全文获取类型
收费全文 | 15896篇 |
免费 | 1414篇 |
国内免费 | 1449篇 |
专业分类
电工技术 | 1258篇 |
综合类 | 836篇 |
化学工业 | 6685篇 |
金属工艺 | 248篇 |
机械仪表 | 505篇 |
建筑科学 | 606篇 |
矿业工程 | 101篇 |
能源动力 | 1110篇 |
轻工业 | 1236篇 |
水利工程 | 104篇 |
石油天然气 | 983篇 |
武器工业 | 36篇 |
无线电 | 200篇 |
一般工业技术 | 694篇 |
冶金工业 | 259篇 |
原子能技术 | 2879篇 |
自动化技术 | 1019篇 |
出版年
2024年 | 57篇 |
2023年 | 226篇 |
2022年 | 577篇 |
2021年 | 647篇 |
2020年 | 559篇 |
2019年 | 542篇 |
2018年 | 490篇 |
2017年 | 542篇 |
2016年 | 591篇 |
2015年 | 514篇 |
2014年 | 870篇 |
2013年 | 1596篇 |
2012年 | 892篇 |
2011年 | 1064篇 |
2010年 | 847篇 |
2009年 | 873篇 |
2008年 | 762篇 |
2007年 | 831篇 |
2006年 | 783篇 |
2005年 | 734篇 |
2004年 | 605篇 |
2003年 | 628篇 |
2002年 | 526篇 |
2001年 | 464篇 |
2000年 | 370篇 |
1999年 | 352篇 |
1998年 | 267篇 |
1997年 | 240篇 |
1996年 | 191篇 |
1995年 | 187篇 |
1994年 | 168篇 |
1993年 | 130篇 |
1992年 | 94篇 |
1991年 | 117篇 |
1990年 | 97篇 |
1989年 | 67篇 |
1988年 | 37篇 |
1987年 | 57篇 |
1986年 | 30篇 |
1985年 | 37篇 |
1984年 | 21篇 |
1983年 | 9篇 |
1982年 | 6篇 |
1981年 | 7篇 |
1980年 | 10篇 |
1979年 | 2篇 |
1975年 | 2篇 |
1974年 | 1篇 |
1959年 | 32篇 |
1951年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
Minimizing the number of tool switches on a flexible machine 总被引:5,自引:0,他引:5
Yves Crama Antoon W. J. Kolen Alwin G. Oerlemans Frits C. R. Spieksma 《International Journal of Flexible Manufacturing Systems》1994,6(1):33-54
This article analyzes a tool switching problem arising in certain flexible manufacturing environments. A batch of jobs have to be successively processed on a single flexible machine. Each job requires a subset of tools, which have to be placed in the tool magazine of the machine before the job can be processed. The tool magazine has a limited capacity, and, in general, the number of tools needed to produce all the jobs exceeds this capacity. Hence, it is sometimes necessary to change tools between two jobs in a sequence. The problem is then to determine a job sequence and an associated sequence of loadings for the tool magazine, such that the total number of tool switches is minimized. This problem has been previously considered by several authors; it is here revisited, both from a theoretical and from a computational viewpoint. Basic results concerning the computational complexity of the problem are established. Several heuristics are proposed for its solution, and their performance is computationally assessed. 相似文献
92.
本文主要完成了液态金属钠高温沸腾实验回路的应力分析与计算,确定了回路高温区连接管系的布置型式和支吊架系统,是该回路总体设计的重要组成部分。 相似文献
93.
对长石、石英、龙岩土、莱阳土4种因素各取4个水平,用正交表L16(45)安排16个试验,分析了这16个试验产品的吸水率、白度、热稳定性与每种因素各水平之间的关系.得出了白瓷坯料的最佳配方。其中,长石19,石英21,龙岩土21.莱阳土0. 相似文献
94.
95.
96.
Optimal Conditions for Preparing Ultra-Fine CeO2 Powders in A Submerged Circulative Impinging Stream Reactor 总被引:1,自引:0,他引:1
Cerium carbonate powders were produced in a submerged circulation impinging stream reactor (SCISR) from Ce(NO3)3·6H2O. NH4HCO3 was used as a precipitant in the reaction. Cerium carbonate powders were roasted to produce ultra-fine cerium dioxide (CeO2) powders. The optimal conditions of such production process were obtained by orthogonal and one-factor experiments. The results showed that ultra-fine and narrowly distributed cerium carbonate powders were produced under the optimal flowing conditions. The concentrations of Ce(NO3)3 and NH4HCO3 solutions were 0.25 and 0.3 mol·L-1, respectively. The concentration of PEG4000 added in these two solutions was 4 g·L-1. The stirring ratio, reaction temperature, feeding time, solution pH, reaction time and digestion time were 900 r·min-1, 80 ℃, 20 min, 5~6, 5 min and 1 h, respectively. The final product, CeO2 powders, was obtained by roasting the produced cerium carbonate in air for 3 h at 500 ℃. The finally produced CeO2 powders were torispherical particles with a narrow size distribution of 0.8~2.5 μm. The crystal structure of CeO2 powders belonged to cubic crystal system and its space point group was O5H-FM3M. Under optimal conditions, powders produced by SCISR were finer and more narrowly distributed than that by Stirred Tank Reactor (STR). 相似文献
97.
Athanasios Eftaxias Josep Font Agusti Fortuny Azael Fabregat Frank Stüber 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2005,80(6):677-687
The wet air oxidation of phenol over a commercial active carbon catalyst was studied in a trickle bed reactor (TBR) in the temperature and oxygen partial pressure ranges of 120–160 °C and 0.1–0.2 MPa, respectively. The performance of the active carbon was compared in terms of phenol and COD destruction. The weight change of active carbon due to reaction was also measured. Finally, oxic phenol adsorption isotherms were assessed in batch conditions at 25, 125 and 160 °C. In order to use the conversion data obtained from the TBR for a kinetic study, special care was taken to check the kinetic control in the TBR experiments. Several kinetic models including power law or Langmuir–Hinshelwood expressions were considered to describe the catalytic oxidation of phenol over active carbon. The simple power law model with first order dependence on both phenol and oxygen concentration predicted satisfactorily the experimental data not only over the entire range of operating conditions studied, but also outside its validity range. Copyright © 2005 Society of Chemical Industry 相似文献
98.
99.
论述R-X图解法计算多级串联理想混合反应器的基本原理,并结合实例,对R-X法的计算步骤予以详细介绍,为多级串联反应器的设计与计算,提供一种新颖适用的图解计算方法。 相似文献
100.
C. Llopis F. Revents L. Batet C. Pretel I. Sol 《Nuclear Engineering and Design》2007,237(18):2014-2023
The Technical University of Catalonia (UPC) has been jointly working with the Asociación Nuclear Ascó-Vandellòs (ANAV) for a number of years in order to establish, qualify and use best estimate (BE) models for the reactors under the control of ANAV. ANAV is the consortium that is responsible for operation of the Ascó and Vandellòs-II reactors. The reactors are Westinghouse-design three-loop PWRs with an approximate electrical power of 1000 MW. The existing integral plant models for each plant are currently used for many different purposes among which are support of plant operation and control. Quite a number of studies have been done in order to improve both safety and plant competitiveness. Most of these dynamic analyses were carried out in relation to transients starting at nominal full power or at least, very close to full power. This paper develops a specific use of the Vandellòs-II plant model for operation and control support at low power involving new ranges of system actuation parameters. It also examines scenarios that are somewhat different from those typically analysed. The study starts showing the results of an assessment case, which is a start-up test and provides some additional qualification, and subsequently attempts to establish calculations to support both an improvement in feed water controls and to set up operating recommendations for low-load manual operation of feed water turbo-pump. Both results hopefully, will produce an outcome, which leads to an improvement in safety and reduces reactor trip probability. 相似文献