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   224515篇
  免费   18026篇
  国内免费   10072篇
电工技术   13886篇
技术理论   12篇
综合类   13485篇
化学工业   34628篇
金属工艺   13578篇
机械仪表   14431篇
建筑科学   14400篇
矿业工程   5807篇
能源动力   5417篇
轻工业   13829篇
水利工程   4903篇
石油天然气   12381篇
武器工业   1859篇
无线电   24565篇
一般工业技术   32010篇
冶金工业   13264篇
原子能技术   5660篇
自动化技术   28498篇
  2024年   1005篇
  2023年   3215篇
  2022年   6492篇
  2021年   8809篇
  2020年   6638篇
  2019年   5500篇
  2018年   6884篇
  2017年   7600篇
  2016年   6940篇
  2015年   8418篇
  2014年   10729篇
  2013年   12851篇
  2012年   14216篇
  2011年   15351篇
  2010年   13281篇
  2009年   12781篇
  2008年   12832篇
  2007年   12154篇
  2006年   10980篇
  2005年   9177篇
  2004年   6811篇
  2003年   6105篇
  2002年   6038篇
  2001年   5422篇
  2000年   4666篇
  1999年   3976篇
  1998年   2996篇
  1997年   2500篇
  1996年   2218篇
  1995年   1960篇
  1994年   1638篇
  1993年   1356篇
  1992年   1310篇
  1991年   1131篇
  1990年   1132篇
  1989年   1035篇
  1988年   921篇
  1987年   860篇
  1986年   775篇
  1985年   722篇
  1984年   704篇
  1981年   675篇
  1979年   746篇
  1978年   777篇
  1977年   740篇
  1976年   755篇
  1975年   713篇
  1974年   720篇
  1973年   723篇
  1972年   705篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
中国古陶艺制品造型,釉色,装饰等艺术符号都与每时期的阶段性精神和物质生活相联系,但在"现代艺术"文化认识领域中,往往从理论思维角度把陶艺实用目的的物质性排斥在文化范畴之外。艺术常常强调物质的观赏性,而陶艺的实用功能就是这种文化类型的主体,陶艺的文化性和功能性,具有实用和审美文化的高度叠合,永久地承载着实用功能和精神功能两大内容。  相似文献   
72.
水泥厂回转窑简体内砌筑了耐火砖隔热,但仍有部分热通过简体以辐射的形式散失到大气中,吸收利用这部分辐射热也是一项节能减排的举措.  相似文献   
73.
The results of experimental study of unsteady effects on local heat transfer coefficients caused by abruptly increasing of the gas flow temperature in the inlet section of a cylindrical channel are presented.  相似文献   
74.
The density functional theory (DFT/B3LYP) calculations were applied to investigate the interaction of a Pt6 particle with the ZSM-5 zeolite framework. The electronic structure of the metal particle is strongly affected by the interaction with basic framework oxygens and acid sites of the zeolite support. Adsorption on basic sites (Eads = 6 kcal/mol) favors the formation of the electron enriched metal cluster. Interaction of the platinum cluster with the acid site characterized by stabilization energy of 47 kcal/mol results in oxidation of the metal particle and suppression of Brønsted acidity of the support. The hypothesis is put forward that the oxidized platinum particle can function as an active site for the alkane isomerisation on platinum supported high silica zeolites.  相似文献   
75.
The results of a computational experiment with a neural-net model simulating the effect of the chemical composition on the plastic properties of ÉP-450 steel are presented. It is shown that computer-aided development of reactor steel with prescribed properties is, in principle, possible.  相似文献   
76.
The results of development work on the SVBR-75/100 modular fast reactor cooled by lead–bismuth coolant are presented. The design is based on the experience gained operating reactors in nuclear-powered submarines. The SVBR-75/100 reactor is inherently safe because of its low power, the chemical inertness and high boiling point of the lead–bismuth coolant, and the integrated basin-type arrangement of the first-loop equipment. This eliminates the conflict between the safety and economic requirements that is characteristic of conventional-type reactors. The lower power makes it possible to build the reactor in a factory and deliver the reactor using any form of transportation to the nuclear power plant site. All safety systems operate passively. Most of these systems are used as normal-operating systems. This creates conditions for multipurpose applications of such reactor modules in developed and developing countries.  相似文献   
77.
Age assessment and control of the reliability of the coolant flow-rate measurement system of the RBMK-1500 reactor at the Ignalina nuclear power plant are examined. A statistical analysis is made of the data obtained from measurements of the techanical characteristics of SHADR-32M flow meters. A mathematical model of the aging of flow meters and reliability estimates is constructed. A strategy is developed for replacing SHADR; this strategy makes it possible to support the required relaibility of the entire coolant flow-rate measurement system.  相似文献   
78.
79.
An investigation of the effect of reaction conditions on product distribution in the skeletal isomerisation reaction of linear butenes has been carried out. The main reaction routes over ferrierite have been identified. Beside the main product isobutene, major by-product formation occurs. The unwanted reactions include dimerisation of butene to form octenes, hydrogen transfer yielding small amounts of saturated C3 and C4 hydrocarbons and disproportionation producing propene and pentenes. The most abundant by-products were pentene and propene, though these were not formed in equimolar amounts as could be expected. Oligomerisation experiments of propene over ferrierite produced large amounts of butene and pentene, revealing the presence of adsorbed nonene. The cracking of this surface species to hexene and propene is the most likely reaction route for the excess propene formation. This additional path to propene formation operates mainly at temperatures above 623 K.  相似文献   
80.
This study investigates the ozonation of CI Reactive Black 5 (RB5) by using the rotating packed bed (RPB) and completely stirred tank reactor (CSTR) as ozone contactors. The RPB, which provides high gravitational force by adjusting the rotational speed, was employed as a novel ozone contactor. The same ozone dosage was separately introduced into either the RPB or the CSTR for the investigation, while the experimental solution was continuously circulated within the apparatus consisting of the RPB and CSTR. The decolorization and mineralization efficiencies of RB5 in the course of ozonation are compared for these two methods. Moreover, the dissolved and off‐gas ozone concentrations were simultaneously monitored for the further analysis. As a result, the ozone mass transfer rate per unit volume of the RPB was significantly higher because of its higher mass transfer coefficient and gas–liquid concentration driving force. Furthermore, ozonation kinetics was found to be independent of the gravitational magnitude of an ozone gas–liquid contactor. Therefore, the results suggest employing RPBs as ozone‐contacting devices with the advantage of volume reduction. The experimental results, which can be used for further modeling of the ozonation process in the RPB, also show the requirement of correct design for the RPB. Consequently, the present study is useful for the understanding of practical application of RPBs. Copyright © 2004 Society of Chemical Industry  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