全文获取类型
收费全文 | 45471篇 |
免费 | 5816篇 |
国内免费 | 2484篇 |
专业分类
电工技术 | 11923篇 |
技术理论 | 1篇 |
综合类 | 4680篇 |
化学工业 | 2938篇 |
金属工艺 | 1020篇 |
机械仪表 | 2326篇 |
建筑科学 | 8588篇 |
矿业工程 | 910篇 |
能源动力 | 1237篇 |
轻工业 | 1403篇 |
水利工程 | 669篇 |
石油天然气 | 1011篇 |
武器工业 | 377篇 |
无线电 | 5722篇 |
一般工业技术 | 3028篇 |
冶金工业 | 2579篇 |
原子能技术 | 216篇 |
自动化技术 | 5143篇 |
出版年
2024年 | 111篇 |
2023年 | 710篇 |
2022年 | 1130篇 |
2021年 | 1417篇 |
2020年 | 1572篇 |
2019年 | 1255篇 |
2018年 | 1161篇 |
2017年 | 1577篇 |
2016年 | 1759篇 |
2015年 | 1959篇 |
2014年 | 3481篇 |
2013年 | 2605篇 |
2012年 | 3675篇 |
2011年 | 3868篇 |
2010年 | 3078篇 |
2009年 | 3131篇 |
2008年 | 2965篇 |
2007年 | 3523篇 |
2006年 | 2982篇 |
2005年 | 2280篇 |
2004年 | 1834篇 |
2003年 | 1585篇 |
2002年 | 1253篇 |
2001年 | 1057篇 |
2000年 | 917篇 |
1999年 | 655篇 |
1998年 | 488篇 |
1997年 | 365篇 |
1996年 | 305篇 |
1995年 | 254篇 |
1994年 | 226篇 |
1993年 | 150篇 |
1992年 | 136篇 |
1991年 | 55篇 |
1990年 | 62篇 |
1989年 | 42篇 |
1988年 | 29篇 |
1987年 | 28篇 |
1986年 | 8篇 |
1985年 | 18篇 |
1984年 | 10篇 |
1983年 | 14篇 |
1982年 | 15篇 |
1980年 | 8篇 |
1979年 | 4篇 |
1978年 | 2篇 |
1974年 | 3篇 |
1959年 | 2篇 |
1956年 | 2篇 |
1951年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 18 毫秒
41.
42.
Ilya Tkachenko Sergey N. Tkachenko Ekaterina S. Lokteva Nadezhda A. Mamleeva Valery V. Lunin 《臭氧:科学与工程》2020,42(4):357-370
ABSTRACT The aim of the research is to choose the most efficient adsorbent for two-stage ozone-sorption purification of groundwater containing both trichloroethylene (TCE) and tetrachloroethylene (PCE) between three carbon sorbents produced in Russia (AUT-M, CAUSORB-221, and AG-3). Sorption isotherms of TCE and PCE on AUT-M and CAUSORB-221 at 296 K were fitted by the Freundlich equation. The better TCE and PCE sorption ability of AUT-M in comparison with CAUSORB – 221 and AG-3 was demonstrated. The optimum parameters for ozonation and sorption stages of groundwater purification from TCE and PCE are elucidated using laboratory and pilot-plant scales. Prolonged test of this technology for purification of ground demonstrated that the higher achievable efficiency of destruction with ozone is 94% for TCE and 38% for PCE. Ozonation-sorption treatment of groundwater allows one to achieve TCE and PCE removal efficiency of 96-97% and 92-94% correspondingly. The most efficient carbon sorbent is microporous carbon fiber AUT-M. Using this sorbent, TCE and PCE concentrations in treated water decrease below the MPC level (5 μg/L) adopted in Russia. It is concluded that the combination of ozonation with sorption of residual contaminants by carbon sorbents is a promising way for the purification of waters containing chlorinated contaminants. 相似文献
43.
富锌涂料在防腐蚀领域具有广泛应用,然而其长效防护性能却受到锌粉活性影响。本文以冷涂锌涂层、传统环氧富锌涂层作为对照,研究了新型具有电化学活性的环氧富锌涂层在盐雾加速腐蚀试验后的耐腐蚀性。宏观形貌分析表明:盐雾加速腐蚀 1 800 h后,活化环氧富锌涂层表面并未出现锈点;采用扫描电子显微镜、维体式显微镜观察试验后涂层的表面形貌和涂层结构,发现活化环氧富锌涂层微观表面更加平滑,锌粉并未出现大面积的氧化,涂层内部大小锌粉颗粒均匀排列;通过电化学方法研究涂层的耐蚀机理与防护性,发现活化富锌涂层具有更持久的低防护电位。以上研究结果表明,较冷涂锌及传统环氧富锌涂层而言,新型活化环氧富锌涂层具有优异的长期防护性能,是值得关注和研究的一种新型技术。 相似文献
44.
Alessandro Brumana Luigi Piroddi 《International Journal of Adaptive Control and Signal Processing》2020,34(7):877-900
The problem of real-time frequency estimation of nonstationary multi-harmonic signals is important in many applications. In this paper, we propose a novel multi-frequency tracker based on a state-space representation of the signal with Cartesian filters and the second-order central divided difference filter (CDDF), which improves the performance of the extended Kalman filter (EKF) by using Stirling's interpolation method to approximate the mean and covariance of the state vector. A crucial element of the method is the adaptive scaling of the process noise covariance matrix appearing in the filter equations, as a function of the innovation sequence, which tunes the accuracy-reactivity trade-off of the filter. The proposed solution is evaluated against two approaches from the literature, namely the factorized adaptive notch filter (FANF) and the extended Kalman filter frequency tracker (EKFFT). Several experiments emphasize the estimation accuracy of the proposed method as well as the improved robustness with respect to initial errors and input signal complexity. The presented method appears to be particularly efficient with rapidly varying frequencies, thanks to the update mechanism that adjusts the filter parameters based on the amplitude of the estimation error. 相似文献
45.
46.
This paper proposes a new methodology for designing robust affine state-feedback control laws, so that wide-range safe and efficient operation of switched-mode DC–DC boost converters is guaranteed. Several undesirable nonlinear phenomena such as unstable attractors and subharmonic oscillations are avoided through bifurcation analysis based on the bilinear averaged model of the converter. The control design procedure also relies on constrained stabilization principles and the generation of safety domains using piecewise linear Lyapunov functions, so that robustness to supply voltage and output load variations is ensured, while input saturation is avoided and additional state constraints are also respected. The technique has been numerically and experimentally validated. 相似文献
47.
48.
A resilient buffer allocation scheme in active queue management: a stochastic cooperative game theoretic approach 下载免费PDF全文
During the last decade, a plentiful number of active queue management schemes have been proposed, but their main objectives are simply allocating the buffer resource to all flows evenly, or protecting responsive flows from being degraded by unresponsive flows. However, the sending rates of the responsive flows can be determined diversely, and not all unresponsive flows have aggressively high sending rates. Furthermore, it is rational to reserve a portion of the buffer resource for certain privileged traffic. Grounded by these evidences, in this paper, we present a resilient active queue management algorithm, named Prior‐Core‐based Buffer Allocation considering diverse congestion control algorithms, fair‐unresponsive flows, and some privileged traffic. Our approach is based on stochastic cooperative game theory, where the payoffs yielded by cooperation are described by random variables, and the core is defined only over the distribution of these random payoffs; the core in this situation is called the prior‐core. As a result, it is shown that our buffer allocation, yielded by the prior‐core, achieves completely fair allocation for those flows whose requirement does not exceed the fair‐share regardless of the responsiveness, whereas aggressive flows are restricted according to availability of the buffer; all these are verified through ns‐2 simulation experiments. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
49.
Optimal Pricing Algorithm in the Electricity Market with Battery and Accumulator and Demand–Supply Balancing 下载免费PDF全文
This paper considers the day‐ahead market with batteries and accumulators to level power generation. First, we model consumers with batteries, generators with batteries, and accumulators, all of whom strive to maximize their own profit. An optimal pricing algorithm based on dual decomposition and the steepest descent method is derived and shown to be stable. Finally, the effectiveness of the algorithm is demonstrated by means of numerical simulations which indicate that it achieves demand–supply balance. 相似文献
50.
以感应电能传输(IPT)谐振变换器为研究对象,研究了谐振变换器的ZVS同步整流(SR)技术。分析了基于SR技术IPT谐振变换器的工作原理,利用系统的谐振工作特性,提出了一种新颖的ZVS软开关SR实现方法。建立了系统频闪映射稳态数学模型,给出了ZVS软开关SR的周期不动点函数、数值求解状态变量及ZVS软开关SR工作周期的算法流程。在设计控制电路的基础上,通过实验验证了提出的同步整流技术的可行性。 相似文献