全文获取类型
收费全文 | 2849篇 |
免费 | 99篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 12篇 |
化学工业 | 696篇 |
金属工艺 | 28篇 |
机械仪表 | 35篇 |
建筑科学 | 149篇 |
矿业工程 | 5篇 |
能源动力 | 53篇 |
轻工业 | 518篇 |
水利工程 | 22篇 |
石油天然气 | 6篇 |
无线电 | 109篇 |
一般工业技术 | 427篇 |
冶金工业 | 624篇 |
原子能技术 | 9篇 |
自动化技术 | 257篇 |
出版年
2023年 | 20篇 |
2022年 | 52篇 |
2021年 | 87篇 |
2020年 | 47篇 |
2019年 | 40篇 |
2018年 | 62篇 |
2017年 | 52篇 |
2016年 | 65篇 |
2015年 | 48篇 |
2014年 | 70篇 |
2013年 | 180篇 |
2012年 | 180篇 |
2011年 | 192篇 |
2010年 | 172篇 |
2009年 | 147篇 |
2008年 | 163篇 |
2007年 | 156篇 |
2006年 | 108篇 |
2005年 | 122篇 |
2004年 | 92篇 |
2003年 | 101篇 |
2002年 | 90篇 |
2001年 | 49篇 |
2000年 | 38篇 |
1999年 | 47篇 |
1998年 | 52篇 |
1997年 | 64篇 |
1996年 | 59篇 |
1995年 | 39篇 |
1994年 | 36篇 |
1993年 | 26篇 |
1992年 | 31篇 |
1991年 | 17篇 |
1990年 | 27篇 |
1989年 | 23篇 |
1988年 | 15篇 |
1987年 | 14篇 |
1986年 | 19篇 |
1985年 | 17篇 |
1984年 | 18篇 |
1983年 | 13篇 |
1982年 | 15篇 |
1980年 | 10篇 |
1979年 | 8篇 |
1978年 | 7篇 |
1977年 | 12篇 |
1976年 | 7篇 |
1975年 | 6篇 |
1973年 | 4篇 |
1948年 | 3篇 |
排序方式: 共有2950条查询结果,搜索用时 15 毫秒
91.
Hai-Dong Wang Catherine Hui Niu Mei Yang Liang-Yin Chu 《Chemical engineering science》2009,64(7):1462-1473
The concept of chiral ligand exchange is employed in the present study to achieve the chiral resolution of tryptophan (Trp) enantiomers by using chitosan (CS) membrane in a sorption resolution mode and copper(II) ion as the complexing ion. CS porous membranes are prepared by freeze-drying method (CS-LT) and sol-gel process at high temperature (CS-HT), respectively, to investigate their sorption resolution characteristics. The proposed CS chiral ligand exchange membranes exhibit good chiral resolution capability. Meanwhile the sorption selectivity of the CS membranes is found to be reversed from L-selectivity at low copper(II) ion concentration to D-selectivity at high copper(II) ion concentration, which is attributable to the stability difference between the copper(II)-L-Trp and copper(II)-D-Trp complexes. Moreover, the CS-HT membrane shows better performance with respect to both sorption selectivity and sorption capability than the CS-LT membrane, which mainly results from its more amorphous structures compared with the more crystalline structures of the CS-LT membrane. The superiority of sorption capability of the CS-HT membrane is also attributable to its larger specific surface area than that of the CS-LT membrane. The results obtained in this study are conducive to the design and fabrication of chiral ligand exchange membranes for enantiomer separation in sorption mode. 相似文献
92.
Constable EC Housecroft CE Mayor M Meier WP Palivan CG Wegner HA Wennemers H 《Chimia》2010,64(12):877-884
The following contributions describe various research activities of the Department of Chemistry, University of Basel in the area of nanochemistry and supramolecular chemistry. 相似文献
93.
Simon L. Desset Ulrich Hintermair Zhenxin Gong Catherine C. Santini David J. Cole-Hamilton 《Topics in Catalysis》2010,53(13-14):963-968
Two processes are described for improving reaction rates for relatively hydrophobic substrates in aqueous biphasic systems. In the first, 1-octyl-3-methylimidazolium bromide ([Octmim]Br) increases the rate of hydroformylation of 1-octene from 8% conversion in 24 h to full conversion of 1.5 h. Phase separation is fast and catalyst retention is good. 1-Hexyl-3-methylimidazolium bromide gives little rate enhancement, whilst 1-decyl-3-methylimidazolium bromide gives stable emulsions., The mechanism of action of these additives is discussed. In the second approach, functionalising PPh3 with amidine groups allows the rhodium catalysed hydroformylation of 1-octene in toluene with a very high reaction rate. The catalyst can be switched between toluene and water by bubbling CO2 and back into toluene by bubbling N2 at 60 °C. This switching has been used to separate the catalyst from hydrophobic (from 1-octene) or hydrophilic (from allyl alcohol) aldehydes obtained from hydroformylation reactions. CO2 expanded liquids have been shown to be effective media for transporting substrates and catalysts over supported ionic liquid phase (SILP) catalysts. The advantages offered over all gas phase and liquid phase catalysts are discussed. 相似文献
94.
Julien Mesnager Anne Lambin Claude Quettier Franck Rataboul Catherine Pinel 《Topics in Catalysis》2010,53(15-18):1282-1284
The synthesis of hydrophobic starch was performed via palladium-catalyzed telomerization of butadiene with native starch. This reaction is efficiently performed in water in the presence of neutral or cationic surfactant with high HLB. After optimization of the reaction conditions, TOF up to 446 was achieved. 相似文献
95.
96.
Luke Mansard David Baux Christel Vach Catherine Blanchet Isabelle Meunier Marjolaine Willems Valrie Faugre Corinne Baudoin Melody Moclyn Julie Bianchi Helene Dollfus Brigitte Gilbert-Dussardier Delphine Dupin-Deguine Dominique Bonneau Isabelle Drumare Sylvie Odent Xavier Zanlonghi Mireille Claustres Michel Koenig Vasiliki Kalatzis Anne-Franoise Roux 《International journal of molecular sciences》2021,22(24)
Usher syndrome is an autosomal recessive disorder characterized by congenital hearing loss combined with retinitis pigmentosa, and in some cases, vestibular areflexia. Three clinical subtypes are distinguished, and MYO7A and USH2A represent the two major causal genes involved in Usher type I, the most severe form, and type II, the most frequent form, respectively. Massively parallel sequencing was performed on a cohort of patients in the context of a molecular diagnosis to confirm clinical suspicion of Usher syndrome. We report here 231 pathogenic MYO7A and USH2A genotypes identified in 73 Usher type I and 158 Usher type II patients. Furthermore, we present the ACMG classification of the variants, which comprise all types. Among them, 68 have not been previously reported in the literature, including 12 missense and 16 splice variants. We also report a new deep intronic variant in USH2A. Despite the important number of molecular studies published on these two genes, we show that during the course of routine genetic diagnosis, undescribed variants continue to be identified at a high rate. This is particularly pertinent in the current era, where therapeutic strategies based on DNA or RNA technologies are being developed. 相似文献
97.
Dynameomics: design of a computational lab workflow and scientific data repository for protein simulations 总被引:1,自引:0,他引:1
Simms AM Toofanny RD Kehl C Benson NC Daggett V 《Protein engineering, design & selection : PEDS》2008,21(6):369-377
Dynameomics is a project to investigate and catalog the native-state dynamics and thermal unfolding pathways of representatives of all protein folds using solvated molecular dynamics simulations, as described in the preceding paper. Here we introduce the design of the molecular dynamics data warehouse, a scalable, reliable repository that houses simulation data that vastly simplifies management and access. In the succeeding paper, we describe the development of a complementary multidimensional database. A single protein unfolding or native-state simulation can take weeks to months to complete, and produces gigabytes of coordinate and analysis data. Mining information from over 3000 completed simulations is complicated and time-consuming. Even the simplest queries involve writing intricate programs that must be built from low-level file system access primitives and include significant logic to correctly locate and parse data of interest. As a result, programs to answer questions that require data from hundreds of simulations are very difficult to write. Thus, organization and access to simulation data have been major obstacles to the discovery of new knowledge in the Dynameomics project. This repository is used internally and is the foundation of the Dynameomics portal site http://www.dynameomics.org. By organizing simulation data into a scalable, manageable and accessible form, we can begin to address substantial questions that move us closer to solving biomedical and bioengineering problems. 相似文献
98.
Blandine Ponsard Isabelle Durot Philippe Delerive Fabien Oudot Catherine Cordelet Alain Grynberg Pierre Athias 《Lipids》1999,34(5):457-466
The purpose of the present investigation was to determine whether the beneficial effects of polyunsaturated fatty acids (PUFA)
may influence ischemia-reperfusion-induced alterations of myocardial α- and β-adrenoceptor (α-AR, β-AR) responsiveness. This
study was carried out using monolayer cultures of neonatal rat ventricular myocytes in a substrate-free, hypoxia-reoxygenation
model of ischemia. The cardiomyocytes (CM) were incubated during 4 days in media enriched either with n−6 PUFA (arachidonic
acid, AA) or with n−3 PUFA (eicosapentaenoic acid, EPA, and docosahexaenoic acid, DHA). The n−6/n−3 ratio in n−3 CM was close
to 1.2, compared to 20.1 in n−6 CM. The contractile parameters of n−6 CM and n−3 CM were similar in basal conditions as well
as during hypoxia and reoxygenation. In basal conditions, the phospholipid (PL) enrichment with long chain n−3 PUFA resulted
in an increased chronotropic response to isoproterenol (ISO) and to phenylephrine (PHE). After posthypoxic reoxygenation,
the chronotropic response to β-AR activation in n−6 CM was significantly enhanced as compared with the control response in
normoxia. In opposition, the ISO-induced rise in frequency in n−3 CM in control normoxia and after reoxygenation was similar.
In these n−3 CM, the changes in contractile parameters, which accompanied the chronotropic response, were also similar in
reoxygenation and in normoxic periods, although the rise in shortening velocity was slightly increased after reoxygenation.
In response to PHE addition, only the chronotropic effect of n−6 CM appeared significantly enhanced after hypoxic treatment.
These results suggested that increasing n−3 PUFA in PL reduced the increase in α- and β-AR functional responses observed after
hypoxia-reoxygenation. This effect may partly account for the assumed cardiac protective effect of n−3 PUFA, through the attenuation
of the functional response to catecholamines in the ischemic myocardium. 相似文献
99.
Preparation of conjugated linoleic acid from safflower oil 总被引:5,自引:0,他引:5
David W. L. Ma Antoni A. Wierzbicki Catherine J. Field Michael T. Clandinin 《Journal of the American Oil Chemists' Society》1999,76(6):729-730
Synthetically prepared mixtures of conjugated linoleic acid (CLA) are widely used in animal and cell culture studies to investigate
the potential effects of the Δ9c, 11t-18:2 isomer found in food products from ruminant animals. Alkali isomerization of linoleic acid is a common method used in
the synthesis of a mixture of CLA isomers containing predominantly the Δ9c, 11t-18:2 and Δ10t, 12c-18:2 isomers. Some biological activity might also be mediated by the Δ10t, 12c-18:2 isomer. Currently few published methodologies exist describing procedures for the enrichment of these two isomers. A
method is described herein to take advantage of an inexpensive oil, safflower oil, for use in synthesis of CLA and a procedure
to enrich the Δ10t, 12c-18:2 isomer. 相似文献
100.
Germán Sierra Gallego Joël Barrault Catherine Batiot-Dupeyrat Fanor Mondragón 《Catalysis Today》2010,149(3-4):365-371
LaNiO3 type perovskite was prepared by the “self-combustion” method and was used as catalyst precursor for the methane decomposition reaction at 600 and 700 °C. CH4 conversion reaches 80% at 700 °C and 65% at 600 °C using pure CH4. The yield of CNT and H2 were 2.2 gCNT g?1 h?1 and 8.2 L g?1 h?1 at 700 °C respectively after 4 h of reaction. When the reaction is prolonged to 22 h the catalytic activity decreases but the catalyst is still active, the production of hydrogen reaches 63.5 L (STP) per gram of catalyst and the production of MWCNT was equal to 17 g per gram of catalyst.Multi-wall carbon nanotubes were characterized by X-ray diffraction (XRD), surface area (BET), transmission electron microscopy (TEM), scanning electron microscopy (SEM), thermogravimetric analysis (TGA) and Raman spectroscopy. TEM micrographs showed that MWCNT longer than 20 μm were formed with inner diameters ranging from 5 to 16 nm and outer diameters up to about 40 nm.The results obtained here clearly show that the use of the perovskite LaNiO3 as catalytic precursor is very effective for the simultaneous production of carbon nanotubes and hydrogen. 相似文献