全文获取类型
收费全文 | 62295篇 |
免费 | 3584篇 |
国内免费 | 2621篇 |
专业分类
电工技术 | 2950篇 |
技术理论 | 3篇 |
综合类 | 3586篇 |
化学工业 | 8543篇 |
金属工艺 | 4660篇 |
机械仪表 | 3731篇 |
建筑科学 | 3400篇 |
矿业工程 | 1116篇 |
能源动力 | 1895篇 |
轻工业 | 4535篇 |
水利工程 | 1059篇 |
石油天然气 | 2088篇 |
武器工业 | 437篇 |
无线电 | 6549篇 |
一般工业技术 | 10427篇 |
冶金工业 | 5433篇 |
原子能技术 | 749篇 |
自动化技术 | 7339篇 |
出版年
2024年 | 71篇 |
2023年 | 350篇 |
2022年 | 945篇 |
2021年 | 1329篇 |
2020年 | 1034篇 |
2019年 | 991篇 |
2018年 | 1233篇 |
2017年 | 1354篇 |
2016年 | 1408篇 |
2015年 | 1870篇 |
2014年 | 2519篇 |
2013年 | 3930篇 |
2012年 | 3742篇 |
2011年 | 4510篇 |
2010年 | 4080篇 |
2009年 | 4209篇 |
2008年 | 4145篇 |
2007年 | 4054篇 |
2006年 | 3813篇 |
2005年 | 3254篇 |
2004年 | 2496篇 |
2003年 | 2041篇 |
2002年 | 2019篇 |
2001年 | 1881篇 |
2000年 | 1486篇 |
1999年 | 1389篇 |
1998年 | 1888篇 |
1997年 | 1415篇 |
1996年 | 1212篇 |
1995年 | 788篇 |
1994年 | 654篇 |
1993年 | 526篇 |
1992年 | 347篇 |
1991年 | 349篇 |
1990年 | 217篇 |
1989年 | 232篇 |
1988年 | 165篇 |
1987年 | 111篇 |
1986年 | 79篇 |
1985年 | 73篇 |
1984年 | 48篇 |
1983年 | 41篇 |
1982年 | 29篇 |
1981年 | 35篇 |
1980年 | 25篇 |
1979年 | 11篇 |
1977年 | 8篇 |
1976年 | 21篇 |
1975年 | 11篇 |
1973年 | 10篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
X. Gong W. Ma J.C. Ostrowski K. Bechgaard G.C. Bazan A.J. Heeger S. Xiao D. Moses 《Advanced functional materials》2004,14(4):393-397
The electronic properties, carrier injection, and transport into poly(9,9‐dioctylfluorene) (PFO), PFO end‐capped with hole‐transporting moieties (HTM), PFO–HTM, and PFO end‐capped with electron‐transporting moieties (ETM), PFO–ETM, were investigated. The data demonstrate that charge injection and transport can be tuned by end‐capping with HTM and ETM, without significantly altering the electronic properties of the conjugated backbone. End‐capping with ETM resulted in more closely balanced charge injection and transport. Single‐layer electrophosphorescent light‐emitting diodes (LEDs), fabricated from PFO, PFO–HTM and PFO–ETM as hosts and tris[2,5‐bis‐2′‐(9′,9′‐dihexylfluorene)pyridine‐κ2NC3′]iridium(III ), Ir(HFP)3 as the guest, emitted red light with brightnesses of 2040 cd m–2, 1940 cd m–2 and 2490 cd m–2 at 290 mA cm–2 (16 V) and with luminance efficiencies of 1.4 cd A–1, 1.4 cd A–1 and 1.8 cd A–1 at 4.5 mA cm–2 for PFO, PFO–HTM, and PFO–ETM, respectively. 相似文献
62.
63.
64.
65.
根据惠斯通电桥工作原理,采用回路法可以简便快捷地确定电视地下电缆接地、短路故障点的位置。电容法也是一种常用的检查开路的检测方法。这样维修人员可以迅速排除故障,保证电视节目的正常传送。 相似文献
66.
A new method has been developed for compressing the matrices that occur in most integral-equation-based computer programs. This method is easy to interface with existing computer programs, and allows them to run significantly faster and with significantly less memory. This method applies not only to electromagnetic and acoustic computation, but also to most programs involving a Green's function or any integral equation with a kernel having some smoothness properties. Our numerical computations, running on a high-end personal computer, have achieved compression ratios of fifty times, and compressed inversion of the matrices fifty times faster than by previous methods. For larger problems, solved on high-performance computers, these ratios would improve to about one thousand to one for larger moment method problems. 相似文献
67.
Towards intelligent dressing 总被引:1,自引:0,他引:1
Egana I. Mendikute A. Urionaguena X. Alberdi H. 《IEEE instrumentation & measurement magazine》2006,9(3):38-43
The aim of this article is to state the principles of an intelligent monitoring and control system for the grinding machine, comprising the dressing process as well as grinding stability. 相似文献
68.
Finite element piezothermoelasticity analysis and the active control of FGM plates with integrated piezoelectric sensors and actuators 总被引:3,自引:0,他引:3
An efficient finite element model is presented for the static and dynamic piezothermoelastic analysis and control of FGM
plates under temperature gradient environments using integrated piezoelectric sensor/actuator layers. The properties of an FGM plate are functionally graded in the thickness
direction according to a volume fraction power law distribution. A constant displacement-cum-velocity feedback control algorithm that couples the direct and inverse piezoelectric effects is applied to provide active feedback
control of the integrated FGM plate in a closed loop system. Numerical results for the static and dynamic control are presented
for the FGM plate, which consists of zirconia and aluminum. The effects of the constituent volume fractions and the influence
of feedback control gain on the static and dynamic responses of the FGM plates are examined.
Received: 13 March 2002 / Accepted: 5 March 2003
The work described in this paper was supported by a grant awarded by the Research Grants Council of the Hong Kong Special
Administrative Region, China (Project No. CityU 1024/01E). 相似文献
69.
70.
Multifilament Ag-sheathed BiPbSrCaCuO (2223) superconducting tapes containing 49 filaments were fabricated by the powder-in-tube route and the roll-anneal process. The transport critical current densityJ
c
was 1.3×104 A cm–2 at 77 K and 7×104 A cm–2 at 4.2 K in self-field. A 12-m-long tape was used to construct superconducting solenoids (50, 28, and 14 mm internal diameters) generating dc fields 380–1070 G at 4.2 K. Measurements of the variation ofJ
c
with field (0–1.6 T) and bend strain (0–5%) are used to explain the performance of the solenoids. The critical bend strain of tapes was about 1.5%. 相似文献