全文获取类型
收费全文 | 376082篇 |
免费 | 4785篇 |
国内免费 | 1109篇 |
专业分类
电工技术 | 6551篇 |
综合类 | 275篇 |
化学工业 | 55164篇 |
金属工艺 | 17005篇 |
机械仪表 | 12030篇 |
建筑科学 | 8288篇 |
矿业工程 | 3148篇 |
能源动力 | 9236篇 |
轻工业 | 27673篇 |
水利工程 | 4791篇 |
石油天然气 | 10546篇 |
武器工业 | 28篇 |
无线电 | 41627篇 |
一般工业技术 | 78647篇 |
冶金工业 | 68029篇 |
原子能技术 | 10330篇 |
自动化技术 | 28608篇 |
出版年
2021年 | 3365篇 |
2019年 | 3309篇 |
2018年 | 5747篇 |
2017年 | 5855篇 |
2016年 | 6243篇 |
2015年 | 3746篇 |
2014年 | 6286篇 |
2013年 | 16587篇 |
2012年 | 9920篇 |
2011年 | 13189篇 |
2010年 | 10615篇 |
2009年 | 11968篇 |
2008年 | 12177篇 |
2007年 | 12167篇 |
2006年 | 10402篇 |
2005年 | 9659篇 |
2004年 | 8971篇 |
2003年 | 8826篇 |
2002年 | 8370篇 |
2001年 | 8514篇 |
2000年 | 8184篇 |
1999年 | 8358篇 |
1998年 | 20568篇 |
1997年 | 14473篇 |
1996年 | 10917篇 |
1995年 | 8306篇 |
1994年 | 7429篇 |
1993年 | 7440篇 |
1992年 | 5739篇 |
1991年 | 5616篇 |
1990年 | 5319篇 |
1989年 | 5324篇 |
1988年 | 5202篇 |
1987年 | 4508篇 |
1986年 | 4499篇 |
1985年 | 5148篇 |
1984年 | 4798篇 |
1983年 | 4490篇 |
1982年 | 4032篇 |
1981年 | 4126篇 |
1980年 | 4040篇 |
1979年 | 4108篇 |
1978年 | 4097篇 |
1977年 | 4489篇 |
1976年 | 5654篇 |
1975年 | 3668篇 |
1974年 | 3494篇 |
1973年 | 3608篇 |
1972年 | 3095篇 |
1971年 | 2845篇 |
排序方式: 共有10000条查询结果,搜索用时 299 毫秒
41.
Fermanelli Carla S. Galarza Emilce D. Pierella Liliana B. Renzini María S. Saux Clara 《Topics in Catalysis》2019,62(12-16):918-930
Topics in Catalysis - In this work, a simple thermal-catalytic system was used to valorize peanut shells (Arachis hypogaea), the residual biomass from the peanut industry. To accomplish this... 相似文献
42.
The role of the following factors in the selection of technological bases for manufacturing is considered: the accessibility of the machined surfaces; their parameters and dimensional relationships; their position relative to the forces acting; and the uniformity of the margin distribution. 相似文献
43.
Kobrakov K. I. Kurnetsov D. N. Ruchkina A. G. Sharpar N. M. 《Theoretical Foundations of Chemical Engineering》2020,54(5):1052-1056
Theoretical Foundations of Chemical Engineering - New research results, as well as those published earlier by the authors, on the synthesis of azo compounds based on nitroanilines obtained by the... 相似文献
44.
Rajesh B. Gujar Parveen K. Verma Bholanath Mahanty Seraj A. Ansari Dibakar Goswami 《分离科学与技术》2020,55(14):2560-2569
ABSTRACT Solvent extraction studies were performed to understand the extraction behavior of Np4+ and NpO2 2+ from acidic feeds with CMPO (octyl (phenyl)-N,N-diisobutyl carbamoyl methyl phosphine oxide) dissolved in 1-butyl-3-methylimidazolium bis(trifluoromethane sulfonyl)imide, a water immiscible ionic liquid. Slope analyses on the distribution data revealed the extraction of ML2 type species, where M = Np4+ or NpO2 2+, and L = CMPO. Studies were also carried out with Pu4+ and UO2 2+ under identical conditions. The nature of the extracted species was found to vary with the nature of the ionic species. 相似文献
45.
Bukin A. N. Moseeva V. S. Marunich S. A. 《Theoretical Foundations of Chemical Engineering》2020,54(5):1102-1106
Theoretical Foundations of Chemical Engineering - The development of a thermostable hydrophobic platinum catalyst is an important scientific and practical problem. The purpose of this work is to... 相似文献
46.
Kathryn C. Sole John Parker Peter M. Cole Michael B. Mooiman 《Mineral Processing and Extractive Metallurgy Review》2019,40(3):194-206
The price of cobalt has increased by some 450% in the past two years, mainly due to increasing demand for lithium–ion batteries. With an official 2017 production of 64 kt, the Democratic Republic of Congo produces more than half of the world’s cobalt. African Copperbelt operations have traditionally focused on copper production; however, it has now become imperative to also consider cobalt recovery from these ores. A plethora of processing routes is possible. Most hydrometallurgical flowsheets recover cobalt from the raffinate of the low-grade copper solvent-extraction circuit. Downstream purification processes include sequential precipitation with a variety of reagents, solvent extraction, and ion exchange. Product choices include hydroxide, carbonate, sulfate, and metal cathode. This study assesses technical and economic advantages and limitations of various approaches to the hydrometallurgical processing of cobalt in an African context. 相似文献
47.
The basic stages in the life cycle of a batch of complex engineering products are considered: design, production, operation, and disposal. A priori cost assessment for each stage is discussed. The cost aggregation in the consideration of multiple stages is analyzed. Requirements on the assessment are formulated. Methodological and implementation aspects of the assessment tools are outlined. The conclusion is that it is expedient to predict the costs on the basis of mathematical models of the product batch in an operational environment. The integration of multiple cost estimates is addressed. 相似文献
48.
Simonov M. Yu. Pertsev A. S. Shaimanov G. S. Simonov Yu. N. 《Metal Science and Heat Treatment》2020,61(9-10):601-609
Metal Science and Heat Treatment - The structure, the strength characteristics and the impact toughness at different temperatures up to –100°C of tubular billets from steel 35 are... 相似文献
49.
Multidimensional Systems and Signal Processing - The paper is devoted to the development of the octonion Fourier transform (OFT) theory initiated in 2011 in articles by Hahn and Snopek. It is also... 相似文献
50.
Dorofeyev V. Yu. Sviridova A. N. Svistun L. I. 《Russian Journal of Non-Ferrous Metals》2020,61(3):354-361
Russian Journal of Non-Ferrous Metals - Rolling bearing rings comprise a large reserve for expanding powder metallurgy production. This reserve is being incompletely implemented. The hot forging of... 相似文献