全文获取类型
收费全文 | 4542篇 |
免费 | 450篇 |
国内免费 | 10篇 |
专业分类
电工技术 | 47篇 |
综合类 | 6篇 |
化学工业 | 1357篇 |
金属工艺 | 71篇 |
机械仪表 | 104篇 |
建筑科学 | 200篇 |
矿业工程 | 14篇 |
能源动力 | 115篇 |
轻工业 | 517篇 |
水利工程 | 33篇 |
石油天然气 | 12篇 |
无线电 | 490篇 |
一般工业技术 | 796篇 |
冶金工业 | 572篇 |
原子能技术 | 47篇 |
自动化技术 | 621篇 |
出版年
2022年 | 43篇 |
2021年 | 49篇 |
2020年 | 63篇 |
2019年 | 103篇 |
2018年 | 121篇 |
2017年 | 130篇 |
2016年 | 161篇 |
2015年 | 140篇 |
2014年 | 201篇 |
2013年 | 311篇 |
2012年 | 220篇 |
2011年 | 248篇 |
2010年 | 223篇 |
2009年 | 216篇 |
2008年 | 232篇 |
2007年 | 177篇 |
2006年 | 187篇 |
2005年 | 152篇 |
2004年 | 145篇 |
2003年 | 133篇 |
2002年 | 126篇 |
2001年 | 95篇 |
2000年 | 106篇 |
1999年 | 73篇 |
1998年 | 91篇 |
1997年 | 73篇 |
1996年 | 83篇 |
1995年 | 63篇 |
1994年 | 75篇 |
1993年 | 61篇 |
1992年 | 52篇 |
1991年 | 35篇 |
1990年 | 55篇 |
1989年 | 50篇 |
1988年 | 31篇 |
1987年 | 36篇 |
1986年 | 33篇 |
1985年 | 44篇 |
1984年 | 48篇 |
1983年 | 41篇 |
1982年 | 39篇 |
1981年 | 37篇 |
1980年 | 34篇 |
1979年 | 45篇 |
1978年 | 17篇 |
1977年 | 42篇 |
1976年 | 30篇 |
1975年 | 23篇 |
1974年 | 23篇 |
1973年 | 24篇 |
排序方式: 共有5002条查询结果,搜索用时 0 毫秒
21.
Fatima Bennour Jacques Rogez Jean Claude Mathieu 《Journal of the American Ceramic Society》1996,79(10):2752-2754
The Na2 O-Cs2O-SiO2 system has been investigated by means of a new differential thermal analysis apparatus. Two compounds have been observed for the first time in the metasilicate and disilicate joins. The CsNaSi2 O5 disilicate melts congruently at 1217 K and the peritectic fusion of the CsNaSiO3 metasilicate occurs at 1120 K. 相似文献
22.
Nowadays different kinds of double-skin facades are developed and used in new architectural projects. The aim of these facades is, on the one hand, to increase internal comfort and, on the other hand, to decrease energy consumption. In order to optimise the overall performance of the double-skin façades, their detailed behaviour needs to be better understood. The prediction of the airflow within the channel (between the two glazings) is very important for understanding of the double-skin facades behaviour, especially in summer conditions. A comprehensive modelling of a compact double-skin facade equipped with a venetian blind and forced ventilation is proposed here. The modelling is done using the CFD (computational fluid dynamics) approach to assess the air movement within the ventilated facade channel. Three-dimensional airflow is modelled using a homogeneous porous media representation, in order to reduce the size of the mathematical model. A parametric study is proposed here, analysing the impact of three parameters on the airflow development: slat tilt angle, blind position and air outlet position. The distance between the blind and the external glazing was found to have a major impact on the velocity profiles inside the double-skin facade channel. 相似文献
23.
We study deterministic finite automata (DFA) with recursive calls, that is, finite sequences of component DFAs that can call each other recursively. DFAs with recursive calls are akin to recursive state machines and unrestricted hierarchic state machines. We show that they are language equivalent to deterministic pushdown automata (DPDA). 相似文献
24.
Jean Poerre 《钢铁》2003,38(Z1):101-103
全球变暖给钢铁工业带来了巨大的挑战,挑战涉及使用碳的多少和能量利用率.低强度生产可以短期内达到减轻排放,使处于京都协议要求的水平.从中期看,更多地使用废钢也有助于减轻排放.但是为了实现更多地减少温室气体GHG的排放,也即等于实现京都协议之后的排放目标,钢铁工业必须设想有一个新的生产面貌,这形成了未来时期对它的最大挑战.碳的收集和吸收,碳使用中的代用剂,工艺流程中绿色来源的电和氢的应用,这些在未来10年中是必须要发展的,希望通过广泛地国际合作加以实现. 相似文献
25.
Trust for Ubiquitous,Transparent Collaboration 总被引:1,自引:0,他引:1
In this paper, trust-based recommendations control the exchange of personal information between handheld computers. Combined with explicit risk analysis, this enables unobtrusive information exchange, while limiting access to confidential information. The same model can be applied to a wide range of mobile computing tasks, such as managing personal address books and electronic diaries, to automatically provide an appropriate level of security. Recommendations add structure to the information, by associating categories with data and with each other, with degrees of trust belief and disbelief. Since categories also in turn confer privileges and restrict actions, they are analogous to rôles in a Rôle-Based Access Control system, while principals represent their trust policies in recommendations. Participants first compute their trust in information, by combining their own trust assumptions with others' policies. Recommendations are thus linked together to compute a considered, local trust assessment. Actions are then moderated by a risk assessment, which weighs up costs and benefits, including the cost of the user's time, before deciding whether to allow or forbid the information exchange, or ask for help. By unifying trust assessments and access control, participants can take calculated risks to automatically yet safely share their personal information. 相似文献
26.
Shiffman Saul; Paty Jean A.; Gnys Maryann; Kassel Jon D.; Elash Celeste 《Canadian Metallurgical Quarterly》1995,14(4):301
From previous studies, chippers (very light, long-time cigarette smokers) seem not to be nicotine dependent, despite decades of smoking. The effect of tobacco deprivation on chippers' withdrawal reactions was examined. Matched groups of 26 chippers and 25 regular smokers were studied while abstaining or smoking for 2-day blocks, with assessments administered 5 times daily by palm-top computers. As hypothesized, chippers showed no changes as a result of nicotine deprivation. In contrast, regular smokers demonstrated distinct changes in craving, mood, arousal, and sleep disturbance. The computers also tested participants' cognitive performance. Unlike chippers, regular smokers' performance on complex tasks was slower under deprivation; the effect could not be explained by changes in motor performance or simple reaction time. Results suggest performance may have been improved by nicotine rather than worsened by withdrawal. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
27.
28.
Genero Nancy P.; Miller Jean B.; Surrey Janet; Baldwin Lawrence M. 《Canadian Metallurgical Quarterly》1992,6(1):36
In an initial validation study of the Mutual Psychological Development Questionnaire (MPDQ), a measure of perceived mutuality in close relationships, 345 respondents completed the scale for spouse or partner and friend relationships. Results indicated high interitem reliability. Construct and concurrent validity were demonstrated. MPDQ ratings were correlated with adequacy of social support, relationship satisfaction, and cohesion. Ratings correlated negatively with depression. Low spouse or partner mutuality was predictive of significant depressive symptoms in women but not in men. In a 2nd study, 81 respondents completed the scale at 2 time points. Test–retest reliability was satisfactory, and high interitem consistency was replicated. The substantive meaning of these findings, gender differences, and possible future research applications of the MPDQ are disscussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
29.
In the first half of the 21st century, a redistribution of the energy data should occur, where nuclear will play a more important role, particularly as coal will become more and more costly to extract.On a worldwide basis, the unability of oil to be replaced in some areas like transportation, and the difficulty of developing countries to find substitutes for this energy source, could also lead developed countries to keep the energy resources for a better utilization, and give the countries which have no access to other resources, a possibility to develop.Thus, France has extensively enhanced nuclear energy for its electricity production, and, consequently, makes the necessary efforts for the knowledge of the whole fuel cycle. 相似文献
30.
This article allows the determination of the induced perturbations at the ends of the coaxial line in wide frequency band enough. The perturbation source is a current direct point injection into the cable screen in any position. For this, we have applied the theory of the state variables, with foundation of the quasi-TEM approximation, in order to simulate the coaxial line above a ground level that has a finished conductivity. This allows us to supply the current and voltage expressions at the ends of the line as their analytic forms for any conditions of charge. Next, the elaborate objective is to verify experimentally on concrete applications if the test obtained results confirm the theoretical expectations supplied by calculation code finalizing. 相似文献