全文获取类型
收费全文 | 142631篇 |
免费 | 13014篇 |
国内免费 | 6761篇 |
专业分类
电工技术 | 8996篇 |
技术理论 | 11篇 |
综合类 | 9686篇 |
化学工业 | 23742篇 |
金属工艺 | 7698篇 |
机械仪表 | 8940篇 |
建筑科学 | 11667篇 |
矿业工程 | 3820篇 |
能源动力 | 4168篇 |
轻工业 | 10839篇 |
水利工程 | 2832篇 |
石油天然气 | 6966篇 |
武器工业 | 1189篇 |
无线电 | 17138篇 |
一般工业技术 | 16596篇 |
冶金工业 | 6645篇 |
原子能技术 | 1355篇 |
自动化技术 | 20118篇 |
出版年
2024年 | 763篇 |
2023年 | 2681篇 |
2022年 | 5040篇 |
2021年 | 6594篇 |
2020年 | 4773篇 |
2019年 | 3886篇 |
2018年 | 4225篇 |
2017年 | 4621篇 |
2016年 | 4206篇 |
2015年 | 5758篇 |
2014年 | 7338篇 |
2013年 | 8629篇 |
2012年 | 9673篇 |
2011年 | 10062篇 |
2010年 | 8811篇 |
2009年 | 8500篇 |
2008年 | 8056篇 |
2007年 | 7654篇 |
2006年 | 7507篇 |
2005年 | 6480篇 |
2004年 | 4530篇 |
2003年 | 4105篇 |
2002年 | 3975篇 |
2001年 | 3484篇 |
2000年 | 3215篇 |
1999年 | 3196篇 |
1998年 | 2742篇 |
1997年 | 2201篇 |
1996年 | 1985篇 |
1995年 | 1653篇 |
1994年 | 1387篇 |
1993年 | 1015篇 |
1992年 | 752篇 |
1991年 | 616篇 |
1990年 | 461篇 |
1989年 | 401篇 |
1988年 | 353篇 |
1987年 | 202篇 |
1986年 | 187篇 |
1985年 | 122篇 |
1984年 | 104篇 |
1983年 | 68篇 |
1982年 | 78篇 |
1981年 | 63篇 |
1980年 | 60篇 |
1979年 | 41篇 |
1978年 | 14篇 |
1977年 | 33篇 |
1976年 | 16篇 |
1975年 | 15篇 |
排序方式: 共有10000条查询结果,搜索用时 9 毫秒
111.
黄健宇 《机械工业标准化与质量》2005,(3):20-25
随着计算机及网络技术在现代企业生产经营管理中的广泛应用,特别是以网络为信息交流平台的企业CMIS、ERP和MRPII等管理系统的应用推广,使得企业生产经营的管理技术和理念相比传统管理的方式、方法也发生了根本性的变化。企业内外形成和交流的信息量成倍增加,组织生产经营信息逐步表现为操作流程规范化、信息应用集成化和信息环境复杂化的趋势,从而使得组织信息交流语言及接口的规范统一,标准化也日显重要。 相似文献
112.
A Low-Power CMOS Linear-in-Decibel Variable Gain Amplifier With Programmable Bandwidth and Stable Group Delay 总被引:1,自引:0,他引:1
Tsou S.-C. Li C.-F. Huang P.-C. 《Circuits and Systems II: Express Briefs, IEEE Transactions on》2006,53(12):1436-1440
This brief presents a new circuit architecture for linear-in-decibel, constant-bandwidth variable gain amplifier (VGA). To obtain high linearity under low-voltage operation, this VGA is a closed-loop structure. In loop amplifier design, two techniques are applied: first, the loop amplifier is given finite input impedance. This arrangement keeps the VGA bandwidth constant under different gain setting. Second, a current-buffered compensation is applied for loop stability. Compared to the Miller compensation, this method achieves wider bandwidth. The prototype chip using 0.18-mum CMOS technology demonstrates that -10- to 20-dB gain and 0.5- to 30-MHz bandwidth can be programmed independently. The group delay difference within 30-dB gain control range is smaller than 1%. The total circuit dissipates 1.35 mA from a 1.8-V supply 相似文献
113.
Xin Sun Qiang Lu Moroz V. Takeuchi H. Gebara G. Wetzel J. Shuji Ikeda Changhwan Shin Tsu-Jae King Liu 《Electron Device Letters, IEEE》2008,29(5):491-493
A tri-gate bulk MOSFET design utilizing a low-aspect-ratio channel is proposed to provide an evolutionary pathway for CMOS scaling to the end of the roadmap. 3-D device simulations indicate that this design offers the advantages of a multi-gate FET (reduced variability in performance and improved scalability) together with the advantages of a conventional planar MOSFET (low substrate cost and capability for dynamic threshold-voltage control). 相似文献
114.
镍氢电池负极用低成本储氢合金的研究 总被引:1,自引:0,他引:1
研究了ABS型储氢合金在低Co含量条件下,随B组元替代元素Co,Al,Si等含量的变化对合金电化学性能的影响规律,同时研究了A组元中不同La/Ce比对合金电化学性能的影响情况。结果表明,随合金中Co含量的降低,合金的活化性能和放电容量得以改善,但合金的循环寿命下降也比较明显;在试验范围内,随Al元素的加入,合金的循环寿命得以改善,但材料的放电容量和活化性能均有所下降;随合金La/Ce比的降低,合金的放电容量略有下降,但其循环寿命和放电电压平台有较大提高。 相似文献
115.
防治水泥稳定碎石基层沥青路面裂缝的措施浅析 总被引:3,自引:0,他引:3
水泥稳定碎石基层沥青路面裂缝产生的原因复杂 ,但非荷载型裂缝更为主要。防治水泥稳定碎石基层沥青路面的裂缝应该从设计和施工两方面考虑 ,其中由结构、材料组成设计 ,以及施工工艺出发控制水泥稳定碎石基层本身的收缩也是一项重要措施。 相似文献
116.
117.
Evolving artificial neural network ensembles 总被引:3,自引:0,他引:3
Using a coordinated group of simple solvers to tackle a complex problem is not an entirely new idea. Its root could be traced back hundreds of years ago when ancient Chinese suggested a team approach to problem solving. For a long time, engineers have used the divide-and-conquer strategy to decompose a complex problem into simpler sub-problems and then solve them by a group of solvers. However, knowing the best way to divide a complex problem into simpler ones relies heavily on the available domain knowledge. It is often a manual process by an experienced engineer. There have been few automatic divide-and-conquer methods reported in the literature. Fortunately, evolutionary computation provides some of the interesting avenues to automatic divide-and-conquer methods. An in-depth study of such methods reveals that there is a deep underlying connection between evolutionary computation and ANN ensembles. Ideas in one area can be usefully transferred into another in producing effective algorithms. For example, using speciation to create and maintain diversity had inspired the development of negative correlation learning for ANN ensembles, and an in-depth study of diversity in ensembles. This paper will review some of the recent work in evolutionary approaches to designing ANN ensembles. 相似文献
118.
Xin Qi Salapaka M.V. Voulgaris P.G. Khammash M. 《Automatic Control, IEEE Transactions on》2004,49(10):1623-1640
In this paper, the design of controllers that incorporate structural and multiobjective performance requirements is considered. The control structures under study cover nested, chained, hierarchical, delayed interaction and communications, and symmetric systems. Such structures are strongly related to several modern-day and future applications including integrated flight propulsion systems, platoons of vehicles, micro-electro-mechanical systems, networked control, control of networks, production lines and chemical processes. It is shown that the system classes presented have the common feature that all stabilizing controllers can be characterized by convex constraints on the Youla-Kucera parameter. Using this feature, a solution to a general optimal performance problem that incorporates time domain and frequency domain constraints is obtained. A synthesis procedure is provided which at every step yields a feasible controller together with a measure of its performance with respect to the optimal. Convergence to the optimal performance is established. An example of a multinode network congestion control problem is provided that illustrates the effectiveness of the developed methodology. 相似文献
119.
A systematic investigation of the magnetic and transport properties of Ti doped La0.67Ca0.33MnO3 was reported. The Ti substitution for Mn ions results in a reduction in ferromagnetism and conductivity. The metal-insulator transition temperature is close to Curie temperature which decreases from 274 to 82 K as x increases from 0 to 0.17. The most important effect of Ti doping is to introduce spin clusters in the samples due to the distortion of local lattice and the inhomogeneous magnetic structure induced primarily by the random distribution of Mn ions. A maximum magnetoresistance ratio as large as 90% in 1 T at 122 K was obtained for the sample with x =0. 055, which is four times larger than that obtained for LCMO sample at 272 K. There is a remarkable field-history dependent MR in the cooling process for the doped samples while such phenomenon disappears in the warming run. The resistivity follows well the variable range hopping behavior in paramagnetic state. Both the size effect and spin dependent hopping of carriers between the spin clusters should be considered in this system. 相似文献
120.