全文获取类型
收费全文 | 298666篇 |
免费 | 22068篇 |
国内免费 | 11218篇 |
专业分类
电工技术 | 15493篇 |
技术理论 | 31篇 |
综合类 | 17431篇 |
化学工业 | 50392篇 |
金属工艺 | 17279篇 |
机械仪表 | 18474篇 |
建筑科学 | 22912篇 |
矿业工程 | 9523篇 |
能源动力 | 7986篇 |
轻工业 | 16669篇 |
水利工程 | 4796篇 |
石油天然气 | 20265篇 |
武器工业 | 2234篇 |
无线电 | 31759篇 |
一般工业技术 | 34475篇 |
冶金工业 | 15316篇 |
原子能技术 | 2943篇 |
自动化技术 | 43974篇 |
出版年
2024年 | 1217篇 |
2023年 | 4678篇 |
2022年 | 7918篇 |
2021年 | 11401篇 |
2020年 | 8526篇 |
2019年 | 7281篇 |
2018年 | 8171篇 |
2017年 | 9215篇 |
2016年 | 8025篇 |
2015年 | 11168篇 |
2014年 | 13976篇 |
2013年 | 16612篇 |
2012年 | 18506篇 |
2011年 | 22390篇 |
2010年 | 17832篇 |
2009年 | 16875篇 |
2008年 | 16086篇 |
2007年 | 15643篇 |
2006年 | 16399篇 |
2005年 | 14702篇 |
2004年 | 9549篇 |
2003年 | 8475篇 |
2002年 | 7575篇 |
2001年 | 6486篇 |
2000年 | 7099篇 |
1999年 | 8514篇 |
1998年 | 6927篇 |
1997年 | 5843篇 |
1996年 | 5463篇 |
1995年 | 4509篇 |
1994年 | 3761篇 |
1993年 | 2630篇 |
1992年 | 2143篇 |
1991年 | 1607篇 |
1990年 | 1182篇 |
1989年 | 939篇 |
1988年 | 767篇 |
1987年 | 529篇 |
1986年 | 400篇 |
1985年 | 271篇 |
1984年 | 206篇 |
1983年 | 131篇 |
1982年 | 135篇 |
1981年 | 92篇 |
1980年 | 70篇 |
1979年 | 24篇 |
1978年 | 2篇 |
1965年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
101.
102.
Yafei Liu Zhilong Fu Xingyu Chen Yaxin Wei Bo Zhang Aimin Chang 《Journal of the American Ceramic Society》2021,104(5):2134-2142
Rare-earth ions doped Ca0.9R0.1CeNbMoO8 (R = Y, Sm, Nd, La) ceramics have been successfully prepared by solid-state method, and their modifications to the microstructure and electrical properties are also investigated. The rare-earth ions doped ceramics exhibit the scheelite structure. With the increase in the radius of rare-earth ions, the lattice distortion and bond interaction will be enhanced, and the consistency of grain size will be reduced. The ceramics exhibit negative temperature coefficient (NTC) thermistor characteristics in the temperature range of 473 K-1273 K, and the activation energy decreases with the increase of the radius of rare-earth ions. Rare-earth ions doping can increase the content of Ce3+ ions and promote the conductivity of ceramics. Except for Sm3+-doped ceramics, the high-temperature aging rate of other ceramics is less than 2%. The existence of some metastable Sm2+ ions in Sm3+-doped ceramics not only increases the activation energy, but also reduces the high-temperature stability of the ceramics. 相似文献
103.
Prediction of methane adsorption content in continental coal-bearing shale reservoir using SLD model
Shale gas, as an important unconventional resource, has drawn global attention. It is mainly composed of adsorption gas and free gas. Adsorption gas content could play an important guiding role on both the selection of favorable perspective area and the exploration and exploitation of shale gas resources. In order to accurately measure adsorption gas content, a new approach was established to predict the adsorption isotherm of methane on shale. Based on the simplified local-density (SLD) method, both the adsorption isotherms of illite, illite/smectite mixed-layer, cholorite and type III kerogen and the total shale rock could be well fitted. The fitting results show good coincidences with the true experimental test data, which proves the method is reasonable and dependable and the prediction results are effective and credible. In addition, the good simulation results show that the SLD parameters can reflect the pore structure characteristics and corresponding adsorption characteristics of the shale samples, which can be used for the quantitative characterization of shale pore system. 相似文献
104.
截至2020年年底,全国垃圾焚烧发电行业垃圾处理能力超60万吨/日,并网装机容量达到1533万千瓦,年焚烧处理垃圾量约为1.4亿吨."十三五"期间行业发展迅猛,生活垃圾焚烧发电项目在守护城乡环境、节约土地资源等方面发挥了重要作用,已是民生兜底工程,城乡协同发展的重要基础设施.在2030年碳达峰、2060年碳中和的大背景下,行业将如何发展.文中对行业现状进行简单分析,对"十四五"期间行业发展趋势进行预判,并提出相关行业发展建议. 相似文献
105.
Zhang Xi Wang Xianhai Zhao Hongke Ordóñez de Pablos Patricia Sun Yongqiang Xiong Hui 《Scientometrics》2019,119(3):1311-1344
Scientometrics - Altmetrics indices are increasingly applied to measure scholarly influence in recent years because they can reflect the influence of research outputs more timely comparing with... 相似文献
106.
Process object is the instance of process. Vertexes and edges are in the graph of process object. There are different types of the object itself and the associations between object. For the large-scale data, there are many changes reflected. Recently, how to find appropriate real-time data for process object becomes a hot research topic. Data sampling is a kind of finding c hanges o f p rocess o bjects. There i s r equirements f or s ampling to be adaptive to underlying distribution of data stream. In this paper, we have proposed a adaptive data sampling mechanism to find a ppropriate d ata t o m odeling. F irst o f all, we use concept drift to make the partition of the life cycle of process object. Then, entity community detection is proposed to find changes. Finally, we propose stream-based real-time optimization of data sampling. Contributions of this paper are concept drift, community detection, and stream-based real-time computing. Experiments show the effectiveness and feasibility of our proposed adaptive data sampling mechanism for process object. 相似文献
107.
Scientometrics - Specialized academic social networking sites are gaining popularity in scientific communication. A huge volume of interdisciplinary information is generated when researchers from... 相似文献
108.
Shuyi Fu Wenrui Feng Ying Jia Tielong Deng Wenzhong Wang Guling Zhang Junli Fu 《International Journal of Hydrogen Energy》2021,46(21):11544-11555
ZnO/Cu2S nanotube arrays are fabricated firstly by a facile and capping-agent-free method, and the photo-electrochemical performance has been studied systematically. The results show that ZnO/Cu2S nanotube arrays achieve enhanced photo-electrochemical water splitting performance and the photocurrent densities of ZnO/Cu2S are 7.9 times than that of ZnO at 0 V versus Ag/AgCl. The performance of the ZnO/Cu2S nanotube arrays can be adjusted by changing the amount of Cu2S microcrystals. The results confirm that the enhanced photo-electrochemical performance of ZnO/Cu2S is due to the significantly improved visible light absorption, effective separation of photo-induced carriers due to the well band energy match and the formed p-n junction between ZnO and Cu2S. 相似文献
109.
110.
Weiguo Cao Wenjuan Li Liang Zhang Jianfa Chen Shuo Yu Zhuanghong Zhou Yun Zhang Xiaobo Shen Yingxin Tan 《International Journal of Hydrogen Energy》2021,46(52):26693-26707
The explosion venting duct can effectively reduce the hazard degree of a gas explosion and conduct the venting energy to the safe area. To investigate the flame quantitative propagation law of explosion venting with a duct, the effects of hydrogen fraction and explosion venting duct length on jet flame propagation characteristics of premixed H2-air mixtures were analyzed through experiment and simulation. The experiment results under initial conditions of room temperature and 1 atm show that when hydrogen fraction was high enough, part of the unburned hydrogen was mixed with air again to reach an ignitable concentration, resulting in the secondary combustion was easier produced and the duration of the secondary flame increased. With the increase of venting duct length, the flame front distance and propagation velocity increased. Meanwhile, the spatial distribution of pressure field and temperature field, and the propagation process and mechanism of the flame venting with a duct were analyzed using FLUENT software. The variation of the pressure wave and the pressure reflection oscillation law in the explosion venting duct was captured. Therefore, in the industrial explosion venting design with a duct, the hazard caused by the coupling of venting pressure and venting flame under different fractions should be considered comprehensively. 相似文献