全文获取类型
收费全文 | 6469篇 |
免费 | 433篇 |
国内免费 | 7篇 |
专业分类
电工技术 | 81篇 |
综合类 | 5篇 |
化学工业 | 1833篇 |
金属工艺 | 102篇 |
机械仪表 | 154篇 |
建筑科学 | 220篇 |
矿业工程 | 38篇 |
能源动力 | 269篇 |
轻工业 | 786篇 |
水利工程 | 47篇 |
石油天然气 | 8篇 |
无线电 | 574篇 |
一般工业技术 | 1068篇 |
冶金工业 | 459篇 |
原子能技术 | 73篇 |
自动化技术 | 1192篇 |
出版年
2024年 | 14篇 |
2023年 | 72篇 |
2022年 | 233篇 |
2021年 | 411篇 |
2020年 | 210篇 |
2019年 | 183篇 |
2018年 | 229篇 |
2017年 | 217篇 |
2016年 | 267篇 |
2015年 | 220篇 |
2014年 | 296篇 |
2013年 | 443篇 |
2012年 | 426篇 |
2011年 | 483篇 |
2010年 | 356篇 |
2009年 | 320篇 |
2008年 | 325篇 |
2007年 | 274篇 |
2006年 | 231篇 |
2005年 | 183篇 |
2004年 | 150篇 |
2003年 | 116篇 |
2002年 | 104篇 |
2001年 | 83篇 |
2000年 | 70篇 |
1999年 | 74篇 |
1998年 | 98篇 |
1997年 | 76篇 |
1996年 | 75篇 |
1995年 | 56篇 |
1994年 | 54篇 |
1993年 | 50篇 |
1992年 | 30篇 |
1991年 | 31篇 |
1990年 | 16篇 |
1989年 | 22篇 |
1988年 | 17篇 |
1987年 | 17篇 |
1986年 | 18篇 |
1985年 | 30篇 |
1984年 | 24篇 |
1983年 | 30篇 |
1982年 | 29篇 |
1981年 | 21篇 |
1980年 | 23篇 |
1979年 | 18篇 |
1977年 | 24篇 |
1975年 | 11篇 |
1972年 | 12篇 |
1943年 | 21篇 |
排序方式: 共有6909条查询结果,搜索用时 0 毫秒
41.
Emmanuel. Delamarche Bruno. Michel Hans A. Biebuyck Christoph Gerber 《Advanced materials (Deerfield Beach, Fla.)》1996,8(9):719-729
Self-assembled monolayers (SAMs) of alkanethiols and disulfides on gold form organic interfaces with properties largely controlled by the end groups of the molecules composing the film. SAMs provide a unique link between the science of organic surfaces and technologies that seek to exploit their adaptable character. Many techniques are useful for probing the structure of SAMs although only scanning tunneling microscopy (STM) at picoamperes reveals the details of the packing of their end groups at the sub-angstrom level. This review demonstrates that STM effectively tests new types of control over the microscopic structure–property relationships characteristic of SAMs on gold that should prove useful to their application. 相似文献
42.
Different modes of activation are described for a postgrafting reaction of acrylic acid on poly(p-phenylene terephthalamid) (PPTA)mitrogen plasma or electron-beam irradiation. Both lead to surface radical formation, and these species are able to initiate grafting. The Functionalization through amino group attachment is characteristic of plasma treatment. Degradation initiated by UV-visible emission of plasma is noticed, leading to the amide clivage. The surface grafting is more important when the PPTA is irradiated with a cold plasma and if water is used as the solvent. The polymer crystallinity degree reduces the grafting of the electron beam-irradiated PPTA even with a high radical concentration. © 1994 John Wiley & Sons, Inc. 相似文献
43.
Carlo Bertucci Piero Salvadori Francesco Ciardelli Graziella Fatti 《Polymer Bulletin》1985,13(5):469-472
Summary Circular dichroism of isotactic samples of poly-(S)-4-methyl-1-hexene and poly-(R)-3,7-dimethyl-1-octene, have been measured in the vacuum ultraviolet spectral region (200-140 nm). The c.d. band at about 160. nm accounts for the optical activity in the visible region and reflects the presence of one screw sense helical conformation of the sample examined.The authors thank Prof. W.C. Johnson, Jr., Department of Biochemistry and Biophysics, Oregon State University, for allowing them to use the vacuum u.v. spectrometer. This work has been partially supported by a N.A.T.O. grant, and by Ministero Pubblica Istruzione (MPI), Roma — Italy. 相似文献
44.
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
45.
46.
Bruno Buchmayr 《国际钢铁研究》1992,63(10):446-446
47.
Schilling D.L. Milstein L.B. Pickholtz R.L. Bruno F. Kanterakis E. Kullback M. Erceg V. Biederman W. Fishman D. Salerno D. 《Communications Magazine, IEEE》1991,29(11):86-93
Multipath propagation in a broadband CDMA environment is described. A propagation model for broadband spread-spectrum signals is presented. Experimental results relating to the sharing of the band by fixed service microwave users and mobile personal communications network (PCN) users are discussed. Field tests indicate that PCN systems can provide high-quality communications when sharing the spectrum with fixed-service microwave systems in suburban and urban areas 相似文献
48.
A model for building integrated photovoltaic systems has been developed and implemented in a dynamic simulation tool. This tool takes into account the thermal interactions between the PV collector and the building. The influence of the type of integration upon the PV collector efficiency has been evaluated and hybrid PV/air collectors have been studied. An overall efficiency is defined, including the production of electricity and heat. A case study has been performed on two different typical buildings. In the case of a multi-crystalline silicon PV collector integrated on the roof of a single family house located in Paris, the efficiency of unventilated PV modules fixed on the roof is 14%. If the PV collector is used to preheat the ventilation air, the efficiency reaches 20%. A proper building integration also improves the environmental balance of PV technologies over their life cycle. 相似文献
49.
50.
Francesco Donsì Stefano Cimino Almerinda Di Benedetto Raffaele Pirone Gennaro Russo 《Catalysis Today》2005,105(3-4):551-559
The oxidative dehydrogenation of ethane is carried out in short contact time reactors over Pt and LaMnO3 based catalysts supported on a large number of different ceramic substrates (45, 60 and 80 ppi foam monoliths and 200, 400, 600, 900 and 1200 cpsi honeycomb monoliths). Experimental results, obtained under the same conditions at varying the C2H6/O2 ratio, showed that the highest performance in terms of ethylene selectivity and yield is always attained on LaMnO3 catalysts. Furthermore, the results are significantly influenced by the morphology and cell density of the support, with 45 and 60 ppi foams and 400 and 600 cpsi honeycombs giving the best performance. The experimental results are explained by means of geometrical and fluid dynamic considerations on the support, and by means of a 2D mathematical model, which clearly indicates an optimal intermediate cell density for maximising ethylene selectivity and yield. 相似文献