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   576534篇
  免费   7675篇
  国内免费   1472篇
电工技术   11532篇
综合类   956篇
化学工业   80978篇
金属工艺   23940篇
机械仪表   20271篇
建筑科学   13570篇
矿业工程   2527篇
能源动力   14560篇
轻工业   48219篇
水利工程   5719篇
石油天然气   8066篇
武器工业   75篇
无线电   72445篇
一般工业技术   114074篇
冶金工业   101357篇
原子能技术   10600篇
自动化技术   56792篇
  2021年   4181篇
  2019年   4185篇
  2018年   13602篇
  2017年   14041篇
  2016年   10939篇
  2015年   5167篇
  2014年   8160篇
  2013年   24122篇
  2012年   15113篇
  2011年   24725篇
  2010年   20649篇
  2009年   21590篇
  2008年   22293篇
  2007年   23750篇
  2006年   15056篇
  2005年   16710篇
  2004年   14794篇
  2003年   14107篇
  2002年   12360篇
  2001年   11877篇
  2000年   11220篇
  1999年   11804篇
  1998年   28667篇
  1997年   20607篇
  1996年   16141篇
  1995年   12972篇
  1994年   11659篇
  1993年   11321篇
  1992年   8718篇
  1991年   8268篇
  1990年   8063篇
  1989年   7586篇
  1988年   7405篇
  1987年   6357篇
  1986年   6339篇
  1985年   7519篇
  1984年   6866篇
  1983年   6352篇
  1982年   5796篇
  1981年   6050篇
  1980年   5604篇
  1979年   5440篇
  1978年   5177篇
  1977年   6130篇
  1976年   7798篇
  1975年   4630篇
  1974年   4460篇
  1973年   4503篇
  1972年   3675篇
  1971年   3315篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
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   
2.
Journal of Materials Science: Materials in Electronics - Non-volatile organic memory devices were fabricated using polystyrene sulfonate (PSS)?+?nitrogen-doped multi-walled carbon...  相似文献   
3.
Journal of Materials Science: Materials in Electronics - Layered transition metal dichalcogenides hold tunable and promising photoelectrochemical properties. MoSe2 is a potential candidate of the...  相似文献   
4.
Journal of Materials Science: Materials in Electronics - Pure PVDF has higher breakdown strength but low dielectric and ferroelectric properties. Thus, we synthesized the LaFeO3 and GdFeO3...  相似文献   
5.
The development of efficient filters is an essential part of industrial machinery design, specifically to increase the lifespan of a machine. In the filter chamber design considered in this study, the magnetic material is placed along the horizontal surface of the filter chamber. The inside of the filter chamber is layered with a porous material to restrict the outflow of unwanted particles. This study aims to investigate the flow, pressure, and heat distribution in a dilating or contracting filter chamber with two outlets driven by injection through a permeable surface. The proposed model of the fluid dynamics within the filter chamber follows the conservation equations in the form of partial differential equations. The model equations are further reduced to a steady case through Lie's symmetry group of transformation. They are then solved using a multivariate spectral-based quasilinearization method on the Chebyshev–Gauss–Lobatto nodes. Insights and analyses of the thermophysical parameters that drive optimal outflow during the filtration process are provided through the graphs of the numerical solutions of the differential equations. We find, among other results, that expansion of the filter chamber leads to an overall decrease in internal pressure and an increase in heat distribution inside the filter chamber. The results also show that shrinking the filter chamber increases the internal momentum inside the filter, which leads to more outflow of filtrates.  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.
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.
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   
9.
Multimedia Tools and Applications - The quality and quantity of agricultural products are significantly affected by plant diseases. The plant diseases could be mitigated if identified at an early...  相似文献   
10.
Wireless Personal Communications - Breast cancer is one of the rapid spreading diseases resulting in the death of younger age group of women. Unfortunately, as the detection of cancer is at later...  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