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   155353篇
  免费   13332篇
  国内免费   6805篇
电工技术   6640篇
技术理论   10篇
综合类   14124篇
化学工业   26588篇
金属工艺   8152篇
机械仪表   5404篇
建筑科学   20560篇
矿业工程   8409篇
能源动力   7253篇
轻工业   9799篇
水利工程   20511篇
石油天然气   12442篇
武器工业   595篇
无线电   5666篇
一般工业技术   12115篇
冶金工业   9112篇
原子能技术   1886篇
自动化技术   6224篇
  2024年   567篇
  2023年   2337篇
  2022年   3681篇
  2021年   4570篇
  2020年   4856篇
  2019年   4275篇
  2018年   3802篇
  2017年   4613篇
  2016年   4987篇
  2015年   5046篇
  2014年   8931篇
  2013年   9099篇
  2012年   10949篇
  2011年   11053篇
  2010年   8259篇
  2009年   8713篇
  2008年   7759篇
  2007年   10241篇
  2006年   9571篇
  2005年   8761篇
  2004年   6998篇
  2003年   6595篇
  2002年   5624篇
  2001年   4616篇
  2000年   3946篇
  1999年   3086篇
  1998年   2317篇
  1997年   1893篇
  1996年   1574篇
  1995年   1385篇
  1994年   1043篇
  1993年   825篇
  1992年   655篇
  1991年   482篇
  1990年   421篇
  1989年   402篇
  1988年   270篇
  1987年   248篇
  1986年   178篇
  1985年   178篇
  1984年   162篇
  1983年   99篇
  1982年   65篇
  1981年   46篇
  1980年   47篇
  1979年   50篇
  1978年   22篇
  1977年   29篇
  1976年   23篇
  1975年   26篇
排序方式: 共有10000条查询结果,搜索用时 11 毫秒
31.
The adsorption of the three metal ions, copper, cadmium and zinc in single component and multi-component mixtures in aqueous solutions by lignite is reported. A comparison is made between the single component saturation uptake and the multi-component uptakes. The isotherms indicate a competitive uptake with copper being preferentially absorbed by the lignite in multi-component solutions. The isotherms are plotted to obtain the Langmuir constants, the Freundlich constants and the Redlich–Peterson constants. Lignite is shown to possess an affinity for the metal ions which make its use as an adsorbent a possible alternative to the use of more expensive activated carbons.  相似文献   
32.
Thermal stratification in a mantled hot water storage tank is analysed numerically for different water inlet velocities. The aim is to obtain higher thermal stratification and supply hot water for usage as long as possible. Twelve different water inlet velocities to the hot water storage tank are considered. The numerical method is validated by comparing its results against experimental and numerical results from the literature. It turned out that the results obtained from the numerical analysis have shown very good agreements with the results from previous works. As a result, the water temperature in the tank increases with the increase of the water inlet velocities to the mantle but this increment is not proportional. After a period of operation of 7.2 h, which corresponds to the average sunshine duration in Turkey, temperature increments of 6.5 and 35 K have been estimated for the hot water inlet velocities of 0.01 and 0.3 m s?1, respectively, at a radial distance of 0.1 m and a height of 1 m inside the storage tank. Copyright © 2005 John Wiley & Sons, Ltd.  相似文献   
33.
34.
本文采用粒子追踪理论对水平管中粒子流动状态进行了数值模拟.文中提出了一种新的粒子碰撞模型,并忽略粒子的旋转和扬力,仅考虑气流阻力和重力对粒子的影响,在输送量为9.13×10~3kg/s,混合比约0.3的条件下,通过数值计算得知:由于粒子间的碰撞,使得异径粒子的速度趋向平均化;粒子间的碰撞是粒子悬浮的原因之一;粒子的浓度沿管轴向是随时间而发生变化的.  相似文献   
35.
36.
任向红  樊秉安  李瑛 《粘接》2002,23(1):1-2,6
坑道水下堵漏剂的研制包括F-1、F-2和F-3型。其中F-1是一种有机堵漏剂,它可以在水中固化;F-2是一种无机防水堵漏剂,施工方便;F-3是速凝型,它可在瞬间固化,能对坑道的涌水口进行堵漏。  相似文献   
37.
Provides the biography of Dante Cicchetti and announces that he has received the APA Award for Distinguished Senior Career Contributions to Psychology in the Public Interest (2004) for his seminal role in bridging theory, research, and practice by fostering the emergence and coalescence of the field of developmental psychopathology. A selected bibliography is also provided. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
38.
介绍首钢2号高炉大修采用的新技术、开炉操作和投产以来的生产情况。  相似文献   
39.
对职业教育的大众性问题进行了论述、实证分析和理论、政策、改革等思考。  相似文献   
40.
The aluminium species in different tea infusions were investigated, by determining their stability constants and concentration. This was done for some particular samples using a simple experimental method based on the sorption of aluminium on the strongly sorbing resin Chelex 100, by a batch procedure. From the thermodynamic information obtained it is possible to calculate the concentration of the different species, and in particular that of the free metal ion, which is very important for evaluating the adsorption of aluminium on biological membranes. It was found that aluminium in the tea infusions here considered is present at high total concentration, approximately 0.1 mM, but mainly linked to strong complexes, for instance with side reaction coefficient higher than 10(5.11) at pH 3.95 in one case (tea 1). This could be the reason for the low toxicity of aluminium in tea. These strong complexes were not dissociated even in the presence of Chelex 100. In this case only a limiting value of the reaction coefficient could be evaluated. The presence of the very strong complexes was found in all the tea sample here considered. In two of the considered samples (one black and one green tea) a part of Al(III) was linked to less strong complexes, for example with a reaction coefficient 10(4.14) (tea 2, pH 4.20). The presence in the considered tea infusions of other substances able to complex aluminium was also detected, by the well known ligand titration procedure, at concentration ranging from 0.65 to 3.37 mM in three tea infusions, and at somewhat higher concentration in the case of the ready drink, which was also considered for comparison.  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