全文获取类型
收费全文 | 187308篇 |
免费 | 22152篇 |
国内免费 | 15377篇 |
专业分类
电工技术 | 17837篇 |
技术理论 | 3篇 |
综合类 | 19129篇 |
化学工业 | 23641篇 |
金属工艺 | 12769篇 |
机械仪表 | 12627篇 |
建筑科学 | 15173篇 |
矿业工程 | 6940篇 |
能源动力 | 5236篇 |
轻工业 | 20666篇 |
水利工程 | 6362篇 |
石油天然气 | 6235篇 |
武器工业 | 2640篇 |
无线电 | 20688篇 |
一般工业技术 | 16328篇 |
冶金工业 | 7041篇 |
原子能技术 | 2871篇 |
自动化技术 | 28651篇 |
出版年
2024年 | 1288篇 |
2023年 | 3528篇 |
2022年 | 7691篇 |
2021年 | 9827篇 |
2020年 | 7014篇 |
2019年 | 5182篇 |
2018年 | 5418篇 |
2017年 | 6173篇 |
2016年 | 5320篇 |
2015年 | 8501篇 |
2014年 | 10471篇 |
2013年 | 11974篇 |
2012年 | 15159篇 |
2011年 | 15977篇 |
2010年 | 14696篇 |
2009年 | 14560篇 |
2008年 | 14569篇 |
2007年 | 14180篇 |
2006年 | 12385篇 |
2005年 | 10061篇 |
2004年 | 7478篇 |
2003年 | 5241篇 |
2002年 | 5132篇 |
2001年 | 4639篇 |
2000年 | 3439篇 |
1999年 | 1516篇 |
1998年 | 633篇 |
1997年 | 490篇 |
1996年 | 385篇 |
1995年 | 333篇 |
1994年 | 272篇 |
1993年 | 256篇 |
1992年 | 199篇 |
1991年 | 150篇 |
1990年 | 112篇 |
1989年 | 117篇 |
1988年 | 90篇 |
1987年 | 64篇 |
1986年 | 56篇 |
1985年 | 26篇 |
1984年 | 19篇 |
1983年 | 15篇 |
1982年 | 28篇 |
1981年 | 19篇 |
1980年 | 53篇 |
1979年 | 43篇 |
1978年 | 1篇 |
1959年 | 26篇 |
1958年 | 2篇 |
1951年 | 29篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
61.
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
62.
63.
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
64.
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
65.
设计了一种适合在低电源电压下工作的前馈型输入级放大结构,在全摆幅的动态工作范围内,输入级跨导保持不变,采用负载电流补偿以保证增益近似恒定,输出采用前馈型AB类输结构,实现全摆幅输出。 相似文献
66.
Colour is the most widely used attribute in image retrieval and object recognition. A technique known as histogram intersection has been widely studied and is considered to be effective for color‐image indexing. The key issue of this algorithm is the selection of an appropriate color space and optimal quantization of the selected color space. The goal of this article is to measure the model performance in predicting human judgment in similarity measurement for various images, to explore the capability of the model with a wide set of color spaces, and to find the optimal quantization of the selected color spaces. Six color spaces and twelve quantization levels are involved in evaluating the performance of histogram intersection. The categorical judgment and rank order experiments were conducted to measure image similarity. The CIELAB color space was found to perform at least as good as or better than the other color spaces tested, and the ability to predict image similarity increased with the number of bins used in the histograms, for up to 512 bins (8 per channel). With more than 512 bins, further improvement was negligible for the image datasets used in this study. © 2005 Wiley Periodicals, Inc. Col Res Appl, 30, 265–274, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/col.20122 相似文献
67.
已往库存论中的决策模型,它是把现实过程用数学的方法进行分析,得到决策值,但不能看到决策的过程,不能反映出现实生活中的不确定性、动态性。运用Delphi 7.0和SQL server 2000对销售过程进行了动态仿真,利用Newsboy模型的推广(S,s)订购策略来监控库存并做出决策,这样就体现出此过程的不确定性、动态性;且举出了一个仿真商品销售的实例,对其中的一些关键技术,如何仿真、算法的实现等进行了阐述。 相似文献
68.
69.
70.
用保形样条方法求解非定常对流扩散方程 总被引:1,自引:0,他引:1
在欧拉-拉格朗日分裂方法的基础上,本文发展了一种固定网格上的欧拉-拉格朗日分裂方法.保形样条方法(SPSM)被用来解决倒特征线插值问题.通过求解几个有精确解的例子,说明SPSM方法的解是单调无振荡的,并且数值耗散也是比较小的. 相似文献