全文获取类型
收费全文 | 14304篇 |
免费 | 1057篇 |
国内免费 | 697篇 |
专业分类
电工技术 | 649篇 |
综合类 | 2016篇 |
化学工业 | 733篇 |
金属工艺 | 851篇 |
机械仪表 | 1203篇 |
建筑科学 | 2056篇 |
矿业工程 | 723篇 |
能源动力 | 232篇 |
轻工业 | 386篇 |
水利工程 | 404篇 |
石油天然气 | 350篇 |
武器工业 | 86篇 |
无线电 | 910篇 |
一般工业技术 | 987篇 |
冶金工业 | 1333篇 |
原子能技术 | 74篇 |
自动化技术 | 3065篇 |
出版年
2024年 | 34篇 |
2023年 | 118篇 |
2022年 | 200篇 |
2021年 | 273篇 |
2020年 | 330篇 |
2019年 | 249篇 |
2018年 | 266篇 |
2017年 | 310篇 |
2016年 | 389篇 |
2015年 | 404篇 |
2014年 | 795篇 |
2013年 | 785篇 |
2012年 | 1066篇 |
2011年 | 1077篇 |
2010年 | 843篇 |
2009年 | 858篇 |
2008年 | 848篇 |
2007年 | 1058篇 |
2006年 | 905篇 |
2005年 | 878篇 |
2004年 | 732篇 |
2003年 | 702篇 |
2002年 | 551篇 |
2001年 | 468篇 |
2000年 | 350篇 |
1999年 | 302篇 |
1998年 | 183篇 |
1997年 | 189篇 |
1996年 | 176篇 |
1995年 | 129篇 |
1994年 | 127篇 |
1993年 | 68篇 |
1992年 | 63篇 |
1991年 | 54篇 |
1990年 | 33篇 |
1989年 | 27篇 |
1988年 | 27篇 |
1987年 | 18篇 |
1986年 | 12篇 |
1985年 | 16篇 |
1984年 | 8篇 |
1983年 | 6篇 |
1982年 | 7篇 |
1981年 | 22篇 |
1980年 | 12篇 |
1979年 | 11篇 |
1964年 | 7篇 |
1963年 | 7篇 |
1957年 | 8篇 |
1955年 | 9篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
In this paper, we present LinkingPark, an automatic semantic annotation system for tabular data to knowledge graph matching. LinkingPark is designed as a modular framework which can handle Cell-Entity Annotation (CEA), Column-Type Annotation (CTA), and Columns-Property Annotation (CPA) altogether. It is built upon our previous SemTab 2020 system, which won the 2nd prize among 28 different teams after four rounds of evaluations. Moreover, the system is unsupervised, stand-alone, and flexible for multilingual support. Its backend offers an efficient RESTful API for programmatic access, as well as an Excel Add-in for ease of use. Users can interact with LinkingPark in near real-time, further demonstrating its efficiency. 相似文献
2.
针对传统低压回路电阻测试仪只能在被测设备停电时使用的一大限制,本文提出并设计了一种新型低压回路电阻测试仪。该仪器可在低压设备运行状态下对其回路电阻进行测量,在保证测量精度的前提下减少了设备停电率,大大提高了工作效率。 相似文献
3.
ABSTRACTA mathematical model has been developed by coupling genetic algorithm (GA) with heat and material balance equations to estimate rate parameters and solid-phase evolution related to the reduction of iron ore-coal composite pellets in a multi-layer bed Rotary hearth Furnace (RHF). The present process involves treating iron ore-coal composite pellets in a crucible over the hearth in RHF. The various solid phases evolved at the end of the process are estimated experimentally, and are used in conjunction with the model to estimate rate parameters. The predicted apparent activation energy for the wustite reduction step is found to be lower than those of the reduction of higher oxides. The thermal efficiency is found to decrease significantly with an increase in the carbon content of the pellet. Thermal efficiency was also found to increase mildly up to three layers. Multilayer bed remains as a potential design parameter to increase thermal efficiency. 相似文献
4.
《Geotextiles and Geomembranes》2021,49(5):1256-1269
This study investigates the seismic performance of geosynthetic-reinforced modular block retaining walls backfilled with cohesive, fine grained clay-sand soil mixture. Shaking table tests were performed for three ½ scaled (wall height 190 cm) and ¼ scaled model walls to investigate the effects of backfill type, the influence of reinforcement length and reinforcement stiffness effects. The El Centro and Kobe earthquake records of varying amplitudes were used as base acceleration. Displacement of the front wall, accelerations at different locations, strains on the reinforcements, and the visual observations of the facing and the backfill surface were used to evaluate the seismic performance of model walls. The model walls were subjected to rigorous shaking and the walls did not exhibit any stability problems or signs of impending failure. The maximum deformations observed on the models with cohesive backfill was less than half of the deformation of the sand model. The load transfers between the geogrid and cohesive soil was comparable to that of sand and hence the needed reinforcement length was similar as well. As a result; the model walls with cohesive backfills performed within acceptable limits under seismic loading conditions when compared with granular backfilled counterparts. 相似文献
5.
最大塑性功原理在烧结体上限分析中的应用 总被引:1,自引:0,他引:1
最大塑性功原理又称第二塑性变分原理,在致密体塑性变形分析叶l是运用能量法进行变形力能计算的基础。本文从分析Drucker公设的亢要条件出发,证明了烧结体塑性变形最大塑性功原理的存在,片在该原理的荩础卜,推导出塑性变形的上限功率表达式,并以平面挤压条件下的上限法应用作为实例加以说明。 相似文献
6.
7.
8.
基于粗糙集信息观的决策表属性约简方法 总被引:2,自引:0,他引:2
粗糙集理论是近年来发展起来的一种有效的处理不精确、不确定、含糊信息的数学理论方法,它被广泛应用于相容和不相容决策表的属性约简和核属性计算。利用反例指出目前基于粗糙集信息观[2、6]的决策表属性约简和核属性计算方法的局限性。对决策表的性质作了深入的研究,研究发现文献[2、6]方法的不足原因是:它们没有考虑U/ind(C)中等价类的相客性。给出了基于U/ind(C)中等价类相客性的属性约简定义和核属性定义,并给出了一种新的基于粗糙集信息观的决策表属性约简和核属性计算方法。讨论了该方法同文献[2、6]方法的区别。最后用相同实例验证了该方法的有效性。 相似文献
9.
10.
Hannerz Harald; Albertsen Karen; Nielsen Martin Lindhardt; Tüchsen Finn; Burr Hermann 《Canadian Metallurgical Quarterly》2004,23(3):283
This study explored whether factors related to the work environment could predict changes in body mass index (BMI) and whether the effect of psychosocial factors was dependent on baseline BMI. The sample consisted of 1,980 male employees from the Danish National Work Environment Cohort Study. Changes in BMI between 1995 and 2000 were analyzed, by multiple regression, as a function of background variables and a series of occupational variables obtained in 1995. Age, baseline BMI, job insecurity, and psychological demands predicted changes in BMI. Job insecurity and high or low psychological demands increased the likelihood of weight gain among obese employees, whereas they increased the likelihood of weight loss among employees with a low BMI. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献