全文获取类型
收费全文 | 83103篇 |
免费 | 9665篇 |
国内免费 | 6556篇 |
专业分类
电工技术 | 6024篇 |
技术理论 | 3篇 |
综合类 | 8381篇 |
化学工业 | 19971篇 |
金属工艺 | 3571篇 |
机械仪表 | 5057篇 |
建筑科学 | 6511篇 |
矿业工程 | 2371篇 |
能源动力 | 6276篇 |
轻工业 | 4794篇 |
水利工程 | 1981篇 |
石油天然气 | 3462篇 |
武器工业 | 1254篇 |
无线电 | 5033篇 |
一般工业技术 | 8826篇 |
冶金工业 | 2766篇 |
原子能技术 | 1098篇 |
自动化技术 | 11945篇 |
出版年
2024年 | 459篇 |
2023年 | 1826篇 |
2022年 | 2788篇 |
2021年 | 2979篇 |
2020年 | 3200篇 |
2019年 | 2804篇 |
2018年 | 2639篇 |
2017年 | 3038篇 |
2016年 | 3265篇 |
2015年 | 3188篇 |
2014年 | 4672篇 |
2013年 | 5055篇 |
2012年 | 6098篇 |
2011年 | 6078篇 |
2010年 | 4779篇 |
2009年 | 4866篇 |
2008年 | 4554篇 |
2007年 | 5556篇 |
2006年 | 4874篇 |
2005年 | 4154篇 |
2004年 | 3540篇 |
2003年 | 2990篇 |
2002年 | 2535篇 |
2001年 | 2243篇 |
2000年 | 2010篇 |
1999年 | 1620篇 |
1998年 | 1312篇 |
1997年 | 1123篇 |
1996年 | 944篇 |
1995年 | 803篇 |
1994年 | 710篇 |
1993年 | 534篇 |
1992年 | 423篇 |
1991年 | 330篇 |
1990年 | 270篇 |
1989年 | 234篇 |
1988年 | 170篇 |
1987年 | 123篇 |
1986年 | 68篇 |
1985年 | 78篇 |
1984年 | 90篇 |
1983年 | 48篇 |
1982年 | 42篇 |
1981年 | 18篇 |
1980年 | 35篇 |
1979年 | 21篇 |
1964年 | 9篇 |
1957年 | 8篇 |
1955年 | 12篇 |
1951年 | 29篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
61.
62.
Wenhui MA Gang XIE Hua WANGFaculty of Materials Metallurgical Engineering Kunming University of Science Technology Kunming China Manuscript received January in revised form May 《材料科学技术学报》2002,18(3):286-287
The thermal expansion behavior of La1-xSrxMn1-yCoyO3-δ (x=0.2-0.4, y=0.1-0.3) perovskites in air has been investigated. The average linear thermal expansion coefficients increased with increasing Sr content up to 40 mole fraction or Co content up to 30 mole fraction. The expansion is generally attributed to an increase in the average cation radius as some of the cations in the perovskite are reduced in valence when oxygen ions are removed from the structure. 相似文献
63.
V. V. Tcherdyntsev S. D. Kaloshkin A. I. Salimon E. A. Leonova I. A. Tomilin J. Eckert F. Schurack V. D. Rogozin S. P. Pisarev Yu. P. Trykov 《Materials and Manufacturing Processes》2002,17(6):825-841
Al-Cu-Fe alloys were prepared from elemental powders in a high-energy planetary ball mill. A sequence of solid state reactions resulting in quasicrystal (QC) phase formation takes place during heating of the as-milled powder. These reactions were studied by both differential scanning calorimetry and x-ray diffraction methods. Mechanically alloyed powders were consolidated by cold and hot pressing, as well as by explosive compaction. After annealing at sufficiently high temperatures, the consolidated samples are single-phase QC, except the ones consolidated by explosion. The high reactivity of the as-milled alloys causes the appearance of high porosity of the consolidated samples after the annealing. 相似文献
64.
《Petroleum Science and Technology》2007,25(10):1293-1304
Aromatic hydrogenation is one of the important classes of hydrotreating reactions and its thermodynamics play a significant role in achieving the product specifications. This article comprehensively reviews the available experimental thermodynamic data as well as the methods to estimate the data for aromatic hydrogenation. The data indicate that aromatic hydrogenation reactions are thermodynamically more favorable at about 200°C-250°C and moderate pressures (3-5 MPa). Industrially, however, these reactions are carried out at 300°C-375°C to have reasonable kinetics. Hence there is a need for highly active catalysts, which can facilitate significant kinetics of hydrotreating reactions at around 200°C-250°C. 相似文献
65.
以网络技术和信息技术为依托,建立职业安全健康动态监控信息系统,进行职业安全健康管理的监控和预警,提高安全管理的现代化水平。 相似文献
66.
一种改进的共同进化遗传算法及其应用 总被引:2,自引:0,他引:2
将共同进化遗传算法应用于临床营养决策优化中,虽然取得了一定成果,但算法中仍存在早熟现象、局部搜索能量弱等问题,为此提出一种改进的共同进化模型。算法使用新的子群体划分方法和交叉算子,引入精英保留策略、信息交换原则和小生境技术。通过对糖尿病营养治疗的仿真表明,改进后的算法在保证群体多样性和避免早熟现象的前提下,提高了算法的局部和全局寻优能力,且膳食配方中营养素达标率符合要求,满足专家建议的糖尿病饮食需求。 相似文献
67.
68.
69.
Review of Arthur R. Jensen (2006)--Clocking the mind: Mental chronometry and individual differences.
Reviews the book Clocking the Mind: Mental chronometry and individual differences by Arthur Jensen (see record 2006-20276-000). Mental chronometry, as Arthur Jensen stresses, is the study of reaction time (RT) in its various guises, contexts, and applications. As with respect to much of experimental psychology (cognitive and other), there is a venerable past here lying in the background, providing a wide-ranging context in which to embed our current (that is, our 40-odd year) preoccupation with RT as a primary dependent measure in cognitive psychology. This recent book, Clocking the Mind: Mental Chronometry and Individual Differences (published by Elsevier), weds both differential psychology's concern with the measurement of individual differences in RT (e.g., Austin, Deary, Gibson, McGregor, & Dent, 1998) and experimental psychology's concern with "the effects of manipulating various external conditions on variation in the measurements of RT" (p. 1). The reader of this journal will most probably be more familiar with the latter use of RT in the literature, especially when embedded within such familiar experimental tasks as those tapping both Garner and Stroop effects (Pansky & Algom, 1999). The book should be perused with care in order to ensure the further profitable use of RT in both experimental and differential lines of research. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
70.