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41.
David W. Gammon Henok H. Kinfe Dirk E. De Vos Pierre A. Jacobs Bert F. Sels 《Journal of carbohydrate chemistry》2013,32(3):141-157
Protected glycals and α‐1,2‐cyclopropanated sugars were converted in high yields and selectivities in less than 2 h at low temperatures to 2‐deoxy‐2‐iodoglycosyl acetates or novel 2‐deoxy‐2‐iodomethylglycosyl acetates using the simple, inexpensive reagent mixture of ammonium iodide, hydrogen peroxide, and acetic anhydride/acetic acid in acetonitrile. The protected glycals gave rise to 2‐deoxy‐2‐bromoglycosyl acetates when ammonium bromide was used instead of the iodide, although longer reaction times were required and selectivities were inferior. Other simple olefins such as styrene and indene were also converted to their corresponding 1,2‐trans‐iodoacetates. 相似文献
42.
Dr. Meiling Guo Prof. Dr. Zhaochi Feng Dr. Jan P. Hofmann Prof. Dr. Bert M. Weckhuysen Dr. Fengtao Fan Prof. Dr. Can Li 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(42):14200-14204
Microporous vanadosilicates with octahedral VO6 and tetrahedral SiO4 units, better known as AM‐6, have been hydrothermally synthesized with different morphologies by controlling the Na/K molar ratio of the initial gel mixtures. The morphology of the AM‐6 materials changed from bulky cube to nanofiber aggregates as the Na/K molar ratio decreased from 1.9 to 0.2. Raman spectroscopy revealed that the VO3? intermediate species plays an important role in the formation of the nanofiber morphology. The orientation of ‐V‐O‐V‐ chains in nanofiber aggregates was examined by confocal polarized micro‐Raman spectroscopy. It was found that these aggregates are assemblies of short ‐V‐O‐V‐ chains perpendicular to the axis of nanofibers. The obtained AM‐6 nanofibers greatly increase the exposed proportion of V? O terminals, and thus improve the catalytic performance. 相似文献
43.
Affinity capillary electrophoresis to evaluate the complex formation between poliovirus and nanobodies
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Hadewych Halewyck Lise Schotte Iuliana Oita Bert Thys Ann Van Eeckhaut Yvan Vander Heyden Bart Rombaut 《Journal of separation science》2014,37(24):3729-3737
It was demonstrated that nanobodies with an in vitro neutralizing activity against poliovirus type 1 interact with native virions. Here, the use of capillary electrophoresis was investigated as an alternative technique for the evaluation of the formation of nanobody–poliovirus complexes, and therefore predicting the in vitro neutralizing activity of the nanobodies. The macromolecules are preincubated offline in a specific nanobody‐to‐virus ratio and analyzed by capillary electrophoresis with UV detection. At low nanobody‐to‐virus ratios, a clear shift in migration time of the viral peak was observed. A broad peak was obtained, indicating the presence of a heterogeneous population of nanobody–virion complexes, caused by the binding of different numbers of nanobodies to the virus particle. At elevated nanobody‐to‐virus ratios, a cluster of peaks appeared, showing an additional increase in migration times. It was shown that, at these high molar excesses, aggregates were formed. The developed capillary electrophoresis method can be used as a rapid, qualitative screening for the affinity between poliovirus and nanobodies, based on a clearly visible and measurable shift in migration time. The advantages of this technique include that there is no need for antigen immobilization as in enzyme‐linked immunosorbent assays or surface plasmon resonance for the use of radiolabeled virus or for the performance of labor‐ and time‐intensive plaque‐forming neutralization assays. 相似文献
44.
Mendels P Bert F de Vries MA Olariu A Harrison A Duc F Trombe JC Lord JS Amato A Baines C 《Physical review letters》2007,98(7):077204
We report muon spin rotation measurements on the S=1/2 (Cu2+) paratacamite ZnxCu4-x(OH)6Cl2 family. Despite a Weiss temperature of approximately -300 K, the x=1 compound is found to have no transition to a magnetic frozen state down to 50 mK as theoretically expected for the kagomé Heisenberg antiferromagnet. We find that the limit between a dynamical and a partly frozen ground state occurs around x=0.5. For x=1, we discuss the relevance to a singlet picture. 相似文献
45.
Columns of metal atoms in the polytypoid compound Fe2O3(ZnO)15 could be resolved by high angle annular dark field imaging in a transmission electron microscopy (TEM)/STEM electron microscope--a result which could not be realized by high-resolution bright field imaging due to inherent strain from inversion domains and inversion domain boundaries (IDBs) in the crystals. The basal plane IDB was imaged in [11 00] yielding the spacing of the two adjacent ZnO domains, while imaging in [21 1 0] yields the position of single metal ions. The images allow the construction of the entire domain structure including the stacking sequence and positions of the oxygen ions. The IDB consists of a single layer of octahedrally co-ordinated Fe3+ ions, and the inverted ZnO domains are related by point symmetry at the iron position. The FeO6 octahedrons are compressed along the ZnO c-axis resulting in a FeO bond length of 0.208 nm which is in the range of FeO distances in iron containing oxides. The model of the basal plane boundary resembles that of the IDB in polytypoid ZnO-In2O3 compounds. 相似文献
46.
Chemically synthesized single‐crystalline gold microplates have been attracting increasing interest because of their potential as high‐quality gold films for nanotechnology. We present the growth of tens of nanometers thick and tens of micrometers large single‐crystalline gold plates directly on solid substrates by solution‐phase synthesis. Compared to microplates deposited on substrates from dispersion phase, substrate‐grown plates exhibit significantly higher quality by avoiding severe small‐particle contamination and aggregation. Substrate‐grown gold plates also open new perspectives to study the growth mechanism via step‐growth and observation cycles of a large number of individual plates. Growth models are proposed to interpret the evolution of thickness, area and shape of the plates. It is found that the plate surface remains smooth after regrowth, implying the applicability of regrowth for producing giant plates as well as unique single‐crystalline nano‐structures. 相似文献
47.
Kay Hettrich Manfred Pinnow Bert Volkert Lars Passauer Steffen Fischer 《Cellulose (London, England)》2014,21(4):2479-2488
Novel nanoscaled cellulose particles were prepared using high-pressure homogenization of aqueous media contenting treated cellulose samples in a Microfluidizer® processor (MF). Here, we present the generation of spherical cellulose nanoparticles as an extension of previously published reports of nano fibrillated cellulose. Although MF treatment of unmodified cellulose yields nanofibrils which are reported in several publications, in the current work different kinds of pretreatments were proven to be necessary to obtain spherical structured cellulose nanoparticles. One such treatment may be the decrystallization of cellulose regenerating it from N-methylmorpholine-N-oxid-monohydrate (NMMNO*H2O). Nanocellulose was then obtained by a subsequent high-pressure mechanical treatment of the precipitate in aqueous dispersion. Decrystallization was also realized by grinding cellulose in a planetary ball mill. The resulting amorphous intermediates were characterized by Raman spectroscopy. Another approach tested was hydrolysis and subsequent mechanical treatment using an Ultra-Turrax® and MF. Another alternative was given by the mechanical treatment of aqueous dispersions of low substituted cellulose derivatives such as carboxymethyl cellulose and oxidized cellulose without any further hydrolysis. 相似文献
48.
Platinum‐Promoted Ga/Al2O3 as Highly Active,Selective, and Stable Catalyst for the Dehydrogenation of Propane
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Jesper J. H. B. Sattler Dr. Ines D. Gonzalez‐Jimenez Dr. Lin Luo Brien A. Stears Dr. Andrzej Malek Dr. David G. Barton Dr. Beata A. Kilos Dr. Mark P. Kaminsky Tiny W. G. M. Verhoeven Eline J. Koers Prof. Dr. Marc Baldus Prof. Dr. Bert M. Weckhuysen 《Angewandte Chemie (International ed. in English)》2014,53(35):9251-9256
A novel catalyst material for the selective dehydrogenation of propane is presented. The catalyst consists of 1000 ppm Pt, 3 wt % Ga, and 0.25 wt % K supported on alumina. We observed a synergy between Ga and Pt, resulting in a highly active and stable catalyst. Additionally, we propose a bifunctional active phase, in which coordinately unsaturated Ga3+ species are the active species and where Pt functions as a promoter. 相似文献
49.
Sustainable Three‐Component Synthesis of Isothioureas from Isocyanides,Thiosulfonates, and Amines
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Pieter Mampuys Dr. Yanping Zhu Dr. Tjøstil Vlaar Dr. Eelco Ruijter Prof. Dr. Romano V. A. Orru Prof. Dr. Bert U. W. Maes 《Angewandte Chemie (International ed. in English)》2014,53(47):12849-12854
Multiple applications of isothioureas as fine chemicals (or their precursors) are known, but a general sustainable method for their synthesis was hitherto unavailable. We report a novel general approach towards S‐alkyl and S‐aryl isothioureas through a copper(I)‐catalyzed three‐component reaction between amines, isocyanides, and thiosulfonates. The formal synthesis of a superpotent sweetener further illustrates the applicability of our method. 相似文献
50.
Jurriën W. Collet Thomas R. Roose Eelco Ruijter Bert U. W. Maes Romano V. A. Orru 《Angewandte Chemie (International ed. in English)》2020,59(2):540-558
Isocyanides are diverse C1 building blocks considering their potential to react with nucleophiles, electrophiles, and radicals. Therefore, perhaps not surprisingly, isocyanides are highly valuable as inputs for multicomponent reactions (MCRs) and other one‐pot cascade processes. In the field of organometallic chemistry, isocyanides typically serve as ligands for transition metals. The coordination of isocyanides to metal centers alters the electronic distribution of the isocyano moiety, and reaction pathways can therefore be accessed that are not possible in the absence of the metal. The tunable reactivity of the isocyanide functional group by transition metals has evolved into numerous useful applications. Especially palladium‐catalyzed isocyanide insertion processes have emerged as powerful reactions in the past decade. However, reports on the use of earth‐abundant and cheap base metals in these types of transformations are scarce and have received far less attention. In this Minireview, we focus on these emerging base metal catalyzed reactions and highlight their potential in synthetic organic chemistry. Although mechanistic studies are still scarce, we discuss distinct proposed catalytic cycles and categorize the literature according to 1) the (hetero)atom bound to and 2) the type of bonding with the transition metal in which the (formal) insertion occurs. 相似文献