首页 | 官方网站   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   521487篇
  免费   5601篇
  国内免费   1144篇
工业技术   528232篇
  2021年   4382篇
  2019年   4330篇
  2018年   13031篇
  2017年   13340篇
  2016年   12034篇
  2015年   5535篇
  2014年   8945篇
  2013年   20770篇
  2012年   14732篇
  2011年   21249篇
  2010年   18175篇
  2009年   18826篇
  2008年   19492篇
  2007年   20207篇
  2006年   13034篇
  2005年   13530篇
  2004年   12398篇
  2003年   11815篇
  2002年   10739篇
  2001年   9943篇
  2000年   9658篇
  1999年   9171篇
  1998年   20200篇
  1997年   15323篇
  1996年   11629篇
  1995年   9351篇
  1994年   8562篇
  1993年   8596篇
  1992年   6870篇
  1991年   6950篇
  1990年   6876篇
  1989年   6709篇
  1988年   6529篇
  1987年   5944篇
  1986年   5878篇
  1985年   6569篇
  1984年   6331篇
  1983年   5905篇
  1982年   5575篇
  1981年   5731篇
  1980年   5633篇
  1979年   5740篇
  1978年   6003篇
  1977年   6428篇
  1976年   7882篇
  1975年   5413篇
  1974年   5353篇
  1973年   5440篇
  1972年   4806篇
  1971年   4406篇
排序方式: 共有10000条查询结果,搜索用时 22 毫秒
1.
Journal of Low Temperature Physics - This study modeled and investigated the magnetocaloric effect in Ni2MnGa Heusler alloy characterized by its magnetic entropy change (ΔSm) and its...  相似文献   
2.
Anzaldo  Alexis  Andrade  Ángel G. 《Wireless Networks》2022,28(8):3613-3620
Wireless Networks - Beyond five generation (B5G) systems will demand strict and heterogeneous service requirements for the emerging applications. One solution to meet these demands is the dense...  相似文献   
3.
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   
4.
Journal of Materials Science: Materials in Electronics - A mixed solution of 2-aminopyridine and succinic acid, with a 1:1 molar ratio, was kept at room temperature to develop a 2-aminopridinium...  相似文献   
5.
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   
6.
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   
7.
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   
8.
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   
9.
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   
10.
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   
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-23

京公网安备 11010802026262号