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   719291篇
  免费   51629篇
  国内免费   28602篇
电工技术   40863篇
技术理论   96篇
综合类   48183篇
化学工业   117577篇
金属工艺   39280篇
机械仪表   45637篇
建筑科学   58754篇
矿业工程   23149篇
能源动力   19843篇
轻工业   44178篇
水利工程   12926篇
石油天然气   47177篇
武器工业   5641篇
无线电   78173篇
一般工业技术   79540篇
冶金工业   38711篇
原子能技术   7066篇
自动化技术   92728篇
  2024年   2545篇
  2023年   9714篇
  2022年   17841篇
  2021年   25248篇
  2020年   19469篇
  2019年   15731篇
  2018年   18306篇
  2017年   20916篇
  2016年   19104篇
  2015年   25889篇
  2014年   33874篇
  2013年   41082篇
  2012年   43791篇
  2011年   49047篇
  2010年   43302篇
  2009年   41153篇
  2008年   40622篇
  2007年   39364篇
  2006年   40810篇
  2005年   36120篇
  2004年   23870篇
  2003年   21386篇
  2002年   19613篇
  2001年   17986篇
  2000年   18321篇
  1999年   20674篇
  1998年   16855篇
  1997年   14183篇
  1996年   13366篇
  1995年   11081篇
  1994年   9152篇
  1993年   6439篇
  1992年   5129篇
  1991年   3979篇
  1990年   3200篇
  1989年   2566篇
  1988年   2118篇
  1987年   1388篇
  1986年   1080篇
  1985年   722篇
  1984年   543篇
  1983年   417篇
  1982年   388篇
  1981年   259篇
  1980年   253篇
  1979年   126篇
  1978年   61篇
  1977年   78篇
  1976年   102篇
  1975年   34篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
1.
2.
3.
Li Xiaodi 《中国油气》2006,13(2):18-20,17
World oil production and reserve additions heavily depend on giant oilfields. Currently, there are more than 4,000 producing oilfields in the world, producing around 68 million barrels of oil per day. Most oilfields in the world are minor ones, with oil production below 20,000 barrels per day; only 3% (about 120) oilfields in the world produce over 100,000 barrels per day with overall daily production exceeding 32 million barrels, which accounts for 47% of the total world oil supply . The scales of the oilfields heavily influence economic indices like investment, production and life spans of the oilfields. Therefore, giant oilfields have always been the dream of oil finders and targets of geologists' researches .  相似文献   
4.
A locomotive cabin adsorption air‐conditioner has been equipped in #DF4B‐2369 locomotive; and has been successfully run for 2 years. It is powered by waste heat from the exhaust of the diesel engine. The influence on heat transfer is described by the equivalent heat transfer coefficient or thermal resistance of components inside the adsorber. The variation of adsorption capacity is expressed by a non‐equilibrium adsorption function. The dynamic heat transfer process of adsorption air‐conditioning system is treated with the lumped parameter method. Some typical running experimental results are present. The diesel engine rotating speed and locomotive speed influenced on the refrigeration system are discussed. The maximum mean refrigeration power is regarded as an objective function. Based on experiments and theoretical analysis, the running characteristics of the air‐conditioning system are optimized. Some techniques of performance improvement are suggested as well. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   
5.
6.
The oxidation/sulphidation behaviour of a Ti‐46.7Al‐1.9W‐0.5Si alloy with a TiAl3 diffusion coating was studied in an environment of H2/H2S/H2O at 850oC. The kinetic results demonstrate that the TiAl3 coating significantly increased the high temperature corrosion resistance of Ti‐46.7Al‐1.9W‐0.5Si. The SEM, EDX, XRD and TEM analysis reveals that the formation of an Al2O3 scale on the surface of the TiAl3‐coated sample was responsible for the enhancement of the corroison resistance. The Ti‐46.7Al‐1.9W‐0.5Si alloy was also modified by Nb ion implantation. The Nb ion implanted and as received sampels were subjected to cyclic oxidation in an open air at 800oC. The Nb ion implantation not only increased the oxidation resistance but also substantially improved the adhesion of scale to the substrate.  相似文献   
7.
8.
Studies on the deactivations and initiations of gas phase polymerizations of 1,3‐butadiene have been achieved by Monte Carlo simulation. Initiation and deactivation control the reaction before and after the peak of the polymerization rate, respectively. The influence of polymerization temperature has been studied. Monte Carlo modeling of polymerization kinetics and mechanism was confirmed by the agreement of experimental data and simulation results of polymerizations run with a temporary evacuation of monomer. The balance of catalysts and active chains is established by both initiation and chain transfer reactions with cocatalyst, which causes a ‘pseudo‐stability’ stage. © 2003 Society of Chemical Industry  相似文献   
9.
For the first time, we successfully fabricated and demonstrated high performance metal-insulator-metal (MIM) capacitors with HfO/sub 2/-Al/sub 2/O/sub 3/ laminate dielectric using atomic layer deposition (ALD) technique. Our data indicates that the laminate MIM capacitor can provide high capacitance density of 12.8 fF//spl mu/m/sup 2/ from 10 kHz up to 20 GHz, very low leakage current of 3.2 /spl times/ 10/sup -8/ A/cm/sup 2/ at 3.3 V, small linear voltage coefficient of capacitance of 240 ppm/V together with quadratic one of 1830 ppm/V/sup 2/, temperature coefficient of capacitance of 182 ppm//spl deg/C, and high breakdown field of /spl sim/6 MV/cm as well as promising reliability. As a result, the HfO/sub 2/-Al/sub 2/O/sub 3/ laminate is a very promising candidate for next generation MIM capacitor for radio frequency and mixed signal integrated circuit applications.  相似文献   
10.
王德宪  郭利娅 《玻璃》2003,30(3):22-27
第三节 常见氧化物膜目前研究最多的氧化物膜可谓二氧化硅和二氧化钛膜 ,这两种薄膜也是接受呈色离子、制备彩色镀膜常用的基体膜 ,所以 ,有必要将它们单独列出 ,加以讨论。1 二氧化钛膜在所有高折射率材料中 ,由钛的化合物制备的氧化物膜具有特殊的实际意义。因此 ,对二氧化  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