全文获取类型
收费全文 | 58323篇 |
免费 | 4929篇 |
国内免费 | 2586篇 |
专业分类
电工技术 | 3647篇 |
技术理论 | 3篇 |
综合类 | 3979篇 |
化学工业 | 9688篇 |
金属工艺 | 3349篇 |
机械仪表 | 3857篇 |
建筑科学 | 4609篇 |
矿业工程 | 1829篇 |
能源动力 | 1696篇 |
轻工业 | 3850篇 |
水利工程 | 1044篇 |
石油天然气 | 3958篇 |
武器工业 | 526篇 |
无线电 | 6332篇 |
一般工业技术 | 7002篇 |
冶金工业 | 2623篇 |
原子能技术 | 588篇 |
自动化技术 | 7258篇 |
出版年
2024年 | 270篇 |
2023年 | 1073篇 |
2022年 | 1804篇 |
2021年 | 2475篇 |
2020年 | 1976篇 |
2019年 | 1593篇 |
2018年 | 1764篇 |
2017年 | 1953篇 |
2016年 | 1690篇 |
2015年 | 2310篇 |
2014年 | 2984篇 |
2013年 | 3337篇 |
2012年 | 3615篇 |
2011年 | 4059篇 |
2010年 | 3515篇 |
2009年 | 3304篇 |
2008年 | 3232篇 |
2007年 | 2990篇 |
2006年 | 3085篇 |
2005年 | 2565篇 |
2004年 | 1843篇 |
2003年 | 1634篇 |
2002年 | 1613篇 |
2001年 | 1394篇 |
2000年 | 1300篇 |
1999年 | 1528篇 |
1998年 | 1287篇 |
1997年 | 1122篇 |
1996年 | 1007篇 |
1995年 | 831篇 |
1994年 | 668篇 |
1993年 | 481篇 |
1992年 | 424篇 |
1991年 | 263篇 |
1990年 | 212篇 |
1989年 | 165篇 |
1988年 | 122篇 |
1987年 | 82篇 |
1986年 | 68篇 |
1985年 | 44篇 |
1984年 | 36篇 |
1983年 | 32篇 |
1982年 | 31篇 |
1981年 | 19篇 |
1980年 | 17篇 |
1979年 | 6篇 |
1940年 | 3篇 |
1933年 | 1篇 |
1929年 | 1篇 |
1928年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
31.
设计了一种以STM32F103微控制器为控制核心,基于24位高精度模数转换器的钻孔深度测量仪器。利用弹性波回波测距原理,通过测量出钻孔中钻杆的长度,实现钻孔深度的快速、无损、准确的测量,主要用于井下瓦斯抽放钻孔、探放水钻孔等煤矿通防工作的施工验收。仪器小巧轻便,操作简单,单人即可完成测量工作,节约下井的人力物力,提高生产效率,最长测量长度可达250米,误差不超过1米。 相似文献
32.
33.
Xueliang Wang Huiqin Yin Wenguan Liu Guojun Yu Jian He Zhongfeng Tang Long Yan 《工业材料与腐蚀》2020,71(6):931-937
Understanding the corrosion of molten ZnCl2 on metal surfaces is significant for the corrosion protection of metals, sustainable use of molten salts, preparation of ZnO coatings, and so on. In this paper, surfaces of pure Ni, Cr, and Fe corroded by molten ZnCl2 were investigated. The results show that Ni suffered very slight corrosion, while Cr experienced more serious corrosion than Ni, but lighter corrosion than Fe. The morphology of the corrosion of Cr and Fe, respectively, presented pitting and intergranular corrosion characteristics. Furthermore, nanostructured ZnO coatings were obtained on the surfaces of Ni and Fe, but not on the surface of Cr. The ZnO coating on the Ni surface was doped with a small amount of Zn5(OH)8Cl2, and the ZnO coating on the Fe surface was doped with ZnFe2O4 and Zn2OCl2. The coatings on the Ni and Fe surfaces had an average thickness of 1.5 and 50 μm, respectively. 相似文献
36.
Ziqian Wang Yalan Chen Yating He Weidong Jiang Yan Long Guangyin Fan 《International Journal of Hydrogen Energy》2021,46(21):11587-11596
Developing high-efficiency and low-cost catalysts for hydrogen evolution from hydrolysis of ammonia borane (AB) is significant and critical for the exploitation and utilization of hydrogen energy. Herein, the in-situ fabrication of well-dispersed and small bimetallic RuNi alloy nanoparticles (NPs) with tuned compositions and concomitant hydrolysis of AB are successfully achieved by using graphitic carbon nitride (g-C3N4) as a NP support without additional stabilizing ligands. The optimized Ru1Ni7.5/g-C3N4 catalyst exhibits an excellent catalytic activity with a high turnover frequency of 901 min?1 and an activation energy of 28.46 kJ mol?1 without any base additives, overtaking the activities of many previously reported catalysts for AB hydrolysis. The kinetic studies indicate that the AB hydrolysis over Ru1Ni7.5/g-C3N4 is first-order and zero-order reactions with respect to the catalyst and AB concentrations, respectively. Ru1Ni7.5/g-C3N4 has a good recyclability with 46% of the initial catalytic activity retained even after five runs. The high performance of Ru1Ni7.5/g-C3N4 should be assigned to the small-sized alloy NPs with abundant accessible active sites and the synergistic effect between the composition-tuned Ru–Ni bimetals. This work highlights a potentially powerful and simple strategy for preparing highly active bimetallic alloy catalysts for AB hydrolysis to generate hydrogen. 相似文献
37.
Climate change raises many concerns for urban water management because of the effects on all aspects of the hydrological cycle. Urban water infrastructure has traditionally been designed using historical observations and assuming stationary climatic conditions. The capability of this infrastructure, whether for storm-water drainage, or water supply, may be over- or under-designed for future climatic conditions. In particular, changes in the frequency and intensity of extreme rainfall events will have the most acute effect on storm-water drainage systems. Therefore, it is necessary to take future climatic conditions into consideration in engineering designs in order to enhance water infrastructure investment planning practices in a long time horizon. This paper provides the initial results of a study that is examining ways to enhance urban infrastructure investment planning practices against changes in hydrologic regimes for a changing climate. Design storms and intensity-duration-frequency curves that are used in the engineering design of storm-water drainage systems are developed under future climatic conditions by empirically adjusting the general circulation model output, and using the Gumbel distribution and the Chicago method. Simulations are then performed on an existing storm-water drainage system from NE Calgary to investigate the resiliency of the system under climate change. 相似文献
38.
连续油管技术与装备发展综述 总被引:41,自引:14,他引:27
自世界上第一台连续油管作业机问世至今,连续油管作业技术与装备已经过了40多年的发展历程,以其占地面积小、作业成本低、搬迁安装方便、保护油层、增加油井产量和使用范围广等诸多不可比拟的优势,得到迅速发展,并广泛应用于钻井、完井、试油、采油、修井和集输等各个作业领域。实践表明,连续油管作业技术与装备是一项具有巨大潜力和生命力的实用性技术。目前,该项技术的应用日趋活跃,备受关注。在总结连续油管作业技术与装备的发展现状和展示其发展趋势的基础上,客观地分析了国内连续油管技术与装备的应用与研究现状,提出相应的发展对策。 相似文献
39.
Online Raman spectra, obtained at different points along the spin line during pilot‐scale nonisothermal melt spinning of high density polyethylene (HDPE) fibers, are presented for the first time. The fraction of the crystalline phase corresponding to each spectrum was determined from the normalized integrated intensity of the 1418 cm?1 Raman band. It is well established that this band represents the orthorhombic crystalline phase in polyethylene. The estimates of percent crystallinity obtained from decomposition of the Raman spectrum were compared with the percent crystallinity from differential scanning calorimetry (DSC) measurements. It is concluded that online Raman spectroscopy can be successfully used to monitor the development of crystallinity in HDPE fibers as a function of distance from the spinneret. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 545–549, 2003 相似文献
40.