全文获取类型
收费全文 | 169886篇 |
免费 | 7887篇 |
国内免费 | 3808篇 |
专业分类
电工技术 | 5676篇 |
技术理论 | 5篇 |
综合类 | 7832篇 |
化学工业 | 26633篇 |
金属工艺 | 10027篇 |
机械仪表 | 8408篇 |
建筑科学 | 9884篇 |
矿业工程 | 3086篇 |
能源动力 | 3443篇 |
轻工业 | 8842篇 |
水利工程 | 2801篇 |
石油天然气 | 5491篇 |
武器工业 | 688篇 |
无线电 | 18284篇 |
一般工业技术 | 26397篇 |
冶金工业 | 6928篇 |
原子能技术 | 1313篇 |
自动化技术 | 35843篇 |
出版年
2024年 | 280篇 |
2023年 | 1408篇 |
2022年 | 2230篇 |
2021年 | 3289篇 |
2020年 | 2558篇 |
2019年 | 2133篇 |
2018年 | 16475篇 |
2017年 | 15802篇 |
2016年 | 12116篇 |
2015年 | 3813篇 |
2014年 | 4309篇 |
2013年 | 5217篇 |
2012年 | 8618篇 |
2011年 | 15111篇 |
2010年 | 13136篇 |
2009年 | 10380篇 |
2008年 | 11393篇 |
2007年 | 12224篇 |
2006年 | 4987篇 |
2005年 | 5530篇 |
2004年 | 3992篇 |
2003年 | 3640篇 |
2002年 | 2820篇 |
2001年 | 2113篇 |
2000年 | 2473篇 |
1999年 | 2732篇 |
1998年 | 2224篇 |
1997年 | 1791篇 |
1996年 | 1855篇 |
1995年 | 1478篇 |
1994年 | 1209篇 |
1993年 | 857篇 |
1992年 | 701篇 |
1991年 | 568篇 |
1990年 | 390篇 |
1989年 | 323篇 |
1988年 | 273篇 |
1987年 | 176篇 |
1986年 | 108篇 |
1985年 | 79篇 |
1984年 | 50篇 |
1982年 | 39篇 |
1968年 | 43篇 |
1966年 | 42篇 |
1965年 | 46篇 |
1959年 | 35篇 |
1958年 | 37篇 |
1957年 | 36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 66 毫秒
61.
Xueli Chen Ke Liu Qianwan Qin Zhenlu Yu Meiqing Li Xingyu Qu Yu Zhou Aichun Dou Mingru Su Yunjian Liu 《Ceramics International》2021,47(11):15400-15407
With excellent specific capacity, superior cycle stability, safety and strong practical, Nb2O5 has been considered as one of the prospective anode materials for lithium-ion batteries (LIBs). However, current study suggests that Nb2O5 electrode materials for LIBs still face the vital issues of low electrical conductivity and poor rate performance. Therefore, carbon-coated TT-Nb2O5 materials are designed and synthesized through solid state method in this work, which present high specific capacity (228 mA h g?1 at 0.2C), satisfactory rate properties (107 mA h g?1 at 20 C). The outstanding electrochemical property can not only give the credit to the pseudocapacitance effect of TT-Nb2O5, but also attribute to introduction of carbon. The homogeneous carbon-coated materials enhance the electrical conductivity, increase the electron transmission speed and alleviate particle crushing. This research not only offers a new method for preparing excellent electrode materials, but also provides a kind of excellent anode material with prospective application for LIBs. 相似文献
62.
在内径120 mm的半圆柱形内循环流化床中,以平均粒径387 nm的Ti O2为原料,考察了单独通入流化气、射流气和同时通入流化气和射流气三种流化方式下超细粉的流化特性以及射流气速对超细粉聚团尺寸的影响。结果表明:同时通入流化气和射流气时,流化气能促进粉体循环,消除环隙死区;高速射流能有效破碎聚团,显著减小聚团尺寸,从而使超细粉在环隙区与导流管之间形成稳定循环,小聚团在环隙区实现平稳流态化。随着射流气速的增大,聚团尺寸减小,粒度分布变窄,在射流气速分别为60,90,120,150 m/s的条件下,聚团平均直径分别为194,158,147,135μm。 相似文献
63.
64.
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
65.
66.
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
67.
Pyrochlore-type WO_3 powder was synthesized via hydrothermal method using aqueous sodium tungstate solution and oxalic acid as raw materials. The as-prepared powder was made into a soliquoid,from which films were made by dip coating process with indium-tin oxide(ITO).The obtained films were characterized by thermogravimetric and differential thermal analysis(TG-DTA), X-ray diffraction(XRD),scanning electron microscopy(SEM),transmission electron microscopy(TEM), cyclic voltammetry(CV), chronoamperometry(CA) and ultravioletvisible(UV-Vis) absorption. Results show that the crystal of the pyrochlore-type WO_3 powder is perfect. When the calcination temperature rises from room temperature to500 ℃,the pyrochlore-type structure first becomes deformed, then it is destroyed and turns into amorphous phase,finally it will completely convert to WO_3 with a monoclinic structure. Electrochemical and optical tests demonstrate that the film calcined at 300 ℃ exhibits the best electrochromic performance and has a coloration efficiency of up to 68.5 cm~2 C~(-1) at 884 nm. 相似文献
68.
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
69.
70.