全文获取类型
收费全文 | 1470篇 |
免费 | 101篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 27篇 |
综合类 | 1篇 |
化学工业 | 497篇 |
金属工艺 | 23篇 |
机械仪表 | 24篇 |
建筑科学 | 45篇 |
矿业工程 | 5篇 |
能源动力 | 67篇 |
轻工业 | 171篇 |
水利工程 | 6篇 |
石油天然气 | 6篇 |
无线电 | 100篇 |
一般工业技术 | 252篇 |
冶金工业 | 67篇 |
原子能技术 | 3篇 |
自动化技术 | 278篇 |
出版年
2024年 | 2篇 |
2023年 | 5篇 |
2022年 | 15篇 |
2021年 | 163篇 |
2020年 | 58篇 |
2019年 | 59篇 |
2018年 | 74篇 |
2017年 | 64篇 |
2016年 | 93篇 |
2015年 | 54篇 |
2014年 | 105篇 |
2013年 | 119篇 |
2012年 | 73篇 |
2011年 | 82篇 |
2010年 | 62篇 |
2009年 | 66篇 |
2008年 | 73篇 |
2007年 | 60篇 |
2006年 | 43篇 |
2005年 | 37篇 |
2004年 | 44篇 |
2003年 | 30篇 |
2002年 | 27篇 |
2001年 | 17篇 |
2000年 | 15篇 |
1999年 | 13篇 |
1998年 | 9篇 |
1997年 | 13篇 |
1996年 | 4篇 |
1995年 | 9篇 |
1994年 | 6篇 |
1993年 | 7篇 |
1992年 | 4篇 |
1991年 | 7篇 |
1990年 | 2篇 |
1989年 | 4篇 |
1987年 | 6篇 |
1986年 | 3篇 |
1985年 | 8篇 |
1984年 | 2篇 |
1983年 | 4篇 |
1982年 | 7篇 |
1981年 | 7篇 |
1980年 | 6篇 |
1979年 | 4篇 |
1977年 | 1篇 |
1976年 | 1篇 |
1975年 | 1篇 |
1974年 | 1篇 |
1970年 | 1篇 |
排序方式: 共有1572条查询结果,搜索用时 203 毫秒
71.
Synthesis of trimethylene carbonate/ϵ‐caprolactone copolymers initiated with zinc alkoxide: influence of copolymer chain microstructure on thermal and mechanical properties 下载免费PDF全文
Malgorzata Pastusiak Piotr Dobrzynski Janusz Kasperczyk Michal Sobota Bozena Kaczmarczyk Henryk Janeczek 《Polymer International》2017,66(9):1259-1268
Ethylzinc(II ) ethoxide is a highly active and efficient initiator for the bulk polymerization of 1,3‐trimethylene carbonate and its copolymerization with ? ‐caprolactone. This initiator allows one to obtain (co)polymers with high molar masses in quite a short time. Significant difference in co‐monomer reactivity and relatively low participation of intermolecular transesterification processes lead to the obtained copolymers being characterized by a gradient chain microstructure. In 13C NMR spectra, in all regions, we observed the presence of triads which were distinctly represented by four peaks for the carbonyl signal. Mechanical tests showed that copolymers containing 70% and more of ? ‐caprolactone presented a relatively high Young's modulus and a very high maximum elongation factor; therefore these materials are promising in many biomedical applications. Due to the high reaction rate, we also made an attempt at copolymerization using reactive extrusion which gave promising results. © 2017 Society of Chemical Industry 相似文献
72.
Majkut Konrad Giergiel Mariusz Kohut Piotr 《Journal of Mechanical Science and Technology》2017,31(2):893-901
The aim of this paper is to analyze the kinematics of a small crawler robot. A mathematical model of kinematics based on a two-wheeled approach is proposed. This model is experimentally verified using vision-based motion measurements of a crawler vehicle equipped with encoders and a remote control system. It is assumed that the vehicle moves along a few curves with different angular speeds of its wheels. Based on the model of motion and the values of these speeds, numerical simulations are investigated. The results obtained from numerical and experimental validation are presented and discussed. The comparison delivered some important conclusions.
相似文献73.
Balaji Raghavan Guenhael Le Quilliec Piotr Breitkopf Alain Rassineux Jean-Marc Roelandt Pierre Villon 《International Journal of Material Forming》2014,7(4):487-501
In this paper, we introduce an original shape representation approach for post-springback characterization based on the automatic generation of parameterized level set functions. The central idea is the concept of the shape manifold representing the design domain in the reduced-order shape-space. Performing Proper Orthogonal Decomposition on the shapes followed by using the Diffuse Approximation allows us to efficiently reduce the problem dimensionality and to interpolate uniquely between admissible input shapes, while also determining the smallest number of parameters needed to characterize the final formed shape. We apply this methodology to the problem of springback assessment for the deep drawing operation of metal sheets. 相似文献
74.
Piotr Piela Jens Mitzel Erich Gülzow Jürgen Hunger Alexander Kabza Ludwig Jörissen Francesco Valle Alberto Pilenga Thomas Malkow Georgios Tsotridis 《International Journal of Hydrogen Energy》2017,42(31):20187-20200
The direct-search simplex method for function optimization has been adapted to performance optimization of polymer electrolyte membrane fuel cells (PEMFCs). The established method is strongly application oriented and uses only experimentally determined data for optimization. It is not restricted to discrete parameters optimums and does not require the use of third-party software or computational resources. Hence, it is easy to implement in fuel cell testing stations. The optimization consists of finding, for a given fuel cell load, an optimum set of values of the 7 fuel cell operating parameters: the fuel cell temperature, the reactants' stoichiometric ratios, the reactants' inlet relative humidity, and the reactants' outlet pressures, resulting in the highest fuel cell performance. The performance is measured using a scalar function of the operating parameters and the load and can be defined according to needs.Two PEMFC performance functions: the fuel cell voltage and the system-related fuel cell efficiency were optimized using the procedure for practically sized PEMFC stacks of two designs. With respect to the nominal operating conditions defined as optimal for each stack design by its manufacturer, the gains from the optimization procedure were up to over 12% and up to over 7% for the stack voltage and efficiency, respectively. The validation of the procedure involved 5 stack specimens and four laboratories and consistent results were obtained. 相似文献
75.
In this work, the analysis of the plasma modification of polydimethylsiloxane (PDMS) substrates was conducted. The influence of the modification onto the changes occurred within the geometrical structure and chemical composition of the surface was analyzed. Due to the study of the atomic force microscopy, it was possible to determine the relationships between the surface development and applied process parameters, defining the conditions facilitating to obtain isotropic or anisotropic orientations of wrinkles. A precise analysis of the chemical composition of the surface, executed before and after the modification processes, enabled to define the changes in their elementary composition. Moreover, the modification influence onto the changes of the contact angle and the surface free energy were also analyzed. So, based on the research it was stated that the increase of value of the surface free energy is proportional to the sp3 phase contents in the DLC coatings. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41635. 相似文献
76.
Amine curing agents pose serious health hazards and controlling their release is crucially important. Extraction of unbounded amine from cured epoxy polymers can improve the ecological characteristics of such products. Even 1 min exposure of cured epoxy resins to hot water reduces three- to ten-fold the residual amount of amine present in the epoxy polymer. Different temperatures and extraction times were tested, enabling the selection of the most optimal extraction conditions, which correspond to 5 min of heating in 100°C. This additional cost-effective extraction step is very easy to perform and leads to a significant reduction of unbounded curing agent, making cured epoxy resins much more eco-friendly products. The documented positive and linear trends of logarithms of viscosity and the amount of released amine suggest the selection from such curing agents and such epoxy resins that are characterized by lowest possible viscosities, which guarantees that there is only a low amount of unbounded amine that needs to be released from the polymer. 相似文献
77.
78.
79.
Piotr Długosz Angelika Rączka Adrian Kopeć Rudolf Krzyżak Paweł Darłak Marek Hebda 《Journal of Materials Engineering and Performance》2016,25(6):2261-2266
This paper presents novel opportunities for management of fly ash by synthesizing the material into cordierite ceramics and using it as a reinforcing phase for light metal alloys. Metal matrix composites (based on magnesium alloy and aluminum alloy) were produced by squeeze casting. The magnesium matrix composites with a suitably selected reinforcing phase content (2 wt.%) exhibited much better strength properties than the unmodified alloy (AM60). It was also demonstrated that the wettability (or the lack thereof) in the metal-ceramic system is critical to successful production of the composites based on the AK7 alloy with cordierite. Light alloy matrix composites reinforced with cordierite ceramics particles are innovative materials that combine high strength with low weight, which may be a key factor of merit for numerous applications of the composite in various branches of industries. 相似文献
80.
Anna Wajler Anna Kozłowska Magdalena Nakielska Kamila Leśniewska‐Matys Agata Sidorowicz Dariusz Podniesiński Piotr Putyra 《Journal of the American Ceramic Society》2014,97(6):1692-1695
Transparent cobalt‐doped magnesium aluminate spinel (Co:MgAl2O4) ceramics with a submicrometer grain size were prepared by spark plasma sintering. For the first time, the nonlinear absorption of Co:MgAl2O4 transparent ceramics was experimentally demonstrated. Both ground state absorption (σGSA) and excited state absorption (σESA) were estimated using the solid‐state slow saturable absorber model based on absorption saturation measurements performed at 1.535 μm. σGSA and σESA for 0.03 at.% Co:MgAl2O4 were found to be 4.1 × 10?19 cm2 and 4.0 × 10?20 cm2, respectively. In the case of 0.06 at.% Co:MgAl2O4 ceramics, σGSA = 2.6 × 10?19 cm2 and σESA= 5.3 × 10?20 cm2 were determined. 相似文献