全文获取类型
收费全文 | 11289篇 |
免费 | 81篇 |
国内免费 | 139篇 |
专业分类
电工技术 | 133篇 |
综合类 | 2篇 |
化学工业 | 445篇 |
金属工艺 | 444篇 |
机械仪表 | 71篇 |
建筑科学 | 103篇 |
矿业工程 | 2篇 |
能源动力 | 72篇 |
轻工业 | 106篇 |
水利工程 | 26篇 |
石油天然气 | 9篇 |
无线电 | 486篇 |
一般工业技术 | 311篇 |
冶金工业 | 269篇 |
原子能技术 | 99篇 |
自动化技术 | 8931篇 |
出版年
2024年 | 5篇 |
2023年 | 9篇 |
2022年 | 22篇 |
2021年 | 30篇 |
2020年 | 24篇 |
2019年 | 38篇 |
2018年 | 32篇 |
2017年 | 41篇 |
2016年 | 60篇 |
2015年 | 34篇 |
2014年 | 258篇 |
2013年 | 242篇 |
2012年 | 820篇 |
2011年 | 3127篇 |
2010年 | 1181篇 |
2009年 | 1057篇 |
2008年 | 715篇 |
2007年 | 628篇 |
2006年 | 480篇 |
2005年 | 598篇 |
2004年 | 551篇 |
2003年 | 601篇 |
2002年 | 291篇 |
2001年 | 17篇 |
2000年 | 14篇 |
1999年 | 36篇 |
1998年 | 144篇 |
1997年 | 75篇 |
1996年 | 47篇 |
1995年 | 24篇 |
1994年 | 22篇 |
1993年 | 27篇 |
1992年 | 22篇 |
1991年 | 11篇 |
1990年 | 24篇 |
1989年 | 15篇 |
1988年 | 14篇 |
1987年 | 9篇 |
1986年 | 14篇 |
1985年 | 14篇 |
1984年 | 27篇 |
1983年 | 20篇 |
1982年 | 9篇 |
1981年 | 19篇 |
1980年 | 8篇 |
1978年 | 6篇 |
1977年 | 11篇 |
1976年 | 11篇 |
1975年 | 7篇 |
1974年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Antoine Depoorter Carmen Kalalian Corinne Emmelin Chantal Lorentz Christian George 《Indoor air》2021,31(3):682-692
People spend approximately 80% of their time indoor, making the understanding of the indoor chemistry an important task for safety. The high surface-area-to-volume ratio characteristic of indoor environments leads the semi-volatile organic compounds (sVOCs) to deposit on the surfaces. Using a long path absorption photometer (LOPAP), this work investigates the formation of nitrous acid (HONO) through the photochemistry of adsorbed nitrate anions and its enhancement by the presence of furfural. Using a high-resolution proton-transfer-reaction time-of-flight mass spectrometer (PTR-TOF-MS), this work also investigates the surface emissions of VOCs from irradiated films of furfural and a mix of furfural and nitrate anions. Among the emitted VOCs, 2(5H)-furanone/2-Butenedial was observed at high concentrations, leading to maleic anhydride formation after UV irradiation. Moreover, the addition of potassium nitrate to the film formed NOx and HONO concentrations up to 10 ppb, which scales to ca. 4 ppb for realistic indoor conditions. This work helps to understand the high levels of HONO and NOx measured indoors. 相似文献
2.
Navab SinghAuthor Vitae Moitreyee Mukherjee-RoyAuthor VitaeSohan Singh MehtaAuthor Vitae 《Microelectronics Journal》2003,34(4):237-245
The patterning of contact holes by selecting out-of-focus image plane (defocus) using attenuated phase shift masks (APSM) has been studied. Defocus is found to enhance the image modulation at low partial coherence for contact holes with negative local average of mask function. Semi-dense holes up to 130 nm in 8% APSM have been printed by 0.5 μm defocus at a partial coherence of 0.31 using KrF scanner with highest numerical aperture of 0.68. However, these holes were closed with in-focus imaging. Defocus is also found to be beneficial for patterning the pitches that have extensive side lobes with in-focus imaging. 相似文献
3.
4.
D. Ballutaud F. Jomard T. Kociniewski E. Rzepka H. Girard S. Saada 《Diamond and Related Materials》2008,17(4-5):451-456
Hot filament and microwave plasma CVD micro- nanocrystalline diamond films are analysed by visible and ultra-violet excitation source Raman spectroscopy. The sample grain size varies from 20 nm to 2 μm. The hydrogen concentration in samples is measured by SIMS and compared to the grain size, and to the ratio of sp2 carbon bonds determined by Raman spectroscopy from the 1332 cm− 1 diamond peak and the sp2 1550 cm− 1 G band. Hydrogen concentration appears to be proportional to the sp2 bonds ratio. The 3000 cm− 1 CHx stretching mode band intensity observed on the Raman spectra is decreasing with the G band intensity. Thermal annealing modifies the sp2 phase structure and concentration, as hydrogen outdiffuses. 相似文献
5.
A stochastic realization problem of a stationary stochastic process is re-visited, and a new stochastically balanced realization algorithm is derived in a Hilbert space generated by second-order stationary processes. The present algorithm computes a stochastically balanced realization by means of the singular value decomposition of a weighted block Hankel matrix derived by a “block LQ decomposition”. Extension to a stochastic subspace identification method explains how the proposed abstract algorithm is implemented in system identification. 相似文献
6.
7.
Chia-Jung Pai Author Vitae Author Vitae Yu-Ming Liang Author Vitae Author Vitae Sei-Wang Chen Author Vitae 《Pattern recognition》2004,37(5):1025-1034
This paper presents a system that can perform pedestrian detection and tracking using vision-based techniques. A very important issue in the field of intelligent transportation system is to prevent pedestrians from being hit by vehicles. Recently, a great number of vision-based techniques have been proposed for this purpose. In this paper, we propose a vision-based method, which combines the use of a pedestrian model as well as the walking rhythm of pedestrians to detect and track walking pedestrians. Through integrating some spatial and temporal information grabbed by a vision system, we are able to develop a reliable system that can be used to prevent traffic accidents happened at crossroads. In addition, the proposed system can deal with the occlusion problem. Experimental results obtained by executing some real world cases have demonstrated that the proposed system is indeed superb. 相似文献
8.
V. Rodin Author Vitae A. Benzinou Author VitaeAuthor Vitae P. Ballet Author VitaeAuthor Vitae J. Tisseau Author VitaeAuthor Vitae 《Pattern recognition》2004,37(4):631-645
In this article, we present a parallel image processing system based on the concept of reactive agents. Our system lies in the oRis language, which allows to describe finely and simply the agents’ behaviors to detect image features. We also present a method of segmentation using a multi-agent system, and two biological applications made with oRis. The stopping of this multi-agent system is implemented through a technique issued from immunology: the apoptosis. 相似文献
9.
10.
Er-Wei Bai Author Vitae 《Automatica》2003,39(9):1521-1530
This paper proposes a frequency domain algorithm for Wiener model identifications based on exploring the fundamental frequency and harmonics generated by the unknown nonlinearity. The convergence of the algorithm is established in the presence of white noise. No a priori knowledge of the structure of the nonlinearity is required and the linear part can be nonparametric. 相似文献