全文获取类型
收费全文 | 251707篇 |
免费 | 4102篇 |
国内免费 | 1044篇 |
专业分类
电工技术 | 4327篇 |
综合类 | 201篇 |
化学工业 | 37110篇 |
金属工艺 | 8217篇 |
机械仪表 | 7263篇 |
建筑科学 | 6785篇 |
矿业工程 | 541篇 |
能源动力 | 7236篇 |
轻工业 | 28638篇 |
水利工程 | 2120篇 |
石油天然气 | 1852篇 |
武器工业 | 5篇 |
无线电 | 33393篇 |
一般工业技术 | 46175篇 |
冶金工业 | 46456篇 |
原子能技术 | 3366篇 |
自动化技术 | 23168篇 |
出版年
2021年 | 1798篇 |
2020年 | 1346篇 |
2019年 | 1667篇 |
2018年 | 2571篇 |
2017年 | 2593篇 |
2016年 | 2875篇 |
2015年 | 2163篇 |
2014年 | 3655篇 |
2013年 | 11955篇 |
2012年 | 6754篇 |
2011年 | 9664篇 |
2010年 | 7444篇 |
2009年 | 8394篇 |
2008年 | 8916篇 |
2007年 | 8930篇 |
2006年 | 8278篇 |
2005年 | 7485篇 |
2004年 | 7208篇 |
2003年 | 7093篇 |
2002年 | 6591篇 |
2001年 | 7020篇 |
2000年 | 6324篇 |
1999年 | 6822篇 |
1998年 | 16377篇 |
1997年 | 11367篇 |
1996年 | 8582篇 |
1995年 | 6543篇 |
1994年 | 5709篇 |
1993年 | 5567篇 |
1992年 | 3996篇 |
1991年 | 3774篇 |
1990年 | 3548篇 |
1989年 | 3369篇 |
1988年 | 3276篇 |
1987年 | 2589篇 |
1986年 | 2487篇 |
1985年 | 3156篇 |
1984年 | 2797篇 |
1983年 | 2559篇 |
1982年 | 2344篇 |
1981年 | 2390篇 |
1980年 | 2201篇 |
1979年 | 2048篇 |
1978年 | 1879篇 |
1977年 | 2176篇 |
1976年 | 2724篇 |
1975年 | 1584篇 |
1974年 | 1489篇 |
1973年 | 1558篇 |
1972年 | 1144篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
992.
Since the end of the Cold War and due to the needs to produce titanium more cost‐efficient and thus more attractive for its civilian use, the electroslag remelting (ESR) process has become an increasingly important topic of international research programmes, because titanium and titanium aluminides can be chemically refined by ESR in some degree. Using ESR, titanium turnings from machining steps and scrap from foundries can be remelted, refined and provided as secondary titanium for the market at relatively favourable prices. This article investigates the removability of the main impurities out of titanium and titanium‐aluminium alloys by electroslag remelting using the active slag system CaF2‐Ca‐(CaO). Thermochemical and kinetic aspects of the ESR process are considered. 相似文献
993.
This paper presents a new concept for symmetric boundary element method (SBEM) applicable to 2-D steady-state and transit potential problems. Two kinds of SBEM formulations are derived. Symmetry is obtained simply through matrix manipulation, and no hypersingularity appears. Therefore, SBEM is much easier than the traditional symmetric Galerkin BEM. Compared with the traditional asymmetric BEM, the present SBEM can reduce the computational cost for time domain problems only. However, when applied to BEM/FEM coupling procedure, SBEM can reduce the computational cost for both steady-state and time domain problems. Three numerical examples are included to illustrate the effectiveness and accuracy of the present formulations. 相似文献
994.
Sang C. Park 《The Visual computer》2003,19(1):38-49
A sweeping operation called polygonal extrusion is defined to improve the modeling power of CSG-based modeling. It is assumed that a 2D cross-sectional polygon (sweeping
polygon) moves in space while its containing plane is kept orthogonal to the tangent direction of the trajectory curve, a planar
polygonal chain having no self-intersections. The objective of the paper is to compute the boundary of the swept volume of
the sweeping polygon as a set of polygons (or triangles). The most significant challenge to accomplishing this objective is
the problem of trimming the swept volume. To solve the trimming problem, 2D-curve offsetting methods are employed. Two algorithms
are presented for polygonal extrusion that are based on different offsetting methods, the Voronoi diagram and PWID offset.
The proposed algorithms have been implemented and tested with various examples.
Published online: 28 January 2003 相似文献
995.
Squeeze-film effects of perforated plates for small amplitude vibration are analyzed through modified Reynolds equation (MRE).
The analytical analysis reckons in most important influential factors: compressibility of the air, border effects, and the
resistance caused by vertical air flow passing through perforated holes. It is found that consideration of air compressibility
is necessary for high operating frequency and small ratio of the plate width to the attenuation length. The analytical results
presented in this paper agree with ANSYS simulation results better than that under the air incompressibility assumption. The
analytical analysis can be used to estimate the squeeze-film effects causing damping and stiffness added to the system. Since
the value of Reynolds number involved in this paper is low (< 1), inertial effects are neglected. 相似文献
996.
Pupils' recall of an interactive storybook on CD-ROM 总被引:1,自引:0,他引:1
Abstract This small-scale study compares two groups of Year 4 (8/9 year-old) pupils either reading or playing an interactive storybook . The study considered pupils' recall of propositions, which formed the story setting and episodes, and of micro-propositions and characters' names, and pupils' responses to inferential items derived from the 'interactive storybook'. The study indicates that, whether reading or playing, pupils' recall of the story setting was sound, but pupils who had read the interactive storybook demonstrated greater recall of the story event structure than those who had engaged in interactive picture-play. Pupils who had played the interactive storybook demonstrated significantly greater recall of micro-propositions and names. 相似文献
997.
Sankaralingam K. Nagarajan R. Haiming Liu Changkyu Kim Jaehyuk Huh Burger D. Keckler S.W. Moore C. 《Micro, IEEE》2003,23(6):46-51
The Tera-op reliable intelligently adaptive processing system (TRIPS) architecture seeks to deliver system-level configurability to applications and runtime systems. It does so by employing the concept of polymorphism, which permits the runtime system to configure the hardware execution resources to match the mode of execution and demands of the compiler and application. 相似文献
998.
999.
Two experiments involving 99 undergraduate participants sought to examine the influence of mood states on encoding speed within lexical decision and pronunciation tasks. Mood states were measured naturalistically in Experiment 1 and manipulated in Experiment 2. Stimuli consisted of nouns representing useful (e.g., food) and nonuseful (e.g., lint) objects. Mood states had no implications for initial encoding speed. However, when the same words were presented a 2nd time (i.e., repeated), happy individuals displayed a tendency to encode useful words faster than nonuseful ones. Thus, mood states influenced repetition priming on the basis of stimulus valence. The authors propose that happiness sensitizes individuals to useful or rewarding objects, which in turn creates a stronger memory trace for such stimuli in the future. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
1000.