全文获取类型
收费全文 | 2528篇 |
免费 | 109篇 |
国内免费 | 3篇 |
专业分类
电工技术 | 31篇 |
综合类 | 8篇 |
化学工业 | 637篇 |
金属工艺 | 44篇 |
机械仪表 | 28篇 |
建筑科学 | 175篇 |
矿业工程 | 6篇 |
能源动力 | 71篇 |
轻工业 | 212篇 |
水利工程 | 20篇 |
石油天然气 | 5篇 |
无线电 | 237篇 |
一般工业技术 | 487篇 |
冶金工业 | 243篇 |
原子能技术 | 16篇 |
自动化技术 | 420篇 |
出版年
2023年 | 40篇 |
2022年 | 50篇 |
2021年 | 103篇 |
2020年 | 55篇 |
2019年 | 57篇 |
2018年 | 58篇 |
2017年 | 56篇 |
2016年 | 85篇 |
2015年 | 67篇 |
2014年 | 119篇 |
2013年 | 136篇 |
2012年 | 154篇 |
2011年 | 187篇 |
2010年 | 116篇 |
2009年 | 116篇 |
2008年 | 131篇 |
2007年 | 120篇 |
2006年 | 116篇 |
2005年 | 105篇 |
2004年 | 84篇 |
2003年 | 57篇 |
2002年 | 58篇 |
2001年 | 31篇 |
2000年 | 46篇 |
1999年 | 37篇 |
1998年 | 59篇 |
1997年 | 44篇 |
1996年 | 50篇 |
1995年 | 34篇 |
1994年 | 36篇 |
1993年 | 21篇 |
1992年 | 14篇 |
1991年 | 19篇 |
1990年 | 15篇 |
1989年 | 13篇 |
1988年 | 8篇 |
1987年 | 10篇 |
1986年 | 7篇 |
1985年 | 11篇 |
1984年 | 8篇 |
1983年 | 12篇 |
1982年 | 10篇 |
1981年 | 9篇 |
1980年 | 6篇 |
1979年 | 10篇 |
1978年 | 11篇 |
1977年 | 6篇 |
1976年 | 10篇 |
1975年 | 5篇 |
1973年 | 6篇 |
排序方式: 共有2640条查询结果,搜索用时 0 毫秒
41.
Stephan van Reenen Piotr Matyba Andrzej Dzwilewski René A. J. Janssen Ludvig Edman Martijn Kemerink 《Advanced functional materials》2011,21(10):1795-1802
Incorporation of ions in the active layer of organic semiconductor devices may lead to attractive device properties like enhanced injection and improved carrier transport. In this paper, we investigate the effect of the salt concentration on the operation of light‐emitting electrochemical cells, using experiments and numerical calculations. The current density and light emission are shown to increase linearly with increasing ion concentration over a wide range of concentrations. The increasing current is accompanied by an ion redistribution, leading to a narrowing of the recombination zone. Hence, in absence of detrimental side reactions and doping‐related luminescence quenching, the ion concentration should be as high as possible. 相似文献
42.
Hasegawa Y Durstberger-Rennhofer K Sponar S Rauch H 《Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment》2011,634(1):S21-S24
The Kochen-Specker theorem shows the incompatibility of noncontextual hidden variable theories with quantum mechanics. Quantum contextuality is a more general concept than quantum non-locality which is quite well tested in experiments using Bell inequalities. Within neutron interferometry we performed an experimental test of the Kochen-Specker theorem with an inequality, which identifies quantum contextuality, by using spin-path entanglement of single neutrons. Here entanglement is achieved not between different particles, but between degrees of freedom of a single neutron, i.e., between spin and path degree of freedom. Appropriate combinations of the spin analysis and the position of the phase shifter allow an experimental verification of the violation of an inequality derived from the Kochen-Specker theorem. The observed violation 2.291±0.008?1 clearly shows that quantum mechanical predictions cannot be reproduced by noncontextual hidden variable theories. 相似文献
43.
44.
Enhancing Cell therapies from the Outside In: Cell Surface Engineering Using Synthetic Nanomaterials
Therapeutic treatments based on the injection of living cells are in clinical use and preclinical development for diseases ranging from cancer to cardiovascular disease to diabetes. To enhance the function of therapeutic cells, a variety of chemical and materials science strategies are being developed that engineer the surface of therapeutic cells with new molecules, artificial receptors, and multifunctional nanomaterials, synthetically endowing donor cells with new properties and functions. These approaches offer a powerful complement to traditional genetic engineering strategies for enhancing the function of living cells. 相似文献
45.
In this paper, we present novel developments in aerodynamic shape optimization based on shape calculus as well as the proper treatment of aleatoric uncertainties in the field of aerodynamic design. 相似文献
46.
Nikolaj Krasokha Sebastian Weber Stephan Huth Kathrin Zumsande Werner Theisen 《Metallurgical and Materials Transactions A》2012,43(11):4237-4246
This work deals with gas?Csolid interactions between a high-alloyed steel powder and the surrounding atmosphere during continuous heating. It is motivated by the recently developed corrosion-resistant CrMnCN austenitic cast steels. Here, powder metallurgical processing would be desirable to manufacture highly homogeneous parts and/or novel corrosion-resistant metal-matrix composites. However, the successful use of this new production route calls for a comprehensive investigation of interactions between the sintering atmosphere and the metallic powder to prevent undesirable changes to the chemical composition, e.g., degassing of nitrogen or evaporation of manganese. In this study, dilatometric measurements combined with residual gas analysis, high-temperature X-ray diffraction (XRD) measurements, and thermodynamic equilibrium calculations provided detailed information about the influence of different atmospheric conditions on the microstructure, constitution, and densification behavior of a gas-atomized CrMnCN steel powder during continuous heating. Intensive desorption of nitrogen led to the conclusion that a vacuum atmosphere is not suitable for powder metallurgical (PM) processing. Exposure to an N2-containing atmosphere resulted in the formation of nitrides and lattice expansion. Experimental findings have shown that the N content can be controlled by the nitrogen partial pressure. Furthermore, the reduction of surface oxides because of a carbothermal reaction at elevated temperatures and the resulting enhancement of the powder??s densification behavior are discussed in this work. 相似文献
47.
Shiro Nishiwaki Andreas Burn Stephan Buecheler Martin Muralt Snke Pilz Valerio Romano Reiner Witte Lukas Krainer Gabriel J. Spühler Ayodhya N. Tiwari 《Progress in Photovoltaics: Research and Applications》2015,23(12):1908-1915
Monolithically integrated Cu(In,Ga)Se2 mini‐modules were fabricated in order to reduce the width of patterning related dead area. The Cu(In,Ga)Se2 layers were prepared on soda‐lime glasses using the multistage process at low substrate temperature below 500 °C. A picosecond laser with a wavelength of 532 nm was used for all of the structuring processes (P1, P2, and P3) for the monolithic integration. A “lift‐off” type structuring was applied for P1 and P3, and an “ablation” type was for P2. The laser structuring was optimized to be minimizing the dead area width, and the width of about 70 µm was successfully achieved. A mini‐module, in which the optimized structuring processes were applied for the integration, demonstrated a certified efficiency of 16.6%. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
48.
Angela Sester Katrin Stüer-Patowsky Prof. Dr. Wolf Hiller Dr. Florian Kloss Prof. Dr. Stephan Lütz Prof. Dr. Markus Nett 《Chembiochem : a European journal of chemical biology》2020,21(16):2268-2273
Enzyme promiscuity has important implications in the field of biocatalysis. In some cases, structural analogues of simple metabolic building blocks can be processed through entire pathways to give natural product derivatives that are not readily accessible by chemical means. In this study, we explored the plasticity of the aurachin biosynthesis pathway with regard to using fluoro- and chloroanthranilic acids, which are not abundant in the bacterial producers of these quinolone antibiotics. The incorporation rates of the tested precursor molecules disclosed a regiopreference for halogen substitution as well as steric limitations of enzymatic substrate tolerance. Three previously undescribed fluorinated aurachin derivatives were produced in preparative amounts by fermentation and structurally characterized. Furthermore, their antibacterial activities were evaluated in comparison to their natural congener aurachin D. 相似文献
49.
Experiments on transition and flow boiling heat transfer with refrigerant R114 inside a horizontal tube were performed at bubble flow, critical heat flux and in the transition region between bubble flow and film boiling at mass fluxes between 1200 and 4000 kg/m2 s and in the pressure range between 5 and 15 bar. In comparison with pool boiling bubble flow heat transfer depends essentially on the mass flow rates and on the vapor quality. The critical heat flux depends less on the temperature difference than in pool boiling heat transfer and exhibits a maximal and a minimal value as a function of the pressure. The critical heat flux increases with mass flow rate as already shown by Collier. In the region of transition boiling the heat flux over the difference between wall and saturation temperature approaches a horizontal curve. Therefore in this region an evaporator may always be operated under stable conditions and burn out does not occur. 相似文献
50.
The layered Li[Li0.07Ni0.1Co0.6Mn0.23]O2 materials were synthesized by sol-gel method with glycine or citric acid as chelating agent. The prepared materials were characterized by means of XRD, SEM and Raman spectroscopy. Li/Li[Li0.07Ni0.1Co0.6Mn0.23]O2 cells were assembled and subjected to charge-discharge studies at different C rates, viz 0.2, 1, 2 and 4 C. Although the samples showed less discharge capacity at 4 C rate the fade in capacity per cycle is lesser than that of capacity fade at 0.2 C rate. The citric acid assisted sample is found to be superior in terms of discharge capacity, capacity retention rate and also in thermal stability to that of sample prepared with glycine as chelating agent. 相似文献