全文获取类型
收费全文 | 107818篇 |
免费 | 10265篇 |
国内免费 | 6185篇 |
专业分类
电工技术 | 7516篇 |
技术理论 | 6篇 |
综合类 | 8012篇 |
化学工业 | 16771篇 |
金属工艺 | 6538篇 |
机械仪表 | 7053篇 |
建筑科学 | 7974篇 |
矿业工程 | 3189篇 |
能源动力 | 2954篇 |
轻工业 | 10170篇 |
水利工程 | 2240篇 |
石油天然气 | 5287篇 |
武器工业 | 1110篇 |
无线电 | 12453篇 |
一般工业技术 | 12070篇 |
冶金工业 | 4897篇 |
原子能技术 | 1212篇 |
自动化技术 | 14816篇 |
出版年
2024年 | 572篇 |
2023年 | 1908篇 |
2022年 | 3677篇 |
2021年 | 4936篇 |
2020年 | 3692篇 |
2019年 | 3073篇 |
2018年 | 3383篇 |
2017年 | 3661篇 |
2016年 | 3411篇 |
2015年 | 4835篇 |
2014年 | 5814篇 |
2013年 | 6914篇 |
2012年 | 7824篇 |
2011年 | 8581篇 |
2010年 | 7413篇 |
2009年 | 7128篇 |
2008年 | 7230篇 |
2007年 | 6559篇 |
2006年 | 6156篇 |
2005年 | 4927篇 |
2004年 | 3568篇 |
2003年 | 3038篇 |
2002年 | 2898篇 |
2001年 | 2486篇 |
2000年 | 1991篇 |
1999年 | 1742篇 |
1998年 | 1298篇 |
1997年 | 1095篇 |
1996年 | 923篇 |
1995年 | 783篇 |
1994年 | 581篇 |
1993年 | 415篇 |
1992年 | 316篇 |
1991年 | 301篇 |
1990年 | 240篇 |
1989年 | 193篇 |
1988年 | 125篇 |
1987年 | 108篇 |
1986年 | 77篇 |
1985年 | 59篇 |
1984年 | 46篇 |
1983年 | 41篇 |
1982年 | 32篇 |
1981年 | 31篇 |
1980年 | 47篇 |
1979年 | 22篇 |
1978年 | 15篇 |
1976年 | 22篇 |
1975年 | 12篇 |
1973年 | 16篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
Yanqiu Shao Jiqing Han Ting Liu Yongzhen Zhao 《International Journal of Speech Technology》2007,10(1):45-55
In real speech, not like lexical words (LWs), prosodic words (PWs) are basic rhythmic units. The naturalness of a Text-to-Speech
(TTS) system is directly influenced by the segmentation of the PWs. Most of the PWs are the combination of several LWs. In
this paper, three Lexical Combination Models are proposed to combine LWs into PWs, including a Directed Acyclic Graph Model,
a Segmentation Model and a Markov Model (MM). To cope with the situation where some long LWs should be segmented into two
or more PWs, a Lexical Split Model (LSM) is applied to the long LWs. Experimental results prove that relatively constant results
with various training data can be obtained from a MM. The Transformation-Based Error Driven Learning (TBED) algorithm, for
its high performance of individual property, is applied in combination with the MM to improve the precision of PW segmentation.
Experiments show that among the three proposed models, the MM combined with TBED and LSM, leads to the best performance, in
which a precision of 93.00% and a recall of 93.23% are achieved. The perception test indicates that by using PWs as the lowest
prosodic units a speech sounds more natural and acceptable than by using LWs.
This paper is supported by NSFC Project (60503071); 973 Natural Basic Research Program of China (2004CB318102); Postdoctor
Science Foundation of P. R. China (20070420275). 相似文献
22.
Xiang‐Dan Li Zhen‐Xin Zhong Sang‐Hoon Han Seung Hee Lee Myong‐Hoon Lee 《Polymer International》2005,54(2):406-411
From chloromethylated polyimide, a useful starting material for modification of aromatic polyimides, a thermocurable transparent polyimide having acrylate side groups was prepared. In the presence of 1,8‐diazabicyclo[5,4,0]undec‐7‐ene, chloromethylated polyimide was esterified with acrylic acid to synthesize poly(imide methylene acrylate). The polymer was soluble in organic solvent, which makes it possible to prepare a planar film by spin coating. The polymer film became insoluble after thermal treatment at 230 °C for 30 min. Optical transparency of the film at 400 nm (for 1 µm thickness) was higher than 98 % and not affected by further heating at 230 °C for 250 min. Adhesion properties measured by the ASTM D3359‐B method ranged from 4B to 5B. Preliminary results of planarization testing showed a high degree of planarization (DOP) value (>0.53). These properties demonstrate that poly(imide methylene acrylate) could be utilized as a thermocurable transparent material in fabricating display devices such as TFT‐LCD. Copyright © 2004 Society of Chemical Industry 相似文献
23.
Colour Centres and Energy Transfer in BaF2-xClx:Eu2+ Phosphors 总被引:1,自引:1,他引:0
The optical absorption spectra of BaF2-xClx:Eu2 after ultraviolet (UV) light excitation were investigated.The differences between the absorption spectra after and before excitation (DAS) were observed.The DAS increase at both the high and the low energy side of F band in BaF2-xClx:Eu2 after 245 nm UV light excitation.The bleach effect of UV light and the absorption of electrons in the valence band may account for the former and the formation of Fa centres (association of F(Cl-) centres), whose absorption band matches the HeNe laser better, may explain the latter.In the write-in process, the transfer of electrons is via tunneling.In the readout process, the transfer of electrons captured in F(F-) and Fa centres is more likely via tunneling, and that of F(Cl-) centres is more likely via conduction band. 相似文献
24.
在第一部分综合讨论的基础上对甘三酯立体专一分析方法作了初步探讨。以液体油(菜油)及固体脂(猪脂)为基质,系统地研究了这一分析方法,取得了经验并补充了一些具体验证方法。分析液体油的结果与文献数据相一致,分析猪脂的结果欠佳,还存在一些问题需待进一步研究。 相似文献
25.
An experimental study of an optical burst switching network based on wavelength-selective optical switches 总被引:1,自引:0,他引:1
Li Xinwan Chen Jianping Wu Guiling Wang Hui Ye Ailun 《Communications Magazine, IEEE》2005,43(5):S3-10
In this article we report the system structure and test results of an experimental optical burst switching network with three edge router's and one core node. Wavelength-selective switches developed for this system and their characteristics are depicted. The implementation and performance of our new scheme for the just-in-time protocol are described. We also report experimental results of FTP and VOD services on this system. Some parameters, including traffic rate, average burst data length, and assembly time, are studied. 相似文献
26.
逆向工程技术在机械领域的应用 总被引:2,自引:0,他引:2
逆向工程技术已成为联系新产品开发过程中各种先进技术的纽带,并成为实现新产品快速开发的重要技术手段.介绍了逆向工程的概念、技术流程、测量系统、常用软件以及实际应用. 相似文献
27.
28.
结合兰州市的水泥标准稠度用水量方法测定 (代用法 )的实例 ,分析代用法测定标准稠度用水量的缺点 ,并对此方法提出了一些改进措施 相似文献
29.
Hui Chen D.T.K. Tong 《Photonics Technology Letters, IEEE》2005,17(4):801-803
Symmetric interference in two-dimensional multimode silicon waveguides is experimentally investigated. For a 100/spl times/100 /spl mu/m/sup 2/ cross section, 2700-/spl mu/m-long waveguide fabricated on silicon-on-insulator substrate, an 8/spl times/8 matrix of replicated images with high contrast ratio is demonstrated for 1530-1570 nm wavelength range. Symmetric interference results in reduced device length, and the actual device length is consistent with the theoretical expectation. The device also exhibits stable imaging in terms of good loss uniformity, and low wavelength and polarization dependencies among the replicated images. 相似文献
30.
Youngmo Han 《IEEE transactions on systems, man, and cybernetics. Part A, Systems and humans : a publication of the IEEE Systems, Man, and Cybernetics Society》2007,37(6):854-863
This paper is about gaze control in active vision. The problem to tackle is, given a camera imaging a particular 3-D point, to place the 3-D point at the center of the image by rotating the camera about its own optical center. For separating this procedure from structure estimation, we use a normalized camera coordinate system, which leads to formulation defined on the unit sphere. In designing the algorithm, we try to avoid the disadvantages of local coordinates or approximation. For this purpose, we design the algorithm by considering the intrinsic geometric properties of the underlying space, not using any kinds of parameterization or approximation. The proposed algorithm is simple and of a closed form, and that makes it suitable for real-time application. 相似文献