全文获取类型
收费全文 | 58013篇 |
免费 | 5111篇 |
国内免费 | 2614篇 |
专业分类
电工技术 | 3410篇 |
综合类 | 4258篇 |
化学工业 | 9472篇 |
金属工艺 | 2947篇 |
机械仪表 | 3573篇 |
建筑科学 | 4327篇 |
矿业工程 | 1677篇 |
能源动力 | 1639篇 |
轻工业 | 4856篇 |
水利工程 | 1216篇 |
石油天然气 | 3317篇 |
武器工业 | 468篇 |
无线电 | 6650篇 |
一般工业技术 | 6834篇 |
冶金工业 | 2459篇 |
原子能技术 | 708篇 |
自动化技术 | 7927篇 |
出版年
2024年 | 248篇 |
2023年 | 1064篇 |
2022年 | 1934篇 |
2021年 | 2747篇 |
2020年 | 2123篇 |
2019年 | 1758篇 |
2018年 | 1857篇 |
2017年 | 2074篇 |
2016年 | 1856篇 |
2015年 | 2652篇 |
2014年 | 3200篇 |
2013年 | 3787篇 |
2012年 | 4071篇 |
2011年 | 4222篇 |
2010年 | 3757篇 |
2009年 | 3587篇 |
2008年 | 3525篇 |
2007年 | 3267篇 |
2006年 | 3162篇 |
2005年 | 2674篇 |
2004年 | 1877篇 |
2003年 | 1395篇 |
2002年 | 1307篇 |
2001年 | 1036篇 |
2000年 | 1044篇 |
1999年 | 1061篇 |
1998年 | 835篇 |
1997年 | 703篇 |
1996年 | 659篇 |
1995年 | 530篇 |
1994年 | 436篇 |
1993年 | 298篇 |
1992年 | 242篇 |
1991年 | 190篇 |
1990年 | 118篇 |
1989年 | 114篇 |
1988年 | 95篇 |
1987年 | 57篇 |
1986年 | 53篇 |
1985年 | 25篇 |
1984年 | 20篇 |
1983年 | 14篇 |
1982年 | 17篇 |
1981年 | 12篇 |
1980年 | 12篇 |
1979年 | 3篇 |
1976年 | 2篇 |
1972年 | 1篇 |
1959年 | 4篇 |
1951年 | 8篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
21.
Cochannel narrowband interference can limit the performance of direct sequence spread spectrum (DSSS) and high frequency (HF) systems. Narrowband interference (NBI) can be single tone, chirped or frequency shift keyed (FSK) in nature and numerous techniques for its removal have been proposed. Linear adaptive prediction filters based on autoregressive modelling have been suggested owing to their ability to perform in a non-stationary environment. In the FSK narrowband interference case, adaptive filters are susceptible to excess residual errors owing to instantaneous frequency step changes and the finite convergence time required for the filter to adapt to a new interference frequency. The signal degradation owing to this type of interference becomes greater in high SNR regimes and has been found to be a function of the frequency parameters of the FSK interference signal. The paper discusses the convergence and frequency tracking properties of the recursive least squares (RLS) adaptive lattice filter using a posteriori estimation errors in the presence of FSK narrowband interference. An optimal exponential weighting factor that balances convergence time and steady state error is derived for this case of NBI. Results are compared to those of a previously proposed fast converging minimum frequency error (FCMFE) RLS lattice filter. 相似文献
22.
随着电容测量技术的迅速发展,电容传感器在非电量测量和自动检测中得到广泛应用,但它在使用过程中也存在一些问题,针对在使用电容传感器过程中存在的几个问题,从电容传感器的原理和工作过程两个方面进行了讨论,并提出行之有效的处理方法。 相似文献
24.
25.
Meng Wai Woo 《Drying Technology》2008,26(1):15-26
Current methods in alleviating the wall deposition problem in spray drying emphasize mainly controlling the stickiness of the drying particles and less attention is placed on the properties of the dryer wall. In this experimental study, the effect of wall surface properties on the deposition mechanism has been investigated. Properties considered in classifying different wall materials were surface energy, roughness, and dielectric properties. The model solution contained sucrose, representing low-molecular-weight sugars commonly encountered in spray drying of fruit and vegetable juices. The effect of wall properties on deposition was explored at different drying rates producing particles of different surface rigidity. Larger surface roughness produced higher deposition fluxes for particles with high impact velocity and moisture. Surface energy and surface roughness were found to have no significant effect for dry rigid particles at the middle and bottom elevation of the drying chamber. However, material with lower surface energy (Teflon) exhibited less deposition for rubbery particles at such elevations. Analysis shows that dielectric wall material (Teflon) tends to enhance deposition of dry particles because of attrition at the surface. Higher wall temperature was found to produce slightly more deposition. The results of this work give a general indication of the effect of wall material on the deposition problem and provide the fundamental understanding for further studies along this line. Proper selection of dryer wall material will provide potential alternatives for reducing the deposition problem. 相似文献
26.
本文分析了"十五"期间农村水电发展情况,对"十一五"农村水电发展政策环境及增长情况进行了预测。 相似文献
27.
蓄热式均热炉生产中存在问题的分析及解决方案 总被引:1,自引:0,他引:1
介绍了高温空气燃烧技术在均热炉上的应用情况,对应用中出现的问题进行了分析,并提出了解决方案。 相似文献
28.
Wei Li Zhang Wei Pan Bin Luo Xi Hua Zou Meng Yao Wang 《Photonics Technology Letters, IEEE》2008,20(9):712-714
A theoretical construction of one-to-many (OTM) and many-to-one (MTO) chaos synchronization communications using semiconductor lasers is presented. One center laser provides strong injections (strong link) to other side lasers, and the side lasers also provide weak injections (weak link) to the center one. Simulation results show that the side lasers synchronize with the center laser through injection-locking. In addition, messages transmitted via the strong links or the weak links experience strong chaos pass filtering, enabling us to realize OTM and MTO communications. 相似文献
29.
In this note, we investigate different concepts of nonlinear identifiability in the generic sense. We work in the linear algebraic framework. Necessary and sufficient conditions are found for geometrical identifiability, algebraic identifiability and identifiability with known initial conditions. Relationships between different concepts are characterized. Constructive procedures are worked out for both generic geometrical and algebraic identifiability of nonlinear systems. As an application of the theory developed, we study the identifiability properties of a four dimensional model of HIV/AIDS. The questions answered in this study include the minimal number of measurement of the variables for a complete determination of all parameters and the best period of time to make such measurements. This information will be useful in formulating guidelines for clinical practice. 相似文献
30.