全文获取类型
收费全文 | 116670篇 |
免费 | 9864篇 |
国内免费 | 4741篇 |
专业分类
电工技术 | 14942篇 |
技术理论 | 26篇 |
综合类 | 17294篇 |
化学工业 | 8602篇 |
金属工艺 | 3895篇 |
机械仪表 | 5259篇 |
建筑科学 | 22351篇 |
矿业工程 | 6003篇 |
能源动力 | 2749篇 |
轻工业 | 4946篇 |
水利工程 | 7383篇 |
石油天然气 | 4677篇 |
武器工业 | 750篇 |
无线电 | 7657篇 |
一般工业技术 | 5948篇 |
冶金工业 | 4646篇 |
原子能技术 | 894篇 |
自动化技术 | 13253篇 |
出版年
2024年 | 312篇 |
2023年 | 919篇 |
2022年 | 2142篇 |
2021年 | 2469篇 |
2020年 | 2371篇 |
2019年 | 1857篇 |
2018年 | 1749篇 |
2017年 | 2490篇 |
2016年 | 2943篇 |
2015年 | 3716篇 |
2014年 | 8511篇 |
2013年 | 5923篇 |
2012年 | 8233篇 |
2011年 | 9207篇 |
2010年 | 7394篇 |
2009年 | 7969篇 |
2008年 | 7186篇 |
2007年 | 9173篇 |
2006年 | 8565篇 |
2005年 | 7178篇 |
2004年 | 5924篇 |
2003年 | 5165篇 |
2002年 | 4177篇 |
2001年 | 3467篇 |
2000年 | 2963篇 |
1999年 | 2159篇 |
1998年 | 1387篇 |
1997年 | 1060篇 |
1996年 | 940篇 |
1995年 | 794篇 |
1994年 | 624篇 |
1993年 | 459篇 |
1992年 | 388篇 |
1991年 | 248篇 |
1990年 | 232篇 |
1989年 | 218篇 |
1988年 | 186篇 |
1987年 | 98篇 |
1986年 | 90篇 |
1985年 | 60篇 |
1984年 | 66篇 |
1983年 | 39篇 |
1982年 | 19篇 |
1981年 | 52篇 |
1980年 | 25篇 |
1979年 | 24篇 |
1978年 | 15篇 |
1977年 | 9篇 |
1975年 | 13篇 |
1959年 | 9篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
1.
边坡位移的时间序列曲线存在复杂的非线性特性,传统的预测模型精度不足以满足预测要求。为此提出了基于变分模态分解的鸟群优化-核极限学习机的预测模型,并用于河北省某水泥厂的边坡位移预测。该方法首先采用VMD把边坡位移序列分解为一系列的有限带宽的子序列,再对各子序列分别采用相空间重构并用核极限学习机预测,采用鸟群算法优化相空间重构的嵌入维度和KELM中惩罚系数和核参数三个数值,以取得最优预测模型。最后将各个子序列预测值叠加,得到边坡位移的最终预测值。结果表明:和KELM、BSA-KELM、EEMD-BSA-KELM模型相比,基于VMD的BSA-KELM预测精度更高,为边坡位移的预测提供一种有效的方法。 相似文献
2.
《Ceramics International》2022,48(12):16808-16812
Flash sintering has been reported in various ceramics. Nevertheless, anion and cation conductors exhibit different flash-sintering behaviors, and the interaction mechanism between the conductive species and the sintering environment has remained unclear. Herein, we report the flash-sintering phenomena of a typical cation conductor, Na3Zr2(SiO4)2(PO4) with anode region surrounded by air and NaNO3 environments. The results prove that the ionic behavior and joule heating distribution can be controlled by changing the electrode environment. Four possible scenarios describing the ion migration behavior and interaction with the environment are proposed for providing a guidance for controlling the ion interaction behavior during flash sintering. 相似文献
3.
《International Journal of Hydrogen Energy》2022,47(3):2040-2049
The motion trajectory of hydrogen leakage is an essential safe issue for the application of hydrogen energy. A dimensionless fast-running motion trajectory prediction model is proposed to predict the dispersion characteristics of the buoyant jet of hydrogen leakage for the accident. The impact of different leakage angles, leakage velocity and thermal stratification of ambient air on hydrogen leakage behavior was analyzed. The new developed model was verified by experimental results in literatures. Leakage hydrogen can flow upwards freely in a uniform environment. However, it shows an oscillating trajectory at a certain height in a thermally stratified environment, which is so called “locking phenomenon”. The trajectory of hydrogen leakage is upward and hydrogen gathers at the top of the space to form stratification in a uniform environment, while the hydrogen leakage shows an oscillating trajectory at a certain height in a thermal stratification environment. With the increase of Froude number Fr, it shows that the stable height and maximum height of the leakage airflow have a trend of rising first and then falling in a thermally stratified environment. The findings are expected to give guidance in real-world situations, for example, a larger Fr value and a larger temperature gradient can lead to a decrease in the stable height in the thermally stratified environment. It is found that the fitting of the stable height with different temperature gradients satisfies the power function relationship. This work is expected to be helpful for reducing hydrogen leakage accumulation and explosion risk. 相似文献
4.
Jean-Claude Malela-Majika Sandile Charles Shongwe Olatunde Adebayo Adeoti 《Quality and Reliability Engineering International》2021,37(8):3314-3322
The sensitivity of a monitoring scheme depends on many factors including the variance of the charting statistic which is very important in the computation of the control limits. This paper discusses the computation of the variance of the recently proposed hybrid homogeneously weighted moving average (HHWMA) scheme which was based on an incorrect assumption. The correct variance is used to evaluate the run-length characteristics of the HHWMA scheme. It is observed that the incorrect variance has a significant impact on the sensitivity (or performance) of the HHWMA scheme. 相似文献
5.
6.
价值观的传播是一个缓慢的过程,在当前工业文明向生态文明过渡的时期,如何有效地提升民众的生态意识是值得探讨的问题。以生态审美意识传播为切入点,通过了解国内外主流的室内环境生态评估指标体系的前后变化,总结当前室内环境生态评估的变化趋势及其主要特征;从指标体系的变化中分析生态审美价值观的渗透方式,探讨当代室内环境生态评估对生态审美价值观传播的促进作用。最后,通过实验设定针对室内传统营造技艺应用的评估工具,并且在评估工具的使用过程中展示传播的模式与效用,通过评估反馈再一次验证室内环境生态评估对生态审美价值观的正向传播作用。 相似文献
7.
冯鹏一 《信息通信技术与政策》2020,(1):12-15
以电信用户入网协议为切入点,电信用户的携号转网行为应受到《合同法》《消费者权益保护法》等私法规范的保护与限制。该行为引起的格式条款解释、合同终止、违约责任、损失赔偿等问题,不能仅靠《电信条例》等公法规范来调整。应当积极引导广大消费者用户以私法领域相关规定为依据,转变争议解决思维,拓宽纠纷处理途径,合理选择维权手段,以保护自身合法民事权益,与行业监管部门共同推动电信行业有序发展。 相似文献
8.
伏彩萍 《有色金属(冶炼部分)》2020,(6):66-69
针对现有柠檬酸铋制备工艺合成时间长、能耗高、产品纯度不高等不足,介绍了一种常温下制备柠檬酸铋的新工艺。新工艺制备时间短,制备的柠檬酸铋产品质量好,合成过程产生的废水可循环利用,废气经碱液循环吸收可生产硝酸钠副产品。 相似文献
9.
10.
The supervision of a hybrid power plant, including solar panels, a gas microturbine and a storage unit operating under varying solar power profiles is considered. The Economic Supervisory Predictive controller assigns the power references to the controlled subsystems of the hybrid cell using a financial criterion. A prediction of the renewable sources power is embedded into the supervisor. Results deteriorate when the solar power is unsteady, owing to the inaccuracy of the predictions for a long-range horizon of 10 s. The receding horizon is switched between an upper and a lower value according to the amplitude of the solar power trend. Theoretical results show the relevance of horizon switching, according to a tradeoff between performance and prediction accuracy. Experimental results, obtained in a Hardware In the Loop (HIL) framework, show the relevance of the variable horizon approach. Power amplifiers allow us to simulate virtual components, such as a gas microturbine, and to blend their powers with that of real devices (storage unit, real solar panels). In this case, fuel savings, reaching 15%, obtained under unsteady operating conditions lead to a better overall performance of the hybrid cell. The overall savings obtained in the experiments amount to 12%. 相似文献