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   95500篇
  免费   9393篇
  国内免费   5886篇
电工技术   7632篇
技术理论   5篇
综合类   8074篇
化学工业   13633篇
金属工艺   5514篇
机械仪表   6611篇
建筑科学   8317篇
矿业工程   2724篇
能源动力   2832篇
轻工业   7776篇
水利工程   2311篇
石油天然气   4301篇
武器工业   1086篇
无线电   10958篇
一般工业技术   9905篇
冶金工业   3941篇
原子能技术   1200篇
自动化技术   13959篇
  2024年   431篇
  2023年   1398篇
  2022年   2725篇
  2021年   3568篇
  2020年   2810篇
  2019年   2223篇
  2018年   2545篇
  2017年   2903篇
  2016年   2649篇
  2015年   3783篇
  2014年   4895篇
  2013年   5561篇
  2012年   6576篇
  2011年   6836篇
  2010年   6368篇
  2009年   6234篇
  2008年   6412篇
  2007年   5892篇
  2006年   5829篇
  2005年   4868篇
  2004年   3754篇
  2003年   3554篇
  2002年   4222篇
  2001年   3562篇
  2000年   2473篇
  1999年   1908篇
  1998年   1261篇
  1997年   1075篇
  1996年   928篇
  1995年   821篇
  1994年   644篇
  1993年   446篇
  1992年   367篇
  1991年   300篇
  1990年   221篇
  1989年   196篇
  1988年   134篇
  1987年   83篇
  1986年   81篇
  1985年   51篇
  1984年   30篇
  1983年   10篇
  1982年   26篇
  1981年   30篇
  1980年   23篇
  1979年   19篇
  1978年   5篇
  1976年   4篇
  1959年   17篇
  1951年   16篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
Over the past few years, large human populations around the world have been affected by an increase in significant seismic activities. For both conducting basic scientific research and for setting critical government policies, it is crucial to be able to explore and understand seismic and geographical information obtained through all scientific instruments. In this work, we present a visual analytics system that enables explorative visualization of seismic data together with satellite-based observational data, and introduce a suite of visual analytical tools. Seismic and satellite data are integrated temporally and spatially. Users can select temporal ;and spatial ranges to zoom in on specific seismic events, as well as to inspect changes both during and after the events. Tools for designing high dimensional transfer functions have been developed to enable efficient and intuitive comprehension of the multi-modal data. Spread-sheet style comparisons are used for data drill-down as well as presentation. Comparisons between distinct seismic events are also provided for characterizing event-wise differences. Our system has been designed for scalability in terms of data size, complexity (i.e. number of modalities), and varying form factors of display environments.  相似文献   
102.
103.
A superhydrophobic micromesh covered with nanoprotrusions has been introduced and its applicability to a waterproof mobile phone speaker has been evaluated. The nanotextured superhydrophobic micromesh showed excellent water repellency, self-cleaning and waterproofing performances. In a waterproof speaker test using the fabricated nanotextured micromesh, the micromesh did not lose its waterproof function at 2 m water depth and did not form a remnant water film after being removed from the water. The packaged speaker showed almost the same sound quality before and after dipping at a 2 m water depth. These results demonstrate that the superhydrophobic nanotextured micromesh could be directly applicable for various products that need to resist water penetration, yet allow the transmission of gases and sound/light waves.  相似文献   
104.
Up to now, it is still an open question of how to construct a chosen-ciphertext secure unidirectional proxy re-encryption scheme in the adaptive corruption model. To address this problem, we propose a new unidirectional proxy re-encryption scheme, and prove its chosen-ciphertext security in the adaptive corruption model without random oracles. Compared with the best known unidirectional proxy re-encryption scheme proposed by Libert and Vergnaud in PKC’08, our scheme enjoys the advantages of both higher effi...  相似文献   
105.
106.
107.
Lu  Gui-Fu  Zou  Jian  Wang  Yong  Wang  Zhongqun 《Multimedia Tools and Applications》2017,76(14):15801-15816
Multimedia Tools and Applications - Null space based linear discriminant analysis (NSLDA) is a well-known feature extraction method, which can make use of the most discriminant information in the...  相似文献   
108.
The aim of this paper is to present a microstructural topology optimization methodology for the structural-acoustic coupled system. In the structural-acoustic system, the structure is considered to be a thin composite plate composed of periodic uniform microstructures. The discrete design variables are used in the microstructural topology optimization, and the constitutive matrix is interpolated by the power-law scheme at the micro scale. The equivalent macro material properties of the microstructure are computed through the homogenization method. The design objective is to minimize the sound pressure level (SPL) in an interior acoustic medium. The sensitivities of the SPL with respect to design variables are derived. The bi-directional evolutionary structural optimization (BESO) method is extended to solve the structural-acoustic coupled optimization problem to find the optimal material distribution of the microstructure. Numerical examples of a hexahedral box and an automobile passenger compartment are given to demonstrate the efficiency of the presented microstructural topology optimization method.  相似文献   
109.
通过对大学英语网络自主学习运行环境和教学模式的研究,介绍了现有网络学习运行环境包含的各种网络结构、软件架构、学习和考核方法等几个方面,讨论了各种环境因素在实际应用中的优劣与取舍原因,给出了开放教学理念下的网络运行环境研究结果。在研究中能给学生提供充分思考的空间、促进学生在学习中的独立思考和探索精神,进而达到学生素质全面发展的目的。  相似文献   
110.
Reachability is one of the most important behavioral properties of Petri nets. We propose in this paper a novel approach for solving the fundamental equation in the reachability analysis of acyclic Petri nets, which has been known to be NP-complete. More specifically, by adopting a revised version of the cell enumeration method for an arrangement of hyperplanes in discrete geometry, we develop an efficient solution scheme to identify firing count vector solution(s) to the fundamental equation on a bounded integer set, with a complexity bound of O((nu)nm), where n is the number of transitions, m is the number of places and u is the upper bound of the number of firings for all individual transitions.  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