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   78183篇
  免费   3262篇
  国内免费   1528篇
电工技术   2413篇
技术理论   4篇
综合类   2454篇
化学工业   9032篇
金属工艺   5211篇
机械仪表   7621篇
建筑科学   10822篇
矿业工程   2223篇
能源动力   4744篇
轻工业   3250篇
水利工程   754篇
石油天然气   2264篇
武器工业   587篇
无线电   5774篇
一般工业技术   6877篇
冶金工业   2884篇
原子能技术   1093篇
自动化技术   14966篇
  2024年   489篇
  2023年   891篇
  2022年   1139篇
  2021年   1602篇
  2020年   1683篇
  2019年   1392篇
  2018年   1438篇
  2017年   1636篇
  2016年   1973篇
  2015年   2286篇
  2014年   4084篇
  2013年   4362篇
  2012年   4603篇
  2011年   5822篇
  2010年   3919篇
  2009年   4223篇
  2008年   3912篇
  2007年   4848篇
  2006年   4710篇
  2005年   4286篇
  2004年   3643篇
  2003年   3394篇
  2002年   2782篇
  2001年   2170篇
  2000年   1960篇
  1999年   1899篇
  1998年   1483篇
  1997年   1241篇
  1996年   1030篇
  1995年   866篇
  1994年   709篇
  1993年   489篇
  1992年   428篇
  1991年   353篇
  1990年   233篇
  1989年   208篇
  1988年   172篇
  1987年   96篇
  1986年   80篇
  1985年   96篇
  1984年   91篇
  1983年   51篇
  1982年   35篇
  1981年   34篇
  1980年   24篇
  1979年   20篇
  1978年   15篇
  1977年   15篇
  1976年   16篇
  1975年   11篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
1.
2.
This article, the first of three articles on the synthesis of rice processing plants, focuses on the development of simplified mathematical models necessary for use in optimizing rice processing plants. The second concentrates on the optimal synthesis of a rice plant and the third on the sensitivity of the optimization to uncertainty in model parameters. Existing models for rice processing unit operations are not suitable for flowsheet optimization and new models need to be developed to overcome numerical difficulties that occur in optimization applications, specifically in mixed integer nonlinear programming (MINLP) applications. Simplified models of the drying, cooling, and tempering units are developed. In addition head rice yield models, used as a quality indicator, energy consumption, and economic models were also developed. Naturally, the new models exhibit some mismatch with respect to the existing models from which they were developed. However, a sensitivity analysis, presented in Part III, has shown that the optimal flowsheet structure was not sensitive to a lack of fit between the simplified and complex models. The simplified models were found adequate to be appropriate for use at the synthesis stage.  相似文献   
3.
A nonstationary model of SO2 absorption from a gas phase to a countercurrent falling film of absorbing slurry was developed. Laminar, wavy and turbulent film structures were considered based on published information. Resistances to the mass transfer on the gas and the liquid sides of the interphase were considered, together with chemical reactions in the liquid phase. Relevant chemical equilibria in the liquid phase were modeled. Original experimental data on the neutralization reagent dissolution rate presented as a polydispersed two‐phase system of solids and on the rate of dissolved sulfite oxidation were used. The model was verified with experimental data from a laboratory‐scale falling‐film absorber using a single vertical tube under various geometrical and operating conditions, and a very good agreement was found with the experiment. Parametric sensitivity analysis showed the critical parts of the model.  相似文献   
4.
5.
对己二腈工业反应器提出了两釜串联带回流的模型,通过模拟计算得出模型的级间返混系数 f=6的结论。该模型能较好地预测工业反应器中物料组分浓度变化和气、液两相的流动特性;指出了现工业反应器的鼓泡中和段体积偏小是造成己二酸浓度偏高的关键;提出了可以通过增加串连一个鼓泡预反应段的改造方案,能有效地降低己二酸的浓度,从7%降至4%左右,从而能较好地减缓腐蚀和结焦。  相似文献   
6.
测定钠中杂质的手动阻塞计的研究   总被引:1,自引:1,他引:0  
文章介绍了测定钠中杂质浓度的手动阻塞计的原理、装置和实验结果。为了减少测量误差,我们研究了影响准确测定阻塞温度的因素,并且找到了减少测量误差的办法。在同样的杂质饱和温度下,该阻塞计测得的高、低阻塞温度所对应的杂质浓度差是很接近的。对氧其差值为1.03ppm;对氢为0.0763ppm。  相似文献   
7.
Action calculi, which generalise process calculi such as Petri nets, π-calculusand ambient calculus, have been presented in terms of action graphs. We here offer linear action graphs as a primitive basis for action calculi. This paper presents the category of embeddings of undirected linear action graphs without nesting, using a novel form of graphical reasoning which simplifies some otherwise complex manipulations in regular algebra. The results are adapted in a few lines to directed graphs. This work is part of a long-term search for a uniform behavioural theory for process calculi. Received October 2000 / Accepted in revised form April 2001  相似文献   
8.
9.
该文介绍了Mall的产生条件和国内发展概况,并结合实例分析,着重论述建筑设计方面的有关问题。  相似文献   
10.
High cycle fatigue of bolted connections Extensive tests regarding the influences on the fatigue of bolt‐nut‐connections of preloading with torsion, of preloading with yielding, of loading with superimposed bending and of the tested lot are processed. These influences are not yet known according to VDI 2230. New testing devices were designed for these tests, which allow a far less expensive operation and may easily be used for bolts of diameters up to M100 and testing frequencies up to 1000 Hz. The validity of fatigue resistance according to VDI 2230 is specified with respect to the test results. The determined influence of the tested lots is unexpectedly high. The manufacturing process of bolts should be improved to minimize this influence.  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