全文获取类型
收费全文 | 44825篇 |
免费 | 4635篇 |
国内免费 | 2466篇 |
专业分类
电工技术 | 3392篇 |
技术理论 | 2篇 |
综合类 | 3592篇 |
化学工业 | 6991篇 |
金属工艺 | 2567篇 |
机械仪表 | 2890篇 |
建筑科学 | 3565篇 |
矿业工程 | 1282篇 |
能源动力 | 1195篇 |
轻工业 | 3843篇 |
水利工程 | 885篇 |
石油天然气 | 2385篇 |
武器工业 | 478篇 |
无线电 | 5424篇 |
一般工业技术 | 4670篇 |
冶金工业 | 1823篇 |
原子能技术 | 777篇 |
自动化技术 | 6165篇 |
出版年
2024年 | 283篇 |
2023年 | 905篇 |
2022年 | 1857篇 |
2021年 | 2351篇 |
2020年 | 1778篇 |
2019年 | 1426篇 |
2018年 | 1558篇 |
2017年 | 1652篇 |
2016年 | 1481篇 |
2015年 | 1954篇 |
2014年 | 2409篇 |
2013年 | 2659篇 |
2012年 | 3036篇 |
2011年 | 3170篇 |
2010年 | 2853篇 |
2009年 | 2732篇 |
2008年 | 2728篇 |
2007年 | 2512篇 |
2006年 | 2462篇 |
2005年 | 2107篇 |
2004年 | 1410篇 |
2003年 | 1281篇 |
2002年 | 1364篇 |
2001年 | 1217篇 |
2000年 | 984篇 |
1999年 | 816篇 |
1998年 | 493篇 |
1997年 | 481篇 |
1996年 | 442篇 |
1995年 | 305篇 |
1994年 | 281篇 |
1993年 | 214篇 |
1992年 | 201篇 |
1991年 | 112篇 |
1990年 | 89篇 |
1989年 | 84篇 |
1988年 | 65篇 |
1987年 | 45篇 |
1986年 | 31篇 |
1985年 | 17篇 |
1984年 | 18篇 |
1983年 | 15篇 |
1982年 | 13篇 |
1981年 | 10篇 |
1980年 | 12篇 |
1979年 | 4篇 |
1959年 | 6篇 |
1951年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 9 毫秒
1.
带关键字搜索的公钥加密(PEKS)是一种有用的加密原语,它允许用户将在加密数据上搜索的功能委托给不可信的第三方服务器,而不影响原始数据的安全性和隐私性。但是,由于缺乏对于数据的加密以及解密能力,PEKS方案不能单独进行使用,必须与标准的公钥加密方案(PKE)相结合。因此,Baek等人在2006年引入了一种新的加密原语,称为结合PKE和PEKS的加密方案(PKE+PEKS),它同时提供了PKE和PEKS的功能。目前,已有文献提出了几种PKE+PEKS方案。然而,他们都没有考虑关键字猜测攻击的问题。本文提出一个新的高效且能够抵抗关键字猜测攻击的PKE+PEKS方案,与已有方案相比,该方案在性能上有很大的提升,并且在生成关键字和数据密文时,不需要使用双线性对,极大地降低了计算和存储成本。安全性分析表明,本文中所提出的方案能够满足密文隐私安全性、陷门不可区分性和抗关键字猜测攻击的安全性。效率分析表明,本分提出的方案更加高效。 相似文献
2.
能源给人类带来光明,能源给社会进步提供了动力,尤其是进入21世纪以来,能源的可持续发展己成为直接影响世界经济社会可持续发展的决定性因素之一。中国政府高瞻远瞩地提出到2020年要实现国民经济翻两番和建设节约型社会的目标,描绘了支撑这一发展目标的十分宏伟的能源发展战略,使人振奋,也对我国钢铁产业的发展提出了更高的要求,作为长期以来与我国 相似文献
3.
4.
Mine K. Kubota N. Morimoto F. Sanada M. Zhang Qi 《Electromagnetic Compatibility, IEEE Transactions on》1994,36(3):253-255
This short paper discusses the method of effectively canceling equal status normal mode noise not only on a sensor line but also on a transmission line of an optical instrument using a sensor with a sensordummy resistance 相似文献
5.
提出了一种用于检测在役车辆车轴产生疲劳裂纹的超声波方法,设计了中心孔探头与斜角探头一起,完成了对车辆车轴的关键区域探伤。 相似文献
6.
A photochromic nanocomposite based on Keggin structure phosphomolybdic acid (PMoA) well dispersed in polyethyleneglycol (PEG) was fabricated. TEM image showed that PMoA nanoparticles with narrow size distribution were finely dispersed in polymer matrix. FT-IR results showed that the Keggin geometry of polyoxometalates was still preserved inside the composites and strong coulombic interaction was built between PMoA and polymer matrix. Under UV irradiation, the film was reduced photochemically to yield a blue species, which was in accordance with a charge-transfer mechanism. 相似文献
7.
Nanofiber bundles of Ag2S, Ag2Se, and Ag have been successfully synthesized by making use of Ag2C2O4 template nanofiber bundles, utilizing both anion‐exchange and redox reactions. The obtained bundles were polycrystalline nanofibers composed of nanoparticles in which the precursor morphology was well‐preserved, indicating that Ag2C2O4 nanofiber bundles acted as a general sacrificial template for the synthesis of silver‐based semiconductor and metal nanofibers. Dispersing media and transforming reactants were found to be key factors influencing the chemical transformation in the system. In particular, separate single‐crystalline Ag nanofibers were obtained via a nontemplate route when ascorbic acid was used as a relatively weak reductant. An electrical transfer and switching device was built with the obtained Ag2S and Ag nanofiber bundles, utilizing the unique ion‐conductor nature of Ag2S and revealing their potential applications in electronics. 相似文献
8.
9.
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
10.
We have fabricated and tested a high-Tc dc-SQUID magnetometer patterned on a YBCO thin film deposited on a SrTiO3 bicrystal substrate. The measurement of noise spectrum at 77 K showed that the magnetometer has a white noise of 333 fT/Hz1/2 without superconducting shield, corresponding to a flux sensitivity of 14.5 μΦ0/Hz1/2. We constructed a test system for eddy current non-destructive evaluation of conducting aluminum plates by using the magnetometer. Flaws over 10 mm below the surface can be clearly identified. By mapping the magnetic field distribution, we can locate the flaw position. The signals caused by flaw were expanded due to the use of double-D type driving coil with a wider central slit. The experimental results confirmed that this test system could operate in a magnetic unshielded environment. 相似文献