全文获取类型
收费全文 | 478668篇 |
免费 | 6942篇 |
国内免费 | 2435篇 |
专业分类
电工技术 | 9740篇 |
技术理论 | 5篇 |
综合类 | 1489篇 |
化学工业 | 73254篇 |
金属工艺 | 19387篇 |
机械仪表 | 14779篇 |
建筑科学 | 11926篇 |
矿业工程 | 2619篇 |
能源动力 | 11180篇 |
轻工业 | 43434篇 |
水利工程 | 5052篇 |
石油天然气 | 9097篇 |
武器工业 | 311篇 |
无线电 | 56479篇 |
一般工业技术 | 90595篇 |
冶金工业 | 87643篇 |
原子能技术 | 9834篇 |
自动化技术 | 41221篇 |
出版年
2021年 | 4148篇 |
2019年 | 3776篇 |
2018年 | 6226篇 |
2017年 | 6261篇 |
2016年 | 6724篇 |
2015年 | 4761篇 |
2014年 | 7886篇 |
2013年 | 20987篇 |
2012年 | 13029篇 |
2011年 | 17450篇 |
2010年 | 13940篇 |
2009年 | 15228篇 |
2008年 | 16601篇 |
2007年 | 16713篇 |
2006年 | 14945篇 |
2005年 | 13261篇 |
2004年 | 12319篇 |
2003年 | 11812篇 |
2002年 | 11474篇 |
2001年 | 11600篇 |
2000年 | 10992篇 |
1999年 | 11072篇 |
1998年 | 25079篇 |
1997年 | 18303篇 |
1996年 | 14290篇 |
1995年 | 10971篇 |
1994年 | 9891篇 |
1993年 | 9721篇 |
1992年 | 7730篇 |
1991年 | 7203篇 |
1990年 | 7152篇 |
1989年 | 6845篇 |
1988年 | 6523篇 |
1987年 | 5703篇 |
1986年 | 5605篇 |
1985年 | 6500篇 |
1984年 | 6146篇 |
1983年 | 5643篇 |
1982年 | 5132篇 |
1981年 | 5423篇 |
1980年 | 5043篇 |
1979年 | 5070篇 |
1978年 | 4842篇 |
1977年 | 5385篇 |
1976年 | 6807篇 |
1975年 | 4391篇 |
1974年 | 4240篇 |
1973年 | 4293篇 |
1972年 | 3541篇 |
1971年 | 3272篇 |
排序方式: 共有10000条查询结果,搜索用时 11 毫秒
981.
There is a growing concern about the importance of interaction effects between neighbouring tall buildings subjected to wind loading. Available results indicate that both the peak dynamic response as well as the mean wind loads may increase substantially due to building interaction.An extensive wind-tunnel study of the interaction between two square prisms with a height-to-base length equal to six was undertaken at the LAC, UFRGS. Fifteen relative prism positions were studied, for wind orientations at every 15°, under smooth-uniform as well as turbulent-shear wind. Mean force and torsional moment coefficients for uniform flow were reported in previous publications. Herein, complete results for turbulent wind are given. In addition, the most important interaction effects observed under both flow conditions are discussed in detail. 相似文献
982.
W D Tiner 《International Journal of Project Management》1985,3(1):13-18
In order to control a project, construction management requires project information. This is obtained through accounting, estimating, cost management and scheduling functions which produce project reports. These reports are best obtained by subdividing the project into small parts. The ways in which each of these functions subdivides a project in order to produce its reports is discussed, together with a means of interrelating this information with a technique known as the work breakdown structure. 相似文献
983.
984.
本工作中我们选择了B2O3-La2O3-Y2O2-ZrO2系统作为玻璃基础组成。最后获得的LaK747/509玻璃组成中,不含有钍的成份。由于该玻璃具有一系列好的性质,如析晶范围窄、析晶速度慢以及粘度大等等,因此可以成功地在12-30L铂埚中进行熔制,并获得了尺寸为φ200×25mm的高质量玻璃。 相似文献
985.
I.L. Lehr 《Corrosion Science》2007,49(5):2210-2225
This work is a study of the electropolymerisation of pyrrole onto iron electrodes in the presence of sodium bis(2-ethylhexyl) sulfosuccinate in a wide pH interval. The characterisation of the films was done using electrochemical techniques, SEM/EDX and IR spectroscopy. We show that it is possible to synthesise homogeneous, adherent and very compact films in the pH range between 7 and 12 under potentiodynamic, galvanostatic and potentiostatic conditions without substrate dissolution. The effects of various parameters on electrodeposition were investigated. The new procedure for the electrochemical synthesis of polypyrrole results in improved anticorrosion properties. The inhibition is proposed to be due to the sum of a repulsion of chloride ions because AOT remains entrapped in the polymer matrix and the presence of the iron oxide. Advantages of the use of surfactants in the electropolymerisation solution are discussed. 相似文献
986.
B. S. Bokshtein D. V. Vaganov S. N. Zhevnenko 《The Physics of Metals and Metallography》2007,104(6):564-570
Surface tension of pure copper and its alloys with Sn has been measured at 1000°C in a hydrogen atmosphere. Surface tension of a free surface equaled 1.81 N/m for pure copper, and 1.55, 1.38, and 1.28 N/m for the alloys with 0.05, 0.22, and 0.33 at % Sn, respectively; surface tension at grain boundaries equaled 0.5 N/m for pure copper, and 0.36, 0.3, and 0.23 N/m for the alloys, respectively. Based on these data, the concentration dependence of tin absorption at a free surface and grain boundaries has been calculated. Parameters of Sn absorption at grain boundaries and a free surface of copper have been compared with those of Sb and Bi. 相似文献
987.
It is essential to automate the scanning path generation process to effectively implement the micro-stereolithography. However, a scanning path that is generated based only on a 3D CAD model introduces dimensional inaccuracies. In micro-stereolithography, the photopolymer solidification is affected by fabrication conditions, such as the optical properties (laser power, laser scanning speed, laser scanning pitch focusing condition, etc.) and material properties of the photopolymer. Thus, the photopolymer solidification phenomena must be considered when generating a laser scanning path. In this paper, a scanning path generation algorithm that uses 3D CAD data and considers the photopolymer solidification phenomena is proposed to improve the dimensional accuracy in micro-stereolithography. Multi-line photopolymer solidification experiments were performed for various laser scanning conditions to examine the photopolymer solidification phenomena. From these experiments, linear relations between the solidification length (width) and scanning length (width) were acquired and stored in a database. Subsequently, these data were utilized to compensate the scanning path of the laser beam. In addition, experiments for determining the layer thickness in the z-direction were performed and these results were also used in the scanning path generation algorithm.This research was supported by the Highly Advanced National Project (http://www.most.go.kr), which performs some of the National R&D Program, and sponsored by the Korean Ministry of Science and Technology under the contract project code M10214000116-02B1500-02010. 相似文献
988.
W. Tang H.Z. Shi G. Xu B.S. Ong Z.D. Popovic J.C. Deng J. Zhao G.H. Rao 《Advanced materials (Deerfield Beach, Fla.)》2005,17(19):2307-2311
989.
V. H. Novyts’kyi V. P. Havrylyuk D. D. Panasenko M. O. Kal’chuk V. Ya. Khoruzhyi 《Materials Science》2006,42(6):799-807
The positive influence of lead (2.5%) on the original structure of a cast composite of the Fe-Cr-Cu-C-Ti system, its wear
rate, friction coefficient, and the formation of secondary structures is established under the conditions of dry friction
and friction with boundary lubrication.
__________
Translated from Fizyko-Khimichna Mekhanika Materialiv, Vol. 42, No. 6, pp. 73–80, November–December, 2006. 相似文献
990.
P Sarkar D Ghosh D Bhattacharya R Kataky SJ Setford SF White APF Turner 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2005,80(12):1389-1394
Allergen levels in indoor environments, leading to many diseases, eg asthma, rhinitis and conjunctivitis, affect a large and increasing fraction of the population. A quite effective and inexpensive method of a rough but very rapid overall assessment of total allergen level in the environment has been developed. The method involved estimation of protein in allergen extracts by screen‐printed electrodes using two different techniques. The biosensor comprised a rhodinised carbon working electrode, a silver/silver chloride reference electrode and a carbon counter electrode. In the first method the enzyme protease reacted with allergen protein to release amino acid, which produced hydrogen peroxide in the presence of amino acid oxidase. This was detected amperometrically. The second method used potassium bromide as electrolyte and the electrode was subjected to dual potential. Bromine, released due to electrolysis at higher potential, was consumed by the allergen protein at lower potential. In the first method, a unique technique was used to microencapsulate the enzyme protease and immobilise it on the surface of the electrode by in‐situ polymerisation to avoid contact with the amino acid oxidase. A total of seven allergens were tested and the results gave a good correlation with the standard protein measurement method. Environmental specimens from indoors, schools and workplaces can be evaluated for the aeroallergens produced by dust mites, animal hairs, cockroach debris, pollens, etc as a means of determining the exposure risk. Copyright © 2005 Society of Chemical Industry 相似文献