全文获取类型
收费全文 | 85622篇 |
免费 | 1102篇 |
国内免费 | 421篇 |
专业分类
电工技术 | 795篇 |
综合类 | 2325篇 |
化学工业 | 11859篇 |
金属工艺 | 4834篇 |
机械仪表 | 3100篇 |
建筑科学 | 2218篇 |
矿业工程 | 569篇 |
能源动力 | 1305篇 |
轻工业 | 3927篇 |
水利工程 | 1281篇 |
石油天然气 | 366篇 |
无线电 | 9345篇 |
一般工业技术 | 16681篇 |
冶金工业 | 2699篇 |
原子能技术 | 282篇 |
自动化技术 | 25559篇 |
出版年
2023年 | 43篇 |
2022年 | 88篇 |
2021年 | 104篇 |
2020年 | 100篇 |
2019年 | 102篇 |
2018年 | 14535篇 |
2017年 | 13465篇 |
2016年 | 10042篇 |
2015年 | 672篇 |
2014年 | 305篇 |
2013年 | 402篇 |
2012年 | 3263篇 |
2011年 | 9527篇 |
2010年 | 8360篇 |
2009年 | 5664篇 |
2008年 | 6901篇 |
2007年 | 7863篇 |
2006年 | 185篇 |
2005年 | 1262篇 |
2004年 | 1162篇 |
2003年 | 1204篇 |
2002年 | 556篇 |
2001年 | 108篇 |
2000年 | 192篇 |
1999年 | 68篇 |
1998年 | 79篇 |
1997年 | 42篇 |
1996年 | 52篇 |
1995年 | 13篇 |
1994年 | 18篇 |
1993年 | 20篇 |
1992年 | 25篇 |
1991年 | 33篇 |
1988年 | 13篇 |
1969年 | 24篇 |
1968年 | 44篇 |
1967年 | 36篇 |
1966年 | 42篇 |
1965年 | 44篇 |
1964年 | 11篇 |
1963年 | 28篇 |
1962年 | 22篇 |
1961年 | 18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 22 毫秒
1.
2.
Telecommunication Systems - This paper proposes two algorithms for hybrid (Analog–Digital) beamforming in a single-user millimeter-wave (mm-wave) multi-input multi-output (MIMO) systems under... 相似文献
3.
4.
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
5.
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
6.
Nidhi Nandu Mustafa Salih Hizir Neil M. Roberston Dr. Birol Ozturk Prof. Dr. Mehmet V. Yigit 《Chembiochem : a European journal of chemical biology》2019,20(14):1861-1867
Two-dimensional MoS2 nanoparticles (2D-nps) exhibit artificial enzyme properties that can be regulated at bio-nanointerfaces. We discovered that protein lipase is able to tune the peroxidase-like activity of MoS2 2D-nps, offering low-nanomolar, label-free detection and identification in samples with unknown identity. The inhibition of the peroxidase-like activity of the MoS2 2D-nps was demonstrated to be concentration dependent, and as low as 5 nm lipase was detected with this approach. The results were compared with those obtained with several other proteins that did not display any significant interference with the nanozyme behavior of the MoS2 2D-nps. This unique response of lipase was characterized and exploited for the successful identification of lipase in six unknown samples by using qualitative visual inspection and a quantitative statistical analysis method. The developed methodology in this approach is noteworthy for many aspects; MoS2 2D-nps are neither labeled with a signaling moiety nor modified with any ligands for signal readout. Only the intrinsic nanozyme activity of the MoS2 2D-nps is exploited for this detection approach. No analytical equipment is necessary for the visual detection of lipase. The synthesis of the water-soluble MoS2 2D-nps is low costing and can be performed in bulk scale. Exploring the properties of 2D-nps and their interactions with biological materials reveals highly interesting yet instrumental features that offer the development of novel bioanalytical approaches. 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