全文获取类型
收费全文 | 152251篇 |
免费 | 23306篇 |
国内免费 | 6915篇 |
专业分类
电工技术 | 9657篇 |
技术理论 | 6篇 |
综合类 | 9999篇 |
化学工业 | 32842篇 |
金属工艺 | 7171篇 |
机械仪表 | 8442篇 |
建筑科学 | 11106篇 |
矿业工程 | 3058篇 |
能源动力 | 3943篇 |
轻工业 | 17060篇 |
水利工程 | 3055篇 |
石油天然气 | 4864篇 |
武器工业 | 1261篇 |
无线电 | 19657篇 |
一般工业技术 | 22621篇 |
冶金工业 | 4815篇 |
原子能技术 | 1431篇 |
自动化技术 | 21484篇 |
出版年
2024年 | 575篇 |
2023年 | 1774篇 |
2022年 | 3725篇 |
2021年 | 5330篇 |
2020年 | 5208篇 |
2019年 | 5865篇 |
2018年 | 5935篇 |
2017年 | 6873篇 |
2016年 | 7045篇 |
2015年 | 8744篇 |
2014年 | 9935篇 |
2013年 | 12142篇 |
2012年 | 11211篇 |
2011年 | 11424篇 |
2010年 | 10879篇 |
2009年 | 10419篇 |
2008年 | 9985篇 |
2007年 | 9234篇 |
2006年 | 8596篇 |
2005年 | 6958篇 |
2004年 | 5308篇 |
2003年 | 4601篇 |
2002年 | 4833篇 |
2001年 | 4319篇 |
2000年 | 3384篇 |
1999年 | 2198篇 |
1998年 | 1151篇 |
1997年 | 999篇 |
1996年 | 805篇 |
1995年 | 632篇 |
1994年 | 524篇 |
1993年 | 395篇 |
1992年 | 306篇 |
1991年 | 263篇 |
1990年 | 178篇 |
1989年 | 174篇 |
1988年 | 121篇 |
1987年 | 92篇 |
1986年 | 61篇 |
1985年 | 51篇 |
1984年 | 30篇 |
1983年 | 29篇 |
1982年 | 23篇 |
1981年 | 25篇 |
1980年 | 35篇 |
1979年 | 19篇 |
1977年 | 6篇 |
1976年 | 8篇 |
1959年 | 11篇 |
1951年 | 8篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
32.
33.
34.
M. Liess R. Hua K. Elsenaar 《The International Journal of Advanced Manufacturing Technology》2002,20(1):58-62
Cables to moving parts on a linear actuator in production machines, such as pick-and-place machines, are a source of unreliability
owing to the possible breaking of a cable. They further reduce the positioning precision of the actuator owing to additional
forces. Slotted waveguide systems for rail vehicles based on 2.4 GHz transmission frequency are well known, but transmitters/receivers
and waveguides are bulky. The paper reports on the reduction in size of the equipment, adapted to 5.8 GHz using a commercial
off-the-shelf RadioLan communication module. Further, the efficient termination of the wave-guide and a new way to reduce
standing-wave effects is also discussed. 相似文献
35.
36.
Flame structure and NO emission characteristics in counterflow diffusion flame of blended fuel of H2/CO2/Ar have been numerically simulated with detailed chemistry. The combination of H2, CO2 and Ar as fuel is selected to clearly display the contribution of hydrocarbon products to flame structure and NO emission characteristics due to the breakdown of CO2. A radiative heat loss term is involved to correctly describe the flame dynamics especially at low strain rates. The detailed chemistry adopts the reaction mechanism of GRI 2.11, which consists of 49 species and 279 elementary reactions. All mechanisms including thermal, NO2, N2O and Fenimore are taken into account to separately evaluate the effects of CO2 addition on NO emission characteristics. The increase of added CO2 quantity causes flame temperature to fall since at high strain rates a diluent effect is prevailing and at low strain rates the breakdown of CO2 produces relatively populous hydrocarbon products and thus the existence of hydrocarbon products inhibits chain branching. It is also found that the contribution of NO production by N2O and NO2 mechanisms are negligible and that thermal mechanism is concentrated on only the reaction zone. As strain rate and CO2 quantity increase, NO production is remarkably augmented. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
37.
38.
Hong Jeong Jeong‐Ho Park 《International Journal of Adaptive Control and Signal Processing》2002,16(1):1-23
Tracking targets of interest is one of the major research areas in radar surveillance systems. We formulate the problem as incomplete data estimation and apply EM to the MAP estimate. The resulting filter has a recursive structure analogous to the Kalman filter. The advantage is that the measurement‐update deals with multiple measurements in parallel and the parameter‐update estimates the system parameters on the fly. Experiments tracking separate targets in parallel show that tracking maintenance ratio of the proposed system is better than that of NNF and RMS position error is smaller than that of PDAF. Also, the system parameters are correctly obtained even from incorrect initial values. Copyright © 2001 John Wiley & Sons, Ltd. 相似文献
39.
宽带建设低潮期实际上是一次优胜劣汰的过程,宽带运营竞争的手段将由低价竞争转向服务质量和特色的竞争。应在重视宽带接入建设的同时,也要重视业务运营管理平台的建设。应从长远考虑,不应仅为了节省投资而降低对设备的要求。由于降低成本的主要方向是在线缆部分,因此EVDSL技术应用的速度将大大超过人们的预期。在网络建设上,IPDSLAM虽有优势但也有不足,还需要进一步的成熟、稳定和实践的检验。 相似文献
40.
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