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   53466篇
  免费   5358篇
  国内免费   3324篇
电工技术   3534篇
技术理论   3篇
综合类   4489篇
化学工业   8712篇
金属工艺   3000篇
机械仪表   2979篇
建筑科学   4639篇
矿业工程   1571篇
能源动力   1673篇
轻工业   4229篇
水利工程   1085篇
石油天然气   2709篇
武器工业   399篇
无线电   6221篇
一般工业技术   5955篇
冶金工业   2234篇
原子能技术   717篇
自动化技术   7999篇
  2024年   304篇
  2023年   1096篇
  2022年   1819篇
  2021年   2493篇
  2020年   1891篇
  2019年   1743篇
  2018年   1776篇
  2017年   1926篇
  2016年   1596篇
  2015年   2243篇
  2014年   2669篇
  2013年   3057篇
  2012年   3226篇
  2011年   3365篇
  2010年   3114篇
  2009年   2875篇
  2008年   2825篇
  2007年   2655篇
  2006年   2576篇
  2005年   2118篇
  2004年   1866篇
  2003年   2389篇
  2002年   3257篇
  2001年   2724篇
  2000年   1491篇
  1999年   1182篇
  1998年   692篇
  1997年   609篇
  1996年   606篇
  1995年   474篇
  1994年   385篇
  1993年   259篇
  1992年   221篇
  1991年   140篇
  1990年   119篇
  1989年   84篇
  1988年   76篇
  1987年   43篇
  1986年   44篇
  1985年   32篇
  1984年   26篇
  1983年   15篇
  1982年   10篇
  1981年   9篇
  1980年   13篇
  1979年   6篇
  1965年   1篇
  1959年   5篇
  1951年   3篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
Interactive Data Language (IDL) is a language in the development of application based on multiplatform and object\|oriented,which has significant advantages in data analysis and visualization.The MATLAB is a software with powerful features in the image of processing and programming in complex numerical analysis,which based on matrix calculation.Programming in combining the IDL with MATLAB,meanwhile using the Extended Linear Mixed Model for endmember unmixing in Hyperion images.To verify the results of endmember unmixing,adopted the Fully Constrained Least Squares for comparative analysis.The results showed that:The method of programming in combining the IDL with MATLAB not noly possess the advantages of both but also enhance the efficiency in programming,it is conducive to remote sensing image processing.Meanwhile endmember unmixing results show that:the Extended Linear Mixing Model unmixing has a higher accuracy when the proportion of local category in the image is large.On the contrary,the Fully Constrained Least Squares unmixing has a higher accuracy.  相似文献   
92.
This paper proposes an evolutionary accelerated computational level set algorithm for structure topology optimization. It integrates the merits of evolutionary structure optimization (ESO) and level set method (LSM). Traditional LSM algorithm is largely dependent on the initial guess topology. The proposed method combines the merits of ESO techniques with those of LSM algorithm, while allowing new holes to be automatically generated in low strain energy within the nodal neighboring region during optimization. The validity and robustness of the new algorithm are supported by some widely used benchmark examples in topology optimization. Numerical computations show that optimization convergence is accelerated effectively.  相似文献   
93.
文章介绍了一种分布式网络指纹识别系统NBFIS(Network-BasedFingerprintIdentifyingSystem)。首先提出模型框架,并对其关键技术特别是指纹图像处理技术及面向对象的数据库技术进行讨论。实现了NBFIS系统的原型并给出实验和性能测试结果。  相似文献   
94.
The existing predictive spatiotemporal indexes can be classified into two categories, depending on whether they are based on the primal or dual methodology. Although we have gained considerable empirical knowledge about various access methods, currently there is only limited understanding on the theoretical characteristics of the two methodologies. In fact, the experimental results in different papers even contradict each other, regarding the relative superiority of the primal and dual techniques. This paper presents a careful study on the query performance of general primal and dual indexes, and reveals important insight into the behavior of each technique. In particular, we mathematically establish the conditions that determine the superiority of each methodology, and provide rigorous justification for well-known observations that have not been properly explained in the literature. Our analytical findings also resolve the contradiction in the experiments of previous work.  相似文献   
95.
It is still not very clear to what extent and how does the amino acid sequences of proteins determine their tertiary structures. In this paper, we report our investigations of the sequence-structure relations of the proteins in the beta-propeller fold family, which adopt highly symmetrical tertiary structures while their sequences appear "random". We analyzed the amino acid sequences by using a similarity matrix plus Pearson correlation method and found that the sequences can show the same symmetries as their tertiary structures only if we deduce the conditions of sequence similarity. This suggests that some key residues may play an important role in the formation of the tertiary structures of these proteins.  相似文献   
96.
Li KW  Yu RF  Han XL 《Applied ergonomics》2007,38(3):259-265
A study on combined manual materials-handling tasks performed on floors under three friction levels was conducted. Eight male subjects participated in the study. The maximum acceptable weight of handling, including lifting, carrying for 3m, lowering, and walking 3m back at twice per minute was determined. The subject then performed the same tasks for 10 min. Heart rate, Vo2, energy efficiency, perceived sense of slip, and rating of perceived exertion for whole body strain were measured. The results showed that the effects of friction level on the maximum acceptable weights of handling, perceived sense of slip, Vo2, and energy efficiency were statistically significant (p相似文献   
97.
一种改进的GA变异算子及其数学分析   总被引:7,自引:0,他引:7  
提出了一种改进的GA变异算子,并对其有效性作了数学分析。实例表明,该算子能改善GA的收敛性能。  相似文献   
98.
给出了AutoCAD环境下的木工成型铣刀CAD系统中 ,用户输入的工件截形曲线通过坐标变换生成木工成型铣刀前刀面截形曲线的方法 ,并进一步讨论了样条曲线最值点的求法  相似文献   
99.
供应链集成化模型与优化   总被引:2,自引:0,他引:2  
本文建立了一个包括供应商、制造商、销售商 在内的集成化模型,这一模型含有线性状态方程和神经网络非线性模型,提出了库存成本、 供应成本、生产水平等在内的供应链目标函数和约束条件.对于供应链集成化模型采用模拟 退火方法进行优化,并以辽化公司为背景进行了初步条件的仿真工作.  相似文献   
100.
PCI是DSP应用系统与通用计算机高速通信的理想接口。介绍了一种双谱段探测系统的PCI接口方案,该方案采用TI公司的TMS320F2812 DSP作为控制单元主控芯片,采用Cypress公司PCIDP系列的CY7C09449PV作为PCI接口芯片,具有接口简单方便易于实现的优点。详细讨论了CY7C09449PV与TMS320F2812的硬件连接、参数配置与时序分析。  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