全文获取类型
收费全文 | 85524篇 |
免费 | 1055篇 |
国内免费 | 407篇 |
专业分类
电工技术 | 791篇 |
综合类 | 2316篇 |
化学工业 | 11994篇 |
金属工艺 | 4835篇 |
机械仪表 | 3073篇 |
建筑科学 | 2222篇 |
矿业工程 | 563篇 |
能源动力 | 1158篇 |
轻工业 | 3961篇 |
水利工程 | 1288篇 |
石油天然气 | 359篇 |
无线电 | 9328篇 |
一般工业技术 | 16569篇 |
冶金工业 | 2774篇 |
原子能技术 | 266篇 |
自动化技术 | 25489篇 |
出版年
2023年 | 23篇 |
2022年 | 113篇 |
2021年 | 145篇 |
2020年 | 69篇 |
2019年 | 90篇 |
2018年 | 14510篇 |
2017年 | 13453篇 |
2016年 | 10031篇 |
2015年 | 647篇 |
2014年 | 312篇 |
2013年 | 345篇 |
2012年 | 3257篇 |
2011年 | 9546篇 |
2010年 | 8365篇 |
2009年 | 5640篇 |
2008年 | 6860篇 |
2007年 | 7839篇 |
2006年 | 164篇 |
2005年 | 1242篇 |
2004年 | 1173篇 |
2003年 | 1199篇 |
2002年 | 554篇 |
2001年 | 111篇 |
2000年 | 188篇 |
1999年 | 72篇 |
1998年 | 97篇 |
1997年 | 58篇 |
1996年 | 71篇 |
1995年 | 27篇 |
1994年 | 35篇 |
1993年 | 23篇 |
1992年 | 16篇 |
1991年 | 26篇 |
1988年 | 16篇 |
1969年 | 24篇 |
1968年 | 43篇 |
1967年 | 33篇 |
1966年 | 42篇 |
1965年 | 44篇 |
1964年 | 11篇 |
1963年 | 28篇 |
1962年 | 22篇 |
1961年 | 18篇 |
1960年 | 30篇 |
1959年 | 35篇 |
1958年 | 37篇 |
1957年 | 36篇 |
1956年 | 34篇 |
1955年 | 63篇 |
1954年 | 68篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
52.
Phase-change read-and-write memory (PRAM) is a promising memory that can solve the problems of conventional memory—scalability, read/write speed, and reliability. We will review the opportunities and technical challenges of PRAM. The most important challenge of PRAM is the reduction of the writing current. Various approaches to reduce the writing current will be reviewed and the prospects of PRAM are discussed. 相似文献
53.
54.
55.
Sandra Aparecida de Assis Pedro Fernandes Bruno Sommer Ferreira Joaquim MS Cabral Olga Maria Mascarenhas Faria Oliveira 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2004,79(3):277-280
A partially purified extract of pectinmethylesterase (PME) from acerola fruit was immobilized on various supports: glass, celite, chrysotile, agarose, concanavalin A Sepharose 4B, egg shell, polyacrylamide and gelatin. In addition, reticulation with glutaraldehyde was assessed, as well as the use of gelatin in the presence of celite, glass and silica. The highest immobilization yields were obtained when the pectinmethylesterase was immobilized in concanavalin A Sepharose 4B (81.7%) and in gelatin‐water (78.0%). Copyright © 2004 Society of Chemical Industry 相似文献
56.
Frantz Rowe 《欧洲信息系统杂志》2006,15(3):244-248
57.
58.
F. A. N. Fernandes 《化学工程与技术》2005,28(8):930-938
The polymerization kinetics of Fischer‐Tropsch reactions on a K‐promoted Fe catalyst was studied. To represent the product distribution, a kinetic model was developed based on alkyl and alkenyl mechanisms for hydrocarbon chain propagation, which were assumed to occur simultaneously in the Fischer‐Tropsch synthesis. The conclusion was drawn that superimposed Anderson‐Schulz‐Flory (ASF) distributions with different chain growth probabilities, on iron catalysts, can be the result of different chain growth mechanisms. The polymerization mechanism was used to obtain the product distribution for several conditions, and the optimum conditions for the production of transportation fuels were found. 相似文献
59.
Barbara K. Reck Robert B. Gordon 《JOM Journal of the Minerals, Metals and Materials Society》2008,60(7):55-59
Nickel and chromium are essential ingredients in alloys increasingly important for energy-efficient, environmentally friendly
modern technology. Quantitative assessment of the flows of these metals through the world economy from resource extraction
to final disposal informs resource policy, energy planning, environmental science, and waste management. This article summarizes
the worldwide technological cycles of nickel and chromium in 2000. Stainless steel is the major use of these metals, but they
serve numerous other special needs, as in superalloys for high-temperature service, as plating materials, and in coinage.
Because they are used primarily in alloys, novel recycling issues arise as their use becomes more widespread.
“... the great New York and St. Louis double track, nickel plated railroad...”
— Norwalk, Ohio, Chronicle 10 March 1881 announces arrival of surveyors for the future Nickel Plate Railway
“Later [1911] I formed an alloy of Iron and Chromium, which showed remarkable resistance to rust and tarnish ... [It was]
rediscovered by an Englishman named Brearley, in 1914.”
—Elwood Haynes to Stephen F. Roberts, 17 January 1925 相似文献
60.
Shafeeque G. Ansari Mushtaq Ahmad Dar Young-Soon Kim Hyung-Kee Seo Gil-Sung Kim Rizwan Wahab Zubaida A. Ansari Jae-Myung Seo Hyung-Shik Shin 《Korean Journal of Chemical Engineering》2008,25(3):593-598
A comparative study for the nucleation of diamond was carried out using surface treatment like (i) surface scratching with
1 μm diamond paste and (ii) surface etching using chlorine plasma at different RF powers (50, 100 and 150 W). Atomic force
microscopic study shows variation in roughness from 31 nm to 110 nm. Scratching results in random scratches, whereas plasma
etches a surface uniformly. Scanning electron microscopic observations show well faceted crystallites with a predominance
of angular shaped grains corresponding to 〈100〉 and 〈110〉 crystallite surfaces for the scratched as well as plasma etched
substrate. Surface etching at 150 W plasma power results in a better growth in comparison with 50 and 100 W plasma powers.
Chlorine-radical is found responsible for the changes in the growth morphology. Raman spectroscopy shows a sharp peak at 1,332
cm−1 and a peak at ∼1,580 cm−1 for both samples. 相似文献