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   1741950篇
  免费   49798篇
  国内免费   18629篇
电工技术   51093篇
技术理论   56篇
综合类   25466篇
化学工业   317545篇
金属工艺   79896篇
机械仪表   60615篇
建筑科学   69649篇
矿业工程   21958篇
能源动力   58740篇
轻工业   123119篇
水利工程   19457篇
石油天然气   58243篇
武器工业   2720篇
无线电   225835篇
一般工业技术   307193篇
冶金工业   147517篇
原子能技术   36656篇
自动化技术   204619篇
  2022年   16641篇
  2021年   27072篇
  2020年   20654篇
  2019年   21565篇
  2018年   22250篇
  2017年   22791篇
  2016年   28717篇
  2015年   28579篇
  2014年   43379篇
  2013年   104709篇
  2012年   52753篇
  2011年   65726篇
  2010年   58719篇
  2009年   66492篇
  2008年   59009篇
  2007年   55251篇
  2006年   60474篇
  2005年   52618篇
  2004年   49418篇
  2003年   48401篇
  2002年   46748篇
  2001年   42674篇
  2000年   42012篇
  1999年   41978篇
  1998年   41329篇
  1997年   38740篇
  1996年   36925篇
  1995年   33248篇
  1994年   30898篇
  1993年   29297篇
  1992年   27832篇
  1991年   24387篇
  1990年   24422篇
  1989年   23200篇
  1988年   21598篇
  1987年   19610篇
  1986年   18860篇
  1985年   22038篇
  1984年   22347篇
  1983年   20230篇
  1982年   19258篇
  1981年   19240篇
  1980年   17840篇
  1979年   18475篇
  1978年   17662篇
  1977年   17051篇
  1976年   17561篇
  1975年   15917篇
  1974年   15476篇
  1973年   15542篇
排序方式: 共有10000条查询结果,搜索用时 93 毫秒
121.
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   
122.
123.
124.
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   
125.
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   
126.
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   
127.
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   
128.
Zhang  Qi  Wang  Yujing  Zhang  Xueling  Song  Jun  Li  Yinlei  Wu  Xuehong  Yuan  Kunjie 《Journal of Materials Science》2022,57(14):7208-7224
Journal of Materials Science - Form-stable composite phase change materials (C-PCMs) prepared by microencapsulation method and porous matrix adsorption method need for compression molding after...  相似文献   
129.
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   
130.
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