全文获取类型
收费全文 | 5906篇 |
免费 | 243篇 |
国内免费 | 31篇 |
专业分类
电工技术 | 48篇 |
综合类 | 33篇 |
化学工业 | 1100篇 |
金属工艺 | 138篇 |
机械仪表 | 130篇 |
建筑科学 | 242篇 |
矿业工程 | 35篇 |
能源动力 | 99篇 |
轻工业 | 594篇 |
水利工程 | 40篇 |
石油天然气 | 6篇 |
武器工业 | 1篇 |
无线电 | 382篇 |
一般工业技术 | 987篇 |
冶金工业 | 1621篇 |
原子能技术 | 30篇 |
自动化技术 | 694篇 |
出版年
2023年 | 38篇 |
2022年 | 48篇 |
2021年 | 107篇 |
2020年 | 91篇 |
2019年 | 73篇 |
2018年 | 177篇 |
2017年 | 163篇 |
2016年 | 174篇 |
2015年 | 149篇 |
2014年 | 148篇 |
2013年 | 371篇 |
2012年 | 313篇 |
2011年 | 312篇 |
2010年 | 235篇 |
2009年 | 199篇 |
2008年 | 271篇 |
2007年 | 209篇 |
2006年 | 187篇 |
2005年 | 168篇 |
2004年 | 127篇 |
2003年 | 159篇 |
2002年 | 140篇 |
2001年 | 102篇 |
2000年 | 103篇 |
1999年 | 100篇 |
1998年 | 537篇 |
1997年 | 303篇 |
1996年 | 194篇 |
1995年 | 123篇 |
1994年 | 101篇 |
1993年 | 107篇 |
1992年 | 27篇 |
1991年 | 43篇 |
1990年 | 30篇 |
1989年 | 36篇 |
1988年 | 30篇 |
1987年 | 25篇 |
1986年 | 23篇 |
1985年 | 38篇 |
1984年 | 25篇 |
1983年 | 24篇 |
1982年 | 36篇 |
1981年 | 36篇 |
1980年 | 23篇 |
1979年 | 20篇 |
1978年 | 25篇 |
1977年 | 48篇 |
1976年 | 46篇 |
1975年 | 22篇 |
1973年 | 17篇 |
排序方式: 共有6180条查询结果,搜索用时 0 毫秒
111.
112.
Hope Badawy Jér?me Brunellière Marina Veryaskina Guillaume Brotons Sophie Sablé Isabelle Lanneluc Kelly Lambert Pascal Marmey Amy Milsted Teresa Cutright Arnaud Nourry Jean-Luc Mouget Pamela Pasetto 《International journal of molecular sciences》2015,16(3):4392-4415
There has been an intense research effort in the last decades in the field of biofouling prevention as it concerns many aspects of everyday life and causes problems to devices, the environment, and human health. Many different antifouling and antimicrobial materials have been developed to struggle against bacteria and other micro- and macro-organism attachment to different surfaces. However the “miracle solution” has still to be found. The research presented here concerns the synthesis of bio-based polymeric materials and the biological tests that showed their antifouling and, at the same time, antibacterial activity. The raw material used for the coating synthesis was natural rubber. The polyisoprene chains were fragmented to obtain oligomers, which had reactive chemical groups at their chain ends, therefore they could be modified to insert polymerizable and biocidal groups. Films were obtained by radical photopolymerization of the natural rubber derived oligomers and their structure was altered, in order to understand the mechanism of attachment inhibition and to increase the efficiency of the anti-biofouling action. The adhesion of three species of pathogenic bacteria and six strains of marine bacteria was studied. The coatings were able to inhibit bacterial attachment by contact, as it was verified that no detectable leaching of toxic molecules occurred. 相似文献
113.
Delphine Antoni Hélène Burckel Elodie Josset Georges Noel 《International journal of molecular sciences》2015,16(3):5517-5527
Cell culture is an important tool for biological research. Two-dimensional cell culture has been used for some time now, but growing cells in flat layers on plastic surfaces does not accurately model the in vivo state. As compared to the two-dimensional case, the three-dimensional (3D) cell culture allows biological cells to grow or interact with their surroundings in all three dimensions thanks to an artificial environment. Cells grown in a 3D model have proven to be more physiologically relevant and showed improvements in several studies of biological mechanisms like: cell number monitoring, viability, morphology, proliferation, differentiation, response to stimuli, migration and invasion of tumor cells into surrounding tissues, angiogenesis stimulation and immune system evasion, drug metabolism, gene expression and protein synthesis, general cell function and in vivo relevance. 3D culture models succeed thanks to technological advances, including materials science, cell biology and bioreactor design. 相似文献
114.
A. Ribotta M. Lezcano M. Kurgansky E. Miroè E. Lombardo J. Petunchi C. Moreaux J.M. Dereppe 《Catalysis Letters》1997,49(1-2):77-85
H-mordenites are active for the SCR reaction but they suffer irreversible partial deactivation after being on stream for one
hour at 650°C. The reaction orders and activation energies are not significantly affected by deactivation. This indicates
that deactivation originates in a decrease in the number of active sites due to dealumination and possible pore blockage.
The NO disappearance rate correlates with TPD NH3 between 300 and 700°C; FTIR confirms these results. 129Xe NMR of adsorbed xenon shows that pore blockage occurs and is due to the presence of aluminum species in the main zeolite
channels. The overall deactivation process and the role of acid sites is discussed in terms of the current literature.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
115.
Ronan Le Hyaric Hassen Benbelkacem Julien Bollon Rémy Bayard Renaud Escudié Pierre Buffière 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2012,87(7):1032-1035
The objective of this study was to evaluate the influence of moisture content on the specific methanogenic activity (SMA) of a fresh dry mesophilic digestate from a municipal solid waste digester plant. For this purpose, SMA tests were performed under mesophilic conditions in 500 mL glass bottles of volume used as batch reactors, during a period of 20–25 days. Cellulose, propionate and acetate were used as substrates (5 gCOD kg?1 digestate) at four different moisture contents, ranging from 65 to 82%. The moisture content strongly influenced the specific methanogenic activity. The highest SMA values were observed at a moisture content of 82% (11.1, 7.8 and 6.0 mgCOD gVS?1 d?1 for cellulose, propionate and acetate spikes, respectively). SMA and moisture content were found to be linearly linked. Dry digestion at low water content is thus detrimental to the biological activity, probably due to physical limitations. Copyright © 2011 Society of Chemical Industry 相似文献
116.
Natural hemp fibers were chemically modified using silane coupling agents to reduce their hydrophilic character. The existence of a chemical bond between coupling agents and hemp fibers was confirmed by ATR‐FTIR spectroscopy, 29Si Nuclear Magnetic Resonance (NMR), thermogravimetric analysis (TGA), energy dispersive spectroscopy (EDS), and BET surface area measurements. It was shown that the initial concentration and the chemical structure of the organosilane coupling agent have an effect on the grafted quantity on the hemp fiber surfaces. The grafted quantity increased proportionally to the initial concentration of silane molecules. The presence of polar amino end group (NH2) in silane structure can cause an increase in the grafted quantity, compared with results obtained in the case of silane molecules containing methacryloxy groups. This effect is attributed to the formation of hydrogen bonds between NH2 and unreacted hydroxyl groups of hemp fibers. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011 相似文献
117.
Marlène Pérignon Jérôme Lecomte Michel Pina Anne Renault Camille Simonneau-Deve Pierre Villeneuve 《Journal of the American Oil Chemists' Society》2012,89(1):89-96
The nutritional profile and rheological behaviors of lipids is both due to fatty acid composition and regiodistribution on
external and internal positions of triacylglycerol. Actual methods for regiodistribution analysis having some restrictions,
there is still a need for investigating a safe, simple and environmentally friendly method for the sn-2 position analysis that could especially be used for the analysis of fats containing medium and short chain fatty acids.
The objective of this study was to evaluate the 1,3-selectivity and typoselectivity of Rhizopus oryzae lipase in the presence of short/medium chain fatty acids in partial hydrolysis conditions used for regiodistribution analysis.
Structured triacylglycerols containing eight-carbon-chain length fatty acids in the sn
-2 position were chemically synthesized using DCC/DMAP coupling agent and purification steps by flash-chromatography. The final
product showed very high purity and was used as the substrate for 1,3-selectivity evaluation. Typoselectivity was assessed
by investigating partial hydrolysis of equimolar blends of homogeneous TAG. This study confirmed the 1,3-selectivity of Rhizopus oryzae lipase in the hydrolysis conditions used, and revealed that this lipase was less influenced by fatty acids chain length than
pancreatic lipase. Considering this, Rhizopus oryzae lipase appeared to be a good candidate for regiodistribution analysis of fats containing medium and short chain fatty acids. 相似文献
118.
Angela Gallardo-López Arturo Domínguez-Rodríguez Claude Estournès Rachel Marder Rachman Chaim 《Journal of the European Ceramic Society》2012,32(12):3115-3121
Nanocrystalline yttrium oxide, Y2O3 with 110 nm average grain size was plastically deformed between 800 °C and 1100 °C by compression at different strain rates and by creep at different stresses. The onset temperature for plasticity was at 1000 °C. Yield stress was strongly temperature dependent and the strain hardening disappeared at 1100 °C. The polyhedral and equiaxed grain morphology were preserved in the deformed specimens. The experimentally measured and theoretically calculated stress exponent n = 2 was consistent with the plastic deformation by grain boundary sliding. Decrease in the grain size was consistent with decrease in the brittle to ductile transition temperature. 相似文献
119.
The copolymerization of zirconium oxo-clusters (Zr12) with 3-methacryloxypropyl (trimethoxy)silane (MPTMS), using a Si/Zr molar ratio of 4, was investigated. The hybrid samples were prepared both with and without organosilane prehydrolysis. Differential scanning calorimetry (DSC), multinuclear liquid, and solid state NMR analyses and Fourier transform infrared (FTIR) spectroscopy were used to characterize the hybrid materials and study the influence of synthesis conditions on condensation and polymerization. The degree of condensation (DOC) of the silsesquioxane network and the polymerization yield are generally high. However, the organosilane prehydrolysis step leads to the reduction of the extent of phase interaction, thus favoring the phase separation between silica-zirconia-based domains. Dynamic mechanical spectroscopy (DMS) analyses were performed on the hybrid polymers obtained by means of the two synthetic pathways. The sample prepared without the organosilane prehydrolysis step presents a higher glass transition temperature (Tg) than the one with silane prehydrolysis. By heating above the Tg, the samples retain shape and size, due to the lack of viscous flow. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012 相似文献
120.
Nassim Ait Mouheb Daniéll Malsch Agnès Montillet Camille Solliec Thomas Henkel 《Chemical engineering science》2012,68(1):278-289
Mass transfer within the T-shaped and cross-shaped micromixers has been studied using CFD and confocal laser scanning microscopy methods. The concentration profiles, based on flow regimes, were used to compare the T- and cross-geometries. The cross-shaped micromixer tends to intensify the mixing and this is occurring for lower flow rates in comparison to the T shape. The improvement made by the cross geometry is attributed to the stronger vortex stretching and high shear rate, which reduces the liquid transfer length. The presence of a single outlet in the T-shaped micromixer induces a smaller degree of freedom for the fluid. A higher pressure drop is calculated in T-shaped micromixer than in cross-shaped micromixer. 相似文献