全文获取类型
收费全文 | 32406篇 |
免费 | 2722篇 |
国内免费 | 1401篇 |
专业分类
电工技术 | 730篇 |
技术理论 | 5篇 |
综合类 | 1974篇 |
化学工业 | 11533篇 |
金属工艺 | 1733篇 |
机械仪表 | 862篇 |
建筑科学 | 1505篇 |
矿业工程 | 653篇 |
能源动力 | 1166篇 |
轻工业 | 3821篇 |
水利工程 | 500篇 |
石油天然气 | 1313篇 |
武器工业 | 184篇 |
无线电 | 2405篇 |
一般工业技术 | 4244篇 |
冶金工业 | 2009篇 |
原子能技术 | 748篇 |
自动化技术 | 1144篇 |
出版年
2024年 | 101篇 |
2023年 | 495篇 |
2022年 | 676篇 |
2021年 | 992篇 |
2020年 | 998篇 |
2019年 | 939篇 |
2018年 | 845篇 |
2017年 | 983篇 |
2016年 | 1057篇 |
2015年 | 1101篇 |
2014年 | 1782篇 |
2013年 | 2045篇 |
2012年 | 2184篇 |
2011年 | 2334篇 |
2010年 | 1739篇 |
2009年 | 1747篇 |
2008年 | 1450篇 |
2007年 | 1957篇 |
2006年 | 1795篇 |
2005年 | 1548篇 |
2004年 | 1395篇 |
2003年 | 1217篇 |
2002年 | 1086篇 |
2001年 | 896篇 |
2000年 | 811篇 |
1999年 | 620篇 |
1998年 | 612篇 |
1997年 | 491篇 |
1996年 | 450篇 |
1995年 | 353篇 |
1994年 | 296篇 |
1993年 | 227篇 |
1992年 | 207篇 |
1991年 | 161篇 |
1990年 | 144篇 |
1989年 | 114篇 |
1988年 | 76篇 |
1987年 | 68篇 |
1986年 | 64篇 |
1985年 | 84篇 |
1984年 | 64篇 |
1983年 | 51篇 |
1982年 | 79篇 |
1981年 | 22篇 |
1980年 | 19篇 |
1977年 | 11篇 |
1976年 | 10篇 |
1975年 | 12篇 |
1964年 | 23篇 |
1963年 | 11篇 |
排序方式: 共有10000条查询结果,搜索用时 250 毫秒
81.
Yu.V. Butenko P.R. Coxon M. Yeganeh A.C. Brieva K. Liddell V.R. Dhanak L. iller 《Diamond and Related Materials》2008,17(6):962-966
It is generally accepted that diamond is resistant to a wide spectrum of electromagnetic radiation from the ultraviolet through to the soft X-ray range, which makes it very attractive for the fabrication of diamond-based photodetectors. However the effect of photon radiation on the diamond structure has not yet been examined. In the work presented here, photoelectron spectroscopy has been used to study the graphitization of nanodiamond crystallites exposed to extreme ultraviolet radiation. Under such irradiation, the surface hydrogen groups and graphite species are found to prevent graphitization. The mechanism of radiation-induced nanodiamond graphitization is discussed. 相似文献
82.
本文探讨了60Si2Mn合金钢发蓝原理,针对其膜层泛红问题,分析了热处理、表面前处理、发蓝及浸油等过程对发蓝质量的影响,由此采取了相应的技术措施,生产实践证明发蓝质量稳定,生产效率明显提高。 相似文献
83.
84.
85.
86.
A task-switching paradigm with a 2:1 mapping between cues and tasks was used to separate cue-switching processes (indexed through pure cue-switch costs) from actual task-switching processes (indexed through additional costs in case of cue and task changes). A large portion of total switch costs was due to cue changes (Experiments 1 and 2), and cue-switch costs but not task-switch costs were sensitive to effects of practice (Experiment 1) and preparation (Experiment 2). In contrast, task-switch costs were particularly sensitive to response-priming effects (Experiments 1 and 2) and task-set inhibition (Experiment 3). Results suggest two processing stages relevant during task-set selection: cue-driven retrieval of task rules from long-term memory and the automatic application of rules to a particular stimulus situation. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
87.
本文研究了具有典型分解特征的Al-Zn-Ce非晶合金的形成和晶化过程,探讨了各种相的生成顺序。XRD和DSC测试结果表明强烈的化合物短程序有利于Al-Zn-Ce非晶合金的形成。在Al-Zn-Ce非晶合金的晶化过程中存在复杂的相选择行为,多种相的竞争形核和有限生长使其具有复杂的结构特点。同时,结果也表明冷速对该体系非晶的形成有很大影响。 相似文献
88.
Berrin-Wasserman Stacy; Winnick Wilma A.; Borod Joan C. 《Canadian Metallurgical Quarterly》2003,17(3):429
Does sentence generation and/or stimulus emotionality enhance verbal memory in patients with neurological impairment? This question was addressed by testing 40 patients with unilateral stroke (20 with left-brain and 20 with right-brain damage) and 20 healthy control participants for recall and recognition of 48 target words. During encoding, emotional and nonemotional words were either presented in sentences (read condition) or used to form sentences (generate condition). Both word emotionality and generative processing improved memory performance in all groups. The authors suggest that a similar influence (i.e., cognitive activation) underlies both of these memory-enhancing effects, although the putative origins of the 2 effects are quite different. Neuropsychological underpinnings and clinical implications of these phenomena are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
89.
A good understanding of environmental effects on structural modal properties is essential for reliable performance of vibration-based damage diagnosis methods. In this paper, a method of combining principal component analysis (PCA) and support vector regression (SVR) technique is proposed for modeling temperature-caused variability of modal frequencies for structures instrumented with long-term monitoring systems. PCA is first applied to extract principal components from the measured temperatures for dimensionality reduction. The predominant feature vectors in conjunction with the measured modal frequencies are then fed into a support vector algorithm to formulate regression models that may take into account thermal inertia effect. The research is focused on proper selection of the hyperparameters to obtain SVR models with good generalization performance. A grid search method with cross validation and a heuristic method are utilized for determining the optimal values of SVR hyperparameters. The proposed method is compared with the method directly using measurement data to train SVR models and the multivariate linear regression (MLR) method through the use of long-term measurement data from a cable-stayed bridge. It is shown that PCA-compressed features make the training and validation of SVR models more efficient in both model accuracy and computational costs, and the formulated SVR model performs much better than the MLR model in generalization performance. When continuously measured data is available, the SVR model formulated taking into account thermal inertia effect can achieve more accurate prediction than that without considering thermal inertia effect. 相似文献
90.
JIANG Zengguo ZHAO Yuan 《武汉理工大学学报(材料科学英文版)》2005,20(3):110-112
1IntroductionLime-flyashstabilizedsoil as a semi-rigid base mate-rial in highwayis widely usedin China.The goodintegri-ty,great bearing capacity,highstiffness and water-proof-ing quality areits special advantages.But itsinherent lowearly strength makes it… 相似文献