全文获取类型
收费全文 | 15516篇 |
免费 | 1271篇 |
国内免费 | 553篇 |
专业分类
电工技术 | 1247篇 |
技术理论 | 1篇 |
综合类 | 1379篇 |
化学工业 | 1053篇 |
金属工艺 | 1216篇 |
机械仪表 | 1709篇 |
建筑科学 | 1738篇 |
矿业工程 | 349篇 |
能源动力 | 548篇 |
轻工业 | 1570篇 |
水利工程 | 257篇 |
石油天然气 | 499篇 |
武器工业 | 249篇 |
无线电 | 567篇 |
一般工业技术 | 1981篇 |
冶金工业 | 1933篇 |
原子能技术 | 105篇 |
自动化技术 | 939篇 |
出版年
2024年 | 110篇 |
2023年 | 247篇 |
2022年 | 386篇 |
2021年 | 446篇 |
2020年 | 501篇 |
2019年 | 384篇 |
2018年 | 407篇 |
2017年 | 469篇 |
2016年 | 549篇 |
2015年 | 567篇 |
2014年 | 911篇 |
2013年 | 873篇 |
2012年 | 842篇 |
2011年 | 1143篇 |
2010年 | 867篇 |
2009年 | 908篇 |
2008年 | 813篇 |
2007年 | 945篇 |
2006年 | 902篇 |
2005年 | 795篇 |
2004年 | 686篇 |
2003年 | 595篇 |
2002年 | 547篇 |
2001年 | 465篇 |
2000年 | 333篇 |
1999年 | 310篇 |
1998年 | 216篇 |
1997年 | 203篇 |
1996年 | 187篇 |
1995年 | 133篇 |
1994年 | 108篇 |
1993年 | 78篇 |
1992年 | 45篇 |
1991年 | 37篇 |
1990年 | 37篇 |
1989年 | 26篇 |
1988年 | 23篇 |
1987年 | 17篇 |
1986年 | 15篇 |
1985年 | 11篇 |
1984年 | 11篇 |
1983年 | 13篇 |
1982年 | 12篇 |
1965年 | 14篇 |
1964年 | 19篇 |
1963年 | 16篇 |
1961年 | 12篇 |
1960年 | 9篇 |
1956年 | 8篇 |
1955年 | 19篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
The environmental and socio‐economic impacts of biomass utilization by co‐firing with brown coal in an existing thermoelectric unit in Greece or through its pure combustion in a new plant were studied and evaluated in this work. The 125 MWe lignite‐fired power plant in Ptolemais Power Station (Western Macedonia) was used as reference system. The environmental benefits of the alternative biomass exploitation options were quantified based on the life cycle assessment methodology, as established by SETAC, while the BIOSEM technique was used to carry out socio‐economic calculations. The obtained results showed clear environmental benefits of both biomass utilization alternatives in comparison with the reference system. In addition, co‐firing biomass with lignite in an existing unit outperforms the combustion of biomass exclusively in a new plant, since it exhibits a better environmental performance and it is a low risk investment with immediate benefits. A biomass combustion unit requires a considerably higher capital investment and its benefits are more evident in the long run. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
32.
Y. FARES M. CHAUSSUMIER A. DAIDIE J. GUILLOT 《Fatigue & Fracture of Engineering Materials & Structures》2006,29(8):588-596
The fatigue behaviour of bolts under axial load has always been considered from the component point of view for which fatigue limit is usually taken equal to 50 MPa, and few results are available to designers for limited lifetimes. Here, we take up this problem from a material point of view using a local approach. For each case of fatigue testing, using finite‐element (FE) model of the bolt, we determine the stabilized local stress at the root of the first thread in contact with the nut. To characterize bolt behaviour with these numerical results, we use Dang Van multiaxial fatigue criterion for which we extend application to the medium fatigue life. These results can be correlated with the experimental numbers of cycles to failure to determine material parameters of the generalized criterion. Using statistical Gauss method, we can make lifetime predictions for any level of risk of failure. In addition, we propose an analytical model to rapidly determine the local stress condition from nominal loading data (mean stress and alternating stress). This model dispenses us from a new modelling if the bolt is stressed in the same manner as the bolts used for behaviour characterization. Using this model and the generalized criterion, it is extremely easy to make lifetime predictions whatever the risk considered. 相似文献
33.
赵惠琴 《有色冶金设计与研究》2004,25(4):4-8
根据所使用的低水泥浇注料的性能,对中铝山西分公司检修厂4号焙烧炉制定了合理的烘烤曲线,提高了耐火内衬的质量,延长了内衬的使用寿命。 相似文献
34.
Peer-assisted learning interventions with elementary school students: A meta-analytic review. 总被引:1,自引:0,他引:1
Rohrbeck Cynthia A.; Ginsburg-Block Marika D.; Fantuzzo John W.; Miller Traci R. 《Canadian Metallurgical Quarterly》2003,95(2):240
A meta-analytic review of group comparison design studies evaluating peer-assisted learning (PAL) interventions with elementary school students produced positive effect sizes (ESs) indicating increases in achievement (unweighted mean ES = 0.59, SD = 0.90; weighted ES, d = 0.33, p 相似文献
35.
Do experiences make people happier than material possessions? In two surveys, respondents from various demographic groups indicated that experiential purchases-those made with the primary intention of acquiring a life experience--made them happier than material purchases. In a follow-up laboratory experiment, participants experienced more positive feelings after pondering an experiential purchase than after pondering a material purchase. In another experiment, participants were more likely to anticipate that experiences would make them happier than material possessions after adopting a temporally distant, versus a temporally proximate, perspective. The discussion focuses on evidence that experiences make people happier because they are more open to positive reinterpretations, are a more meaningful part of one's identity, and contribute more to successful social relationships. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
36.
Schnurr Paula P.; Hayes Andrew F.; Lunney Carole A.; McFall Miles; Uddo Madeline 《Canadian Metallurgical Quarterly》2006,74(4):707
This study examined how change in posttraumatic stress disorder (PTSD) symptoms relates to change in quality of life. The sample consisted of 325 male Vietnam veterans with chronic PTSD who participated in a randomized trial of group psychotherapy. Latent growth modeling was used to test for synchronous effects of PTSD symptom change on psychosocial and physical health-related quality of life within the same time period and lagged effects of initial PTSD symptom change on later change in quality of life. PTSD symptoms were associated with reduced quality of life before treatment. There were synchronous effects of symptom change on change in quality of life but no significant lagged effects. Results indicate the importance of measuring quality of life in future investigations of PTSD treatment. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
37.
通过在三种不同的强化负荷下进行深沟球轴承疲劳寿命试验,并与常规试验一组结果对比。结果表明,适当地加大滚动轴承疲劳寿命试验负荷,可以大大缩短试验时间,而疲劳寿命依然服从Weibul分布,且与常规试验结果基本一致,同时疲劳破坏的形式仍是表面下萌生裂纹,然后扩展至表面形成剥落。 相似文献
38.
39.
《International Journal of Pressure Vessels and Piping》1996,66(1-3):187-198
The limit carrying capacity of gas pipelines having corrosion defects were evaluated by means of an improved FEM analysis, together with the ANSI/ASME defect judgement and an experimental verification. When compared with our past presentation at the proceedings of the CAPE'93 Colloquium (dealing with reproduced defects), this paper evaluates the remaining lifetime of a pipeline having natural faults. The new improved analysis includes geometrical nonlinearities leading to a modification of limit state parameters and thus matching better with actuality. This presented work was initiated by the firm of Trans-Gas in Prague after having had a pipeline inspected proving some parts of it as being heavily corroded. The task in hand was to determine the remaining pipeline lifetime with the view to at least a two-year period. 相似文献
40.