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   315篇
  免费   54篇
  国内免费   13篇
化学   98篇
力学   2篇
数学   44篇
物理学   238篇
  2024年   1篇
  2023年   10篇
  2022年   2篇
  2021年   4篇
  2020年   7篇
  2019年   7篇
  2018年   8篇
  2017年   17篇
  2016年   18篇
  2015年   15篇
  2014年   49篇
  2013年   22篇
  2012年   14篇
  2011年   18篇
  2010年   14篇
  2009年   23篇
  2008年   21篇
  2007年   29篇
  2006年   16篇
  2005年   19篇
  2004年   17篇
  2003年   6篇
  2002年   8篇
  2001年   5篇
  2000年   1篇
  1999年   6篇
  1998年   4篇
  1997年   8篇
  1996年   3篇
  1995年   1篇
  1994年   3篇
  1993年   2篇
  1991年   1篇
  1990年   1篇
  1988年   1篇
  1985年   1篇
排序方式: 共有382条查询结果,搜索用时 15 毫秒
21.
ICF靶用空心玻璃微球耐压性能测试   总被引:2,自引:1,他引:2       下载免费PDF全文
 利用自行研制的空心微球耐外压装置和充气装置,测试了目前激光惯性约束聚变实验打靶使用的空心玻璃微球耐内压能力和耐外压能力。空心玻璃微球采用液滴法制备,直径为180~250 mm、壁厚为0.8~4.0 mm。理论计算表明,当微球纵横比超过90时,耐外压能力与球壳材料的杨氏模量有关,由此测量得到的空心玻璃微球杨氏模量为55~75 GPa。玻璃微球的耐内压能力主要与球壳材料的抗拉强度有关,实验测量得到的玻璃微球抗拉强度为90~140 MPa。  相似文献   
22.
Target detection is one of the key technology of precision chemical application.Previously the digital coding modulation technique was commonly used to emit and receive the optical signal in the target detection systems previously in China.It was difficult to adjust the output power,and the anti-interference ability was weak in these systems.In order to resolve these problems,the target detection method based on analog sine-wave modulation was studied.The spectral detecting system was set up in the aspects ...  相似文献   
23.
After the financial tsunami in 2008, how to adjust the target inventory level dynamically and instantly in order to reduce the risk that an enterprise encountered in a rapid demand changing market has become a crucial issue in the field of supply chain management. This paper explores the strategies of supply chain collaboration by utilizing theory of constraint to achieve the goal of adjusting the target inventory level dynamically. Three time-series-data-mining techniques – Sequential Probability Ratio Test (SPRT), CUSUM chart and Auto-regression Test (AR(1)) are used to detect the timing of market demand change. The results are used to adjust the target inventory level. Simulation techniques are used to explore the relative efficiency of the demand-change detection for the three methods. The techniques are also used to explore the effectiveness of various inventory management strategies on inventory performance based on the three demand change detection methods.  相似文献   
24.
Transition of spiral wave in the regular networks of Hodgkin-Huxley (H-H) neurons is simulated and discussed in detail when the effect of membrane temperature and forcing current is considered. Neurons are distributed in the sites of two-dimensional array, neurons are connected with complete nearest-neighbor connections, no-flux boundary conditions, appropriate initial values and physiological parameters are used to develop a stable rotating spiral wave. A statistic factor of synchronization is defined to discuss the transition and development of spiral wave in the two parameters space (membrane temperature T and forcing current I), and it is found that spiral wave keeps alive due to positive current forcing and the spiral wave can be removed completely when the temperature is increased to a threshold about T = 22.3 °C at a fixed current intensity. Periodical forcing current is imposed on the networks of neurons globally and locally, respectively. It is found that spiral wave could be suppressed by the new generated traveling wave or target wave when periodical forcing current is imposed on the border of networks of neurons, and the most effective frequency of the external forcing current is close to the intrinsic frequency of the spiral wave of the networks.  相似文献   
25.
In this paper, we present experimental results of target current (TCS) and LEED investigation of well-oriented InSb(1 1 0) and InSb(1 1 1)-A and InSb(1 1 1)-B crystals. TCS results are interpreted in terms of very low electron diffraction (VLEED) and empty band signatures. To examine to which extent the TCS spectra reflect the bulk or surface electronic properties of InSb(1 1 0), thin layers of indium have been evaporated and the corresponding spectrum changes have been investigated.  相似文献   
26.
Due to the complexity of the scene, target detection in forward-looking infrared (FLIR) imagery is a challenging problem, especially for occluded target. The main contribution of this paper is to propose an indirect detection method for improving the recognition probability and effectiveness of target detection method in FLIR image sequences under complex conditions. The proposed method mainly includes four steps: preparation of forward-looking reference image of landmark, extraction of the real-time scene image, template matching and target location, in which some key technologies are proposed, such as perspective transformation used to solve projective problems, position prediction for improving real-time performance, and target location used for identifying the target’s position. Experimental results are shown to demonstrate the robustness and efficiency of proposed method in FLIR image sequences.  相似文献   
27.
§1. DiscreteWaveletTransformationThemultiresolutionalanaysisthoughtisthatwedecomposethesignalwhichisdeakedtodifferentresolutionlevelusingwavelettransformation,thelowerresolutionsignaldecomposedinsmothingsignal,thesignalthatexistinhigherresolutionleve…  相似文献   
28.
Moving Target Defense (MTD) prevents adversaries from being able to predict the effect of their attacks by adding uncertainty in the state of a system during runtime. In this paper, we present an MTD algorithm that randomly changes the availability of the sensor data, so that it is difficult for adversaries to tailor stealthy attacks while, at the same time, minimizing the impact of false-data injection attacks. Using tools from the design of state estimators, namely, observers, and switched systems, we formulate an optimization problem to find the probability of the switching signals that increase the visibility of stealthy attacks while decreasing the deviation caused by false data injection attacks. We show that the proposed MTD algorithm can be designed to guarantee the stability of the closed-loop system with desired performance. In addition, we formulate an optimization problem for the design of the parameters so as to minimize the impact of the attacks. The results are illustrated in two case studies, one about a generic linear time-invariant system and another about a vehicular platooning problem.  相似文献   
29.
化学遗传学是20世纪90年代开始兴起的交叉学科,是利用生物活性小分子与蛋白相互作用研究生物学系统功能的一种方法,是经典遗传学的补充。化学遗传学的历史可以追溯到几百年前。在现代药物靶标的发现上,化学遗传学起着非常重要的作用。  相似文献   
30.
We describe here an analytical method of A431 cell membrane chromatography (A431/CMC) (CMC, cell membrane chromatography) combined with RPLC for recognition, separation, and identification of target components from traditional Chinese medicines (TCMs) Radix Caulophylli. The A431 cells with high expressed epidermal growth factor receptor (EGFR) were used to prepare the stationary phase in the CMC model. Retention fractions on the A431-CMC model were collected using an automated fraction collection and injection module (FC/I). Each fraction was analyzed by RPLC under the optimized conditions. Gefitinib and erlotinib were used as standard compounds to investigate the suitability and reliability of the A431 cell membrane chromatography-RPLC method prior to screening target component from Radix Caulophylli total alkaloids. The results indicated that caulophine and taspine were the target component acting on the epidermal growth factor receptor. This method could be an efficient way in drug discovery using natural medicinal herbs as a source of novel compounds.  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