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   1593465篇
  免费   31969篇
  国内免费   9207篇
电工技术   37705篇
技术理论   2篇
综合类   9814篇
化学工业   274366篇
金属工艺   67289篇
机械仪表   46785篇
建筑科学   50107篇
矿业工程   12724篇
能源动力   51469篇
轻工业   121570篇
水利工程   16503篇
石油天然气   39868篇
武器工业   611篇
无线电   202751篇
一般工业技术   296037篇
冶金工业   195024篇
原子能技术   34979篇
自动化技术   177037篇
  2021年   17512篇
  2020年   13536篇
  2019年   15933篇
  2018年   18527篇
  2017年   17944篇
  2016年   23371篇
  2015年   19331篇
  2014年   31006篇
  2013年   90530篇
  2012年   39910篇
  2011年   53556篇
  2010年   46602篇
  2009年   54391篇
  2008年   49458篇
  2007年   46650篇
  2006年   48164篇
  2005年   42816篇
  2004年   44043篇
  2003年   43699篇
  2002年   42621篇
  2001年   39656篇
  2000年   37617篇
  1999年   37117篇
  1998年   55273篇
  1997年   45581篇
  1996年   39457篇
  1995年   33151篇
  1994年   30759篇
  1993年   30646篇
  1992年   26850篇
  1991年   23875篇
  1990年   24152篇
  1989年   23229篇
  1988年   21709篇
  1987年   19948篇
  1986年   18902篇
  1985年   22198篇
  1984年   22176篇
  1983年   20105篇
  1982年   19148篇
  1981年   19291篇
  1980年   17929篇
  1979年   18351篇
  1978年   17663篇
  1977年   17819篇
  1976年   19453篇
  1975年   15841篇
  1974年   15342篇
  1973年   15462篇
  1972年   12997篇
排序方式: 共有10000条查询结果,搜索用时 234 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.
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   
95.
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   
96.
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   
97.
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   
98.
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   
99.
100.
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   
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