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   229207篇
  免费   17485篇
  国内免费   9149篇
电工技术   12479篇
技术理论   24篇
综合类   14175篇
化学工业   38826篇
金属工艺   13182篇
机械仪表   14550篇
建筑科学   17580篇
矿业工程   7513篇
能源动力   6426篇
轻工业   13463篇
水利工程   3607篇
石油天然气   16650篇
武器工业   1663篇
无线电   25144篇
一般工业技术   27359篇
冶金工业   12809篇
原子能技术   2247篇
自动化技术   28144篇
  2024年   994篇
  2023年   3806篇
  2022年   6496篇
  2021年   9120篇
  2020年   7096篇
  2019年   6019篇
  2018年   6740篇
  2017年   7541篇
  2016年   6755篇
  2015年   8870篇
  2014年   11261篇
  2013年   13283篇
  2012年   14216篇
  2011年   15466篇
  2010年   13439篇
  2009年   12698篇
  2008年   12364篇
  2007年   11862篇
  2006年   12359篇
  2005年   10768篇
  2004年   7273篇
  2003年   6233篇
  2002年   5474篇
  2001年   4894篇
  2000年   5443篇
  1999年   6457篇
  1998年   5442篇
  1997年   4457篇
  1996年   4195篇
  1995年   3505篇
  1994年   2815篇
  1993年   1966篇
  1992年   1540篇
  1991年   1231篇
  1990年   937篇
  1989年   744篇
  1988年   537篇
  1987年   336篇
  1986年   280篇
  1985年   196篇
  1984年   139篇
  1983年   114篇
  1982年   124篇
  1981年   98篇
  1980年   70篇
  1979年   36篇
  1978年   26篇
  1977年   20篇
  1976年   35篇
  1973年   13篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
In this study, distribution and history of residual stresses in plaque-like geometries are simulated based on linear thermoviscoelastic model, which helps to understand the mechanics and evolution of the residual stresses in the injection molding process. The numerical calculation of direction, combined with the specified boundary conditions. Results show that the stress variation across the thickness exhibits a high surface tensile value changing to a compressive peak value close to the surface, with the core region experiencing a parabolic tensile peak. Residual stress distribution throughout the thickness is almost same along the flowpath and the final residual stresses value near the gate is lower than the value near the end of flowpath.  相似文献   
42.
Inversion of Rayleigh wave dispersion curves is challenging for most local-search methods due to its high nonlinearity and to its multimodality. In this paper, we implemented and tested a Rayleigh wave dispersion curve inversion scheme based on GPS Positive Basis 2N, a commonly used pattern search algorithm. Incorporating complete poll and complete search strategies based on GPS Positive Basis 2N into the inverse procedure greatly enhances the performance of pattern search algorithms because the two steps can effectively locate the promising areas in the solution space containing the global minima and significantly reduce the computation cost, respectively.The proposed inverse procedure was applied to nonlinear inversion of fundamental-mode Rayleigh wave dispersion curves for a near-surface shear (S)-wave velocity profile. The calculation efficiency and stability of the inversion scheme are tested on three synthetic models and a real example from a roadbed survey in Henan, China. Effects of the number of data points, the reduction of the frequency range of the considered dispersion curve, errors in P-wave velocities and density, the initial S-wave velocity profile as well as the number of layers and their thicknesses on inversion results are also investigated in the present study to further evaluate the performance of the proposed approach.Results demonstrate that pattern search algorithms applied to nonlinear inversion of high-frequency surface wave data should be considered good not only in terms of accuracy but also in terms of the computation effort due to their global and deterministic search process.  相似文献   
43.
宣钢l260m^3高炉大修改造时将炉容扩大到l350m^3,对高炉本体系统设备及冷却系统、自动控制及检测系统进行了全面的改造更新,在炉腹、炉腰及炉身下部高热负荷区域采用铜冷却壁,取消炉身中上部铸铁冷却壁凸台,并采用薄内衬等先进、适用、可靠、成熟的技术。  相似文献   
44.
The Tera-op reliable intelligently adaptive processing system (TRIPS) architecture seeks to deliver system-level configurability to applications and runtime systems. It does so by employing the concept of polymorphism, which permits the runtime system to configure the hardware execution resources to match the mode of execution and demands of the compiler and application.  相似文献   
45.
46.
47.
Voltage switching induced by long-wavelength infrared light from a CO2 laser was observed using a double-barrier resonant tunneling diode (RTD) biased in the bistable region and the intersubband transition (IT) between the quantum confined states. Possible optoelectronic and all-optical switching applications involving hysteresis are proposed and discussed  相似文献   
48.
49.
50.
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