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   92993篇
  免费   6755篇
  国内免费   3374篇
电工技术   4733篇
技术理论   9篇
综合类   5220篇
化学工业   16500篇
金属工艺   4706篇
机械仪表   5657篇
建筑科学   7536篇
矿业工程   2162篇
能源动力   2671篇
轻工业   5364篇
水利工程   1603篇
石油天然气   5070篇
武器工业   581篇
无线电   11140篇
一般工业技术   12030篇
冶金工业   4939篇
原子能技术   965篇
自动化技术   12236篇
  2024年   360篇
  2023年   1411篇
  2022年   2478篇
  2021年   3396篇
  2020年   2558篇
  2019年   2197篇
  2018年   2448篇
  2017年   2711篇
  2016年   2534篇
  2015年   3206篇
  2014年   4371篇
  2013年   5436篇
  2012年   5702篇
  2011年   6009篇
  2010年   5316篇
  2009年   5086篇
  2008年   4890篇
  2007年   4798篇
  2006年   5009篇
  2005年   4449篇
  2004年   2982篇
  2003年   2663篇
  2002年   2361篇
  2001年   2174篇
  2000年   2439篇
  1999年   2729篇
  1998年   2495篇
  1997年   1987篇
  1996年   1832篇
  1995年   1529篇
  1994年   1268篇
  1993年   914篇
  1992年   679篇
  1991年   565篇
  1990年   429篇
  1989年   393篇
  1988年   343篇
  1987年   179篇
  1986年   174篇
  1985年   115篇
  1984年   101篇
  1983年   67篇
  1982年   62篇
  1981年   59篇
  1980年   42篇
  1979年   32篇
  1978年   14篇
  1977年   33篇
  1976年   17篇
  1975年   15篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
黄元民 《河南冶金》2006,14(Z1):14-16
简述了炼钢工序在柳钢"十五"期间工艺和装备的变化及其特点.对工序变化进行了初步分析.  相似文献   
102.
基于蒙特卡罗模拟的费用与进度集成风险分析,可以获得更为精确的费用估算结果,同时得到进度风险分析的结果,使得风险分析的应对措施可以针对时间类与费用类风险采取不同的措施.笔者结合国外相关文献的成果,讨论并分析了采用蒙特卡罗模拟的费用与进度集成风险分析的顺序分析程序与一体化分析程序两种分析方法及其特点,并依据讨论结果推荐优先选用顺序分析程序.  相似文献   
103.
This paper presents a new MSDI (mold surface data integration) method for presenting ruled mold-surface data for CAPP applications. The method makes use of adjacency and feature-data matrices to establish a framework of feature-based data. The MSDI method enables the storage, retrieval and operations of geometries, topologies, and machining information of a given ruled mold surface. The matrices of adjacency and feature-data effectively represent the relations. Boolean algebra and group technology (GT) methods are introduced to generate the desired process plans. A sample mold made of ruled surfaces is made and used to show the effectiveness of the proposed data representation and the integrated mold surface processing method. A compact computer program is implemented to enhance the speed and accuracy of the MSDI method. The numerical results indicate that the mold surface decomposition and integration procedure presented in this paper are systematic and effective. The paper provides a novel modular mold surface modeling tool and procedure that can be further extended to accommodate more features appearing in complicated ruled mold surfaces.  相似文献   
104.
Orbital-free density functional theory (OF-DFT) can be made to scale linearly with sample size, allowing thousands of atoms to be treated explicitly with quantum mechanics. State-of-the-art kinetic energy density functionals and ion–electron pseudopotentials are used to obtain accurate structural property predictions for nanoparticles, nanowires, extended surfaces, and nanoindentation of simple metals.  相似文献   
105.
A nonlinear method named detrended fluctuation analysis (DFA) was utilized to investigate the scaling behavior of the human electroencephalogram (EEG) in three emotional music conditions (fear, happiness, sadness) and a rest condition (eyes-closed). The results showed that the EEG exhibited scaling behavior in two regions with two scaling exponents β1 and β2 which represented the complexity of higher and lower frequency activity besides α band respectively. As the emotional intensity decreased the value of β1 increased and the value of β2 decreased. The change of β1 was weakly correlated with the 'approach-withdrawal' model of emotion and both of fear and sad music made certain differences compared with the eyes-closed rest condition. The study shows that music is a powerful elicitor of emotion and that using nonlinear method can potentially contribute to the investigation of emotion.  相似文献   
106.
107.
On the elemental effect of AlCoCrCuFeNi high-entropy alloy system   总被引:1,自引:0,他引:1  
The AlCoCrCuFeNi high-entropy alloy system was synthesized using a well-developed arc melting and casting method. Their elemental effect on microstructures and hardness was investigated with X-ray diffraction, scanning electron microscopy and Vickers hardness testing. The alloys exhibit quite simple FCC and BCC solid solution phases. Co, Cu and Ni elements enhance the formation of the FCC phase while Al and Cr enhance that of the BCC phase in the alloy system. BCC phases form a spinodal structure during cooling. Copper tends to segregate at the interdendrite region and forms a Cu-rich FCC phase. Low copper content renders the interdendrite as a thin film and the as-cast structure like recrystallized grain structure. The formation of BCC phases significantly increases the hardness level of the alloy system. The strengthening mechanism is discussed.  相似文献   
108.
In this paper, we report that low-density InAs/GaAs quantum dots (QDs) can be formed by postgrowth annealing the samples with 1.5-monolayer (ML) InAs coverage, which is thinner than the critical layer thickness for the Stranski-Krastanov growth. The annealing procedure was performed immediately after the deposition of the InAs layer. The effects of annealing time and annealing temperature on the dot density, dot size, and optical characteristics of the QDs were investigated. The optimum annealing conditions to obtain low-density QDs are longer than 60 s and higher than 500degC . Meanwhile, no luminescence can be observed for the wetting-layer, which may suggest that the postgrowth annealing will make the wetting layer thinner and thus reduce the effects of wetting layer on carrier relaxation and recombination. On the other hand, we observe that a decrease of the PL intensity at the annealing conditions of 60 s and 515degC , which is possibly due to the increasing surface dislocations resulted from the In adatom desorption at higher annealing temperature.  相似文献   
109.
黄细阳 《冶金能源》2004,23(5):30-33
介绍了综合应用新型无水冷技术和热管技术的轧钢加热炉高效运行的新模式,并结合首钢第一线材厂的实践,进一步阐明了该模式的实用性和给企业带来的良好效益。  相似文献   
110.
知识经济时代,人力资源的管理与开发成为企业在激烈的市场竞争中决定成败的关键。然而,由于受到传统文化思想潜移默化的影响和束缚,一些企业的领导者在对待人才的管理、培养和使用上存在误区,导致企业的“核心软件”即人力资源管理不能正常发挥作用。企业领导者应以史为鉴,更新人才管理理念。  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