全文获取类型
收费全文 | 19863篇 |
免费 | 1489篇 |
国内免费 | 799篇 |
专业分类
电工技术 | 1031篇 |
技术理论 | 4篇 |
综合类 | 1031篇 |
化学工业 | 3610篇 |
金属工艺 | 887篇 |
机械仪表 | 1188篇 |
建筑科学 | 1350篇 |
矿业工程 | 525篇 |
能源动力 | 558篇 |
轻工业 | 1084篇 |
水利工程 | 289篇 |
石油天然气 | 1123篇 |
武器工业 | 127篇 |
无线电 | 2661篇 |
一般工业技术 | 2652篇 |
冶金工业 | 1030篇 |
原子能技术 | 170篇 |
自动化技术 | 2831篇 |
出版年
2024年 | 69篇 |
2023年 | 324篇 |
2022年 | 531篇 |
2021年 | 766篇 |
2020年 | 565篇 |
2019年 | 514篇 |
2018年 | 574篇 |
2017年 | 593篇 |
2016年 | 559篇 |
2015年 | 689篇 |
2014年 | 896篇 |
2013年 | 1219篇 |
2012年 | 1137篇 |
2011年 | 1288篇 |
2010年 | 997篇 |
2009年 | 1030篇 |
2008年 | 1019篇 |
2007年 | 975篇 |
2006年 | 1018篇 |
2005年 | 915篇 |
2004年 | 613篇 |
2003年 | 597篇 |
2002年 | 521篇 |
2001年 | 450篇 |
2000年 | 528篇 |
1999年 | 584篇 |
1998年 | 528篇 |
1997年 | 458篇 |
1996年 | 442篇 |
1995年 | 318篇 |
1994年 | 300篇 |
1993年 | 214篇 |
1992年 | 171篇 |
1991年 | 139篇 |
1990年 | 125篇 |
1989年 | 95篇 |
1988年 | 78篇 |
1987年 | 52篇 |
1986年 | 44篇 |
1985年 | 37篇 |
1984年 | 21篇 |
1983年 | 18篇 |
1982年 | 31篇 |
1981年 | 22篇 |
1980年 | 15篇 |
1979年 | 10篇 |
1978年 | 11篇 |
1977年 | 11篇 |
1976年 | 12篇 |
1971年 | 8篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
111.
随着网络带宽的进一步提高,视频点播的瓶颈基本卡在视频服务器端。文章提供的服务器端的流式拷贝,能进一步提高整个系统的服务能力。文章对流式拷贝的过程进行描述,对其中的数学模型进行分析,并与没有流式拷贝的系统进行比较分析。 相似文献
112.
Buller G.S. Warburton R.E. Pellegrini S. Ng J.S. David J.P.R. Tan L.J. Krysa A.B. Cova S. 《Optoelectronics, IET》2007,1(6):249-254
The application of quantum key distribution (QKD) has raised particular demands for single-photon detectors. One of the most promising candidates at the low-loss optical fibre communications windows is the planar geometry InGaAs/InP single-photon avalanche diode. These detectors have been modelled, fabricated and characterised at 1.55 mum wavelength. Their performance in terms of single-photon detection efficiency, dark count rate, timing jitter and afterpulsing behaviour are reported and compared with the best commercially available, linear multiplication avalanche photodiodes operated in Geiger-mode. Their use in the application of QKD is discussed. 相似文献
113.
The effects of boiling Aqua Regia (AQ), N2/Cl2 plasma followed by AQ and O2 plasma followed by AQ surface treatments prior to Ni/Au (20 nm/20 nm) metallization to p-GaN:Mg (∼ 3 × 1017 cm− 3) have been investigated. N2/Cl2 plasma was employed in a bid to lower the Ga/N and O/Ga ratios of the GaN surface to improve the contact properties to p-GaN, while O2 plasma was employed as an alternative to incorporate O into the Ni/Au system. Results show that a low Ga/N ratio does not necessarily correspond to a better contact. The positive effect of O2 over N2 anneal is observed only for the AQ-treated sample, although the mechanisms responsible for its positive effect: NiO formation and Ni/Au layer-reversal were observed for all O2-annealed contacts. We conclude that the effect of O2 anneal on the Ni/Au contact is dependant on the p-GaN surface prior to metallization. 相似文献
114.
The influence of Zr addition on magnetic properties and temperature coefficient for nanocomposite Nd10Fe78.5-xCO5ZrxB6.5 (x=0~4) bonded magnets was investigated. It was found that the room-temperature magnetic properties were remarkably improved with Zr addition due to the grain refinement and increasing volume fraction of the hard magnetic phase. The optimal magnetic properties of Jr=0.689T, iHc=769.4kA·m-1 and (BH)max=84kJ·m-3 were obtained for 2.5% Zr addition. The temperature coefficient of remanence (α) increases slightly and the temperature coefficient of coercivity (β) decreases obviously with increasing Zr content for nanocomposite Nd10Fe78.5-xCo5ZrxB6.5 (x=0~4) bonded magnets. 相似文献
115.
116.
Duringthelastdecade ,thedesignandsynthesisoftripodalligandsandtheirmetalcomplexeshaveattractedconsiderableattentionduetotheirpotentialusesaslumi nescentprobesinmedicineandbiochemistry[1~ 7] ,ascatalysts[8] andelectrochemicalmaterials[9] .However ,thecomplexesofrareearthmetalwithtripodalligandshavefewreported[10 ] .Asanextensionofourstudiesoncomplexesofmetalwithtripodalligands ,anewtripodalligand (tris { 2 [N (pyridine methanoyl)amino]ethyl}amine ,L)anditscomplexeswithrareearthnitratesweresyn… 相似文献
117.
Decentralized control design for large-scale systems with strong interconnections using neural networks 总被引:2,自引:0,他引:2
We propose a decentralized neural network (NN) controller for a class of large-scale nonlinear systems with the strong interconnections. The NNs are used to approximate the unknown subsystems and interconnections. Due to the functional approximation capabilities of NNs, the additional precautions are not required to be made for avoiding the possible control singularity problems. Semiglobal asymptotic stability results are obtained and the tracking error converges to zero. Furthermore, the issue of transient performance of the subsystems is also addressed under an analytical framework. 相似文献
118.
119.
AK Tan 《Canadian Metallurgical Quarterly》1998,39(9):403-405
AIM OF STUDY: This study was done to examine the usefulness of botulinum toxin A injections in treating various neurological disorders such as hemifacial spasm, blepharospasm, focal dystonia and task-specific dystonia. METHODS: This was a prospective, open-labelled trial of patients seen in a Movement Disorders Clinic with dyskinesias potentially treatable with botulinum toxin. All patients were assessed before and after injections using clinical rating scales, and those with focal and task-specific dystonias were also recorded on videotape. RESULTS: There were 102 patients with hemifacial spasm, 3 with blepharospasm, 13 with neck dystonia, 6 with writer's cramp, I with musician's cramp, and I with jaw dystonia. All patients with hemifacial spasm and blepharospasm obtained good results, while 77% of those with cervical dystonia received substantial benefit. Only half of those with writer's cramp improved. Hemifacial spasm seems more prevalent in Singapore compared with Western populations. CONCLUSION: Injections of botulinum toxin are useful in treating the various neurological disorders studied. This is an advancement in the treatment of these dyskinesias which respond poorly to oral medications. 相似文献
120.
A new colour quantisation and quadtree based image compression scheme is proposed. The features of the new scheme are that colour palette ordering and requantisation of the decoded image for palette-based monitor displays are not required. Thus, fast decoding and displaying can be achieved 相似文献