全文获取类型
收费全文 | 211086篇 |
免费 | 21171篇 |
国内免费 | 12512篇 |
专业分类
电工技术 | 16579篇 |
技术理论 | 6篇 |
综合类 | 16621篇 |
化学工业 | 30763篇 |
金属工艺 | 12842篇 |
机械仪表 | 14246篇 |
建筑科学 | 17152篇 |
矿业工程 | 6887篇 |
能源动力 | 6306篇 |
轻工业 | 15726篇 |
水利工程 | 4847篇 |
石油天然气 | 10678篇 |
武器工业 | 2327篇 |
无线电 | 25643篇 |
一般工业技术 | 22477篇 |
冶金工业 | 9062篇 |
原子能技术 | 2378篇 |
自动化技术 | 30229篇 |
出版年
2024年 | 1081篇 |
2023年 | 3559篇 |
2022年 | 6977篇 |
2021年 | 9635篇 |
2020年 | 7182篇 |
2019年 | 5752篇 |
2018年 | 6346篇 |
2017年 | 7309篇 |
2016年 | 6438篇 |
2015年 | 9402篇 |
2014年 | 11728篇 |
2013年 | 13879篇 |
2012年 | 15867篇 |
2011年 | 16755篇 |
2010年 | 15166篇 |
2009年 | 14372篇 |
2008年 | 14216篇 |
2007年 | 13308篇 |
2006年 | 12373篇 |
2005年 | 9704篇 |
2004年 | 6833篇 |
2003年 | 5845篇 |
2002年 | 5583篇 |
2001年 | 4924篇 |
2000年 | 4081篇 |
1999年 | 3485篇 |
1998年 | 2412篇 |
1997年 | 1995篇 |
1996年 | 1806篇 |
1995年 | 1545篇 |
1994年 | 1240篇 |
1993年 | 795篇 |
1992年 | 646篇 |
1991年 | 506篇 |
1990年 | 412篇 |
1989年 | 359篇 |
1988年 | 245篇 |
1987年 | 186篇 |
1986年 | 144篇 |
1985年 | 88篇 |
1984年 | 74篇 |
1983年 | 61篇 |
1982年 | 59篇 |
1981年 | 62篇 |
1980年 | 65篇 |
1979年 | 42篇 |
1978年 | 24篇 |
1976年 | 28篇 |
1975年 | 18篇 |
1973年 | 18篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
51.
美国21世纪前期的军事战略重点将是争夺外空优势,夺取制天权和制信息权。分析了美国夺取外空优势的原因,及其为夺取外空优势在国家政策、航天发展和技术准备等方面采取的措施。 相似文献
52.
53.
54.
我国是陶瓷生产大国,近几年发展速度很快.2001年,我国的建筑陶瓷产量约20亿平方米,卫生瓷5000万件以上,全年全行业出口额超过2亿美元,创历史最好水平.加入WTO给我国陶瓷行业带来了很多机遇和挑战,但我们究竟与意大利、西班牙等陶瓷强国差距在哪里呢?记者最近走访了中国建筑陶瓷协会秘书长缪斌先生.恰逢秘书长刚从欧洲考察回来,便聊起这次欧洲之行…… 相似文献
55.
56.
Propolis collected by bees has many components that possess antifungal, anticancer and antioxidant properties. Cured ground pork meat was treated separately with 0.4% w/w ethanol‐extracted propolis (EEP 0.4%), 0.6% w/w water‐extracted propolis (WEP 0.6%), 0.8% w/w dried residue of ethanol‐extracted propolis (DREEP 0.8%) and 0.1% w/w potassium sorbate (PS 0.1%) and made into sausages. Thiobarbituric acid‐reactive substances (TBARS) were measured in the sausages to assess the effects of storage at 5, 10 and 20 °C after 0, 2 and 4 weeks. After 4 weeks of storage at 5 °C the sausages treated with EEP 0.4%, DREEP 0.8%, WEP 0.6% and PS 0.1% yielded TBARS values which were 50, 59, 35 and 91% respectively of the control value. There was an increase of 0.33 mg MDA kg?1, the lowest of all treatments, in TBARS for the 0.4% w/w EEP‐treated sausages. The curing process will control microbiological spoilage, as will potassium sorbate. © 2002 Society of Chemical Industry 相似文献
57.
Woo-Jin Han Eun-Kyoung Kim Yung-Hwan Oh 《Electronics letters》2002,38(6):292-294
A novel frame interpolation technique for two-band linear predictive coding (LPC) vocoders is proposed for maintaining natural speech quality at bit rates below 1 kbit/s. Experimental results show that the speech quality of the proposed vocoder is quite natural at bit rates 880 bit/s and comparable to that of 4.8 kbit/s CELP 相似文献
58.
Rotating-bending uniaxial fatigue tests and micro-fatigue crack initiation tests were carried out using a permanent mold cast
(PMC) and semi-solid die cast (SDC) with Al−7%Si−0.35%Mg composition in order to examine the relationship between solidification
structures and fatigue behaviors. The crack length was measured using a replication method. Fatigue strength was improved
in SDC, which was almost consistent with the predicted fatigue strength using the size of Si particle cluster. Resistance
to fatigue crack initiation and fatigue strength were improved in SDC owing to the finer Si cluster and to higher ultimate
tensile strength. Fatigue crack in PMC was preferentially initiated at pores. For SDC, the fatigue crack was initiated at
the Si particle/matrix interface, and then sucessively grew along eutectic cell boundaries. 相似文献
59.
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
60.
Successful operation of the Synchronous Overlap and Add (SOLA) algorithm for Time Scale Modification (TSM) of speech is closely tied to the proper choice of parameters. This paper investigates the quality of time scale modified speech under different values of primary parameters. Based on Mean Opinion Score (MOS) tests and Bark Spectral Distortion (BSD) measure, the proper choices of synthesis shift (Ss) and the duration of the shift search interval (K max?) are given experimentally. The conclusions can be helpful for operating the SOLA algorithm for time scale modification of speech. 相似文献