全文获取类型
收费全文 | 3524篇 |
免费 | 221篇 |
国内免费 | 10篇 |
专业分类
电工技术 | 38篇 |
综合类 | 1篇 |
化学工业 | 929篇 |
金属工艺 | 56篇 |
机械仪表 | 91篇 |
建筑科学 | 171篇 |
矿业工程 | 7篇 |
能源动力 | 158篇 |
轻工业 | 449篇 |
水利工程 | 22篇 |
石油天然气 | 8篇 |
无线电 | 341篇 |
一般工业技术 | 581篇 |
冶金工业 | 174篇 |
原子能技术 | 35篇 |
自动化技术 | 694篇 |
出版年
2024年 | 9篇 |
2023年 | 43篇 |
2022年 | 115篇 |
2021年 | 192篇 |
2020年 | 101篇 |
2019年 | 100篇 |
2018年 | 117篇 |
2017年 | 125篇 |
2016年 | 140篇 |
2015年 | 99篇 |
2014年 | 158篇 |
2013年 | 275篇 |
2012年 | 226篇 |
2011年 | 250篇 |
2010年 | 175篇 |
2009年 | 163篇 |
2008年 | 185篇 |
2007年 | 158篇 |
2006年 | 125篇 |
2005年 | 103篇 |
2004年 | 98篇 |
2003年 | 101篇 |
2002年 | 84篇 |
2001年 | 57篇 |
2000年 | 34篇 |
1999年 | 40篇 |
1998年 | 37篇 |
1997年 | 39篇 |
1996年 | 42篇 |
1995年 | 37篇 |
1994年 | 24篇 |
1993年 | 32篇 |
1992年 | 17篇 |
1991年 | 20篇 |
1990年 | 14篇 |
1989年 | 19篇 |
1988年 | 15篇 |
1987年 | 21篇 |
1986年 | 12篇 |
1985年 | 8篇 |
1984年 | 14篇 |
1983年 | 14篇 |
1982年 | 14篇 |
1981年 | 12篇 |
1980年 | 11篇 |
1979年 | 15篇 |
1978年 | 9篇 |
1977年 | 7篇 |
1974年 | 13篇 |
1973年 | 9篇 |
排序方式: 共有3755条查询结果,搜索用时 31 毫秒
51.
The crystal structure and molecular conformation of 2-cyano-4-bromo-4′-N,N-diethylaminoazobenzene (C17H17N4Br, mol. wt. = 357·2 a.m.u) has been determined from X-ray diffraction data; triclinic, P (No. 2), a = 10·132(11) Å, b = 12·216(16) Å, c = 6·966(11) Å, α = 104·21(9)°, β = 92·67(12)°, γ = 97·22(7)°, V = 826·5(9) Å3, Z = 2, Dc = 1·436 g cm?3, F(000) = 378, λ(MoKα) = 0·71069 Å, μ(MoKα) = 26·0 cm?1. The structure was solved by the multiple solution direct method and refined by full-matrix least-squares to R = 0·059 for 1538 independent observed reflections. The azobenzene skeleton is planar to within 0·06 Å. Most significant bonding data are: NN, 1·290(8) Å; BrC, 1·866(6) Å; mean CN (azo) 1·380(8) Å; NNC, 113·6(4) and 115·3(4)°; NCC (cis relative to NN) 125·9(4)° and 126·7(4)°; NCC (trans) 116·8°(5)° and 116·1(4)°. 相似文献
52.
Charles P. Gibson David S. Bem Jeffrey E. Cortopassi 《Journal of Inorganic and Organometallic Polymers》1991,1(2):231-238
Reaction of 2,3,4,5-tetramethylcyclopent-2-enone (1) withp-LiC6H4OC-Me2OMe, followed by treatment with aqueous acid afforded 1-(p-hydroxyphenyl)-2,3,4,5-tetramethylcyclopentadiene (2). This new ligand was then used in the synthesis of the functionally substituted organomolybdenum reagent (5-C5Me4-p-C6H5OH)Mo(CO)2(NO) (3). Treatment of a preformed 1/1 styrene/maleic anhydride copolymer (
) with 5 mol% 3 led to chemical incorporation of the organometallic species into the polymer. The final product contained 3 mol% of the organometallic moiety. 相似文献
53.
Information Systems Frontiers - What is happening in hacker’s minds when they are committing criminal activities? How black hat hackers manage nerves, which is about managing fear and... 相似文献
54.
Tellez Eric S. Ruiz Guillermo Chavez Edgar Graff Mario 《Pattern Analysis & Applications》2021,24(2):763-777
Pattern Analysis and Applications - Nearest neighbor search is a powerful abstraction for data access; however, data indexing is troublesome even for approximate indexes. For intrinsically... 相似文献
55.
Mario Schmidt 《化学,工程师,技术》2021,93(11):1707-1716
The extraction of raw materials is associated with energy input and CO2 emissions. What is obvious for extraction from mining, however, also applies to recycling. Mostly, recycling is preferred for reasons of climate protection or because of the geological scarcity of raw materials, which is controversially discussed. While in mining, the declining ore grade is a driver for the energy demand, in case of recycling it is the dissipation of materials into products or waste. As concentration decreases, the effort required also increases disproportionately. The “closing the loop” metaphor of Circular Economy is therefore inappropriate in its stricter meaning. It is rather about optimizing the overall system and finding the optimal recycling rate. However, first, it must be clarified what the political goals for Circular Economy are. 相似文献
56.
Mario Bragaglia Tony McNally Francesca R. Lamastra Valeria Cherubini Francesca Nanni 《应用聚合物科学杂志》2021,138(20):50423
Immiscible blends of ethylene-propylene-diene-monomer (EPDM) and polyoxymethylene (POM), when EPDM is the major phase were compatibilized on the addition of an ionomer, poly(ethylene-co-methacrylic acid). The inclusion of the ionomer reduced the interfacial tension between the two phases, such that the diameter of the POM domains were significantly reduced to between 0.5 and 2 μm, typical of that required to toughen ductile polymers. The mechanical properties of the resultant compatibilized blends were significantly enhanced with increases in Young's modulus (↑54%), tensile strength (σ, ↑139%), elongation at break (ε, ↑97%), and tensile toughness (↑500%) with increasing ionomer content, relative to EPDM rubber alone. The ShoreA hardness of the compatibilized blend was 70.1 compared with 56.8 for the immiscible binary blend and, 50.2 for neat EPDM rubber. 相似文献
57.
Mario Garcia‐Sanz 《国际强度与非线性控制杂志
》2016,26(12):2643-2651
》2016,26(12):2643-2651
The Nyquist stability criterion is a widely used technique for determining in the complex s‐plane the stability of a dynamical system with feedback. This paper presents a practical and comprehensive method to compute the Nyquist stability criterion directly in the Nichols (magnitude/phase) chart. The proposed method also gives guidelines to design controllers to stabilize unstable plants when dealing with frequency domain techniques like the quantitative feedback theory robust control. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
58.
Francis George C. Cabarle Henry N. Adorna Mario J. Pérez-Jiménez 《Natural computing》2016,15(4):533-539
Spiking neural P systems (in short, SN P systems) are membrane computing models inspired by the pulse coding of information in biological neurons. SN P systems with standard rules have neurons that emit at most one spike (the pulse) each step, and have either an input or output neuron connected to the environment. A variant known as SN P modules generalize SN P systems by using extended rules (more than one spike can be emitted each step) and a set of input and output neurons. In this work we continue relating SN P modules and finite automata. In particular, we amend and improve previous constructions for the simulatons of deterministic finite automata and state transducers. Our improvements reduce the number of neurons from three down to one, so our results are optimal. We also simulate finite automata with output, and we use these simulations to generate automatic sequences. 相似文献
59.
Miguel A. Martínez-del-Amor Luis F. Macías-Ramos Luis Valencia-Cabrera Mario J. Pérez-Jiménez 《Natural computing》2016,15(4):565-573
Population Dynamics P systems are a type of multienvironment P systems that serve as a formal modeling framework for real ecosystems. The accurate simulation of these probabilistic models, e.g. with Direct distribution based on Consistent Blocks Algorithm, entails large run times. Hence, parallel platforms such as GPUs have been employed to speedup the simulation. In 2012, the first GPU simulator of PDP systems was presented. However, it was able to run only randomly generated PDP systems. In this paper, we present current updates made on this simulator, involving an input modu le for binary files and an output module for CSV files. Finally, the simulator has been experimentally validated with a real ecosystem model, and its performance has been tested with two high-end GPUs: Tesla C1060 and K40. 相似文献
60.
The evaluation of the emergent behaviour in complex systems requires an analytical framework which allows the observation of different phenomena that take place at different levels. In order to observe the dynamics of complex systems, it is necessary to perform simulations so that both local and the emergent behaviour can be observed. To this end, the way in which complex system simulators are built must be examined so that it will be feasible to model large scale scenarios. In this paper, the use of Model Driven Engineering methodology is proposed to deal with this issue. Among other benefits, it is shown that this methodology allows the representation and simulation of a complex system providing support for the analysis. This analysis is supported by a metamodel which describes the system components that are under study. The application of this methodology to the development of large scale simulators is explored through a case study. This case study analyses a complex socio-technical system: a power grid. 相似文献