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   207189篇
  免费   2437篇
  国内免费   566篇
电工技术   3523篇
综合类   145篇
化学工业   32118篇
金属工艺   10280篇
机械仪表   7044篇
建筑科学   4025篇
矿业工程   2171篇
能源动力   4663篇
轻工业   12961篇
水利工程   2935篇
石油天然气   7732篇
武器工业   22篇
无线电   21583篇
一般工业技术   45358篇
冶金工业   34724篇
原子能技术   6635篇
自动化技术   14273篇
  2021年   2056篇
  2019年   2001篇
  2018年   3693篇
  2017年   3729篇
  2016年   4004篇
  2015年   2246篇
  2014年   3802篇
  2013年   8788篇
  2012年   5710篇
  2011年   7261篇
  2010年   5894篇
  2009年   6531篇
  2008年   6656篇
  2007年   6535篇
  2006年   5613篇
  2005年   5153篇
  2004年   4661篇
  2003年   4582篇
  2002年   4406篇
  2001年   4503篇
  2000年   4203篇
  1999年   4222篇
  1998年   10242篇
  1997年   7225篇
  1996年   5540篇
  1995年   4158篇
  1994年   3627篇
  1993年   3868篇
  1992年   3007篇
  1991年   3015篇
  1990年   2923篇
  1989年   2886篇
  1988年   2900篇
  1987年   2530篇
  1986年   2587篇
  1985年   2876篇
  1984年   2707篇
  1983年   2570篇
  1982年   2321篇
  1981年   2293篇
  1980年   2360篇
  1979年   2370篇
  1978年   2399篇
  1977年   2498篇
  1976年   2897篇
  1975年   2201篇
  1974年   2081篇
  1973年   2180篇
  1972年   1945篇
  1971年   1762篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
102.
103.
104.
The heat capacity of ytterbium orthovanadate was first measured by adiabatic calorimetry in the temperature range T?=?12.28–344.06?K. No obvious anomalies were observed on the curve obtained. The values of standard thermodynamic functions in the temperature range T?=?0–400 K were calculated. Based on low-temperature calorimetry data obtained, previously published data on the high-temperature heat capacity of ytterbium orthovanadate were corrected. The anomalous contribution to heat capacity for YbVO4 was compared with the data known for YbPO4.  相似文献   
105.
106.
The molten salt method was used to synthesise the MAX phase compounds Ti2AlC and Ti3AlC2 from elemental powders. Between 900–1000?°C, Ti2AlC was formed alongside ancillary phases TiC and TiAl, which decreased in abundance with increasing synthesis temperature. Changing the stoichiometry and increasing the synthesis temperature to 1300?°C resulted in formation of Ti3AlC2 alongside Ti2AlC and TiC. The type of salt flux used had little effect on the product formation. The reaction pathway for Ti2AlC was determined to be the initial formation of TiC1-x templating on the graphite and titanium aluminides.  相似文献   
107.
Sidorov  G. V.  Myasoedov  N. F. 《Radiochemistry》2020,62(2):260-263
Radiochemistry - Reaction of solid-phase catalytic heterogeneous isotope exchange of 2-deoxy-D-glucose and its derivative, O(6)-(4-bromothiophenyl)guanine-C8-β-D-glucose with tritium has been...  相似文献   
108.
109.
Programming and Computer Software - Modern computer systems often include specialized processors that are programmed in domain-specific languages. The compiler-in-the-loop technology, which assumes...  相似文献   
110.
This study addresses the thermo‐diffusion and the diffusion‐thermo phenomena in a semi‐infinite absorbent channel whose walls are contracting/expanding, with heat source/sink effects. The governing partial differential equations with suitable boundary conditions are transformed to a system of dimensionless ordinary differential equations. An analytic solution of the problem has been found using a technique called homotopy analysis method (HAM). HAM gives consistently valid answers to the problem over an extensive variety of parameters and also provides better accuracy. To validate the analytical results, a comparison has been presented with a numerical solution calculated by using the parallel shooting method. The effects of dimensionless parameters, that is, deformation parameter, Reynolds number, Soret and Dufour numbers, and heat source/sink parameter on the expressions of velocity, temperature, and concentration profiles are analyzed graphically to understand the physics of the deformable channel. It has been noted that the velocity across the channel is higher for the expanding channel, as compared to that for the contracting channel. Also the Soret and Dufour number increases the temperature of the fluid, and decreases the concentration. The temperature profile has an increasing behavior in the case of heat source, and a decreasing behavior in the case of heat sink.  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