全文获取类型
收费全文 | 121289篇 |
免费 | 10587篇 |
国内免费 | 6123篇 |
专业分类
电工技术 | 7855篇 |
技术理论 | 6篇 |
综合类 | 8725篇 |
化学工业 | 19153篇 |
金属工艺 | 7581篇 |
机械仪表 | 8486篇 |
建筑科学 | 9556篇 |
矿业工程 | 4259篇 |
能源动力 | 3474篇 |
轻工业 | 8898篇 |
水利工程 | 2470篇 |
石油天然气 | 8006篇 |
武器工业 | 1035篇 |
无线电 | 12989篇 |
一般工业技术 | 13403篇 |
冶金工业 | 5933篇 |
原子能技术 | 1764篇 |
自动化技术 | 14406篇 |
出版年
2024年 | 580篇 |
2023年 | 2107篇 |
2022年 | 3948篇 |
2021年 | 5298篇 |
2020年 | 4021篇 |
2019年 | 3220篇 |
2018年 | 3447篇 |
2017年 | 3972篇 |
2016年 | 3625篇 |
2015年 | 5095篇 |
2014年 | 6100篇 |
2013年 | 7202篇 |
2012年 | 7974篇 |
2011年 | 8564篇 |
2010年 | 7372篇 |
2009年 | 7251篇 |
2008年 | 7218篇 |
2007年 | 6925篇 |
2006年 | 7092篇 |
2005年 | 6085篇 |
2004年 | 3958篇 |
2003年 | 3503篇 |
2002年 | 3274篇 |
2001年 | 3018篇 |
2000年 | 2805篇 |
1999年 | 2803篇 |
1998年 | 2120篇 |
1997年 | 1755篇 |
1996年 | 1724篇 |
1995年 | 1424篇 |
1994年 | 1166篇 |
1993年 | 753篇 |
1992年 | 655篇 |
1991年 | 443篇 |
1990年 | 356篇 |
1989年 | 310篇 |
1988年 | 232篇 |
1987年 | 152篇 |
1986年 | 125篇 |
1985年 | 73篇 |
1984年 | 56篇 |
1983年 | 46篇 |
1982年 | 44篇 |
1981年 | 33篇 |
1980年 | 28篇 |
1979年 | 19篇 |
1978年 | 1篇 |
1965年 | 1篇 |
1959年 | 24篇 |
1951年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
41.
42.
43.
44.
一种语音混沌保密通信方案的研究与硬件实现 总被引:7,自引:0,他引:7
在硬件实验研究的基础上,建立一种环形蔡氏电路,提出用环蔡氏电路实现语音混沌保密通信的一种闭环逆系统方案,其特点是利用环形蔡氏电路的单向耦合原理,通过反馈的方法形成一个包括有用信号在内的极联闭合环路,从而实现改善端与接收端之间混沌系统的严格同步而不受有用信息调制的影响。理论分析与硬件实验结果证明,该方案同现有的其它混沌通信方案相比较,具有非线性失真小、保真度高的优点,完全能够满足传送语音信号的要求。 相似文献
45.
A nuclear microprobe with high spatial resolution and high analytical sensitivity was applied to analyze trace elements,especially lead,in vehicle exhaust of Shanghai city.The result shows that the chemical composition and its corresponding x-ray relative intensity are different among different vehicle exhausts.There are many kinds of metal elements in particles of vehicle exhaust.most are harmful to people,such as Ti,Cr,Mn,Pb,etc.We found that the lead concentration was 6820μg/g and the bromine concentration was 5300μg/g in the exhaust from Santana using leaded gasoline(SULG).which is higher than any other kinds of vehicle exhausts.We have also detected the minimum lead in the particles of unleaded gasoline and its content varies from one to another.Its mean concentration was 450μg/g and the highest reached 6210μg/g.The unleaded gasoline‘s Pb existed in the whole particle while the leaded gasoline‘s enriched in the surface of the particle and was more harmful to the human beings. 相似文献
46.
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
47.
48.
A novel series of temperature‐sensitive poly[(N‐isopropylacrylamide)‐co‐(ethyl methacrylate)] (p(NIPAM‐co‐EMA)) microgels was prepared by the surfactant‐free radical polymerization of N‐isopropylacrylamide (NIPAM) with ethyl methacrylate (EMA). The shape, size dispersity and volume‐phase transition behavior of the microgels were investigated by transmission electron microscopy (TEM), ultraviolet–visible (UV–Vis) spectroscopy, dynamic light scattering (DLS) and differential scanning calorimetry (DSC). The transmission electron micrographs and DLS results showed that microgels with narrow distributions were prepared. It was shown from UV–Vis, DLS and DSC measurements that the volume‐phase transition temperature (VPTT) of the p(NIPAM‐co‐EMA) microgels decreased with increasing incorporation of EMA, but the temperature‐sensitivity was impaired when more EMA was incorporated, causing the volume‐phase transition of the microgels to become more continuous. It is noteworthy that incorporation of moderate amounts of EMA could not only lower the VPTT but also enhance the temperature‐sensitivity of the microgels. The reason for this phenomenon could be attributed to changes in the complicated interactions between the various molecules. Copyright © 2004 Society of Chemical Industry 相似文献
49.
50.