全文获取类型
收费全文 | 2368篇 |
免费 | 76篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 41篇 |
综合类 | 2篇 |
化学工业 | 610篇 |
金属工艺 | 86篇 |
机械仪表 | 23篇 |
建筑科学 | 69篇 |
矿业工程 | 4篇 |
能源动力 | 40篇 |
轻工业 | 211篇 |
水利工程 | 16篇 |
石油天然气 | 5篇 |
无线电 | 169篇 |
一般工业技术 | 404篇 |
冶金工业 | 490篇 |
原子能技术 | 22篇 |
自动化技术 | 253篇 |
出版年
2022年 | 31篇 |
2021年 | 50篇 |
2020年 | 29篇 |
2019年 | 40篇 |
2018年 | 39篇 |
2017年 | 38篇 |
2016年 | 47篇 |
2015年 | 38篇 |
2014年 | 48篇 |
2013年 | 81篇 |
2012年 | 82篇 |
2011年 | 114篇 |
2010年 | 61篇 |
2009年 | 66篇 |
2008年 | 81篇 |
2007年 | 97篇 |
2006年 | 84篇 |
2005年 | 55篇 |
2004年 | 51篇 |
2003年 | 51篇 |
2002年 | 39篇 |
2001年 | 52篇 |
2000年 | 54篇 |
1999年 | 50篇 |
1998年 | 153篇 |
1997年 | 96篇 |
1996年 | 82篇 |
1995年 | 61篇 |
1994年 | 43篇 |
1993年 | 42篇 |
1992年 | 23篇 |
1991年 | 20篇 |
1990年 | 24篇 |
1989年 | 30篇 |
1988年 | 41篇 |
1987年 | 23篇 |
1986年 | 28篇 |
1985年 | 23篇 |
1984年 | 20篇 |
1983年 | 14篇 |
1982年 | 24篇 |
1981年 | 19篇 |
1979年 | 21篇 |
1977年 | 16篇 |
1976年 | 42篇 |
1975年 | 19篇 |
1974年 | 16篇 |
1973年 | 21篇 |
1972年 | 14篇 |
1967年 | 14篇 |
排序方式: 共有2445条查询结果,搜索用时 13 毫秒
61.
62.
Stadler LK Hoffmann T Tomlinson DC Song Q Lee T Busby M Nyathi Y Gendra E Tiede C Flanagan K Cockell SJ Wipat A Harwood C Wagner SD Knowles MA Davis JJ Keegan N Ferrigno PK 《Protein engineering, design & selection : PEDS》2011,24(9):751-763
Constrained binding peptides (peptide aptamers) may serve as tools to explore protein conformations and disrupt protein-protein interactions. The quality of the protein scaffold, by which the binding peptide is constrained and presented, is of crucial importance. SQT (Stefin A Quadruple Mutant-Tracy) is our most recent development in the Stefin A-derived scaffold series. Stefin A naturally uses three surfaces to interact with its targets. SQT tolerates peptide insertions at all three positions. Peptide aptamers in the SQT scaffold can be expressed in bacterial, yeast and human cells, and displayed as a fusion to truncated pIII on phage. Peptides that bind to CDK2 can show improved binding in protein microarrays when presented by the SQT scaffold. Yeast two-hybrid libraries have been screened for binders to the POZ domain of BCL-6 and to a peptide derived from PBP2', specific to methicillin-resistant Staphylococcus aureus. Presentation of the Noxa BH3 helix by SQT allows specific interaction with Mcl-1 in human cells. Together, our results show that Stefin A-derived scaffolds, including SQT, can be used for a variety of applications in cellular and molecular biology. We will henceforth refer to Stefin A-derived engineered proteins as Scannins. 相似文献
63.
64.
Khanderi J Contiu C Engstler J Hoffmann RC Schneider JJ Drochner A Vogel H 《Nanoscale》2011,3(3):1102-1112
Cuprous oxide agglomerates composed of 4-10 nm Cu2O nanoparticles were deposited on multiwalled carbon nanotubes (MWCNTs) and on ZnO/MWCNTs to give binary [Cu2O/MWCNT] and ternary [Cu2O/ZnO/MWCNT] composites. Di-aqua-bis[2-(methoxyimino)propanoato]copper Cu[O2CCCH3NOMe](2)·2H2O 1 in DMF was used as single source precursor for the deposition of nanoscaled Cu2O. The precursor decomposes either in air or under argon to yield CuO2 by in situ redox reaction. Thermogravimetric coupled mass spectroscopic analysis (TG-MS) of 1 revealed that methanol formed during the decomposition of 1 acts as a potential in situ reducing agent. Scanning electron microscopy (SEM) of the binary [Cu2O/MWCNT] nano-composite shows an increase of cuprous oxide loading depending on the precursor amount, along the periphery of the MWCNTs as well as formation of larger particle agglomerates. Transmission electron microscopy (TEM) of the sample shows crystalline domains of size 4-10 nm surrounded by an amorphous region within the larger particles. SEM and TEM of ternary [Cu2O/ZnO/MWCNT] clearly reveal that Cu2O nanoparticles are primarily deposited on ZnO rather than on MWCNTs. The catalytic activities of the [Cu2O/MWCNT] and [Cu2O/ZnO/MWCNT] binary and ternary composites were studied for the selective partial oxidation of ethanol to acetaldehyde with molecular oxygen. While using binary [Cu2O/MWCNT] (13.8 wt% Cu) as catalyst, acetaldehyde was obtained with a yield of 87% at 355 °C (selectivity 96% and conversion 91%). When nanoscale ZnO is present, the resulting [Cu2O/ZnO/MWCNT] composite shows preferential hydrogen and CO2 formation due to the fact that the dehydrogenation and total oxidation pathway is more favoured compared to the binary composite. Significant morphological changes of the catalyst during the catalytic process were observed. 相似文献
65.
Kristina Hoffmann Tatjana Friedrich Bernd Tieke 《Polymer Engineering and Science》2011,51(8):1497-1506
Polyelectrolyte blend films and membranes were prepared upon alternating electrostatic adsorption of polyallylamine hydrochloride (PAH) and mixtures of polystyrene sulfonate (PSS) and polyacrylic acid (PAA) in different ratio on solid supports. Infrared studies indicated that the PSS‐PAA blend composition of the films always differed from the mixture composition in the dipping solution, PSS being preferentially adsorbed. Films deposited on porous supporting membranes (polyacrylonitrile/polyethylene terephthalate) were studied on their ion permeation under diffusion dialysis conditions, and their flux and salt rejection under nanofiltration and reverse osmosis (RO) conditions. Blend membranes prepared at pH 1.7 exhibit a significantly improved anion separation and salt rejection, the ideal separation factor α(NaCl/Na2SO4) of a membrane prepared from a PSS:PAA mixture of 1:1 (w/w) being 197 ± 10 (pure PAH/PSS: 45). The NaCl and Na2SO4 rejections under RO conditions are 85 and 97% (pure PAH/PSS: 15 and 27%), respectively. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers 相似文献
66.
67.
68.
Schüth F. Busch O. Hoffmann C. Johann T. Kiener C. Demuth D. Klein J. Schunk S. Strehlau W. Zech T. 《Topics in Catalysis》2002,21(1-3):55-66
High-throughput experimentation in catalysis comprises the following components: (i) automated high-throughput synthesis, (ii) testing in Stage I and Stage II, for which to some extent novel assays are necessary, (iii) data handling and experimental design tools, and (iv) robotics. This contribution covers these topics, using examples from the research of the authors, but also from the literature, in order to illustrate the problems and opportunities associated with high-throughput experimentation in catalysis, focusing particularly on heterogeneous catalysis. 相似文献
69.
Silphinene Sesquiterpenes as Model Insect Antifeedants 总被引:3,自引:0,他引:3
González-Coloma A Valencia F Martín N Hoffmann JJ Hutter L Marco JA Reina M 《Journal of chemical ecology》2002,28(1):117-129
Silphinene sesquiterpenes are established chrysomelid antifeedants. In this work, nine silphinene analogs, 11-acetoxy-5-angeloyloxysilphinen-3-one (1), 11-acetoxy-5-tigloyloxysilphinen-3-one (2), 11-acetoxy-5-iso- butyryloxysilphinen-3-one (3), 11-hydroxy-5-angeloyloxysilphinen-3-one (4), 11,5-dihydroxysilphinen-3-one (5), 11,5-diacetoxysilphinen-3-one (6), 5,11-diisobutyryloxysilphinen-3-one (7), silphinen-3,5,11-trione (8), and O-methyl-5-epicantabrenolic acid methyl ester (10), and a presilphiperfolane sesquiterpene (9) were tested against several divergent insect species, including the lepidopteran Spodoptera littoralis, the chrysomelid Leptinotarsa decemlineata, and five aphid species, and their antifeedant effects were compared with those of picrotoxinin, a GABA-antagonist, and thymol, an allosteric modulator for insect GABA receptors. All insects tested responded to at least one silphinene analog and/or GABA antagonist. Compound 3 and thymol were effective antifeedants against all species tested except S. littoralis, with varying potencies according to their feeding ecologies. The toxicity of these compounds was species-dependent and did not correlate with their antifeedant effect. 相似文献
70.
Robert J. Reuvekamp Madhumita B. Ray Alex C. Hoffmann 《Chemical Engineering Communications》2002,189(6):849-864
The deposition of a very fine powder in a horizontal, lean-phase pneumatic conveying conduit containing a 90° bend has been studied experimentally. The total deposition and the deposition pattern were studied as a function of superficial gas velocity, solids loading and bend geometry: one sharp and three smooth bends of different radii of curvature were used. Most deposition was seen in the sharp bend, while in the smooth bends the deposition did not vary much with radius of curvature. The deposition decreased significantly with increasing superficial gas velocity. The experimental results were compared with CFD simulations of the flow field. The observations are consistent with the notion of deposition in regions with low near-wall gas velocity, indicating that models for deposition should be sought in considerations of the deposit stability for this type of system. 相似文献