首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   11729篇
  免费   1490篇
  国内免费   302篇
电工技术   402篇
综合类   1028篇
化学工业   1463篇
金属工艺   263篇
机械仪表   684篇
建筑科学   408篇
矿业工程   102篇
能源动力   218篇
轻工业   448篇
水利工程   70篇
石油天然气   176篇
武器工业   197篇
无线电   3563篇
一般工业技术   2879篇
冶金工业   149篇
原子能技术   463篇
自动化技术   1008篇
  2025年   75篇
  2024年   250篇
  2023年   264篇
  2022年   259篇
  2021年   356篇
  2020年   384篇
  2019年   353篇
  2018年   274篇
  2017年   375篇
  2016年   446篇
  2015年   418篇
  2014年   666篇
  2013年   714篇
  2012年   756篇
  2011年   792篇
  2010年   622篇
  2009年   671篇
  2008年   504篇
  2007年   633篇
  2006年   601篇
  2005年   547篇
  2004年   439篇
  2003年   420篇
  2002年   344篇
  2001年   317篇
  2000年   289篇
  1999年   239篇
  1998年   186篇
  1997年   195篇
  1996年   158篇
  1995年   160篇
  1994年   131篇
  1993年   120篇
  1992年   96篇
  1991年   89篇
  1990年   67篇
  1989年   60篇
  1988年   41篇
  1987年   20篇
  1986年   19篇
  1985年   38篇
  1984年   36篇
  1983年   22篇
  1982年   39篇
  1980年   6篇
  1979年   3篇
  1976年   5篇
  1974年   3篇
  1959年   4篇
  1955年   4篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
The width of the transition layer between the crystalline and amorphous zones in nylon 1010 was determined by SAXS with point collimation and long-slit collimation, respectively. The width of the transition layer, E, was found to be 1.7 nm. The results show that the width of the transition layer is independent of crystallinity.  相似文献   
2.
As the result of vibration emission in air, a machine sound signal carries important information about the working condition of machinery. But in practice, the sound signal is typically received with a very low signal-to-noise ratio. To obtain features of the original sound signal, uncorrelated sound signals must be removed and the wavelet coefficients related to fault condition must be retrieved. In this paper, the blind source separation technique is used to recover the wavelet coefficients of a monitored source from complex observed signals. Since in the proposed blind source separation (BSS) algorithms it is generally assumed that the number of sources is known, the Gerschgorin disk estimator method is introduced to determine the number of sound sources before applying the BSS method. This method can estimate the number of sound sources under non-Gaussian and non-white noise conditions. Then, the partial singular value analysis method is used to select these significant observations for BSS analysis. This method ensures that signals are separated with the smallest distortion. Afterwards, the time-frequency separation algorithm, converted to a suitable BSS algorithm for the separation of a non-stationary signal, is introduced. The transfer channel between observations and sources and the wavelet coefficients of the source signals can be blindly identified via this algorithm. The reconstructed wavelet coefficients can be used for diagnosis. Finally, the separation results obtained from the observed signals recorded in a semi-anechoic chamber demonstrate the effectiveness of the presented methods .  相似文献   
3.
This paper reports a study undertaken using techniques of static and dynamic light scattering to investigate the influence of sodium salicylate and methyl salicylate on droplet size of oil-in-water emulsions. The rates of changes were measured by determining the size and distribution of the oil droplet in the material. All emulsions showed a bimodal size distribution; the mean diameters and polydispersity were calculated from intensity. These data were analyzed with nonlinear regressions and bootstrap methodology. An amount of methyl salicylate component induced a decrease of mean diameter and standard deviation. On the contrary, sodium salicylate entailed the growth of all droplet populations and coalescence for the highest concentration.  相似文献   
4.
In this paper, the cone-shaped patterned sapphire substrates (PSS) were etched by an inductively couple plasma with BCl 3 as the reacting gas. The influence of the operating pressure and the RF bias power on subtrenches of the cone-shaped PSS and the formation mechanism of subtrenches were investigated. The profiles of patterns were characterized by FESEM (field emission scanning electron microscope). It showed that the subtrench size varied with the operating pressure and the RF bias power. As the operatin...  相似文献   
5.
在诗歌翻译中,译文会因为译者的不同在风格上表现出差异.然而,译文的质量不外乎经受形美、音美和意美的考量.译者应从本国读者的文化背景上结合时代的脉搏来进行“再创造”,做到形式、音律和意蕴的完美统一.歌德的诗歌《中德四季晨昏杂咏》(之八)的四种中文译本各有特色,均在不同程度上实现了“三美”的融合.  相似文献   
6.
肖乾广  肖岚 《遥感信息》2006,(2):29-30,F0002
主要探索用EOS/MODIS极轨卫星监测闪电的可行性,应用大气和云辐射原理以及云中水滴mie散射的原理,从EOS/MODIS的中红外通道及热红外通道中提取夜间强对流云团产生的闪电信息,并可由强对流卫星云图的云顶温度确定可能出现冰雹的区域,对减灾、预警提供宏观信息。  相似文献   
7.
The calculations of the elastic scattering properties of ultra-cold francium isotopes are reported in detail. A parametric model potential for the triplet molecular states of the Fr2 is represented, and the scattering lengths at and the effective range re are calculated using WKB and Numerov methods for Fr--Fr in the triplet state. The convergence of these scattering properties depending on a K0 parameter and core radius is also investigated using two methods: Quantum Defect Theory and analytical formula of Symskoviski.  相似文献   
8.
In order to understand the relationship between crystal structure and thermoelectric properties, the neutron diffraction patterns of the thermoelectric materials with the nominal composition CexCo4Sb12 (x = 0.5, 1.0) were measured at room temperature, the data were fitted by the Rietveld profile refinement method using the Fullprof2k program. It is found that the sample Ce0.5Co4Sb12 is composed of two phases, its major phase is CoSb3 with skutterudite-structure and the Ce atom is not incorporated into the lattice, the impurity is monoclinic CoSb2. In the case of Ce1.0Co4Sb12, the major phase is filled skutterudite, about 10% of the 2a site is occupied by Ce atom, the second phase is monoclinic CoSb2.  相似文献   
9.
This paper introduces a measuring method of early lateral energy fraction in the scale model experiments. According to the interference principle of half wave length making the high frequency figure-8 directional microphone. With the signal-processing technique, a receiving and analyzing system, for the measurements of lateral energy fraction in the scale model is realized.  相似文献   
10.
木地板改善混凝土楼板撞击声的隔声性能研究   总被引:1,自引:0,他引:1  
谭华 《建筑科学》2007,23(9):66-69
通过对混凝土楼板和各种木地板构造方案的撞击声隔声性能的对比测试,对其隔声机理的定性理论分析,以及对铺装方法、弹性垫层等影响因素的讨论,研究了木地板对混凝土楼板撞击声的隔绝作用。结果表明,木地板可有效降低楼板撞击噪声的透射,其中浮筑木地板构造的隔声效果尤为显著,它可以使楼板对撞击声的隔声性能达到一级标准的要求。  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号