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   2640篇
  免费   131篇
  国内免费   3篇
电工技术   32篇
综合类   8篇
化学工业   652篇
金属工艺   46篇
机械仪表   28篇
建筑科学   174篇
矿业工程   6篇
能源动力   74篇
轻工业   220篇
水利工程   20篇
石油天然气   5篇
无线电   257篇
一般工业技术   531篇
冶金工业   271篇
原子能技术   17篇
自动化技术   433篇
  2023年   42篇
  2022年   51篇
  2021年   109篇
  2020年   55篇
  2019年   63篇
  2018年   60篇
  2017年   64篇
  2016年   92篇
  2015年   69篇
  2014年   122篇
  2013年   142篇
  2012年   156篇
  2011年   197篇
  2010年   118篇
  2009年   119篇
  2008年   135篇
  2007年   125篇
  2006年   118篇
  2005年   109篇
  2004年   84篇
  2003年   62篇
  2002年   58篇
  2001年   31篇
  2000年   47篇
  1999年   48篇
  1998年   75篇
  1997年   48篇
  1996年   53篇
  1995年   37篇
  1994年   35篇
  1993年   23篇
  1992年   13篇
  1991年   21篇
  1990年   12篇
  1989年   17篇
  1988年   10篇
  1987年   10篇
  1986年   9篇
  1985年   11篇
  1984年   11篇
  1983年   12篇
  1982年   11篇
  1981年   11篇
  1980年   6篇
  1979年   9篇
  1978年   12篇
  1977年   5篇
  1976年   11篇
  1973年   5篇
  1916年   4篇
排序方式: 共有2774条查询结果,搜索用时 0 毫秒
31.

In recent years, we face an increasing interest in protecting multimedia data and copyrights due to the high exchange of information. Attackers are trying to get confidential information from various sources, which brings the importance of securing the data. Many researchers implemented techniques to hide secret information to maintain the integrity and privacy of data. In order to protect confidential data, histogram-based reversible data hiding with other cryptographic algorithms are widely used. Therefore, in the proposed work, a robust method for securing digital video is suggested. We implemented histogram bit shifting based reversible data hiding by embedding the encrypted watermark in featured video frames. Histogram bit shifting is used for hiding highly secured watermarks so that security for the watermark symbol is also being achieved. The novelty of the work is that only based on the quality threshold a few unique frames are selected, which holds the encrypted watermark symbol. The optimal value for this threshold is obtained using the Firefly Algorithm. The proposed method is capable of hiding high-capacity data in the video signal. The experimental result shows the higher capacity and video quality compared to other reversible data hiding techniques. The recovered watermark provides better identity identification against various attacks. A high value of PSNR and a low value of BER and MSE is reported from the results.

  相似文献   
32.
33.
Simultaneous detection and confirmation of several N-nitrosodialkylamines are accomplished by on-line coupling of a photolysis reactor with an HPLC-electrospray ionization mass spectrometer. Several parameters such as irradiation wavelength, irradiation time, mobile-phase composition, and pH, as well as different organic acid modifiers are investigated, and their impact on the detection of the N-nitrosodialkylamine-acid complex and its dissociative photolysis products is presented here. Additionally, the type of structural information obtained from the photolytic processes of N-nitrosodialkylamines is compared to that obtained by using in-source collision-induced dissociation. To demonstrate the potential of this technique, six N-nitrosodialkylamines are studied to determine the linearity of the response, the limits of detection and confirmation, and the reproducibility. The technique's versatility is also exhibited by utilizing negative-ion mode as a complementary means for analysis of the compounds. Finally, an illustrative application for N-nitrosodimethylamine analysis in beer is described.  相似文献   
34.
35.
This study explores how distributing the controls of a video game among multiple players affects the sociality and engagement experienced in game play. A video game was developed in which the distribution of game controls among the players could be varied, thereby affecting the abilities of the individual players to control the game. An experiment was set up in which eight groups of three players were asked to play the video game while the distribution of the game controls was increased in three steps. After each playing session, the players’ experiences of sociality and engagement were assessed using questionnaires. The results showed that distributing game control among the players increased the level of experienced sociality and reduced the level of experienced control. The game in which the controls were partly distributed led to the highest levels of experienced engagement, because the game allowed social play while still giving the players a sense of autonomy. The implications for interaction design are discussed.  相似文献   
36.
Service orientation has been a major buzz-word in recent years. While the buzz is on a decline, organizations are slowly, but steadily moving towards service oriented designs. However, service orientation turns out to be as much of a managerial challenge as of a technical one. The most important complexity drivers in the service oriented design of information systems seem to be (a) inconsistent design goals of stakeholders and (b) the pursuit of exhaustive service orientation coverage. This research focuses on the following two questions: (1) What are the characteristics of successful implementations of service oriented information systems, and (2) what are the critical success factors influencing, driving and/or determining these characteristics? Data of an empirical analysis is used to test a set of cause-effect relationship hypotheses based on nine latent variables. In the core of this model we differentiate the variables ??overall service orientation infrastructure success?? and ??service orientation project success??. The hypothesized interrelationships between the nine variables lead to a causal model which is proven to hold.  相似文献   
37.
A Lie-algebra based recipe for smoothing gauge links in lattice field theory is presented, building on the matrix logarithm. With or without hypercubic nesting, this LOG/HYL smearing yields fat links which are differentiable with respect to the original ones. This is essential for defining UV-filtered (“fat link”) fermion actions which may be simulated with a HMC-type algorithm. The effect of this smearing on the distribution of plaquettes and on the residual mass of tree-level O(a)-improved clover fermions in quenched QCD is studied.  相似文献   
38.
The current paper focuses on several mechanical aspects of a waferlevel packaging approach using a direct face-to-face Chip-to-Wafer (C2W) bonding of a MEMS device on an ASIC substrate wafer. Requirements of minimized inherent stress from packaging and good decoupling from forces applied in manufacturing and application are discussed with particular attention to the presence of through-silicon vias (TSV) in the substrate wafer. The paper deals with FEM analysis of temperature excursion, pressure during molding, materials used and handling load influence on mechanical stress within the TSV system and on wafer level, which can be large enough to disintegrate the system.  相似文献   
39.
Wool handling is an important rural occupation where workers process 200 or more fleeces daily, separating them into various quality components. Loads and postures they experience carry substantial risk of low back pain (LBP). Although a formal skill training structure exists, interaction with loads and LBP is unknown. We examined whether skill and LBP influenced trunk postures and loads of 60 wool handlers representing 3 skill levels. LBP prevalence ranged from 20% for junior (lowest skill) to 45% for open class (highest skill) wool handlers. Open class wool handlers demonstrated increased lateral bend and more axially twisted postures, generating greater medio-lateral shear forces and lateral bend and axial twist moments. LBP was associated with open class wool handlers spending more time in severe axially twisted postures. These findings suggest that skill-based training needs to be reviewed to reduce the quantity of axially twisted posture which may help reduce the prevalence of LBP in this workforce.  相似文献   
40.
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