全文获取类型
收费全文 | 9306篇 |
免费 | 858篇 |
国内免费 | 435篇 |
专业分类
电工技术 | 523篇 |
技术理论 | 1篇 |
综合类 | 748篇 |
化学工业 | 1460篇 |
金属工艺 | 529篇 |
机械仪表 | 625篇 |
建筑科学 | 743篇 |
矿业工程 | 227篇 |
能源动力 | 256篇 |
轻工业 | 838篇 |
水利工程 | 206篇 |
石油天然气 | 423篇 |
武器工业 | 72篇 |
无线电 | 999篇 |
一般工业技术 | 982篇 |
冶金工业 | 445篇 |
原子能技术 | 82篇 |
自动化技术 | 1440篇 |
出版年
2024年 | 36篇 |
2023年 | 163篇 |
2022年 | 257篇 |
2021年 | 406篇 |
2020年 | 328篇 |
2019年 | 241篇 |
2018年 | 276篇 |
2017年 | 295篇 |
2016年 | 265篇 |
2015年 | 365篇 |
2014年 | 453篇 |
2013年 | 539篇 |
2012年 | 615篇 |
2011年 | 646篇 |
2010年 | 585篇 |
2009年 | 538篇 |
2008年 | 555篇 |
2007年 | 464篇 |
2006年 | 508篇 |
2005年 | 405篇 |
2004年 | 319篇 |
2003年 | 382篇 |
2002年 | 376篇 |
2001年 | 331篇 |
2000年 | 203篇 |
1999年 | 233篇 |
1998年 | 153篇 |
1997年 | 145篇 |
1996年 | 120篇 |
1995年 | 92篇 |
1994年 | 84篇 |
1993年 | 53篇 |
1992年 | 47篇 |
1991年 | 32篇 |
1990年 | 27篇 |
1989年 | 17篇 |
1988年 | 16篇 |
1987年 | 9篇 |
1986年 | 4篇 |
1985年 | 6篇 |
1984年 | 4篇 |
1982年 | 1篇 |
1981年 | 2篇 |
1980年 | 2篇 |
1959年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Da-Wang Tan Zhen-Yong Lao Zhan Zhang Wei-Ming Guo Shi-Kuan Sun Hua-Tay Lin 《Journal of the American Ceramic Society》2021,104(6):2860-2867
B4C-TiB2 ceramics (TiB2 ranging 5~70 vol%) with Mo-Co-WC as the sintering additive were prepared by spark plasma sintering. In comparison with B4C-TiB2 without additive, the enhanced densification was evident in the sintered specimen with Mo-Co-WC additive. Core-rim structured grain was observed around TiB2 grains. The interface of the rim between TiB2 and B4C phases demonstrated different feature: the inner borderline of the rim exhibited a smooth feature, whereas a sharp curved grain boundary was observed between the rim and the B4C grain. The formation mechanism is discussed: the epitaxial growth of (Ti,Mo,W)B2 rim around the TiB2 core may occur as a result of the solid solution and dissolution-precipitation between TiB2 phase and the sintering additive. It was revealed that the fracture toughness increased as the content of TiB2 content increased, alongside the decreased hardness. B4C-30 vol% TiB2 specimen demonstrated the optimal combination of mechanical properties, reaching Vickers hardness of 24.3 GPa and fracture toughness of 3.33 MPa·m1/2. 相似文献
2.
Chengkai Li Zheyi Zhang Haifei Zhan Zhuoqun Zheng Jingshuai Bai Yuantong Gu 《大分子材料与工程》2021,306(10):2100292
Low-dimensional carbon nanostructures are ideal nanofillers to reinforce the mechanical performance of polymer nanocomposites due to their excellent mechanical properties. Through molecular dynamics simulations, the mechanical performance of poly(vinyl alchohol) (PVA) nanocomposites reinforced with a single-layer diamond – diamane is investigated. It is found the PVA/diamane exhibits similar interfacial strengths and pull-out characteristics with the PVA/bilayer-graphene counterpart. Specifically, when the nanofiller is fully embedded in the nanocomposite, it is unable to deform simultaneously with the PVA matrix due to the weak interfacial load transfer efficiency, thus the enhancement effect is not significant. In comparison, diamane can effectively promote the tensile properties of the nanocomposite when it has a laminated structure as it deforms simultaneously with the matrix. With this configuration, the interlayer sp3 bonds endows diamane with a much higher resistance under compression and shear tests, thus the nanocomposite can reach very high compressive and shear stress. Overall, enhancement on the mechanical interlocking at the interface as triggered by surface functionalization is only effective for the fully embedded nanofiller. This work provides a fundamental understanding of the mechanical properties of PVA nanocomposites reinforced by diamane, which can shed lights on the design and preparation of next generation high-performance nanocomposites. 相似文献
4.
Lü Qing Xu Bin Yu Yang Zhan Wei Zhao Yu Zheng Jun Ji Jian 《Bulletin of Engineering Geology and the Environment》2021,80(8):6513-6525
Bulletin of Engineering Geology and the Environment - Many uncertainties exist in pile-stabilized slopes which make their design substantially complicated. In this paper, a first-order reliability... 相似文献
5.
为解决共享交通下的共乘用户群体发现效率低、准确率不高问题,依据R-树原理建立GeoOD-Tree索引,并在此基础上提出以最大化共乘率为目标的群体发现策略。首先,对原始时空轨迹数据进行特征提取与标定处理,挖掘有效出行起讫点(OD)轨迹;其次,针对用户起讫点轨迹的特征,建立GeoOD-Tree索引进行有效的存储管理;最后,给出以最大化共乘行程为目标的群体发现模型,并运用K最近邻(KNN)查询对搜索空间剪枝压缩,提高群体发现效率。采用西安市近12000辆出租车营运轨迹数据,选取动态时间规整(DTW)等典型算法与所提算法在查询效率与准确率上进行性能对比分析。与DTW算法相比,所提算法的准确率提高了10.12%,查询效率提高了约15倍。实验结果表明提出的群体发现策略能有效提高共乘用户群体发现的准确率和效率,可有效提升共乘出行方式的出行率。 相似文献
6.
7.
8.
Multimedia Tools and Applications - We present three stages of a novel backgrounds subtraction method in this paper: a new pixel-block based randomized arrangement is utilized to preprocess all the... 相似文献
9.
10.