全文获取类型
收费全文 | 159647篇 |
免费 | 15068篇 |
国内免费 | 8436篇 |
专业分类
电工技术 | 11727篇 |
技术理论 | 4篇 |
综合类 | 11655篇 |
化学工业 | 23448篇 |
金属工艺 | 9622篇 |
机械仪表 | 10184篇 |
建筑科学 | 11972篇 |
矿业工程 | 3976篇 |
能源动力 | 4895篇 |
轻工业 | 11534篇 |
水利工程 | 3660篇 |
石油天然气 | 7141篇 |
武器工业 | 1673篇 |
无线电 | 20280篇 |
一般工业技术 | 18551篇 |
冶金工业 | 7626篇 |
原子能技术 | 1928篇 |
自动化技术 | 23275篇 |
出版年
2024年 | 516篇 |
2023年 | 2062篇 |
2022年 | 4091篇 |
2021年 | 6103篇 |
2020年 | 4337篇 |
2019年 | 3533篇 |
2018年 | 3969篇 |
2017年 | 4739篇 |
2016年 | 4381篇 |
2015年 | 6185篇 |
2014年 | 8081篇 |
2013年 | 9908篇 |
2012年 | 11556篇 |
2011年 | 12522篇 |
2010年 | 11386篇 |
2009年 | 10966篇 |
2008年 | 10795篇 |
2007年 | 10283篇 |
2006年 | 9637篇 |
2005年 | 7895篇 |
2004年 | 5732篇 |
2003年 | 5014篇 |
2002年 | 5180篇 |
2001年 | 4480篇 |
2000年 | 3414篇 |
1999年 | 2982篇 |
1998年 | 2377篇 |
1997年 | 2066篇 |
1996年 | 1809篇 |
1995年 | 1491篇 |
1994年 | 1164篇 |
1993年 | 921篇 |
1992年 | 719篇 |
1991年 | 551篇 |
1990年 | 463篇 |
1989年 | 358篇 |
1988年 | 286篇 |
1987年 | 212篇 |
1986年 | 173篇 |
1985年 | 140篇 |
1984年 | 105篇 |
1983年 | 78篇 |
1982年 | 75篇 |
1981年 | 67篇 |
1980年 | 58篇 |
1979年 | 40篇 |
1978年 | 34篇 |
1977年 | 33篇 |
1976年 | 54篇 |
1973年 | 21篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
72.
The capture of particles by charged droplets was simulated by considering the electrostatic interactions of droplet-droplet and droplet-particle. The results indicate that the electrostatic repulsion between droplets leads to a dynamic accumulation mode of particles. However, the droplet spacing has an insignificant effect on the capture efficiency when the electrostatic deposition predominates. The increase of droplet charge remarkably improves the capture efficiency, in which the capture of fine particles accounts for the largest proportion. Compared to the droplet charge, the droplet size shows a limited improvement in the capture efficiency. Reducing the droplet velocity prolongs the capture time instead of enhancing the capture capacity per unit time, thereby improving capture efficiency. 相似文献
73.
74.
Biyun Fang Chuanfeng Zhang Zeliang Qi Chunyan Li Jun Ni Xiuyun Wang Jianxin Lin Chak-Tong Au Bingyu Lin Lilong Jiang 《American Institute of Chemical Engineers》2022,68(11):e17849
The design of an efficient non-noble metal catalyst is of burgeoning interest for ammonia synthesis. Herein, we report a Mo2C/CeO2 catalyst that is superior in ammonia synthesis activity. In this catalyst, molybdenum carbide coexisted with the ceria overlayers which is from the ceria support as the strong metal–support interaction. There is a high proportion of low-valent Mo species, as well as high concentration of Ce3+ and surface oxygen species. The presence of Mo2C and CeO2 overlayers not only leads to enhancement of hydrogen and nitrogen adsorption, but also facilitates the desorption and exchange of adsorbed species with the gaseous reagents. Compared with the Mo/CeO2 catalyst prepared without carbonization, the Mo2C/CeO2 catalyst is more than sevenfold higher in ammonia synthesis rate. This work not only presents an explicit example of designing Mo-based catalyst that is highly efficient for ammonia synthesis by tuning the adsorption and desorption properties of the reactant gases, but opens a perspective for other elements in ammonia synthesis. 相似文献
75.
76.
食物成瘾的研究进展及启示 总被引:2,自引:0,他引:2
食物成瘾是一种复杂的慢性疾病,导致人们在日常生活中对某种食物产生过度依赖与过度进食等相关行为特征,近年来已被认为是影响欧美发达国家肥胖症、暴食症、糖尿病等发病率持续升高的关键原因,引起学术界的极大关注,成为研究热点。本文主要介绍食物成瘾的概念、诊断标准,综述了食物成瘾的病理机制、影响因素和应对措施等方面的研究进展,并探讨食物成瘾对我国食品界的启示,为预防食物成瘾,保障公众健康提供有益借鉴。 相似文献
77.
在内径120 mm的半圆柱形内循环流化床中,以平均粒径387 nm的Ti O2为原料,考察了单独通入流化气、射流气和同时通入流化气和射流气三种流化方式下超细粉的流化特性以及射流气速对超细粉聚团尺寸的影响。结果表明:同时通入流化气和射流气时,流化气能促进粉体循环,消除环隙死区;高速射流能有效破碎聚团,显著减小聚团尺寸,从而使超细粉在环隙区与导流管之间形成稳定循环,小聚团在环隙区实现平稳流态化。随着射流气速的增大,聚团尺寸减小,粒度分布变窄,在射流气速分别为60,90,120,150 m/s的条件下,聚团平均直径分别为194,158,147,135μm。 相似文献
78.
A novel AlSiMgAl2O4Al2O3 composite brick was prepared and evaluated in the low vessel of an RH (the initials of Ruhrstahl and Hereaeus) secondary refining furnace; it was characterized by X-ray diffraction, scanning electron microscopy, and energy-dispersive spectroscopy. The results show that after use, the AlSiMgAl2O4Al2O3 composite has a functional gradient with an erosion zone–reinforced zone–original zone phase distribution, in which the phases in the erosion zone (0–1.8?cm) are a Mg-hercynite spinel solid solution, α-Al2O3, and minor amount of Al3Fe5O12. Furthermore, the phases in the reinforced zone (1.8–5.0?cm) are γ-AlON, 21RSiAlON, SiC, Mg0.388Al2.408O4, and α-Al2O3; i.e., the Al and Si in the composite are completely converted into non-oxide reinforced phases. Finally, the phases in the original zone (>5.0?cm) show no change. The reaction mechanism is as follows. During operation, a Mg-hercynite spinel solid solution is formed in the erosion zone due to a reaction between MgAl2O4 and FeO from a refinery operation. Therefore, the slag erosion of the material is improved. The Al and Si metals undergo active oxidation, and 21RSiAlON flakes are subsequently formed from the products of the metastable Al2O(g), SiO(g), and N2(g) in the ambient. The γ-AlON is formed by a carbothermal reduction nitridation of the α-Al2O3 and residual active carbon from the resin binder. The 21RSiAlON and γ-AlON reinforce the composite brick and improve its high temperature performance accordingly. Its service life is 110% that of the magnesia-chrome bricks used in the same period. The reaction model was also established. 相似文献
79.
煤电平均供电煤耗作为评价能源系统效率的指标已在行业内广泛应用。但该项指标无法很好地反映一个国家、地区的用电结构与用电能耗水平。为此,参照行业内普遍采用的火电厂发电煤耗和供电煤耗指标,定义“综合用电煤耗”,即用户每用1 kW?h电“消耗”的标准煤量(单位:g/(kW?h))。在此基础上,提出“综合发电煤耗”与“综合供电煤耗”的概念,形成完整的指标评价体系。对近年典型省份指标值的研究表明,该指标体系能够很好地反映供给侧国家、省区或企业的发电结构与电能生产能耗水平。这一指标体系能够为正确理解和计算用电、输电与电能替代项目的化石能源消耗量及其排放量提供依据。 相似文献