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   253456篇
  免费   2793篇
  国内免费   870篇
电工技术   4814篇
综合类   193篇
化学工业   36173篇
金属工艺   9522篇
机械仪表   7556篇
建筑科学   6122篇
矿业工程   880篇
能源动力   7234篇
轻工业   21108篇
水利工程   2204篇
石油天然气   3230篇
武器工业   15篇
无线电   34310篇
一般工业技术   50086篇
冶金工业   48771篇
原子能技术   5078篇
自动化技术   19823篇
  2021年   2176篇
  2020年   1564篇
  2019年   1916篇
  2018年   3276篇
  2017年   3314篇
  2016年   3409篇
  2015年   2224篇
  2014年   3965篇
  2013年   11500篇
  2012年   6246篇
  2011年   8587篇
  2010年   6916篇
  2009年   7900篇
  2008年   8425篇
  2007年   8313篇
  2006年   7383篇
  2005年   6511篇
  2004年   6307篇
  2003年   6572篇
  2002年   6049篇
  2001年   6527篇
  2000年   5988篇
  1999年   6410篇
  1998年   16551篇
  1997年   11453篇
  1996年   8821篇
  1995年   6623篇
  1994年   5915篇
  1993年   5856篇
  1992年   4135篇
  1991年   4029篇
  1990年   3867篇
  1989年   3651篇
  1988年   3569篇
  1987年   3023篇
  1986年   2945篇
  1985年   3210篇
  1984年   2927篇
  1983年   2830篇
  1982年   2642篇
  1981年   2543篇
  1980年   2466篇
  1979年   2314篇
  1978年   2111篇
  1977年   2610篇
  1976年   3572篇
  1975年   1768篇
  1974年   1732篇
  1973年   1671篇
  1972年   1465篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
992.
993.
Fluor公司开发的Fluor SO_2净化工艺具有广泛多样的工艺布局,可以通过经济的方式定制脱除烟气中的有害组成。该工艺几乎能去除全部SO_2并减少CO排放。Fluor SO_x净化工艺的主要步骤已在多套工业装置中得到成功的证实。除技术可行、经济合理之外,Fluor SO_x净化工艺不会产生任何有害副产物,也不会遇到与SO_3 有关的腐蚀问题。此外,该工艺生产高纯度可市售的元素硫。论述了Fluor SO_x净化工艺的特征、技术和成本优势、设计和操作的简易性以及实施的便利性。  相似文献   
994.
In a bench-scale, stainless steel reactor, experiments were carried out to investigate fluidized bed behavior by means of on-line process control. The non-catalytic thermal decomposition of sodium hydrogen carbonate to sodium carbonate, carbon dioxide and water was used a model reaction. The experimental equipment was provided with control systems and reulating units which were connected to a PDP 11/40 computer by means of suitable analogue and digital input/output interfaces. The operating conditions are highly influenced by the chemical reaction as well as by the fluid-dynamical behavior of the reactor. Several experiments were carried out to evaluate the kinetics of the model reaction. The fluid-dynamics was investigated by means of on-line experiments with and without chemical reaction. Based on the experimental results, a model was developed to describe the whole process so that model simulations should yield information on the process itself. With this model, strategies are tested before they are applied to the process computer for on-line process control.  相似文献   
995.
The effect of adding urea to the dyebath on the rate of absorption of reactive and acid dyes by wool, and of acid dyes by other protein bres, has been studied. Possible modesof action of aqueous solutions of urea on wool are discussed. The observed increase in the ite of dyeing in the presence of urea is due to disaggregation of the dye in solution and reduction in dye-protein hydrophobic interactions. The action of urea in promoting fibre swelling is also likely to be a contributory factor.  相似文献   
996.
“Pure” poly(vinyl chloride) resin and four compositions containing poly(vinyl chloride) were subjected to oxidative thermal degradation in air at &400°C both in a quiescent and a flow system. The volatiles formed were identified and quantitatively determined on a gram-per-gram basis. Hydrogen chloride was the main product found. The nature and relative concentration of the produced organic chlorinated species appeared to be dependent not only on the poly(vinyl chloride) constituent but also on the other ingredients. All the compositions contained phthalate ester plasticizers. In the dynamic system, these distilled largely unchanged, whereas under static conditions transformation into phthalic anhydride occurred.  相似文献   
997.
998.
The pheromone system of the summer fruit tortrix mothAdoxophyes orana (Fischer von Röslerstamm) consists of a mixture ofcis-9- andcis-11-tetradecen-1-ol acetate (cis-9- andcis-11-TDA, respectively) in a ratio of 9:1. Substitution of one or both of these compounds by related unsaturated acetates reduced the attractancy. Onlycis-11-TDA could be replaced bycis-11-tridecen-1-ol acetate (cis-11-TriDA), although the 9:1 mixture ofcis-9-TDA andcis-11-TriDA was less attractive in the field than the pheromone system itself. The major component of the pheromone system of the leaf rollerClepsis spectrana (Treitschke)(cis-9-TDA:cis-11-TDA=1:9) could also be replaced bycis-11-TriDA, again with some reduction in attractancy.  相似文献   
999.
Molecular diffusivity of a solute in a solvent may be determined by measuring the extent of dispersion of solute in solvent flowing in a straight circular tube under the conditions of laminar flow. This simple and rapid method for determination of molecular diffusivity in aquous polymer solutions is discussed. Experimental results show a substantial reduction in the solute diffusivity with increase in polymer concentration.  相似文献   
1000.
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