全文获取类型
收费全文 | 3827篇 |
免费 | 53篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 25篇 |
综合类 | 1篇 |
化学工业 | 467篇 |
金属工艺 | 41篇 |
机械仪表 | 51篇 |
建筑科学 | 62篇 |
矿业工程 | 9篇 |
能源动力 | 77篇 |
轻工业 | 134篇 |
水利工程 | 13篇 |
石油天然气 | 18篇 |
无线电 | 211篇 |
一般工业技术 | 378篇 |
冶金工业 | 2044篇 |
原子能技术 | 27篇 |
自动化技术 | 323篇 |
出版年
2021年 | 45篇 |
2020年 | 31篇 |
2019年 | 32篇 |
2018年 | 32篇 |
2017年 | 32篇 |
2016年 | 21篇 |
2015年 | 28篇 |
2014年 | 48篇 |
2013年 | 79篇 |
2012年 | 65篇 |
2011年 | 65篇 |
2010年 | 66篇 |
2009年 | 64篇 |
2008年 | 80篇 |
2007年 | 77篇 |
2006年 | 71篇 |
2005年 | 61篇 |
2004年 | 57篇 |
2003年 | 67篇 |
2002年 | 47篇 |
2001年 | 60篇 |
2000年 | 52篇 |
1999年 | 81篇 |
1998年 | 564篇 |
1997年 | 359篇 |
1996年 | 260篇 |
1995年 | 166篇 |
1994年 | 152篇 |
1993年 | 124篇 |
1992年 | 43篇 |
1991年 | 58篇 |
1990年 | 48篇 |
1989年 | 48篇 |
1988年 | 59篇 |
1987年 | 46篇 |
1986年 | 33篇 |
1985年 | 58篇 |
1984年 | 35篇 |
1983年 | 26篇 |
1982年 | 40篇 |
1981年 | 38篇 |
1980年 | 27篇 |
1979年 | 23篇 |
1978年 | 31篇 |
1977年 | 70篇 |
1976年 | 109篇 |
1975年 | 18篇 |
1974年 | 22篇 |
1973年 | 18篇 |
1972年 | 17篇 |
排序方式: 共有3881条查询结果,搜索用时 15 毫秒
41.
42.
N. Klein M. Levy-Carciente D. Cohn G. Marom G. Uretzky H. Peleg 《Journal of materials science. Materials in medicine》1993,4(3):285-291
This paper deals with the effect of water absorption on the mechanical performance of selectively biodegradable filament-wound composite soft tissue prostheses. It shows how the water absorption phenomenon can be utilized as a new concept of material design, in contrast to the current view that associates moisture absorption by composite materials exclusively with damage. Harnessing water absorption to property design of vascular grafts has two advantages. The first is the controlled increase of the compliance of the graft during healing, aiming to reach a final stage of isocompliance with the host artery. The second is the water-induced biodegradation which enables regulation of the mural porosity during healing of an initially impervious graft. Filament-wound composite vascular prostheses comprising partially biodegradable matrices, different compositions and various winding angles are studied. Water absorption and material degradation are expressed in terms of relative weight gain/loss, which in turn is correlated with changes in the compliance and in the ultimate strength of the grafts. 相似文献
43.
Three experiments, with 98 undergraduates, investigated the effects of increasing task difficulty and noise intensity on postnoise persistence on the Feather tolerance for frustration puzzles. In Exp I, greater persistence occurred both after exposure to moderate noise levels (55 db [A]) and an easy perceptual-motor task and after high noise levels (90 db [A]) and a more difficult task. The same pattern of persistence was obtained in Exp II, with more attempts to solve the Feather puzzles occurring after moderate noise and an easy cognitive task and after loud noise and a more difficult cognitive task. In Exp III, a modified Feather task was presented with instructions to determine solvability. A similar U-shaped relationship was obtained, with longer correct response times to unsolvable puzzles following low noise and high noise. Such aftereffect patterns are more easily explained as the result of residual arousal than of frustration tolerance. (21 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
44.
45.
Results of simulations, designed to illustrate the influence of power system stabilizers (PSS) on inter-area and local oscillations in interconnected power systems, are reported. It is shown that the PSS location and the voltage characteristics of the system loads are significant factors in the ability of a PSS to increase the damping of interarea oscillations. It is also shown that an interaction between modes in two distinct parts of a power system is possible, due to resonance, and that this might cause distortions in mode shape and participation factors 相似文献
46.
47.
We investigate the transverse modal properties of cylindrical subwavelength metal-clad nanowire and micropost lasers via rigorous theoretical waveguide analysis, including the effects of finite thickness metal cladding and gain in the core. The results of this analysis show that air-metal surface guided TM01 and some hybrid surface guided modes suffer less loss but are less confined to the core, while core-metal surface guided modes are better confined to the core but suffer greater loss. An increase in the thickness of the metal cladding reduces the loss of the core-metal surface guided modes. The modal gain and confinement of the metal-clad cavity are compared to an unclad cavity. 相似文献
48.
Wei Wei Craig A. BennettRyuzo Tanaka Gang HouMichael T. Klein Jr. Michael T. Klein 《Fuel Processing Technology》2008
The complexity of many chemical and refining reaction systems and the thus-derived tedious and time-consuming process of building the associated kinetic models have been major obstacles in the use of fundamental kinetics in the solution of chemical engineering problems. This review summarizes work aimed at removing theses obstacles. Our recent work that has led to the enhancement of the Kinetic Modeler's Toolbox (KMT) and the development of the Kinetic Model Editor (KME) presents an end-to-end solution to the kinetic modeling process, including automated feedstock modeling, reaction network construction, kinetic rate estimation, model programming, process system configurations, model customizations, compilations, model execution and results analysis. 相似文献
49.
A case of a 66 years old patient suffering from a sigmoido-vaginal fistula and diverticulosis, previously treated with a total laparohysterectomy, is reported. Retrograde studies demonstrated the presence of fistula, whereas colonoscopy and barium enema failed. After laparotomy and an appropriate bowel preparation, surgery was restricted to the bowel resection and anastomosis, whereas the vaginal defect was not closed. 相似文献
50.
GI Kempen MJ van Heuvelen RH van den Brink AC Kooijman M Klein PJ Houx J Ormel 《Canadian Metallurgical Quarterly》1996,25(6):458-464
Molecular electrostatic potential (MEP) maps of certain 3-methoxy flavone derivatives having different anti-picornavirus activities have been studied. Geometries of the molecules were optimised and charge distributions computed using the AM1 molecular orbital method. Hybridization displacement charges (HDC) were combined with the L?wdin charge distributions to compute the MEP maps. Reliability of the method of computing MEP maps was tested by studying certain other molecules for which ab initio MEP results are available. The anti-picornavirus activities of the flavones have been shown to be related with negative MEP values in two regions, one near the 3-methoxy group and another in a diagonally opposite region near the substituent attached to the C7 atom of the molecules. 相似文献