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   386962篇
  免费   4138篇
  国内免费   768篇
电工技术   6521篇
综合类   213篇
化学工业   58686篇
金属工艺   21002篇
机械仪表   14124篇
建筑科学   7223篇
矿业工程   4745篇
能源动力   7808篇
轻工业   20458篇
水利工程   5898篇
石油天然气   16104篇
武器工业   41篇
无线电   36671篇
一般工业技术   91392篇
冶金工业   59034篇
原子能技术   13974篇
自动化技术   27974篇
  2021年   3874篇
  2019年   3932篇
  2018年   7426篇
  2017年   7676篇
  2016年   8150篇
  2015年   4491篇
  2014年   7645篇
  2013年   16489篇
  2012年   11029篇
  2011年   13950篇
  2010年   11314篇
  2009年   12610篇
  2008年   12847篇
  2007年   12393篇
  2006年   10349篇
  2005年   9324篇
  2004年   8826篇
  2003年   8552篇
  2002年   8113篇
  2001年   7931篇
  2000年   7613篇
  1999年   7226篇
  1998年   15962篇
  1997年   11711篇
  1996年   8822篇
  1995年   7026篇
  1994年   6356篇
  1993年   6646篇
  1992年   5335篇
  1991年   5411篇
  1990年   5357篇
  1989年   5145篇
  1988年   5069篇
  1987年   4750篇
  1986年   4717篇
  1985年   5161篇
  1984年   4938篇
  1983年   4726篇
  1982年   4397篇
  1981年   4423篇
  1980年   4495篇
  1979年   4682篇
  1978年   4798篇
  1977年   5007篇
  1976年   5752篇
  1975年   4436篇
  1974年   4452篇
  1973年   4534篇
  1972年   4044篇
  1971年   3685篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
1.
Journal of Materials Science: Materials in Electronics - The Co1?xZnxFe2O4 (Co–Zn) ferrite nanoparticles with x varying from 0.0 to 0.4 have been manufactured by facile chemical...  相似文献   
2.
Journal of Materials Science: Materials in Electronics - The ZnO and TiO2 nanopowders have been prepared by means of the pulsed laser reactive ablation of metallic (Zn, Ti) targets. The Structural,...  相似文献   
3.
In the present study, a prebiotic acerola juice containing gluco-oligosaccharides and dextran was produced and processed by high-intensity ultrasound (HIUS). After a simulated in vitro digestion, the gluco-oligosaccharides and dextran maintained 90% and 80% of their initial concentration in all prebiotic’s juices. At the same time, Vitamin C and phenolic compounds concentration increased significantly by 19% and 7% (P < 0.05). After the in vitro digestion, the prebiotic juice HIUS processed by 10 min showed the highest increase in gluco-oligosaccharides and bioactive compound concentrations. The HIUS processing imparted some dextran hydrolysis and improved its fermentability by Lacticaseibacillus casei. Gluco-oligosaccharides were extensively consumed as substrate in simulated intestinal conditions, promoting the L. casei NRRL B-442 growth and production of organic acids and short-chain organic acids. The prebiotic juice HIUS processed for 6 min showed the best responses regarding the metabolism of L. casei NRRL B-442. The results showed high-intensity ultrasound processed acerola juices containing gluco-oligosaccharides and dextran as a prebiotic food.  相似文献   
4.
In the present paper, therapeutic treatment of infected tumorous cells has been studied through mathematical modeling and simulation of heat transfer in tissues by using a nonlinear dual-phase lag bioheat transfer model with Dirichlet boundary condition. The components of volumetric heat source in this model such as blood perfusion and metabolism are assumed experimentally validated temperature-dependent function, which gives more accurate temperature distribution in tissues through this model. We have used the finite difference and RK (4, 5) techniques of numerical methods to solve the proposed problem and obtained the exact solution in a particular case. After comparison, we got a good agreement between them. We have used dimensionless quantities throughout this paper. The effect of relaxation and thermalization time with respect to dimensionless temperature distribution has been analyzed in the treatment process.  相似文献   
5.
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   
6.
Journal of Computer and Systems Sciences International - A method for the synthesis of fast finite state machines on programmable logic integrated circuits such as field-programmable gate arrays is...  相似文献   
7.
Inorganic Materials - We have studied the effect of annealing on the chemical and physical properties of mineral-like host matrices for immobilization of the rare-earth–actinide fraction from...  相似文献   
8.
Telecommunication Systems - Internet of Things (IoT) has changed the way people live by transforming everything into smart systems. Wireless Sensor Network (WSN) forms an important part of IoT....  相似文献   
9.
Semiconductors - The results of the effect of irradiation with Ar ions on the structural, electrophysical, and optical characteristics of ultraviolet Cr/4H-SiC photodetectors in the spectral range...  相似文献   
10.
Chemistry and Technology of Fuels and Oils - This article considers the alternatives for treatment of the raffinate produced at a unit for the extraction of benzene-containing fractions and the...  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