全文获取类型
收费全文 | 18258篇 |
免费 | 1657篇 |
国内免费 | 1406篇 |
专业分类
电工技术 | 829篇 |
技术理论 | 2篇 |
综合类 | 2284篇 |
化学工业 | 1880篇 |
金属工艺 | 882篇 |
机械仪表 | 1007篇 |
建筑科学 | 2035篇 |
矿业工程 | 621篇 |
能源动力 | 278篇 |
轻工业 | 684篇 |
水利工程 | 436篇 |
石油天然气 | 1669篇 |
武器工业 | 315篇 |
无线电 | 1391篇 |
一般工业技术 | 1054篇 |
冶金工业 | 597篇 |
原子能技术 | 107篇 |
自动化技术 | 5250篇 |
出版年
2024年 | 17篇 |
2023年 | 135篇 |
2022年 | 263篇 |
2021年 | 322篇 |
2020年 | 400篇 |
2019年 | 369篇 |
2018年 | 358篇 |
2017年 | 475篇 |
2016年 | 493篇 |
2015年 | 584篇 |
2014年 | 929篇 |
2013年 | 949篇 |
2012年 | 1174篇 |
2011年 | 1261篇 |
2010年 | 1089篇 |
2009年 | 1155篇 |
2008年 | 1178篇 |
2007年 | 1577篇 |
2006年 | 1326篇 |
2005年 | 1125篇 |
2004年 | 996篇 |
2003年 | 925篇 |
2002年 | 736篇 |
2001年 | 669篇 |
2000年 | 524篇 |
1999年 | 445篇 |
1998年 | 349篇 |
1997年 | 286篇 |
1996年 | 258篇 |
1995年 | 189篇 |
1994年 | 157篇 |
1993年 | 130篇 |
1992年 | 103篇 |
1991年 | 74篇 |
1990年 | 54篇 |
1989年 | 57篇 |
1988年 | 43篇 |
1987年 | 25篇 |
1986年 | 23篇 |
1985年 | 13篇 |
1984年 | 12篇 |
1983年 | 12篇 |
1982年 | 11篇 |
1981年 | 12篇 |
1980年 | 7篇 |
1979年 | 6篇 |
1978年 | 6篇 |
1977年 | 3篇 |
1976年 | 5篇 |
1975年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
《International Journal of Hydrogen Energy》2022,47(36):16121-16131
Ammonia is considered as a promising hydrogen or energy carrier. Ammonia absorption or adsorption is an important aspect for both ammonia removal, storage and separation applications. To these ends, a wide range of solid and liquid sorbents have been investigated. Among these, the deep eutectic solvent (DES) is emerging as a promising class of ammonia absorbers. Herein, we report a novel type of DES, i.e., metal-containing DESs for ammonia absorption. Specifically, the NH3 absorption capacity is enhanced by ca. 18.1–36.9% when a small amount of metal chlorides, such as MgCl2, MnCl2 etc., are added into a DES composed of resorcinol (Res) and ethylene glycol (EG). To our knowledge, the MgCl2/Res/EG (0.1:1:2) DES outperforms most of the reported DESs. The excellent NH3 absorption performances of metal–containing DESs have been attributed to the synergy of Lewis acid–base and hydrogen bonding interactions. Additionally, good reversibility and high NH3/CO2 selectivity are achieved over the MgCl2/Res/EG (0.1:1:2) DES, which enables it to be a potential NH3 absorber for further investigations. 相似文献
2.
《International Journal of Hydrogen Energy》2022,47(61):25511-25521
Metal/carbon composite materials are highly promising electrocatalysts for water electrolysis. In this work, three composites of metal cobalt nanoparticles highly dispersed in N-doped carbon materials were facilely constructed by pyrolysis of different phenylenediamine based Schiff base-Co complexes (PDBs). Interestingly, the composites derived from PDBs based on different phenylenediamine exhibited different morphologies. The superior case is that rodlike composite catalyst was derived from o-phenylenediamine based PDBs. The obtained catalyst exhibited remarkable performances for both cathodic hydrogen evolution reaction (HER) and anodic oxygen evolution reaction (OER), as well as overall water electrolysis. Only 172 and 289 mV of overpotentials and 1.57 V of cell voltage were exhibited at 10 mA cm?2 for HER, OER and water splitting in 1.0 M KOH, respectively. The catalyst also displayed robust stability and high Faraday efficiency, and thus are potential high-performance catalyst for commercial water electrolysis. 相似文献
3.
《Geotextiles and Geomembranes》2022,50(5):1020-1035
This paper presents a numerical study on the load-bearing performance of reinforced slopes under footing load using a finite element limit analysis (FELA) method where a non-associated flow rule is assumed in the analysis. The method was validated against results from full-scale model tests and a limit equilibrium (LE) analytical method. A series of parametric analyses was subsequently carried out to examine the influences that the soil dilation angle, footing location, and reinforcement design (i.e. length, tensile strength, and vertical spacing) could have on the load-bearing performance of reinforced slopes. Results indicate that dilation angle has a significant influence on the predicted magnitudes of bearing capacity, slope deformation, and mobilized reinforcement load. The predicted values of bearing capacity using the FELA are smaller than those from the Meyerhof's analytical method for unreinforced semi-infinite foundation, especially for larger friction angle values. Additionally, the ultimate bearing capacity of the slope and its corresponding horizontal deformation increase with the reinforcement tensile strength. Finally, the slip planes under the applied footing load are found to be y-shaped and primarily occur in the upper half of the slope. 相似文献
4.
5.
分别采用共沉淀法、清洁法制备焙烧态水铝钙石,通过低温N2吸脱附法、CO2-TPD、XRD、DTA和FT-IR表征结构,并将其作为大豆油与甲醇酯交换合成生物柴油的催化剂,探讨制备方法对焙烧态水铝钙石催化合成生物柴油的影响。此外,考察了Ca/Al摩尔比、焙烧温度、甲醇与大豆油摩尔比(醇油比)、催化剂用量和反应时间对酯交换合成生物柴油的影响。结果表明,清洁法制备的焙烧态水铝钙石具有更高的比表面积,强碱中心的表面碱量更大,催化活性更高。当Ca/Al摩尔比为2∶1,焙烧温度为600℃时,制备的Ca2Al O-2-600催化剂的催化活性最高,在醇油比8∶1、催化剂用量3%、反应温度65℃、反应时间4 h的条件下,大豆油转化率达到98. 0%。催化剂经重复使用3次后仍保持较高催化活性。 相似文献
6.
电信业的客户投诉不断增多而又亟待高效处理。针对电信客户投诉数据的特点,提出了一种面向高维数据的改进的集成学习分类方法。该方法综合考虑客户投诉中的文本信息及客户通讯状态信息,基于Random Subspace方法,以支持向量机(Support Vector Machine,SVM)为基分类器,采用证据推理(Evidential Reasoning,ER)规则为一种新的集成策略,构造分类模型对电信客户投诉进行分类。所提模型和方法在某电信公司客户投诉数据上进行了验证,实验结果显示该方法能够显著提高客户投诉分类的准确率和投诉处理效率。 相似文献
7.
8.
ABSTRACTFeature selection is an important task to improve the classifier’s accuracy and to decrease the problem size. A number of methodologies have been presented for feature selection problems using metaheuristic algorithms. In this paper, an improved self-adaptive inertia weight particle swarm optimisation with local search and combined with C4.5 classifiers for feature selection algorithm is proposed. In this proposed algorithm, the gradient base local search with its capacity of helping to explore the feature space and an improved self-adaptive inertia weight particle swarm optimisation with its ability to converge a best global solution in the search space. Experimental results have verified that the SIW-APSO-LS performed well compared with other state of art feature selection techniques on a suit of 16 standard data sets. 相似文献
9.
为了避免和减轻由过大隔震层位移引起的损害,对基础隔震框架结构装设调频液柱阻尼器(tuned liquid column damper,简称TLCD)后混合系统的减振效果进行研究。建立了单层和多层混合控制系统在地震作用下的运动方程,采用TLCD-结构体系转化为调频质量阻尼器(tuned mass damper,简称TMD)-结构体系的等效方法,利用TMD参数优化公式,得到单个TLCD初始设计参数,并采用状态空间方程得到多个TLCD最优设计参数。通过对某8层基础隔震结构进行模拟,证明了该理论设计方法的合理性。该混合结构不仅可以减小隔震层位移和加速度,而且对上部结构位移和加速度反应都能更有效的控制。 相似文献
10.
采用伪布尔模型和启发式算法来求解无容量设施选址问题。首先给出了问题的伪布尔(pseudo-Boolean)表示,然后基于Khumawala规则对问题进行预处理,最后提出两种启发式分支准则来求解问题。实验结果表明所提算法简单有效。 相似文献