全文获取类型
收费全文 | 554330篇 |
免费 | 53460篇 |
国内免费 | 28852篇 |
专业分类
电工技术 | 71383篇 |
技术理论 | 54篇 |
综合类 | 55280篇 |
化学工业 | 56461篇 |
金属工艺 | 21822篇 |
机械仪表 | 36349篇 |
建筑科学 | 57175篇 |
矿业工程 | 26117篇 |
能源动力 | 18537篇 |
轻工业 | 30186篇 |
水利工程 | 19512篇 |
石油天然气 | 24348篇 |
武器工业 | 7415篇 |
无线电 | 47689篇 |
一般工业技术 | 37133篇 |
冶金工业 | 23178篇 |
原子能技术 | 4887篇 |
自动化技术 | 99116篇 |
出版年
2024年 | 2341篇 |
2023年 | 6744篇 |
2022年 | 14633篇 |
2021年 | 17827篇 |
2020年 | 16384篇 |
2019年 | 12453篇 |
2018年 | 12002篇 |
2017年 | 15862篇 |
2016年 | 19367篇 |
2015年 | 21844篇 |
2014年 | 37303篇 |
2013年 | 32393篇 |
2012年 | 40131篇 |
2011年 | 42469篇 |
2010年 | 32085篇 |
2009年 | 32586篇 |
2008年 | 31445篇 |
2007年 | 39269篇 |
2006年 | 35759篇 |
2005年 | 31414篇 |
2004年 | 25578篇 |
2003年 | 22917篇 |
2002年 | 18028篇 |
2001年 | 14929篇 |
2000年 | 12531篇 |
1999年 | 9922篇 |
1998年 | 7107篇 |
1997年 | 5900篇 |
1996年 | 5166篇 |
1995年 | 4320篇 |
1994年 | 3505篇 |
1993年 | 2456篇 |
1992年 | 2058篇 |
1991年 | 1477篇 |
1990年 | 1282篇 |
1989年 | 1081篇 |
1988年 | 728篇 |
1987年 | 466篇 |
1986年 | 362篇 |
1985年 | 400篇 |
1984年 | 342篇 |
1983年 | 256篇 |
1982年 | 189篇 |
1981年 | 180篇 |
1980年 | 188篇 |
1979年 | 108篇 |
1978年 | 65篇 |
1977年 | 65篇 |
1962年 | 79篇 |
1959年 | 72篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
3.
In this paper, we investigate how adaptive operator selection techniques are able to efficiently manage the balance between exploration and exploitation in an evolutionary algorithm, when solving combinatorial optimization problems. We introduce new high level reactive search strategies based on a generic algorithm's controller that is able to schedule the basic variation operators of the evolutionary algorithm, according to the observed state of the search. Our experiments on SAT instances show that reactive search strategies improve the performance of the solving algorithm. 相似文献
4.
5.
6.
7.
Klaus Reinhardt Hans Georg Breunig Aisada Uchugonova Karsten K?nig 《Journal of the Royal Society Interface》2015,12(110)
We explore the possibility of characterizing sperm cells without the need to stain them using spectral and fluorescence lifetime analyses after multi-photon excitation in an insect model. The autofluorescence emission spectrum of sperm of the common bedbug, Cimex lectularius, was consistent with the presence of flavins and NAD(P)H. The mean fluorescence lifetimes showed smaller variation in sperm extracted from the male (tau m, τm = 1.54–1.84 ns) than in that extracted from the female sperm storage organ (tau m, τm = 1.26–2.00 ns). The fluorescence lifetime histograms revealed four peaks. These peaks (0.18, 0.92, 2.50 and 3.80 ns) suggest the presence of NAD(P)H and flavins and show that sperm metabolism can be characterized using fluorescence lifetime imaging. The difference in fluorescence lifetime variation between the sexes is consistent with the notion that female animals alter the metabolism of sperm cells during storage. It is not consistent, however, with the idea that sperm metabolism represents a sexually selected character that provides females with information about the male genotype. 相似文献
8.
9.
The supervision of a hybrid power plant, including solar panels, a gas microturbine and a storage unit operating under varying solar power profiles is considered. The Economic Supervisory Predictive controller assigns the power references to the controlled subsystems of the hybrid cell using a financial criterion. A prediction of the renewable sources power is embedded into the supervisor. Results deteriorate when the solar power is unsteady, owing to the inaccuracy of the predictions for a long-range horizon of 10 s. The receding horizon is switched between an upper and a lower value according to the amplitude of the solar power trend. Theoretical results show the relevance of horizon switching, according to a tradeoff between performance and prediction accuracy. Experimental results, obtained in a Hardware In the Loop (HIL) framework, show the relevance of the variable horizon approach. Power amplifiers allow us to simulate virtual components, such as a gas microturbine, and to blend their powers with that of real devices (storage unit, real solar panels). In this case, fuel savings, reaching 15%, obtained under unsteady operating conditions lead to a better overall performance of the hybrid cell. The overall savings obtained in the experiments amount to 12%. 相似文献
10.
The development of a sustainable energy system throughout an enterprise is a complex task, which requires an agile holistic approach. Such an approach needs to include a variety of objectives including energy strategy formation and strategic decision-making, which are directly related to the analysis and management of the main areas of sustainable development:The economic, technological, environmental, and social. These multidimensional requirements of sustainability are often difficult to achieve within the enterprise, because these aspects are interrelated and influenced by various internal and external environment factors. This paper first reviews the main challenges for an energy system, and then demonstrates how a strategic agile enterprise architecture driven approach could effectively guide the sustainable energy system development. The study presented in this paper provides a holistic approach that contributes to the advancement and usage of literature dealing with issues of sustainable energy system development and agile enterprise architecture, which has not been discussed before to any great extent. 相似文献