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   489篇
  免费   33篇
  国内免费   2篇
电工技术   7篇
化学工业   111篇
金属工艺   11篇
机械仪表   36篇
建筑科学   23篇
能源动力   35篇
轻工业   49篇
水利工程   9篇
石油天然气   7篇
无线电   41篇
一般工业技术   95篇
冶金工业   9篇
自动化技术   91篇
  2024年   1篇
  2023年   5篇
  2022年   17篇
  2021年   37篇
  2020年   34篇
  2019年   42篇
  2018年   36篇
  2017年   35篇
  2016年   30篇
  2015年   25篇
  2014年   38篇
  2013年   62篇
  2012年   31篇
  2011年   30篇
  2010年   28篇
  2009年   20篇
  2008年   11篇
  2007年   6篇
  2006年   6篇
  2005年   4篇
  2004年   4篇
  2003年   6篇
  2002年   4篇
  1998年   5篇
  1997年   1篇
  1996年   1篇
  1995年   1篇
  1985年   2篇
  1982年   1篇
  1979年   1篇
排序方式: 共有524条查询结果,搜索用时 93 毫秒
41.

We theoretically analyze the detection of a cancer cell in the one-dimensional photonic crystal by infiltrating different sample cells in the cavity layer. The defect modes appear in their transmission spectra only if the nanocomposite layers are included on either side of the cavity layer. This analysis is carried out by a dielectric constant and the transmittance peak of the cancer cell is compared with the normal cell. The transmittance peak shifts are analyzed with various filling factors for optimization purposes. Through the shifting spectrum, the sensitivity of cancer cell from the normal cell is obtained from a minimum of 42 nm/RIU to a maximum of 43 nm/RIU.

  相似文献   
42.
The bootstrap method is a computer intensive statistical method that is widely used in performing nonparametric inference. Categorical data analysis, in particular the analysis of contingency tables, is commonly used in applied field. This work considers nonparametric bootstrap tests for the analysis of contingency tables. There are only a few research papers which exploit this field. The p-values of tests in contingency tables are discrete and should be uniformly distributed under the null hypothesis. The results of this article show that corresponding bootstrap versions work better than the standard tests. Properties of the proposed tests are illustrated and discussed using Monte Carlo simulations. This article concludes with an analytical example that examines the performance of the proposed tests and the confidence interval of the association coefficient.  相似文献   
43.
A miniaturized inset‐fed on‐body meandered bowtie antenna designed for brain microwave imaging systems is presented in this article. The proposed on‐body antenna can contribute to the realization of a wearable and portable brain microwave imaging system. The size of 18 × 18 mm2 is achieved at a frequency range of 0.75 to 4 GHz by the simultaneous use of self‐complementary structures and meandered lines. The frequency band is a trade‐off between penetration depth and spatial resolution. The proposed antenna performance was studied at different positions on the human head voxel model in terms of several parameters such as reflection coefficient, near‐field directivity, and fidelity factor. In addition, the antenna bandwidth was surveyed on several volunteers using a wearable measurement setup. It has been found that the averages of measured reflection coefficients in different scenarios are in good agreement with the corresponding simulation results, and the antenna shows stable performance under different practical situations. The proposed antenna takes advantage of a small footprint and body matching, which make it an eligible choice for compact, portable, and wearable head microwave imaging systems.  相似文献   
44.
The Persian language is one of the dominant languages in the Middle East, so there are significant amount of Persian documents available on the Web. Due to the different nature of the Persian language compared to the other languages such as English, the design of information retrieval systems in Persian requires special considerations. However, there are relatively few studies on retrieval of Persian documents in the literature and one of the main reasons is the lack of a standard test collection. In this paper, we introduce a standard Persian text collection, named Hamshahri, which is built from a large number of newspaper articles according to TREC specifications. Furthermore, statistical information about documents, queries and their relevance judgments are presented in this paper. We believe that this collection is the largest Persian text collection, so far.  相似文献   
45.
In this paper, a new procedure is developed to monitor a two-stage process with a second stage Poisson quality characteristic. In the proposed method, log and square root link functions are first combined to introduce a new link function that establishes a relationship between the Poisson variable of the second stage and the quality characteristic of the first stage. Then, the standardized residual statistic, which is independent of the quality characteristic in the previous stage and follows approximately standardized normal distribution, is computed based on the proposed link function. Then, Shewhart and exponentially weighted moving average (EWMA) cause-selecting charts are utilized to monitor standardized residuals. Finally, two examples and a case study with a Poisson response variable are investigated, and the performance of the charts is evaluated by using average run length (ARL) criterion in comparison with the best literature method.  相似文献   
46.
In problem of portfolio selection, financial Decision Makers (DMs) explain objectives and investment purposes in the frame of multi-objective mathematic problems which are more consistent with decision making realities. At present, various methods have introduced to optimize such problems. One of the optimization methods is the Compromise Programming (CP) method. Considering increasing importance of investment in financial portfolios, we propose a new method, called Nadir Compromising Programming (NCP) by expanding a CP-based method for optimization of multi-objective problems. In order to illustrate NCP performance and operational capability, we implement a case study by selecting a portfolio with 35 stock indices of Iran stock market. Results of comparing the CP method and proposed method under the same conditions indicate that NCP method results are more consistent with DM purposes.  相似文献   
47.
48.
The Journal of Supercomputing - In this paper, physical layer impairment (PLI)-aware shared path protection (SPP) scheme for single-link failures in transparent optical WDM mesh networks is...  相似文献   
49.
Aït-Mokhtar  A.  Amiri  O.  Dumargue  P.  Bouguerra  A. 《Materials and Structures》2004,37(2):107-113
Materials and Structures - This paper deals with flow properties of mercury (Mercury Intrusion Porosimetry, MIP) and water (permeability measurements and capillarity) in building materials. The aim...  相似文献   
50.
This paper addresses the experimental and numerical investigations of the dynamic parameters, natural frequencies and mode shapes, of fixed roof, ground supported, steel storage tanks. Three tall liquid storage tanks with aspect ratios greater than unity are considered. The considered tanks have similar height of 12.190 m and different radius of 6.095, 8.00, and 9.144 m. The effect of the aspect ratio, along with the liquid level on dynamic parameters is discussed. Finite element models of tanks are constructed using the finite element package ANSYS. The fluid-structure interaction is governed in the models. Yet, before using numerical techniques for analyzing the tank-liquid systems, they should be validated by experimental results. For this purpose, a series of ambient vibration tests are carried out to determine the natural frequencies and, if possible, the modes of the vibration. Comparison between numerical and experimental values shows good agreement. The new feature considered in the paper is the influence of roof on the natural frequencies and the modes of vibration. It is found that the influence of roof on the natural frequency of vibration of the considered tanks is negligible, while it does restrain the tank top against radial deformations and has significant effect on the mode shapes of tank.  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