全文获取类型
收费全文 | 444931篇 |
免费 | 9737篇 |
国内免费 | 3634篇 |
专业分类
电工技术 | 10767篇 |
技术理论 | 2篇 |
综合类 | 3759篇 |
化学工业 | 66339篇 |
金属工艺 | 18814篇 |
机械仪表 | 16185篇 |
建筑科学 | 11735篇 |
矿业工程 | 3365篇 |
能源动力 | 12661篇 |
轻工业 | 32056篇 |
水利工程 | 5080篇 |
石油天然气 | 10097篇 |
武器工业 | 479篇 |
无线电 | 54269篇 |
一般工业技术 | 87243篇 |
冶金工业 | 76639篇 |
原子能技术 | 9936篇 |
自动化技术 | 38876篇 |
出版年
2022年 | 4195篇 |
2021年 | 6004篇 |
2020年 | 4572篇 |
2019年 | 5094篇 |
2018年 | 7897篇 |
2017年 | 7974篇 |
2016年 | 8290篇 |
2015年 | 6142篇 |
2014年 | 9412篇 |
2013年 | 22526篇 |
2012年 | 14286篇 |
2011年 | 18245篇 |
2010年 | 14859篇 |
2009年 | 16311篇 |
2008年 | 16648篇 |
2007年 | 16217篇 |
2006年 | 14761篇 |
2005年 | 13104篇 |
2004年 | 11838篇 |
2003年 | 11655篇 |
2002年 | 11146篇 |
2001年 | 10916篇 |
2000年 | 10073篇 |
1999年 | 10303篇 |
1998年 | 24786篇 |
1997年 | 17166篇 |
1996年 | 13222篇 |
1995年 | 9806篇 |
1994年 | 8626篇 |
1993年 | 8579篇 |
1992年 | 6242篇 |
1991年 | 5800篇 |
1990年 | 5761篇 |
1989年 | 5394篇 |
1988年 | 5105篇 |
1987年 | 4460篇 |
1986年 | 4328篇 |
1985年 | 4826篇 |
1984年 | 4438篇 |
1983年 | 4006篇 |
1982年 | 3667篇 |
1981年 | 3738篇 |
1980年 | 3439篇 |
1979年 | 3330篇 |
1978年 | 3334篇 |
1977年 | 3750篇 |
1976年 | 4847篇 |
1975年 | 2850篇 |
1974年 | 2663篇 |
1973年 | 2730篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Zienko S. I. Zhbanova V. L. 《Journal of Communications Technology and Electronics》2022,67(4):395-402
Journal of Communications Technology and Electronics - A quantitative comparison of the spectral characteristics of the human visual system and matrix photodetectors is carried out. Criteria for a... 相似文献
2.
Atomic Energy - The history and direction of further development of space nuclear energetics are examined. The functional diagram and principle of operation of a promising, powerful,... 相似文献
3.
Xiao Zhu Chen Yanxun Jiang Hongbo Hu Zhenzhen Lui John C. S. Min Geyong Dustdar Schahram 《Wireless Networks》2022,28(7):3305-3322
Wireless Networks - Unmanned aerial vehicles (UAV) have been widely used in various fields because of their high mobility and portability. At the same time, due to the rapid development of... 相似文献
4.
5.
Can Ercan S. Esra Safran Artuğ Türkmenoğlu Uğur Karabakal 《Journal of surfactants and detergents》2021,24(1):139-147
Garzan oil field is located at the south east of Turkey. It is a mature oil field and the reservoir is fractured carbonate reservoir. After producing about 1% original oil in place (OOIP) reservoir pressure started to decline. Waterflooding was started in order to support reservoir pressure and also to enhance oil production in 1960. Waterflooding improved the oil recovery but after years of flooding water breakthrough at the production wells was observed. This increased the water/oil ratio at the production wells. In order to enhance oil recovery again different techniques were investigated. Chemical enhanced oil recovery (EOR) methods are gaining attention all over the world for oil recovery. Surfactant injection is an effective way for interfacial tension (IFT) reduction and wettability reversal. In this study, 31 different types of chemicals were studied to specify the effects on oil production. This paper presents solubility of surfactants in brine, IFT and contact angle measurements, imbibition tests, and lastly core flooding experiments. Most of the chemicals were incompatible with Garzan formation water, which has high divalent ion concentration. In this case, the usage of 2-propanol as co-surfactant yielded successful results for stability of the selected chemical solutions. The results of the wettability test indicated that both tested cationic and anionic surfactants altered the wettability of the carbonate rock from oil-wet to intermediate-wet. The maximum oil recovery by imbibition test was reached when core was exposed 1-ethly ionic liquid after imbibition in formation water. Also, after core flooding test, it is concluded that considerable amount of oil can be recovered from Garzan reservoir by waterflooding alone if adverse effects of natural fractures could be eliminated. 相似文献
6.
Xin Li Yurui Wang Minxuan Xu Yueqin Shi Hemiao Wang Xin Yang Haoting Ying Qi Zhang 《应用聚合物科学杂志》2021,138(19):50406
Polymer electrets have revealed great potential application in electromechanical devices because of the low weight, large quasi-piezoelectric sensitivity, and excellent flexibility. For an electret, a permanent and macroscopic electric field exists on the surface, principally led by a macroscopic electrostatic charge on the surface or a net orientation of polar groups inside the object. Here, progress in the development of polymer electrets is reviewed. After a brief retrospect of the research courses and those typical polymer electrets that are classified into fluorine polymer and nonfluorine polymer, we present a survey on the charging methods, including corona, soft X-ray, contact, thermal and monoenergetic particle beams. The latest representative applications (i.e., power harvesting, sensors, field effect transistors, and biomedicine) based on polymer electrets are also summarized. Finally, we complete this review with a discussion on perspectives and challenges in this field. 相似文献
7.
Chenchen Zhou Jia Man Haibo Yu He Xia Luming Man Bin Qi Jianfeng Li 《Ceramics International》2021,47(8):10866-10872
Ceramic microparticles have great potentials in various fields such as materials engineering, biotechnology, microelectromechanical systems, etc. Morphology of the microparticle performs an important role on their application. To date, it remains difficult to find an effective and controllable way for fabricating nonspherical ceramic microparticles with 3D features. This work demonstrates a method that combines UV light lithography and single emulsion opaque-droplet-templated microfluidic molding to prepare the crescent-shaped ceramic microparticles. By tailoring the intensity of UV light and flow rate of fluid, the shapes of microparticles are accordingly tuned. Therefore, varieties of crescent-shaped microparticles and their variations have been fabricated. After sintering, the crescent-shaped alumina ceramic microparticles were obtained. Benefitting from the light absorption and scattering behavior of most ceramic nanoparticles, this system can serve as a general platform to produce crescent-shaped microparticles made from different materials, and hold great potentials for applications in microrobotics, structural materials in MEMS, and biotechnology. 相似文献
8.
Combustion, Explosion, and Shock Waves - Results of a numerical study of mixing, ignition, and combustion of a cold hydrogen jet propagating along the lower wall of a channel parallel to a... 相似文献
9.
盾构隧道施工物料无人运输有助于提升运输效率、降低运输成本、减少运输安全事故率。与公路汽车无人驾驶、港口车辆无人驾驶、轨道交通无人驾驶等逐步成熟的无人驾驶技术不同,在隧道场景下实施施工物料无人运输存在运输物料种类繁多、运输调度困难、地下定位信号拒止、狭窄车道频繁会车、行车路面工况复杂、地上地下联动响应慢等诸多挑战。从实现盾构隧道施工物料无人运输的关键问题分析入手,综述当前盾构隧道施工物料运输方式、运输需求、无人运输发展现状及存在的挑战,提出盾构隧道施工物料无人运输的五大关键技术:多种类物料智能货控能效管理技术,无人化垂直装卸门机控制技术,多传感器融合同步定位与地图构建技术,隧道复杂环境路径规划与自主避障技术,隧-地一体化联动响应的高可靠性无线通信技术。 相似文献
10.
Telecommunication Systems - Energy saving in User Equipment (UE) is one of the important issues for limited sources of power in the device. It is critical for the UE to maximize its energy... 相似文献