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   32571篇
  免费   2491篇
  国内免费   1307篇
电工技术   1738篇
技术理论   1篇
综合类   1980篇
化学工业   5640篇
金属工艺   1641篇
机械仪表   2135篇
建筑科学   2569篇
矿业工程   1024篇
能源动力   836篇
轻工业   2000篇
水利工程   562篇
石油天然气   2105篇
武器工业   214篇
无线电   3803篇
一般工业技术   3960篇
冶金工业   1612篇
原子能技术   385篇
自动化技术   4164篇
  2024年   176篇
  2023年   589篇
  2022年   897篇
  2021年   1285篇
  2020年   944篇
  2019年   845篇
  2018年   935篇
  2017年   997篇
  2016年   877篇
  2015年   1162篇
  2014年   1550篇
  2013年   1829篇
  2012年   1963篇
  2011年   2063篇
  2010年   1807篇
  2009年   1777篇
  2008年   1629篇
  2007年   1650篇
  2006年   1787篇
  2005年   1602篇
  2004年   1027篇
  2003年   940篇
  2002年   897篇
  2001年   783篇
  2000年   898篇
  1999年   958篇
  1998年   792篇
  1997年   699篇
  1996年   673篇
  1995年   539篇
  1994年   449篇
  1993年   332篇
  1992年   262篇
  1991年   202篇
  1990年   151篇
  1989年   117篇
  1988年   96篇
  1987年   50篇
  1986年   35篇
  1985年   28篇
  1984年   17篇
  1983年   17篇
  1982年   22篇
  1981年   13篇
  1980年   3篇
  1979年   2篇
  1959年   3篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
In order to improve decision-making efficiency about emergency event, this paper proposes a novel concept, i.e., Agile-Delphi Method, which is an integration of agile decision and Delphi Method implicating that the decision-makers instantly deliver, respond, treat, and utilize information via Delphi process while conducting group decision-making about emergency event. The paper details the mechanism of group decision-making about emergency event based on network technology and Agile-Delphi Method. Finally, the paper conducts an empiric analysis taking the “111 event”, i.e., the liquid ammonia spill event happened on November 1, 2006 in a phosphorus chemical company in China, as an example.  相似文献   
82.
Surgery to reshape the nose with an implant has been a regular procedure for enhancing a patient’s appearance and self-confidence. The purpose of this study was to establish a computed tomography (CT) based three-dimensional assistant plastic surgery systems, which can provide the patients with realistic prediction of their own postoperative appearance in computer and specifically produce a nose implant for an individual patient. Preoperative CT data and 3D reconstruction techniques were employed to generate 3D model of the patient’s skull. 3D collision detection and finite elements model deformation were then applied to simulate nose augmentation surgery and predict postoperative appearance. According to the patient’s expectation, digital models of the nose implants were constantly modified. When the patient is satisfied with the simulated results, custom made silicone implants were produced by a computer controlled device. Accurately regeneration of 3D images and realistic operative simulations could be achieved with this system. The implants produced exactly conformed to the results of simulation. No curving and reshaping were needed during operating. The clinical results extremely matched with the simulations. The system enhances surgeon patient communication and facilitates preoperative planning. It is especially desirable for implant surgery with less guesswork of size, contour, and orientation of the implant. The best chance of optimal results could be achieved.  相似文献   
83.
基于粒子系统和音频系统的烟花模拟   总被引:2,自引:1,他引:1  
针对模糊物体的模拟方法存在着粒子数量绘制巨大、粒子运动状态复杂、计算耗时、实时性及逼真性不够等问题,提出了一种基于粒子系统和音频系统的烟花模拟方法,以三角形格作为绘制烟花粒子的基本图元,结合纹理映射,色彩融合技术来绘制烟花粒子,在显示列表中生成纹理,再结合FMOD引擎技术,加入音频系统,实验结果表明提出的方法增强了模拟的逼真性.  相似文献   
84.
85.
The successful launch of the Landsat 8 satellite continues the Earth observation of the Landsat series, which has been taking place for nearly 40 years. With the increase in the band number and the improved spectral range compared with the previous Landsat imagery, it will be possible to expand the application of the new Landsat 8 imagery. The purpose of this study is to explore water extraction based on the new Landsat 8 Operational Land Imager (OLI) imagery. According to the specific inland water conditions (clear water, turbid water, and eutrophic water), a number of highly adaptable water indices are assessed for water extraction using Landsat OLI imagery. The results show that clear water is the easiest to extract among the different types of waterbodies, with the highest average accuracy of 97%. The highest-accuracy methods are the automated water extraction index for shadow pixels (AWEIsh), the normalized difference water index using bands 4 and 7 (NDWI47), and the normalized difference water index using bands 3 and 7 (NDWI37), with accuracies of 98.55%, 95.50%, and 96.61%, corresponding to clear water, turbid water, and eutrophic water, respectively. Through the analysis of the different methods for optimal band selection, the seventh band OLI7 (shortwave infrared 2, SWIR-2) of Landsat OLI shows the best performance in water identification. When applying the water indices to water extraction, Otsu’s algorithm has been used to automatically select the water threshold. Using extensive experiments with Otsu’s algorithm and a manual method, it was found that Otsu’s algorithm can replace manual selection and has the ability to select an accurate threshold for water extraction.  相似文献   
86.
Physical activity monitoring for youth is an area of increasing scientific and public health interest due to the high prevalence of obesity and downward trend in physical activity. However, accurate assessment of such activity remains a challenging problem because of the complex nature in which certain activities are performed. In this study, we formulated the issue as a machine learning problem—using a diverse set of 19 physical activities commonly performed by youth—via two approaches: activity recognition and intensity estimation. With the aid of training data, we implemented a distance metric learning method called DML-KNN that utilizes time-frequency features and is capable of effectively classifying both continuous and intermittent movement in youth subjects. Four different time-frequency feature extraction methods were then systematically evaluated. Our results show that the DML-KNN method performed competitively, especially when using features extracted by the Tamura method for intensity estimation, and by the Square Coefficient method for activity recognition.  相似文献   
87.
The surface tension of the Ni3S2-FeS-Cu2S ternary mattes have been calculated from those of the Ni3S2-FeS·FeS-Cu2S and Cu2S-Ni3S2 pseudo-binary boundary systems by using geometric models (Kohler and Toop model) and a general solution model (Chou model). Taking account of the experimental accuracy of ±2.5%, the respective calculated results are in agreement with the experimental data. At the same time, surface tensions of molten Ni3S2-FeS-Cu2S mattes and their pseudo-binary boundary systems are predicted based on Butler's original treatment with great attention to the model parameter β. The predicted results also agree with the experimental data. Therefore, the resulting iso-surface tension curves in molten Ni3S2-FeS-Cu2S mattes at 1473K, especially calculated by using Kohler, Toop and Chou models, are generally acceptable.  相似文献   
88.
基于双链式存储的可靠通信网合并   总被引:2,自引:0,他引:2  
本文介绍图的双链式存储结构在可靠通讯网合并算法中的应用.  相似文献   
89.
本文从建筑结构中构件裂缝的概念和表征出发,面向图形对象建立裂缝仿真模型,并 从计算机图形学的角度,运用粘贴技术来处理裂缝图形。为了使裂缝更逼真,在知识 推理的基础上,本文运用了随机处理技术。  相似文献   
90.
More and more universities and colleges are providing online courses not only for on-campus students but also for off-campus students. Tutors have to consider the differences between on- and off-campus students in order to improve effective instruction. Comparisons are made in this paper between on- and off-campus performances in online learning from four areas: learning time, path of browsing courseware, intercommunication and adaptability towards online learning. The last two areas are emphasized. Multiple approaches were adopted to collect data, which include questionnaires, posted documents, online logs, interviews and observations. This study shows that the rush time of online learning, paths of browsing courseware and favourite intercommunication means of on- and off-campus students are similar. But there are also some differences between these two groups such as competence of self-learning, enthusiasm of interpersonal exchange, dependence on tutors, feeling of learning stress, etc.  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