全文获取类型
收费全文 | 779529篇 |
免费 | 9985篇 |
国内免费 | 1560篇 |
专业分类
电工技术 | 14740篇 |
综合类 | 973篇 |
化学工业 | 121233篇 |
金属工艺 | 30283篇 |
机械仪表 | 24296篇 |
建筑科学 | 18459篇 |
矿业工程 | 4899篇 |
能源动力 | 20238篇 |
轻工业 | 66573篇 |
水利工程 | 8673篇 |
石油天然气 | 16699篇 |
武器工业 | 43篇 |
无线电 | 87175篇 |
一般工业技术 | 154800篇 |
冶金工业 | 138346篇 |
原子能技术 | 17888篇 |
自动化技术 | 65756篇 |
出版年
2021年 | 6879篇 |
2019年 | 6617篇 |
2018年 | 11399篇 |
2017年 | 11453篇 |
2016年 | 11953篇 |
2015年 | 7693篇 |
2014年 | 12979篇 |
2013年 | 36004篇 |
2012年 | 20367篇 |
2011年 | 27591篇 |
2010年 | 22047篇 |
2009年 | 24663篇 |
2008年 | 25258篇 |
2007年 | 25098篇 |
2006年 | 21818篇 |
2005年 | 19940篇 |
2004年 | 19227篇 |
2003年 | 18749篇 |
2002年 | 18131篇 |
2001年 | 17903篇 |
2000年 | 17177篇 |
1999年 | 17279篇 |
1998年 | 40519篇 |
1997年 | 29350篇 |
1996年 | 22925篇 |
1995年 | 17640篇 |
1994年 | 16030篇 |
1993年 | 15675篇 |
1992年 | 12112篇 |
1991年 | 11591篇 |
1990年 | 11498篇 |
1989年 | 11235篇 |
1988年 | 10837篇 |
1987年 | 9572篇 |
1986年 | 9469篇 |
1985年 | 10889篇 |
1984年 | 9842篇 |
1983年 | 9354篇 |
1982年 | 8434篇 |
1981年 | 8687篇 |
1980年 | 8187篇 |
1979年 | 8270篇 |
1978年 | 8042篇 |
1977年 | 9067篇 |
1976年 | 11504篇 |
1975年 | 7165篇 |
1974年 | 6846篇 |
1973年 | 6988篇 |
1972年 | 5928篇 |
1971年 | 5470篇 |
排序方式: 共有10000条查询结果,搜索用时 692 毫秒
881.
The nature of pairing mechanism as well as transition temperature of yttrium cuprates is discussed using the strong coupling
theory. An interaction potential has been developed for the layered structure with two conducting CuO2(a–b) layers in a unit cell. The interaction potential properly takes care of electron-electron, electron-phonon and electron-plasmon
interactions. Furthermore, the electron-phonon coupling parameter (λ), the modified Coulomb repulsive parameter (μ*) and the 2D acoustic phonon (plasmon) energy as a function of oxygen deficiency is worked out. Finally, the superconducting
transition temperature (T
c) is then evaluated by using these coupling parameters and obtainedT
c = 95(92)K for Y(Yb)Ba2Cu3O7−δ
superconductors withδ = 0·0. The model parameters estimated from the layered structure approach are consistent with the strong coupling theory.
The result deduced on the variation ofT
c withδ are in fair agreement with the earlier reported data on yttrium cuprates. The analysis of the above results are discussed. 相似文献
882.
Storage performance-metrics and benchmarks 总被引:2,自引:0,他引:2
Chen P.M. Patterson D.A. 《Proceedings of the IEEE. Institute of Electrical and Electronics Engineers》1993,81(8):1151-1165
The metrics and benchmarks used in storage performance evaluation are discussed. The technology trends taking place in storage systems, such as disk and tape evolution, disk arrays, and solid-state disks, are highlighted. The current popular I/O benchmarks are then described, reviewed, and run on three systems: a DECstation 5000/200 running the Sprite Operating System, a SPARCstation 1+ running SunOS, and an HP Series 700 (Model 730) running HP-UX. Two approaches to storage benchmarks-LADDIS and a self-scaling benchmark with predicted performance-are also described 相似文献
883.
Ion beam assisted deposition (IBAD) of thin films is still a new technology with respect to the number of applications. A broader industrial application depends on the availability and versatility of facilities which are able to process various kinds of workpieces under appropriate conditions. Recently, IBAD facilities of the second generation were described in literature and are partially commercially available. In the present report such IBAD machines with their special features such as number and kind of ion sources and evaporators are described. Particularly, the set-up of the ALLIGATOR, a versatile IBAD device for coating complex workpieces under ion bombardment with a broad range of ion energies, is described. As an application example, recent results on the treatment of medical implants are discussed. In -vivo tests of coated cardiovascular stents showed that the deposited noble metal films were effective in influencing the corrosivity and thromboresistance of the implant 相似文献
884.
The thermal expansion of tellurides of germanium, bismuth, and intermetallic compounds is investigated over the temperature range 293-973 K.Belarusian Agricultural Technical University, Minsk. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 66, No. 5, pp. 612–616, May 1994. 相似文献
885.
886.
D Galasko T Saitoh Y Xia LJ Thal R Katzman LR Hill L Hansen 《Canadian Metallurgical Quarterly》1994,44(10):1950-1951
We determined apolipoprotein E (ApoE) genotypes in 122 autopsied demented patients. The frequency of the ApoE epsilon 4 allele was 39.6% in Alzheimer's disease (AD), 29.0% in the Lewy body variant of AD (LBV), and 6.25% in diffuse Lewy body disease. For AD and LBV patients, the epsilon 4 frequency was significantly higher than that reported in nondemented controls (10 to 15%). Therefore, LBV and AD share ApoE epsilon 4 as a genetic risk factor, providing further evidence that these conditions overlap. 相似文献
887.
F Abadía-Molina R Calvente R Carmona R Luján F Abadía-Fenoll 《Canadian Metallurgical Quarterly》1993,8(2):297-304
In this study chick embryo optic cups at HH stage 13 of development were analyzed under normal conditions and after inoculation with colchicine for 1, 2, 4, and 8 h. Several changes were seen after these periods of treatment: 1) modifications of the structure, with thicker regions in the cup and a general decrease in the total volume according to the duration of exposure to the drug (about 4 times less than normal, 5,035 x 10(3) microns 3 vs 1,334 x 10(3) microns 3 after 8 h of treatment); 2) enlargement of the ventricular cavity and its closure, due to failure of approximation of retinal and pigmentary layers; 3) failure of lens development, with delay and impairment of pit formation and deformation of all structures; lens volume was less than normal (about 4 times less, 2,148 x 10(3) microns 3 vs 658 x 10(3) microns 3 after 8 h of treatment); 4) a general segregation of the cells making up the structure, principally in the more active proliferating zones. The local alterations found are described. 相似文献
888.
889.
890.