全文获取类型
收费全文 | 140770篇 |
免费 | 9515篇 |
国内免费 | 5384篇 |
专业分类
电工技术 | 8093篇 |
技术理论 | 23篇 |
综合类 | 13022篇 |
化学工业 | 18177篇 |
金属工艺 | 7863篇 |
机械仪表 | 7695篇 |
建筑科学 | 17505篇 |
矿业工程 | 5677篇 |
能源动力 | 3656篇 |
轻工业 | 8455篇 |
水利工程 | 5446篇 |
石油天然气 | 4974篇 |
武器工业 | 883篇 |
无线电 | 9017篇 |
一般工业技术 | 9844篇 |
冶金工业 | 10828篇 |
原子能技术 | 899篇 |
自动化技术 | 23612篇 |
出版年
2024年 | 259篇 |
2023年 | 1216篇 |
2022年 | 2466篇 |
2021年 | 3242篇 |
2020年 | 3562篇 |
2019年 | 2574篇 |
2018年 | 2331篇 |
2017年 | 3117篇 |
2016年 | 3861篇 |
2015年 | 4228篇 |
2014年 | 10059篇 |
2013年 | 9067篇 |
2012年 | 10219篇 |
2011年 | 10928篇 |
2010年 | 8142篇 |
2009年 | 8582篇 |
2008年 | 8037篇 |
2007年 | 10029篇 |
2006年 | 9142篇 |
2005年 | 7834篇 |
2004年 | 6775篇 |
2003年 | 6013篇 |
2002年 | 4983篇 |
2001年 | 3952篇 |
2000年 | 3196篇 |
1999年 | 2538篇 |
1998年 | 1870篇 |
1997年 | 1436篇 |
1996年 | 1259篇 |
1995年 | 1019篇 |
1994年 | 813篇 |
1993年 | 552篇 |
1992年 | 450篇 |
1991年 | 355篇 |
1990年 | 235篇 |
1989年 | 238篇 |
1988年 | 180篇 |
1987年 | 99篇 |
1986年 | 128篇 |
1985年 | 112篇 |
1984年 | 115篇 |
1983年 | 117篇 |
1982年 | 43篇 |
1981年 | 35篇 |
1980年 | 37篇 |
1979年 | 26篇 |
1977年 | 28篇 |
1961年 | 14篇 |
1959年 | 17篇 |
1951年 | 20篇 |
排序方式: 共有10000条查询结果,搜索用时 140 毫秒
51.
概述了氢的主要工业生产方法和实际应用,详细介绍了氯碱氢三级脱水工艺过程,并运用在线分析手段,准确显示了干燥过程中的氯碱氢水分含量变化规律。 相似文献
52.
Wai-Ching Liu Huey-Yuan Wang Lung-Chien Chen Shih-Wei Huang Chengtie Wu Ren-Jei Chung 《Ceramics International》2019,45(5):5668-5679
Tricalcium silicate (C3S) and hydroxyapatite (HAp) composites were fabricated through the sol-gel process. The aim of this research is to improve the biocompatibility of C3S through HAp addition and study the potential of using this as coating materials. The composites (HAp/C3S) were characterised by Fourier transform infrared spectrometry, thermal gravity-differential thermal analysis and X-ray diffraction. The working and setting times of cement pastes were tested using Gillmore needle. Mechanical properties were examined by nanoindentation and material testing system. In vitro biocompatibility of the materials were studied by cell attachment and viability of L929 and MG-63 cells. HAp/C3S as a coating material on gelatin film were measured with the surface roughness and imaged by scanning electron microscope. With the addition of HAp, no undesirable free CaO was detected with the synthesis by the sol-gel preparation. The pH values of HAp added groups were between 7.54 and 8.76, which were much lower than pure C3S group (pH?=?11.75). For in vitro studies, the presence of HAp could effectively enhance the cell attachment and viability of both L929 and MG-63 cells grown in the extract or directly on the composites. However, the mechanical properties of the composites were impaired as compared to pure C3S. Lastly, HAp/C3S cement could be evenly coated on gelatin film. HAp is successfully demonstrated to improve C3S biocompatibility with this new composites HAp/C3S. C-75 (75% C3S and 25% HAp), in particular, has good biocompatibility, relatively high compressive strength and can be uniformly coated onto gelatin film. Thus, C-75 is a promising material for further investigation as a coating on other biopolymers. 相似文献
53.
针对煤矿“双重预防体系”如何落地生根问题,结合陈四楼煤矿在风险分级管控和隐患排查治理方面的实用方法和“双重预防体系”的建设经验,深入研究了“双重预防体系”的相关标准、风险隐患事故之间的关系及其各自的产生和发展机理、安全风险的有关辨识评估方法、事故隐患的排查和治理方法,分析了传统安全管理模式与“双重预防体系”的新型安全管理模式的差别,总结出了“123456双重预防体系”这个囊括了事前安全风险辨识、事中隐患排查治理、事后安全现状评估的创新成果,实现了“事前、事中、事后”的全过程控制,对夯实煤矿安全管理根基、促进矿井平稳有序发展发挥着越来越重要的作用,为煤炭行业“双重预防体系”的落地生根提供了借鉴和参考。 相似文献
54.
Three N-heteroleptic Pt(II) complexes, [Pt(C^C)(O^O)] [O^O = acetylacetonate, C^C = 1-phenyl-1,2,4-triazol-5-ylidene (1), C^C = 4-phenyl-1,2,4-triazol-5-ylidene (2), C^C = 2-phenylpyrazine (3)] have been investigated with density functional theory (DFT) and time-dependent density functional theory (TDDFT). The radiative decay rate constants of complexes 1–3 have been discussed with the oscillator strength (fn), the strength of spin–orbit coupling (SOC) interaction between the lowest energy triplet excited state (T1) and singlet excited states (Sn), and the energy gaps between E(T1) and E(Sn). To illustrate the nonradiative decay processes, the transition states between triplet metal-centered (3MC) and T1 states have been optimized and were verified with the calculations of vibrational frequencies and intrinsic reaction coordinate (IRC). In addition, the minimum energy crossing points (MECPs) between 3MC and ground states (S0) were optimized. At last, the potential energy curves relevant to the nonradiative decay pathways are simulated. The results show that complex 3 has the biggest photoluminescence quantum yield because the complex 3 has the biggest radiative decay rate constant and the smallest nonradiative decay rate constant in complexes 1–3. 相似文献
55.
电网的安全水平主要取决于其使用产品的质量是否过关。如果产品的质量较好,则能建造出优质的电网,电网的安全水平便会随之提高。因此,应加强对产品质量的监督管理,从而提高电网的安全水平。我们可建立质量监督管理系统,及时抽检出质量不过关的产品,从而消除电网运行过程中潜在的安全隐患。 相似文献
56.
为将我国最严格水资源管理制度的实践与二元水循环理论相结合,提高“三条红线”控制指标的科学性与合理性,本文以SWAT模型为基础,通过改进子流域划分方法、添加经济社会模块和人工用水模块,对其人工侧支循环模拟进行了系统的完善,开发了基于SWAT的水量-水质-水效联合调控模型SWAT_WAQER。以广西南流江流域为例,从国民经济用水量、河道径流与水质等方面对模型进行校验,并在此基础上划分了2030年“三条红线”控制指标。结果表明:该模型性能良好,能够用于不同节水情景下的国民经济用水量、污染物排放量、水功能区水质达标结果分析,可以作为科学制定“三条红线”控制指标的有力支撑工具。 相似文献
57.
Hoang V. Le Phuong T. Pham Ly T. Le Anh D. Nguyen Ngoc Quang Tran Phong D. Tran 《International Journal of Hydrogen Energy》2021,46(44):22852-22863
WO3 is a potential material candidate for construction of photoanode for solar driven water splitting. In this work, μm-thick porous WO3 photoanode is prepared by depositing a stable ink made of WO3 nanoparticles and Aristoflex velvet polymer in water using the doctor blade technique, followed by a sintering in air. The nature of WO3 nanoparticles, its loading mass on F-doped tin oxide electrode as well as sintering temperature are examined in order to optimize the photocatalytic activity of the resultant WO3 photoanode. The operation of WO3 photoanode is investigated by varying the light illumination direction and light incident intensity as well as changing the nature of the electrolyte. Dissolved tungsten in electrolyte is quantified by ICP-MS providing insights into the influences of electrolyte nature and operating conditions to the corrosion of WO3. It is proposed that the H2O2 and OH. radical generated as by-products of the photo-driven water oxidation on the photoanode surface are harmful species that accelerate the dissolution of WO3. 相似文献
58.
59.
Hitoshi Muta 《Journal of Nuclear Science and Technology》2019,56(5):367-368
Recent activities in the field of Nuclear Operational Management and Nuclear Safety Engineering, the studies related to risk analysis methodology, design, and operational management, physical phenomena, and emergency preparedness and nuclear security, have been progressed. Especially, ‘risk analysis methodology’ and ‘design and operational management’ are the main categories of the field, in which more than half of published articles on Journal of Nuclear Science and Technology are related to these categories. 相似文献
60.