全文获取类型
收费全文 | 478篇 |
免费 | 29篇 |
专业分类
电工技术 | 2篇 |
化学工业 | 102篇 |
金属工艺 | 39篇 |
机械仪表 | 9篇 |
建筑科学 | 9篇 |
矿业工程 | 1篇 |
能源动力 | 9篇 |
轻工业 | 19篇 |
水利工程 | 12篇 |
石油天然气 | 6篇 |
无线电 | 34篇 |
一般工业技术 | 145篇 |
冶金工业 | 51篇 |
原子能技术 | 8篇 |
自动化技术 | 61篇 |
出版年
2023年 | 6篇 |
2022年 | 12篇 |
2021年 | 22篇 |
2020年 | 11篇 |
2019年 | 8篇 |
2018年 | 20篇 |
2017年 | 22篇 |
2016年 | 20篇 |
2015年 | 17篇 |
2014年 | 20篇 |
2013年 | 31篇 |
2012年 | 31篇 |
2011年 | 24篇 |
2010年 | 25篇 |
2009年 | 19篇 |
2008年 | 25篇 |
2007年 | 23篇 |
2006年 | 21篇 |
2005年 | 16篇 |
2004年 | 15篇 |
2003年 | 12篇 |
2002年 | 15篇 |
2001年 | 18篇 |
2000年 | 5篇 |
1999年 | 5篇 |
1998年 | 5篇 |
1997年 | 7篇 |
1996年 | 3篇 |
1995年 | 5篇 |
1994年 | 4篇 |
1993年 | 3篇 |
1991年 | 4篇 |
1990年 | 2篇 |
1989年 | 2篇 |
1987年 | 1篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1981年 | 1篇 |
1979年 | 1篇 |
1976年 | 4篇 |
1975年 | 3篇 |
1974年 | 4篇 |
1973年 | 2篇 |
1972年 | 3篇 |
1971年 | 2篇 |
1970年 | 1篇 |
1968年 | 1篇 |
1966年 | 1篇 |
1964年 | 1篇 |
1962年 | 1篇 |
排序方式: 共有507条查询结果,搜索用时 15 毫秒
71.
Modular reconfigurable machines offer the possibility to efficiently produce a family of different parts. This paper formalises a cost optimisation problem for flow lines equipped with reconfigurable machines which carry turrets, machining modules and single spindles. The proposed models take into account constraints related to: (i) design of machining modules, turrets, and machines, (ii) part locations, and (iii) precedence relations among operations. The goal is to minimise equipment cost while reaching a given output and satisfying all the constraints. A mixed integer programming model is developed for the considered optimisation problem. The approach is validated through an industrial case study and extensive numerical experiments. 相似文献
72.
Chernov Yacov Filatov Eugene Shurov Nikolay Smolenski Valery Tkachev Nikolai 《Metallurgical and Materials Transactions B》2019,50(4):1745-1751
Metallurgical and Materials Transactions B - Formation of calcium hexaboride by means of electrodeposition of boron oxide in molten CaCl2 with additives of CaO and B2O3 was analyzed. It was shown... 相似文献
73.
Chao Wen Alexander G. Banshchikov Yury Y. Illarionov Werner Frammelsberger Theresia Knobloch Fei Hui Nikolai S. Sokolov Tibor Grasser Mario Lanza 《Advanced materials (Deerfield Beach, Fla.)》2020,32(34):2002525
Mechanically exfoliated 2D hexagonal boron nitride (h-BN) is currently the preferred dielectric material to interact with graphene and 2D transition metal dichalcogenides in nanoelectronic devices, as they form a clean van der Waals interface. However, h-BN has a low dielectric constant (≈3.9), which in ultrascaled devices results in high leakage current and premature dielectric breakdown. Furthermore, the synthesis of h-BN using scalable methods, such as chemical vapor deposition, requires very high temperatures (>900 °C) , and the resulting h-BN stacks contain abundant few-atoms-wide amorphous regions that decrease its homogeneity and dielectric strength. Here it is shown that ultrathin calcium fluoride (CaF2) ionic crystals could be an excellent solution to mitigate these problems. By applying >3000 ramped voltage stresses and several current maps at different locations of the samples via conductive atomic force microscopy, it is statistically demonstrated that ultrathin CaF2 shows much better dielectric performance (i.e., homogeneity, leakage current, and dielectric strength) than SiO2, TiO2, and h-BN. The main reason behind this behavior is that the cubic crystalline structure of CaF2 is continuous and free of defects over large regions, which prevents the formation of electrically weak spots. 相似文献
74.
Nikolai Kashaev Dmitrii Ushmaev Volker Ventzke Benjamin Klusemann Fedor Fomin 《Fatigue & Fracture of Engineering Materials & Structures》2020,43(7):1500-1513
The present study aims to investigate the extent to which the fatigue behaviour of laser beam‐welded AA6056‐T6 butt joints with an already existing crack can be improved through the application of laser shock peening. Ultrasonic testing was utilized for in situ (nondestructive) measurement of fatigue crack growth during the fatigue test. This procedure allowed the preparation of welded specimens with surface fatigue cracks with a depth of approximately 1.2 mm. The precracked specimens showed a 20% reduction in the fatigue limit compared with specimens without cracks in the as‐welded condition. Through the application of laser shock peening on the surfaces of the precracked specimens, it was possible to recover the fatigue life to the level of the specimens tested in the as‐welded condition. The results of this study show that laser shock peening is a very promising technique to recover the fatigue life of welded joints with surface cracks, which can be detected by nondestructive testing. 相似文献
75.
76.
Twinned Growth of Metal‐Free,Triazine‐Based Photocatalyst Films as Mixed‐Dimensional (2D/3D) van der Waals Heterostructures 下载免费PDF全文
Dana Schwarz Yu Noda Jan Klouda Karolina Schwarzová‐Pecková Ján Tarábek Jiří Rybáček Jiří Janoušek Frank Simon Maksym V. Opanasenko Jiří Čejka Amitava Acharjya Johannes Schmidt Sören Selve Valentin Reiter‐Scherer Nikolai Severin Jürgen P. Rabe Petra Ecorchard Junjie He Miroslav Polozij Petr Nachtigall Michael J. Bojdys 《Advanced materials (Deerfield Beach, Fla.)》2017,29(40)
Design and synthesis of ordered, metal‐free layered materials is intrinsically difficult due to the limitations of vapor deposition processes that are used in their making. Mixed‐dimensional (2D/3D) metal‐free van der Waals (vdW) heterostructures based on triazine (C3N3) linkers grow as large area, transparent yellow‐orange membranes on copper surfaces from solution. The membranes have an indirect band gap (E g,opt = 1.91 eV, E g,elec = 1.84 eV) and are moderately porous (124 m2 g?1). The material consists of a crystalline 2D phase that is fully sp2 hybridized and provides structural stability, and an amorphous, porous phase with mixed sp2–sp hybridization. Interestingly, this 2D/3D vdW heterostructure grows in a twinned mechanism from a one‐pot reaction mixture: unprecedented for metal‐free frameworks and a direct consequence of on‐catalyst synthesis. Thanks to the efficient type I heterojunction, electron transfer processes are fundamentally improved and hence, the material is capable of metal‐free, light‐induced hydrogen evolution from water without the need for a noble metal cocatalyst (34 µmol h?1 g?1 without Pt). The results highlight that twinned growth mechanisms are observed in the realm of “wet” chemistry, and that they can be used to fabricate otherwise challenging 2D/3D vdW heterostructures with composite properties. 相似文献
77.
Ultralong 20 Milliseconds Charge Separation Lifetime for Photoilluminated Oligophenylenevinylene–Azafullerene Systems 下载免费PDF全文
Georgios Rotas Kati Stranius Nikolai Tkachenko Nikos Tagmatarchis 《Advanced functional materials》2018,28(7)
The synthesis and characterization of oligophenylenevinylene (OPV)–azafullerene (C59N) systems in the form of OPV–C59N donor–acceptor dyad 1 and C59N–OPV–C59N acceptor–donor–acceptor triad 2 is accomplished. Photoinduced electronic interactions between OPV and C59N within 1 and 2 are assessed by UV–vis and photoluminescence. The redox properties of 1 and 2 are investigated, revealing a set of one‐electron oxidation and three one‐electron reduction processes owed to OPV and C59N, respectively. The electrochemical bandgap for 1 and 2 is calculated as 1.44 and 1.53 eV, respectively, and the free energy for the formation of the charge‐separated state for 1 and 2 via the singlet‐excited state of OPV is found negative, proving a thermodynamically favorable the process. Photoexcitation assays are performed in toluene and o‐dichlorobenzene (oDCB) and the reactions are monitored with time‐resolved absorption and emission spectroscopies. Competitive photoinduced energy and electron transfer are identified to occur in both systems, with the former being dominant in 2 . Markedly, the charge‐separated state in oDCB exhibits a much longer lifetime compared to that in toluene, reaching 20 ms for 1 , the highest ever reported value for fullerene‐based materials. These unprecedented results are rationalized by considering conformational phenomena affecting the charge‐separated state. 相似文献
78.
Functionalized Graphene as Extracellular Matrix Mimics: Toward Well‐Defined 2D Nanomaterials for Multivalent Virus Interactions 下载免费PDF全文
Mohammad Fardin Gholami Daniel Lauster Kai Ludwig Julian Storm Benjamin Ziem Nikolai Severin Christoph Böttcher Jürgen P. Rabe Andreas Herrmann Mohsen Adeli Rainer Haag 《Advanced functional materials》2017,27(15)
Polysulfated nanomaterials that mimic the extracellular cell matrix are of great interest for their potential to modulate cellular responses and to bind and neutralize pathogens. However, control over the density of active functional groups on such biomimetics is essential for efficient interactions, and this remains a challenge. In this regard, producing polysulfated graphene derivatives with control over their functionality is an intriguing accomplishment in order to obtain highly effective 2D platforms for pathogen interactions. Here, a facile and efficient method for the controlled attachment of a heparin sulfate mimic on the surface of graphene is reported. Dichlorotriazine groups are conjugated to the surface of graphene by a one‐pot [2+1] nitrene cycloaddition reaction at ambient conditions, providing derivatives with defined functionality. Consecutive step by step conjugation of hyperbranched polyglycerol to the dichlorotriazine groups and eventual conversion to the polyglycerol sulfate result in the graphene based heparin biomimetics. Scanning force microscopy, cryo‐transmission electron microscopy, and in vitro bioassays reveal strong interactions between the functionalized graphene (thoroughly covered by a sulfated polymer) and vesicular stomatitis virus. Infection experiments with highly sulfated versions of graphene drastically promote the infection process, leading to higher viral titers compared to nonsulfated analogues. 相似文献
79.