全文获取类型
收费全文 | 26418篇 |
免费 | 2609篇 |
国内免费 | 1873篇 |
专业分类
电工技术 | 589篇 |
技术理论 | 2篇 |
综合类 | 2894篇 |
化学工业 | 1185篇 |
金属工艺 | 1837篇 |
机械仪表 | 1776篇 |
建筑科学 | 6384篇 |
矿业工程 | 641篇 |
能源动力 | 498篇 |
轻工业 | 312篇 |
水利工程 | 497篇 |
石油天然气 | 533篇 |
武器工业 | 200篇 |
无线电 | 5076篇 |
一般工业技术 | 4495篇 |
冶金工业 | 706篇 |
原子能技术 | 1171篇 |
自动化技术 | 2104篇 |
出版年
2024年 | 82篇 |
2023年 | 260篇 |
2022年 | 531篇 |
2021年 | 620篇 |
2020年 | 733篇 |
2019年 | 686篇 |
2018年 | 627篇 |
2017年 | 803篇 |
2016年 | 826篇 |
2015年 | 892篇 |
2014年 | 1441篇 |
2013年 | 1604篇 |
2012年 | 1792篇 |
2011年 | 2094篇 |
2010年 | 1562篇 |
2009年 | 1748篇 |
2008年 | 1631篇 |
2007年 | 1870篇 |
2006年 | 1639篇 |
2005年 | 1378篇 |
2004年 | 1129篇 |
2003年 | 1020篇 |
2002年 | 904篇 |
2001年 | 800篇 |
2000年 | 685篇 |
1999年 | 592篇 |
1998年 | 516篇 |
1997年 | 447篇 |
1996年 | 376篇 |
1995年 | 301篇 |
1994年 | 278篇 |
1993年 | 206篇 |
1992年 | 156篇 |
1991年 | 129篇 |
1990年 | 129篇 |
1989年 | 89篇 |
1988年 | 82篇 |
1987年 | 54篇 |
1986年 | 52篇 |
1985年 | 24篇 |
1984年 | 36篇 |
1983年 | 15篇 |
1982年 | 21篇 |
1981年 | 7篇 |
1980年 | 11篇 |
1979年 | 7篇 |
1978年 | 1篇 |
1959年 | 14篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
Neural Machine Translation (NMT) is an end-to-end learning approach for
automated translation, overcoming the weaknesses of conventional phrase-based translation
systems. Although NMT based systems have gained their popularity in commercial
translation applications, there is still plenty of room for improvement. Being the most
popular search algorithm in NMT, beam search is vital to the translation result. However,
traditional beam search can produce duplicate or missing translation due to its target
sequence selection strategy. Aiming to alleviate this problem, this paper proposed neural
machine translation improvements based on a novel beam search evaluation function. And
we use reinforcement learning to train a translation evaluation system to select better
candidate words for generating translations. In the experiments, we conducted extensive
experiments to evaluate our methods. CASIA corpus and the 1,000,000 pairs of bilingual
corpora of NiuTrans are used in our experiments. The experiment results prove that the
proposed methods can effectively improve the English to Chinese translation quality. 相似文献
12.
Ali Mohamed 《Journal of Modern Optics》2019,66(13):1392-1407
Anisoplanatic electromagnetic (EM) propagation across a turbulent atmosphere has been recently examined for an unmodulated carrier propagating over an image-bearing transparency through optical lensing, and for the embedded information inside a carrier recovered using heterodyning and digital demodulation. Carrier modulation yielded better recovery than simple lens-based imaging. A possible mitigation strategy is proposed whereby the image information is encrypted on an RF chaotic carrier, thereafter secondarily embedded onto an optical carrier. Results based on the modified von Karman (MVKS) and the Hufnagel-Valley (H-V) models showed that the signal/image recovery under turbulence is improved compared with non-chaotic propagation. The case of time-varying/dynamic images is also taken up; it is demonstrated via cross-correlation products that turbulence is mitigated by the use of chaotic carrier encryption. Overall, transmission via chaos offers mitigation against distortions due to turbulence along with the security feature inherent via the chaos keys which prevent signal recovery without key-matching. 相似文献
13.
The investigation of phase transformations in metastable ceramic systems such as zirconia often requires local phase analysis within the areas of interest. Electron backscatter diffraction is a suitable method in combination with focused ion beam sample preparation. The interaction between ion beam and sample has to be carefully considered. In case of metastable Y-PSZ and Mg-PSZ, phase transformations were observed after FIB preparation with 30?kV, 30?nA and 5° incidence angle. Damage was the dominating effect for angles of 72°. The expected local temperature increase due to the ion bombardment with 30?kV and 30?nA is 700?K for ZrO2. Thus, the observed phase transformations can be explained on the basis of the temperature increase in the corresponding Y-PSZ phase diagram. In case of Mg-PSZ, the transition temperature is 1083?°C. The local temperature increase was obviously lower. The excitation energy for the observed phase transformation was smaller than expected from the phase diagrams of the thermodynamic equilibrium. Using 5?kV, 4.8?nA and 5° incidence angle, no phase transformations and no damage were observed. Thus, these conditions are well suited for the FIB preparation of metastable zirconia. 相似文献
14.
15.
16.
1 Introduction High power laser diode arrays (LDA) have many advan- tages such as small volume, long working life, high slope efficiency and high optical density, so they have many applications in medical treatment, material pro- cessing, and for the pumping source of solid laser and etc. But unfortunately, the LDA can not be easy to use directly in these fields because of their poor beam quality and extremely asymmetric divergent beams (!x≈ 5°~10°and !y≈20°~35°, for example), so it … 相似文献
17.
目前需求预测在整个印制电路板产业的生产活动控制中正扮演着越来越重要的角色。分析了影响印制电路板需求的因素和现有的预测方法,提出了一种适用于PCB产业需求预测的有效方法——遗传/BP—神经网络。实验表明该方法能够进一步改善印制电路板预测的准确度和减少生产成本的消耗。 相似文献
18.
19.
Study of elastic wave propagation induced by piezoelectric actuators for crack identification 总被引:1,自引:0,他引:1
The current paper provides a theoretical study of elastic wave propagation in a cracked elastic medium induced by an embedded piezoelectric actuator. The formulation of the problem is based on a newly developed actuator model and the solution of coupled crack and actuator problems. The interaction between an actuator and a crack is studied to develop basic understanding of the effect of the crack upon the wave field generated. The resulting wave field is used to simulate 'sensor signals'. Scattered wave from the crack is then regenerated by solving a reverse elastodynamic problem and used in an imaging technique to identify the crack. 相似文献
20.