首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   828篇
  免费   68篇
  国内免费   9篇
电工技术   20篇
综合类   4篇
化学工业   240篇
金属工艺   26篇
机械仪表   39篇
建筑科学   40篇
矿业工程   3篇
能源动力   41篇
轻工业   53篇
水利工程   9篇
石油天然气   5篇
无线电   58篇
一般工业技术   138篇
冶金工业   33篇
原子能技术   12篇
自动化技术   184篇
  2024年   1篇
  2023年   14篇
  2022年   21篇
  2021年   48篇
  2020年   56篇
  2019年   54篇
  2018年   93篇
  2017年   57篇
  2016年   60篇
  2015年   42篇
  2014年   67篇
  2013年   87篇
  2012年   66篇
  2011年   72篇
  2010年   50篇
  2009年   31篇
  2008年   24篇
  2007年   10篇
  2006年   10篇
  2005年   7篇
  2004年   5篇
  2003年   4篇
  2002年   3篇
  2001年   2篇
  1999年   1篇
  1998年   5篇
  1997年   2篇
  1995年   2篇
  1994年   1篇
  1993年   1篇
  1991年   3篇
  1989年   1篇
  1987年   1篇
  1981年   2篇
  1977年   1篇
  1975年   1篇
排序方式: 共有905条查询结果,搜索用时 15 毫秒
1.
Thermal history and solute precipitation behavior of suspended solution droplets of sodium chloride (NaCl), magnesium sulphate (MgSO4), and zirconium hydroxychloride (ZrO(OH)Cl) evaporating at atmospheric and reduced pressures are studied. Experimental measurements on the variation of droplet diameter, solution concentration, and temperature during the evaporation period are presented and discussed. The results of solute precipitation behavior in solution droplets observed under an optical microscope are displayed and discussed. Results indicate that reducing the pressure (∼ 33 kPa) results in a change in the solution droplet evaporation rate, but the thermal histories of a particular solution droplet are similar at the atmospheric and reduced pressures. At atmospheric and reduced pressures used in this study, the d2 law for solution droplets is valid at early stages of the evaporation and before the solute precipitation initiates. Drying of MgSO4 and ZrO(OH)Cl solution droplets results in the formation of spherical particles, whereas drying of spherical NaCl solution droplets results in the formation of cubic particles.  相似文献   
2.
A new open-loop high-speed CMOS sample-and-hold is presented. Based on new method for further reduction of voltage-dependent charge injection, a new CMOS sample-and-hold was designed. Simulation results confirm the effectiveness of this method. Over 10 dB improvement in signal-to-noise ratio, compared to the signal-to-noise ratio of conventional bottom plate sampling S/Hs was achieved with this method. A comparison between newly designed S/H and the bottom-plate sampling S/H is presented.  相似文献   
3.
Reserve estimation is a key to find the correct NPV in a mining project. The most important factor in reserve estimation is the metal price. Metal price fluctuations in recent years were exaggerated, and imposed a high degree of uncertainty to the re-serve estimation, and in consequence to the whole mine planning procedure. Real option approach is an efficient method of deci-sion making in the uncertain conditions. This approach has been used for evaluation of defined natural resources projects until now. This study considering the metal price uncertainty used real option approach to prepare a methodology for reserve estimation in open pit mines. This study was done on a copper cylindrical deposit, but the achieved methodology can be adjusted for all kinds of deposits. This methodology was comprehensively described through the examples in such a manner that can be used by the mine planners.  相似文献   
4.
Intravascularultrasound (IVUS) sequences recorded in vivo are subject to a wide array of motion artifacts as the majority of these studies are performed within the coronary arteries of a beating heart. To eliminate these artifacts, an electrocardiogram (ECG) signal is typically used to gate (collect) those frames recorded at the points in time associated with a particular fraction of the cardiac cycle. However, this technique may be suboptimal for a number of reasons, among which is the difficulty of determining the optimal fraction at which to gate. This value is generally nonobvious. To circumvent this problem, we introduce a frame-gating method for IVUS pullbacks that mimics ECG (i.e., in the sense that it selects only one frame per cardiac cycle), but will automatically choose the fraction of the cycle that renders the most stable gated frame set. Stability here is gauged by measuring interframe similarity. Our method operates exclusively on the imagery data and does not require ECG or any form of image segmentation or other high-level image analysis. To validate our algorithm, we compare its behavior versus true ECG gating.  相似文献   
5.
6.
Wireless body area networks (WBANs) are a network designed to gather critical information about the physical conditions of patients and to exchange this information. WBANs are prone to attacks, more than other networks, because of their mobility and the public channel they use. Therefore, mutual authentication and privacy protection are critical for WBANs to prevent attackers from accessing confidential information of patients and executing undetectable physical attacks. In addition, in the authentication and key agreement process, messages should be transferred anonymously such that they are not linkable. In this paper, we first indicate that one of the most recently introduced authentication protocol is vulnerable to the wrong session key agreement attack and desynchronization attack. Second, we propose a lightweight authentication and key agreement protocol, which can withstand the well‐known attacks and provide the anonymity feature. Eventually, we analyze the security of our proposed protocol using both Automated Validation of Internet Security Protocols and Applications (AVISPA) and random oracle model and compare its performance with the related works. The results demonstrate the superiority of our proposed protocol in comparison with the other protocols.  相似文献   
7.
Reliability of the current microprocessor technology is seriously challenged by radiation-induced soft errors. Accurate Vulnerability Factor (VF) modeling of system components is crucial in designing cost-effective protection schemes in high-performance processors. Although Statistical Fault Injection (SFI) techniques can be used to provide relatively accurate VF estimations, they are often very time-consuming. Unlike SFI techniques, recently proposed analytical models can be used to compute VF in a timely fashion. However, VFs computed by such models are inaccurate as the system-level impact of soft errors is overlooked.  相似文献   
8.
9.
In this paper the neural networks is utilized to estimate the “filter coefficients” needed to estimate heat flux in a particular system. In developing the training phase of the network inspiration is drawn from the Burgraff's exact solution of the IHCP as well as the filter method. Thus, the estimation phase neither requires any temperature field nor the sensitivity coefficients calculations. The neural network used in this work is a 2-layer perceptron. It is shown via classical triangular heat flux test cases that the method can yield very accurate, very efficient as well as stable estimations.  相似文献   
10.
A standard method has been developed to bake barbari flat-type bread. Instron was used to measure the hardness of the crumb of bread samples as a criterion of staling. Different combinations of emulsifiers, sugar, shortening and soya flour were added to the formula of barbari bread to find their effect on the retardation of hardness. Addition of soya flour increased the loaf weight but decreased its total organoleptic score. Added amounts of different additives tried in this experiment improved the hardness approximately to the same level. The best result was obtained by the addition of sodium stearoyl-2-lactylate and shortening.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号