全文获取类型
收费全文 | 220224篇 |
免费 | 28901篇 |
国内免费 | 26128篇 |
专业分类
电工技术 | 19774篇 |
技术理论 | 9篇 |
综合类 | 15598篇 |
化学工业 | 46578篇 |
金属工艺 | 10930篇 |
机械仪表 | 14508篇 |
建筑科学 | 11222篇 |
矿业工程 | 3165篇 |
能源动力 | 7308篇 |
轻工业 | 19798篇 |
水利工程 | 3243篇 |
石油天然气 | 5067篇 |
武器工业 | 2253篇 |
无线电 | 30088篇 |
一般工业技术 | 24868篇 |
冶金工业 | 5944篇 |
原子能技术 | 5119篇 |
自动化技术 | 49781篇 |
出版年
2024年 | 829篇 |
2023年 | 3628篇 |
2022年 | 6439篇 |
2021年 | 8679篇 |
2020年 | 7958篇 |
2019年 | 7368篇 |
2018年 | 6790篇 |
2017年 | 8862篇 |
2016年 | 9666篇 |
2015年 | 10941篇 |
2014年 | 11213篇 |
2013年 | 14957篇 |
2012年 | 16615篇 |
2011年 | 18666篇 |
2010年 | 13357篇 |
2009年 | 13295篇 |
2008年 | 14383篇 |
2007年 | 16309篇 |
2006年 | 15386篇 |
2005年 | 13179篇 |
2004年 | 11148篇 |
2003年 | 8855篇 |
2002年 | 6796篇 |
2001年 | 5201篇 |
2000年 | 4363篇 |
1999年 | 3683篇 |
1998年 | 3090篇 |
1997年 | 2508篇 |
1996年 | 2008篇 |
1995年 | 1654篇 |
1994年 | 1448篇 |
1993年 | 1120篇 |
1992年 | 905篇 |
1991年 | 729篇 |
1990年 | 602篇 |
1989年 | 460篇 |
1988年 | 350篇 |
1987年 | 224篇 |
1986年 | 215篇 |
1985年 | 261篇 |
1984年 | 235篇 |
1983年 | 164篇 |
1982年 | 230篇 |
1981年 | 124篇 |
1980年 | 126篇 |
1979年 | 37篇 |
1978年 | 21篇 |
1977年 | 26篇 |
1959年 | 24篇 |
1951年 | 22篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
MODELING LIQUID MASS TRANSFER IN HIGEE SEPARATION PROCESS 总被引:1,自引:0,他引:1
Correspondence concerning this paper should be addressed to Professor Richard S.H. Mah. Hsien-Hsin Tung is now affiliated with Department of Chemical Engineering, California Institute of Technology
Penetration theory is used to describe the liquid mass transfer in Higee separation process. Within a possible range of effective areas, it is shown that the predicted mass transfer coefficients are in reasonable agreement with the estimated mass transfer coefficients. The estimated coefficients were calculated from the experimental data and the possible effective areas. Hence it is concluded the penetration theory is generally applicable to describe liquid mass transfer in Higee separation process. The comparison also suggests that liquid mixing at the junctions of packing materials may be more complete in Higee process than in traditional process. 相似文献
Penetration theory is used to describe the liquid mass transfer in Higee separation process. Within a possible range of effective areas, it is shown that the predicted mass transfer coefficients are in reasonable agreement with the estimated mass transfer coefficients. The estimated coefficients were calculated from the experimental data and the possible effective areas. Hence it is concluded the penetration theory is generally applicable to describe liquid mass transfer in Higee separation process. The comparison also suggests that liquid mixing at the junctions of packing materials may be more complete in Higee process than in traditional process. 相似文献
992.
等离子体氧化nc-Si/SiO_2多层膜的蓝光发射 总被引:1,自引:0,他引:1
报道了在等离子体增强化学气相沉积 (PECVD)系统中用交替淀积 a-Si对其进行原位等离子体氧化的方法制备了 a-Si∶H/ Si O2 多层膜。随着 a-Si∶H子层的厚度从 3 .8nm减小到 1 .5 nm,a-Si∶H/ Si O2 多层膜的光吸收边和光致发光 (PL )出现了蓝移。在晶化的 a-Si∶ H/ Si O2 多层膜中不仅观察到室温下的红光带 (80 0nm)的发光峰 ,而且还观察到蓝光发射 (4 2 5 nm) ,结合 Raman,TEM和 PL测试 ,对其原因作了简单的分析 相似文献
993.
Thermodynamic parameters have been determined for the interaction of methyl orange and poly(vinylpyrrolidone) in aqueous solutions containing tris, tris and hydrochloric acid, or water only. Enthalpy changes were determined by use of a flow microcalorimeter. Free energy changes were calculated from the results of equilbrium dialysis studies. The results are interpreted in terms of the behaviour of poly(vinylpyrrolidone) in these systems. Analysis of data shows that the hydrophobic interactions in the systems are in the order: tris > wateronly > tris-HC1. 相似文献
994.
An outline of the characteristics of PEEK and the versatility of its compositional forms (micro and macro composites) are given to illustrate its wide potential for success in engineering applications. Although it is necessary to have particular tabulations of mechanical properties for engineering design, these are seldom available and consequently it is argued that an understanding of stiffness, toughness and strength properties are required to fully exploit available manufacturer's data and thus develop the full potential of PEEK and its composites. Stiffness characteristics are considered in terms of a modulus function which is dependent on time under load and temperature. In its composite forms, whether reinforced with short or continuous fibres, stiffness anistropy can be both considerable and complex, but some empirical ground-rules are apparent. For continuous fibre composites even in the form of complex lay-ups, it is also possible to attempt some stiffness prediction from certain pseudo-elastic constants. Toughness of PEEK and its composites is described in terms of both comparative and intrinsic properties. Instrumented falling weight impact data, particularly as a function of temperature enable some insight into ductile-brittle transitions for the unreinforced material, but crack initiation and crack propagation processes for the various fibre reinforced forms. Intrinsic toughness is described in terms of linear elastic fracture mechanics theory. Strength properties are described for static and dynamic loading configurations. In particular, PEEK and its composites are evaluated for increasing test severities for strength characteristics; stress concentration, loading form and test temperature are considered. 相似文献
995.
C. N. Cacaval E. C. BuruianÎ D. Rou E. Rusu G. E. Grigoriu V. Brboiu 《Polymer International》1985,17(4):343-346
Thermogravimetry and pyrolysis in combination with gas chromatography and infrared spectroscopy were the experimental techniques applied to the thermal degradation of cinnamoylated poly(vinyl alcohol) samples, constituted from vinyl alcohol-vinyl cinnamate photocrosslinkable copolymers. The thermal decomposition products include gases, liquids and solids. The gases are formed from saturated and unsaturated volatile hydrocarbons C1? C4, carbon monoxide and carbon dioxide. The liquid fraction includes aromatic hydrocarbons and some oxygenated organic compounds. The solid product identified in the greatest amount was cinnamic acid. The content in the thermal decomposition products varies considerably both with copolymer composition and temperature. 相似文献
996.
997.
998.
999.
1000.