 | 215篇 |
2013年 | 186篇 |
2012年 | 207篇 |
2011年 | 196篇 |
2010年 | 184篇 |
2009年 | 195篇 |
2008年 | 251篇 |
2007年 | 202篇 |
2006年 | 189篇 |
2005年 | 182篇 |
2004年 | 197篇 |
2003年 | 141篇 |
2002年 | 113篇 |
2001年 | 104篇 |
2000年 | 74篇 |
1999年 | 61篇 |
1998年 | 68篇 |
1997年 | 53篇 |
1996年 | 50篇 |
1995年 | 37篇 |
1994年 | 35篇 |
1993年 | 45篇 |
1992年 | 39篇 |
1991年 | 21篇 |
1990年 | 31篇 |
1989年 | 29篇 |
1988年 | 4篇 |
1987年 | 2篇 |
1986年 | 5篇 |
1984年 | 2篇 |
1982年 | 1篇 |
1959年 | 1篇 |
排序方式: 共有3998条查询结果,搜索用时 15 毫秒
71.
72.
提出一种基于MLX90614和ZigBee技术的非接触式体温实时测量无线监控系统的设计方案.MLX90614红外测温模块测量得到人的额头温度,DS18B20数字温度传感器测量环境温度,在经过大量测试得到的温度数据的基础上,通过拟合得到环境温度、人的额头温度和人体体温之间的关系,从而修正人的额头温度与人体体温的温差.再利用ZigBee无线通信模块将人体体温数据传送至计算机终端.实践表明,该系统能在3s内快速、准确地测量出人体体温,精确度达±0.2℃,对于人群中温度异常者的排查率高达92%,适用于中小学校等人流量大的场合. 相似文献
73.
在分析箱形渡槽产生日照温差及温度应力的基础,利用ANSYS有限元软件对某渡槽日照温差及温度应力进行了有效的仿真模拟,结果表明:日照温差作用下,在混凝土箱形渡槽槽身内表面无论沿纵向和横向都将产生可观的温度应力,其值均已超过混凝土的抗拉设计强度。所以,在箱形渡槽槽身结构设计中对日照温差作用产生的温度应力必须予以重视,在设计中应配置适当的温度钢筋。 相似文献
74.
通过采用汽车尾气的余热和太阳能的热量进行发电,将温差发电机、太阳能发电机合成,对汽车的电源进行优化设计,为汽车提供电源,借以减少汽车的油耗和废气的排放.通过与传统汽车油耗对比,确实达到节能减排的目的. 相似文献
75.
A simplified dual-pressure ammonia-water absorption power cycle (DPAPC-a) using low grade energy resources is presented and
analyzed. This cycle uses turbine exhaust heat to distill the basic solution for desorption. The structure of the cycle is
simple which comprises evaporator, turbine, regenerator (desorber), absorber, pump and throttle valves for both diluted solution
and vapor. And it is of high efficiency, because the working medium has large temperature difference in evaporation and small
temperature difference in absorptive condensation, which can match the sensible exothermal heat resource and the cooling water
simultaneously. Orthogonal calculation was made to investigate the influence of the working concentration, the basic concentration
and the circulation multiple on the cycle performance, with 85–110 °C heat resource and 20–32°C cooling water. An optimum
scheme was given in the condition of 110 °C sensitive heat resource and 20 °C cooling water, with the working concentration
of 0.6, basic concentration of 0.385, and circulation multiple of 5. The thermal efficiency and the power recovery efficiency
are 8.06 % and 6.66%, respectively. The power recovery efficiency of the DPAPC-a is 28.8% higher than that of the steam Rankine
cycle (SRC) and 12.7% higher than that of ORC (R134a) under the optimized situation. 相似文献
76.
To explore the energy saving effect of building envelope, the experiments were carried out through a comparison of basic cubicle
in summer. Experiments show that if energy efficiency measures are applied only in the external walls and windows, the energy
saving cubicles have an average energy efficiency ratio of 27.75% and 27.05% when the air change rates are 1.1 and 1.4 h−1 in summer, with both values being over the standard target value by 25%. And the indoor air temperature of the energy saving
cubicle is below that of the basic cubicle. The daily mean temperature difference between the interior surface of insulation
wall and no insulation reaches 1.47 °C, and the mean temperature difference is up to 8.52 °C between the interior surface
and exterior surface of insulating glass and single glass. The two cubicles were simulated for energy consumption using VisualDOE4.0
software under real weather conditions in summer. The results show that the mean deviation is 10.02% between experimental
and simulated energy efficiency ratio. The correctness and validity of simulation results of the VisualDOE4.0 software are
proved. 相似文献
77.
混凝土施工中产生裂缝有多种原因,通过对下车亭隧洞洞身衬砌混凝土进行温度量测与裂缝发展情况的观测,采取了裂缝预防措施。实践表明,控制施工温度及改善约束条件是防止裂缝产生行之有效的措施,为混凝土施工中预防裂缝的产生提供了借鉴和参考。 相似文献
78.
The extreme temperature differences in fiat steel box girder of a cable-stayed bridge were studied.Firstly,by using the long-term measurement data collected by the structural health monitoring system installed on the Runyang Cable-stayed Bridge,the daily variations as well as seasonal ones of measured temperature differences in the box girder cross-section area were summarized.The probability distribution models of temperature differences were further established and the extreme temperature differences were estimated with a return period of 100 years.Finally,the temperature difference models in cross-section area were proposed for bridge thermal design.The results show that horizontal temperature differences in top plate and vertical temperature differences between top plate and bottom plate are considerable.All the positive and negative temperature differences can be described by the weighted sum of two Weibull distributions.The maximum positive and negative horizontal temperature differences in top plate are 10.30 ℃ and -13.80 ℃,respectively.And the maximum positive and negative vertical temperature differences between top plate and bottom plate are 17.30 ℃ and-3.70 ℃,respectively.For bridge thermal design,there are two vertical temperature difference models between top plate and bottom plate,and six horizontal temperature difference models in top plate. 相似文献
79.
针对工业高温旋转环境下对温度采集仪器的供电比较困难的问题,该文设计了利用温差发电产生的电能作为能量的一种锂离子电池充电装置。分析了温差发电模块的输出电压/输出功率与温差的关系,然后根据温差发电模块输出电压不稳定的特点,设计了稳压电路,并用BQ2057W芯片实现对锂离子电池的智能充电管理。实验结果显示,该装置能够实现对电能的良好管理。 相似文献
80.
在斜面上布置管路时,虽然设计上满足了管子自重下滑力与其摩擦力的平衡,但工程实际中管子仍会下滑从而造成变形破坏。详细分析了破坏的原因,认为是由于温差引起管子在斜面上蠕动而造成的。 相似文献