全文获取类型
收费全文 | 317482篇 |
免费 | 29128篇 |
国内免费 | 17984篇 |
专业分类
电工技术 | 22369篇 |
技术理论 | 9篇 |
综合类 | 25742篇 |
化学工业 | 45274篇 |
金属工艺 | 20533篇 |
机械仪表 | 21055篇 |
建筑科学 | 21286篇 |
矿业工程 | 10818篇 |
能源动力 | 7397篇 |
轻工业 | 27788篇 |
水利工程 | 8095篇 |
石油天然气 | 14963篇 |
武器工业 | 3502篇 |
无线电 | 32655篇 |
一般工业技术 | 38625篇 |
冶金工业 | 17186篇 |
原子能技术 | 7362篇 |
自动化技术 | 39935篇 |
出版年
2024年 | 1699篇 |
2023年 | 4831篇 |
2022年 | 10708篇 |
2021年 | 13960篇 |
2020年 | 10406篇 |
2019年 | 7769篇 |
2018年 | 9180篇 |
2017年 | 10591篇 |
2016年 | 9315篇 |
2015年 | 12631篇 |
2014年 | 16077篇 |
2013年 | 18996篇 |
2012年 | 22039篇 |
2011年 | 23313篇 |
2010年 | 21299篇 |
2009年 | 20766篇 |
2008年 | 20904篇 |
2007年 | 19753篇 |
2006年 | 17502篇 |
2005年 | 14315篇 |
2004年 | 10730篇 |
2003年 | 8522篇 |
2002年 | 8209篇 |
2001年 | 7446篇 |
2000年 | 6313篇 |
1999年 | 4108篇 |
1998年 | 2821篇 |
1997年 | 2350篇 |
1996年 | 2079篇 |
1995年 | 1828篇 |
1994年 | 1534篇 |
1993年 | 1323篇 |
1992年 | 1275篇 |
1991年 | 1125篇 |
1990年 | 1157篇 |
1989年 | 1068篇 |
1988年 | 930篇 |
1987年 | 878篇 |
1986年 | 791篇 |
1985年 | 731篇 |
1984年 | 719篇 |
1981年 | 688篇 |
1979年 | 766篇 |
1978年 | 777篇 |
1977年 | 739篇 |
1976年 | 755篇 |
1975年 | 713篇 |
1974年 | 719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.
73.
74.
Yu. G. Volodin 《Thermal Engineering》2007,54(5):399-402
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
75.
针对6314 ZZz轴承在运行过程中出现异常声的现象,对轴承进行了拆套检查和寿命校核计算,分析得出润滑脂失效是造成异常声的原因,润滑脂的选用应根据实际工况确定. 相似文献
76.
Heidi Bernas Arie J. Plomp Johannes H. Bitter Dmitry Yu. Murzin 《Catalysis Letters》2008,120(1-2):8-13
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
77.
S. M. Obraztsov G. A. Birzhevoi Yu. V. Konobeev V. A. Solov'ev O. S. Silkina 《Atomic Energy》2004,96(2):111-116
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
78.
M. Kangas J. Villegas N. Kumar T. Salmi D.Yu. Murzin F. Sandelin E. Harlin 《Catalysis Today》2005,100(3-4):363-366
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
79.
Yi‐Hung Chen Ching‐Yuan Chang Wei‐Ling Su Chun‐Yu Chiu Yue‐Hwa Yu Pen‐Chi Chiang Chiung‐Fen Chang Je‐Lueng Shie Chyow‐San Chiou Sally IM Chiang 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2005,80(1):68-75
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
80.