全文获取类型
收费全文 | 105886篇 |
免费 | 2754篇 |
国内免费 | 1324篇 |
专业分类
电工技术 | 2023篇 |
技术理论 | 2篇 |
综合类 | 3766篇 |
化学工业 | 14977篇 |
金属工艺 | 5920篇 |
机械仪表 | 4445篇 |
建筑科学 | 4083篇 |
矿业工程 | 1221篇 |
能源动力 | 1716篇 |
轻工业 | 5029篇 |
水利工程 | 1664篇 |
石油天然气 | 1698篇 |
武器工业 | 197篇 |
无线电 | 11738篇 |
一般工业技术 | 18874篇 |
冶金工业 | 3755篇 |
原子能技术 | 463篇 |
自动化技术 | 28393篇 |
出版年
2024年 | 97篇 |
2023年 | 359篇 |
2022年 | 624篇 |
2021年 | 817篇 |
2020年 | 647篇 |
2019年 | 480篇 |
2018年 | 14963篇 |
2017年 | 13930篇 |
2016年 | 10490篇 |
2015年 | 1432篇 |
2014年 | 1205篇 |
2013年 | 1465篇 |
2012年 | 4433篇 |
2011年 | 10830篇 |
2010年 | 9519篇 |
2009年 | 6702篇 |
2008年 | 8000篇 |
2007年 | 8850篇 |
2006年 | 1377篇 |
2005年 | 2413篇 |
2004年 | 1895篇 |
2003年 | 1901篇 |
2002年 | 1261篇 |
2001年 | 724篇 |
2000年 | 767篇 |
1999年 | 807篇 |
1998年 | 611篇 |
1997年 | 556篇 |
1996年 | 482篇 |
1995年 | 372篇 |
1994年 | 326篇 |
1993年 | 216篇 |
1992年 | 204篇 |
1991年 | 162篇 |
1990年 | 119篇 |
1989年 | 97篇 |
1988年 | 87篇 |
1987年 | 37篇 |
1986年 | 29篇 |
1968年 | 43篇 |
1967年 | 33篇 |
1966年 | 42篇 |
1965年 | 44篇 |
1960年 | 30篇 |
1959年 | 35篇 |
1958年 | 37篇 |
1957年 | 36篇 |
1956年 | 34篇 |
1955年 | 63篇 |
1954年 | 68篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
2.
3.
Chuangang Yao Jixing Yang Haixia Zhang Sigeng Chen Jian Meng Kedi Cai 《Ceramics International》2021,47(17):24589-24596
Bismuth doped La2-xBixNiO4+δ (x = 0, 0.02 and 0.04) oxides are investigated as SOFC cathodes. The effects of Bi doping on the phase structure, thermal expansion, electrical conduction behavior as well as electrochemical performance are studied. All the samples exist as a tetragonal Ruddlesden-Popper structure. Bi-doped LBNO-0.02 and LBNO-0.04 have good chemical and thermal compatibility with LSGM electrolyte. The average TEC over 20–900°С was 13.4 × 10?6 and 14.2 × 10?6 K?1 for LBNO-0.02 and LBNO-0.04, respectively. The electrical conductivity was decreasing with the rise of Bi doping content. EIS measurement indicates Bi doping can decrease the ASR values. At 750 °C, the obtained ASR for LBNO-0.04 is 0.18 Ωcm2, which is 56% lower than that of the sample without Bi doping, suggesting Bi doping is beneficial to the electrochemical catalytic activity of LBNO cathodes. 相似文献
4.
Baofu Qiu Xiaoming Duan Zhuo Zhang Delong Cai Ning Liao Peigang He Dechang Jia Yu Zhou 《Ceramics International》2021,47(1):73-79
The effects of La2O3–Al2O3–SiO2 addition on the thermal conductivity, coefficient of thermal expansion (CTE), Young's modulus and cyclic thermal shock resistance of hot-pressed h-BN composite ceramics were investigated. The samples were heated to 1000 °C and then quenched to room temperature with 1–50 cycles, and the residual flexural strength was used to evaluate cyclic thermal shock resistance. h-BN composite ceramics containing 10 vol% La2O3–Al2O3 and 20 vol% SiO2 addition exhibited the highest flexural strength, thermal conductivity and relatively low CTE, which were beneficial to the excellent thermal shock resistance. In addition, the viscous amorphous phase of ternary La2O3–Al2O3–SiO2 system could accommodate and relax thermal stress contributing to the high thermal shock resistance. Therefore, the residual flexural strength still maintained the value of 234.3 MPa (86.9% of initial strength) after 50 cycles of thermal shock. 相似文献
5.
Mobile software applications have to cope with a particular environment that involves small size, limited resources, high autonomy requirements, competitive business models and many other challenges. To provide development guidelines that respond to these needs, several practices have been introduced; however, it is not clear how these guidelines may contribute to solve the issues present in the mobile domain. Furthermore, the rapid evolution of the mobile ecosystem challenges many of the premises upon which the proposed practices were designed. In this paper, we present a survey of the literature on software assurance practices for mobile applications, with the objective of describing them and assessing their contribution and success. We identified, organized and reviewed a body of research that spans in three levels: software development processes, software product assurance practices, and software implementation practices. By carrying out this literature survey, we reviewed the different approaches that researchers on Software Engineering have provided to address the needs that raise in the mobile software development arena. Moreover, we review the evolution of these practices, identifying how the constant changes and modernization of the mobile execution environment has impacted the methods proposed in the literature. Finally, we introduced discussion on the application of these practices in a real productive setting, opening an area for further research that may determine if practitioners have followed the proposed assurance paradigms. 相似文献
6.
This paper presents an integrated passive damping approach in hybrid metal-CFRP parts for structural applications. In this concept a viscoelastic material is embedded in the joint zone of the hybrid component. To examine the connection strength single-lap-joint specimens were produced and tested and the influence of the used material combinations, different surface structures, and different process parameters i.e. the moment of cross-linking were evaluated. Afterwards, the metal-CFRP hybrids were tested in quasi-static tests to assess their connection strength and failure behaviour. Dynamic cyclic tensile tests with step-wise increased loading conditions were performed to determine the specimens damping behaviour and to estimate their fatigue performance. Finally, these results are compared to a state of the art metal-CFRP hybrid with rivets connecting both materials. 相似文献
7.
In this paper, we consider the classical finite mixture model, which is an effective tool for modeling lifetime distributions for random samples from heterogeneous populations. We discuss new results on stochastic comparison for two finite mixtures when each of them is drawn from one of the following semiparametric families, i.e., proportional hazards, accelerated lifetime and proportional reversed hazards. 相似文献
8.
9.
10.
Variations of Incomplete Open Cubes is the major project by the twentieth-century conceptual artist Sol LeWitt. In this paper we interpret the enumerative component of the project as embeddings of graphs. This formulation permits use of an algorithm to check the completeness of the list of the structures produced by the artist. Our conclusion is that the artist found the correct number of structures (that is, 122), but that his list contains a mistake in the presentation of a pair of incomplete cubes, a discovery that appears not to have been noted before. 相似文献