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   1560828篇
  免费   27915篇
  国内免费   7005篇
电工技术   34637篇
综合类   6391篇
化学工业   273702篇
金属工艺   65192篇
机械仪表   44253篇
建筑科学   47302篇
矿业工程   11545篇
能源动力   50564篇
轻工业   120079篇
水利工程   15758篇
石油天然气   37769篇
武器工业   140篇
无线电   198536篇
一般工业技术   294228篇
冶金工业   188993篇
原子能技术   34176篇
自动化技术   172483篇
  2021年   15853篇
  2020年   12163篇
  2019年   14940篇
  2018年   16998篇
  2017年   16339篇
  2016年   22152篇
  2015年   17571篇
  2014年   28962篇
  2013年   88290篇
  2012年   36972篇
  2011年   50176篇
  2010年   43580篇
  2009年   51858篇
  2008年   46525篇
  2007年   44075篇
  2006年   45800篇
  2005年   40744篇
  2004年   42762篇
  2003年   42462篇
  2002年   41384篇
  2001年   38458篇
  2000年   36765篇
  1999年   36098篇
  1998年   52604篇
  1997年   43889篇
  1996年   38574篇
  1995年   32791篇
  1994年   30461篇
  1993年   30236篇
  1992年   26785篇
  1991年   24039篇
  1990年   24241篇
  1989年   23401篇
  1988年   21909篇
  1987年   20052篇
  1986年   19572篇
  1985年   22929篇
  1984年   22718篇
  1983年   20748篇
  1982年   19539篇
  1981年   19667篇
  1980年   18326篇
  1979年   18841篇
  1978年   17976篇
  1977年   18347篇
  1976年   20128篇
  1975年   16195篇
  1974年   15702篇
  1973年   15796篇
  1972年   13272篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
We considered the magnetohydrodynamic (MHD) free convective flow of an incompressible electrically conducting viscous fluid past an infinite vertical permeable porous plate with a uniform transverse magnetic field, heat source and chemical reaction in a rotating frame taking Hall current effects into account. The momentum equations for the fluid flow during absorbent medium are controlled by the Brinkman model. Through the undisturbed state, both the plate and fluid are in a rigid body rotation by the uniform angular velocity perpendicular to an infinite vertical plate. The perpendicular surface is subject to the homogeneous invariable suction at a right angle to it and the heat on the surface varies about a non-zero unvarying average whereas the warmth of complimentary flow is invariable. The systematic solutions of the velocity, temperature, and concentration distributions are acquired systematically by utilizing the perturbation method. The velocity expressions consist of steady-state and fluctuating situations. It is revealed that the steady part of the velocity field has a three-layer characteristic while the oscillatory part of the fluid field exhibits a multi-layer characteristic. The influence of various governing flow parameters on the velocity, temperature, and concentration are analyzed graphically. We also discuss computational results for the skin friction, Nusselt number, and Sherwood number in the tabular forms.  相似文献   
92.
93.
94.
Silicon - Quadruple gate FinFET is a promising candidate among other multi-gate MOS devices due to it’s better scalability and higher short channel effect suppression capability in advanced...  相似文献   
95.
Reliable joints of Ti3SiC2 ceramic and TC11 alloy were diffusion bonded with a 50 μm thick Cu interlayer. The typical interfacial structure of the diffusion boned joint, which was dependent on the interdiffusion and chemical reactions between Al, Si and Ti atoms from the base materials and Cu interlayer, was TC11/α-Ti + β-Ti + Ti2Cu + TiCu/Ti5Si4 + TiSiCu/Cu(s, s)/Ti3SiC2. The influence of bonding temperature and time on the interfacial structure and mechanical properties of Ti3SiC2/Cu/TC11 joint was analyzed. With the increase of bonding temperature and time, the joint shear strength was gradually increased due to enhanced atomic diffusion. However, the thickness of Ti5Si4 and TiSiCu layers with high microhardness increased for a long holding time, resulting in the reduction of bonding strength. The maximum shear strength of 251 ± 6 MPa was obtained for the joint diffusion bonded at 850 °C for 60 min, and fracture primarily occurred at the diffusion layer adjacent to the Ti3SiC2 substrate. This work provided an economical and convenient solution for broadening the engineering application of Ti3SiC2 ceramic.  相似文献   
96.
Fluorescent fusion proteins are powerful tools for studying biological processes in living cells, but universal application is limited due to the voluminous size of those tags, which might have an impact on the folding, localization or even the biological function of the target protein. The designed biocatalyst trypsiligase enables site-directed linkage of small-sized fluorescence dyes on the N terminus of integral target proteins located in the outer membrane of living cells through a stable native peptide bond. The function of the approach was tested by using the examples of covalent derivatization of the transmembrane proteins CD147 as well as the EGF receptor, both presented on human HeLa cells. Specific trypsiligase recognition of the site of linkage was mediated by the dipeptide sequence Arg-His added to the proteins’ native N termini, pointing outside the cell membrane. The labeling procedure takes only about 5 minutes, as demonstrated for couplings of the fluorescence dye tetramethyl rhodamine and the affinity label biotin as well.  相似文献   
97.
Journal of Communications Technology and Electronics - Abstract—The matrix coefficients of projection models of strip lines obtained using the Chebyshev basis are presented as a sum of...  相似文献   
98.
Analog Integrated Circuits and Signal Processing - This paper presents the complete design of a phase locked loop-based clock synthesizer for reconfigurable analog-to-digital converters. The...  相似文献   
99.
Catalysis Letters - An environmentally benign process for synthesizing 4-methoxyphenol through methylation of hydroquinone using polystyrene immobilized Bronsted acidic ionic liquid is presented....  相似文献   
100.
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