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   359368篇
  免费   28954篇
  国内免费   15805篇
电工技术   21231篇
技术理论   45篇
综合类   25563篇
化学工业   60016篇
金属工艺   20986篇
机械仪表   22634篇
建筑科学   27890篇
矿业工程   11787篇
能源动力   9735篇
轻工业   24181篇
水利工程   6814篇
石油天然气   23703篇
武器工业   2824篇
无线电   39122篇
一般工业技术   39586篇
冶金工业   18624篇
原子能技术   3684篇
自动化技术   45702篇
  2024年   1491篇
  2023年   5634篇
  2022年   10003篇
  2021年   14008篇
  2020年   10574篇
  2019年   8626篇
  2018年   9938篇
  2017年   11195篇
  2016年   10238篇
  2015年   13998篇
  2014年   17610篇
  2013年   21068篇
  2012年   22856篇
  2011年   25392篇
  2010年   22414篇
  2009年   21237篇
  2008年   20805篇
  2007年   19829篇
  2006年   20196篇
  2005年   17769篇
  2004年   12039篇
  2003年   10752篇
  2002年   9962篇
  2001年   8866篇
  2000年   8818篇
  1999年   9449篇
  1998年   7223篇
  1997年   6170篇
  1996年   5853篇
  1995年   4807篇
  1994年   3904篇
  1993年   2630篇
  1992年   2078篇
  1991年   1572篇
  1990年   1235篇
  1989年   998篇
  1988年   830篇
  1987年   526篇
  1986年   413篇
  1985年   259篇
  1984年   206篇
  1983年   164篇
  1982年   129篇
  1981年   76篇
  1980年   97篇
  1979年   44篇
  1978年   17篇
  1977年   23篇
  1976年   28篇
  1973年   9篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
111.
OA系统中的工作流技术及其新的模式   总被引:1,自引:0,他引:1  
本文在对工作流技术的理论、实现和应用研究的基础上,提出了审批平台中应用的工作流管理模型,详细讨论了该技术的实现方法,并提出了工作流技术的新模式.  相似文献   
112.
IP网络实施QoS的策略分析   总被引:2,自引:0,他引:2  
介绍了衡量IP QoS的技术指标和业务等级的划分,提出了IP网络中QoS的实施建议。  相似文献   
113.
With the creation of a pattern recognition system for metal transfer mode, this article has collected five kinds of spectrum signals in gas metal arc welding (MIG, MAG and CO2) and take them as training samples. These samples have been pretreated by computer, several key characteristic parameters of the spectrum signal have been creatively extracted, and a corresponding recognition function and a minimum-distance-classifier have been constructed. The results show that the pattern recognition of several kinds of metal transfer modes for the metal gas arc welding can be done successfully, and relative important parameters in welding process, such as the frequency of droplet transfer and the approximate diameter of each droplet, can also be obtained.  相似文献   
114.
余满春  张立红 《辽宁化工》2003,32(8):354-356
介绍了书籍装订热熔胶生产工艺及产品的技术指标,对1000t/a生产装置的投资与产品成本进行了核算。分析结果表明,总投资110万元,年利润达266万元。  相似文献   
115.
116.
人工智能的原理及应用   总被引:7,自引:0,他引:7  
介绍了人工智能的发展,并对改进的神经网络专家系统的优越性做了介绍,指出了神经网络专家系统广阔的应用前景及实现。  相似文献   
117.
We consider the effect of multiple fibers on wavelength division multiplexing networks without wavelength conversion. We study networks with dynamic wavelength routing and develop accurate analytical models to compare various possible options using single- and multiple-fiber networks. We use results of an analytical model and simulation-based studies to evaluate the blocking performance and cost of multifiber networks. The number of fibers required providing high performance in multifiber networks and their costs are compared. A case is made for using multiple fibers in each link with fewer wavelengths instead of using a single fiber with many wavelengths. In particular, we show that a network with four fibers per link and with four wavelengths on each fiber without any wavelength conversion on any node yields similar same performance as the networks with one fiber per link and 16 wavelengths per fiber on each link and with full wavelength conversion capability on all nodes. In addition, the multifiber network may also offer the cost advantage depending on the relative cost of components. We develop a parametric cost model to show that multiple fibers in each link are an attractive option. Finally, such multifiber networks also has fault tolerance, with respect to a single fiber failure, already built into the system.  相似文献   
118.
In this paper, the moving least-squares differential quadrature (MLSDQ) method is employed for free vibration of thick antisymmetric laminates based on the first-order shear deformation theory. The generalized displacements of the laminates are independently approximated with the centered moving least-squares (MLS) technique within each domain of influence. The MLS nodal shape functions and their partial derivatives are computed quickly through back-substitutions after only one LU decomposition. Subsequently, the weighting coefficients in the MLSDQ discretization are determined with the nodal partial derivatives of the MLS shape functions. The MLSDQ method combines the merits of both the differential quadrature and meshless methods which can be conveniently applied to complex domains and irregular discretizations without loss of implementation efficiency and numerical accuracy. The natural frequencies of the laminates with various edge conditions, ply angles, and shapes are calculated and compared with the existing solutions to study the numerical accuracy and stability of the MLSDQ method. Effects of support size, order of completeness of basis functions, and node irregularity on the numerical accuracy are investigated in detail.  相似文献   
119.
For the first time, we successfully fabricated and demonstrated high performance metal-insulator-metal (MIM) capacitors with HfO/sub 2/-Al/sub 2/O/sub 3/ laminate dielectric using atomic layer deposition (ALD) technique. Our data indicates that the laminate MIM capacitor can provide high capacitance density of 12.8 fF//spl mu/m/sup 2/ from 10 kHz up to 20 GHz, very low leakage current of 3.2 /spl times/ 10/sup -8/ A/cm/sup 2/ at 3.3 V, small linear voltage coefficient of capacitance of 240 ppm/V together with quadratic one of 1830 ppm/V/sup 2/, temperature coefficient of capacitance of 182 ppm//spl deg/C, and high breakdown field of /spl sim/6 MV/cm as well as promising reliability. As a result, the HfO/sub 2/-Al/sub 2/O/sub 3/ laminate is a very promising candidate for next generation MIM capacitor for radio frequency and mixed signal integrated circuit applications.  相似文献   
120.
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