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   33635篇
  免费   2714篇
  国内免费   1062篇
电工技术   1369篇
技术理论   3篇
综合类   1466篇
化学工业   6563篇
金属工艺   1504篇
机械仪表   1832篇
建筑科学   2193篇
矿业工程   973篇
能源动力   997篇
轻工业   3721篇
水利工程   539篇
石油天然气   1502篇
武器工业   158篇
无线电   3221篇
一般工业技术   4873篇
冶金工业   1981篇
原子能技术   283篇
自动化技术   4233篇
  2024年   140篇
  2023年   579篇
  2022年   802篇
  2021年   1330篇
  2020年   1020篇
  2019年   936篇
  2018年   1115篇
  2017年   1176篇
  2016年   1224篇
  2015年   1317篇
  2014年   1713篇
  2013年   2433篇
  2012年   2362篇
  2011年   2265篇
  2010年   1917篇
  2009年   1784篇
  2008年   1810篇
  2007年   1677篇
  2006年   1599篇
  2005年   1327篇
  2004年   991篇
  2003年   890篇
  2002年   895篇
  2001年   719篇
  2000年   673篇
  1999年   694篇
  1998年   622篇
  1997年   521篇
  1996年   465篇
  1995年   407篇
  1994年   374篇
  1993年   291篇
  1992年   218篇
  1991年   155篇
  1990年   93篇
  1989年   101篇
  1988年   104篇
  1987年   78篇
  1986年   62篇
  1985年   58篇
  1984年   45篇
  1983年   28篇
  1982年   41篇
  1981年   31篇
  1980年   30篇
  1979年   34篇
  1978年   23篇
  1977年   28篇
  1976年   24篇
  1973年   18篇
排序方式: 共有10000条查询结果,搜索用时 9 毫秒
81.
In this paper, a new approximation to off-line signature verification is proposed based on two-class classifiers using an expert decisions ensemble. Different methods to extract sets of local and a global features from the target sample are detailed. Also a normalization by confidence voting method is used in order to decrease the final equal error rate (EER). Each set of features is processed by a single expert, and on the other approach proposed, the decisions of the individual classifiers are combined using weighted votes. Experimental results are given using a subcorpus of the large MCYT signature database for random and skilled forgeries. The results show that the weighted combination outperforms the individual classifiers significantly. The best EER obtained were 6.3 % in the case of skilled forgeries and 2.31 % in the case of random forgeries.  相似文献   
82.
Adaptive anisotropic refinement of finite element meshes allows one to reduce the computational effort required to achieve a specified accuracy of the solution of a PDE problem. We present a new approach to adaptive refinement and demonstrate that this allows one to construct algorithms which generate very flexible and efficient anisotropically refined meshes, even improving the convergence order compared to adaptive isotropic refinement if the problem permits.  相似文献   
83.
Model-based testing is focused on testing techniques which rely on the use of models. The diversity of systems and software to be tested implies the need for research on a variety of models and methods for test automation. We briefly review this research area and introduce several papers selected from the 22nd International Conference on Testing Software and Systems (ICTSS).  相似文献   
84.
We discuss how the standard Cost-Benefit Analysis should be modified in order to take risk (and uncertainty) into account. We propose different approaches used in finance (Value at Risk, Conditional Value at Risk, Downside Risk Measures, and Efficiency Ratio) as useful tools to model the impact of risk in project evaluation. After introducing the concepts, we show how they could be used in CBA and provide some simple examples to illustrate how such concepts can be applied to evaluate the desirability of a new project infrastructure.  相似文献   
85.
The influence of different centralised pre-packaging systems (PVC, modified atmosphere packaging (MAP), 25% CO(2) and 75% O(2), vacuum skin packaging (VSP) and the mother bag concept, 100% CO(2)) on the shelf-life (0, 7, 14 and 21 days at 0°C) of fresh pork was determined using microbiological, colour, odour and acceptability characteristics. All the packaging treatments were equally efficient for the first 4 days of retail display. In the extended shelf-life study (7, 14 and 21 days) the mother bag centralised packaging system gave the most promising shelf-life results (21 days) and was also judged superior in terms of odour. Modified atmosphere packaging (14 days) and VSP (7 days) may be considered as other possible options.  相似文献   
86.
This study attempted to identify the major sources of work-related stress among telephone operators, with special emphasis on computer monitoring and telephone surveillance. A cross-sectional random sample of over 700 telephone operators participated in a questionnaire survey (response rate = 88%). The survey included items designed to measure perceived stress, management practices, specific job stressors and monitoring preferences. Call-time pressure items were most strongly linked to job stress by operators, with 70% reporting that difficulty in serving a customer well and still keeping call-time down contributed to their feelings of stress to a large or very large extent. About 55% of operators reported that telephone monitoring contributed to their feelings of job stress. If given the opportunity, 44% of operators stated they would prefer not to be monitored by telephone at all, while 23% stated they would prefer some monitoring; 33% had no preference. The setting of inappropriate individual-call-time objectives, which may be consistently unachievable for some operators and which create conflict between management demands for quantity and quality and also between workers values concerning quality and productivity demands, appears to be the most stress-inducing aspect of the job. In terms of telephone surveillance, the issues of timeliness and specificity of feedback appear to be less important than call-time pressure.  相似文献   
87.
本文设计了一种基于AT89C2051芯片为CPU的家用报警系统,以烟雾探测器、门磁报警器、燃气体探测器等传感器为节点,当收集到异常信息后,由无线网络节点送至报警主机,通过主机报告给预留电话,从而完成了家庭报警系统的硬件组成、软件设计、数据采集与通信策略以及主程序设计,实现对家庭的非法入侵、火灾、燃气泄漏等事故的报警保护。  相似文献   
88.
89.
90.
《无机及分析化学》在多媒体教学的应用及思考   总被引:1,自引:0,他引:1  
任春霞  商少明 《广东化工》2006,33(10):91-92,80
对多媒体技术在无机及分析化学教学的应用进行了,阐述和分析,指出使用多媒体教学应注意的问题。  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