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81.
Marino Grozdek Rahmatollah Khodabandeh Per Lundqvist 《Experimental Thermal and Fluid Science》2009,33(2):357-370
Pressure drop behaviour of ice slurry based on ethanol–water mixture in circular horizontal tubes has been experimentally investigated. The secondary fluid was prepared by mixing ethyl alcohol and water to obtain initial alcohol concentration of 10.3% (initial freezing temperature ?4.4 °C). The pressure drop tests were conducted to cover laminar and slightly turbulent flow with ice mass fraction varying from 0% to 30% depending on test conditions. Results from flow tests reveal much higher pressure drop for higher ice concentrations and higher velocities in comparison to the single phase flow. However for ice concentrations of 15% and higher, certain velocity exists at which ice slurry pressure drop is same or even lower than for single phase flow. It seems that higher ice concentration delay flow pattern transition moment (from laminar to turbulent) toward higher velocities. In addition experimental results for pressure drop were compared to the analytical results, based on Poiseulle and Buckingham–Reiner models for laminar flow, Blasius, Darby and Melson, Dodge and Metzner, Steffe and Tomita for turbulent region and general correlation of Kitanovski which is valid for both flow regimes. For laminar flow and low buoyancy numbers Buckingham–Reiner method gives good agreement with experimental results while for turbulent flow best fit is provided with Dodge–Metzner and Tomita methods.Furthermore, for transport purposes it has been shown that ice mass fraction of 20% offers best ratio of ice slurry transport capability and required pumping power. 相似文献
82.
BACKGROUND: Selective recognition and binding of IgG molecules is the basis for a host of immunological and affinity purification techniques. Capture of an IgG in these procedures relies chiefly on its interaction with one of a variety of reengineered bacterial receptors which bind to the Fc region of IgG molecules with very high affinity. While this interaction is extremely efficient in trapping IgG molecules, the tight interaction between the binding partners often requires denaturing conditions for disruption of the complex, which can adversely affect the yield of purified IgG and also limit the lifetime of the receptor matrix. An effective receptor/IgG binding system which could be modulated by less extreme conditions is of considerable general interest. RESULTS: We describe the properties of a series of modified Fc receptor domains which are competent to bind IgG with high affinity but which can be reversibly unfolded upon addition of modest amounts of transition metal ions. Data are presented demonstrating loss of the secondary structural content of the domains as a function of increasing metal concentration, with a concomitant decrease in IgG binding affinity. Variants of the Fc receptor differing at a single amino acid position display increased sensitivity to metal-induced unfolding, while retaining comparable IgG binding ability in the absence of metal. CONCLUSIONS: The interaction of this series of Fc receptors with metal ions abolishes IgG binding, but removal of metal ions allows refolding of the domains with restoration of the IgG binding function. Examples of the utility and potential applications of these metal-modulated IgG binding domains are discussed. 相似文献
83.
84.
H. Ellinger Siemens Halske A. -G. H. v. Uslar R. Sewig E. Hoffmann M. Matsui Mitarbeiter A. del Campo F. Burriel L. G. Escolar und W. G. Exton 《Fresenius' Journal of Analytical Chemistry》1939,116(3-4):142-143
Ohne Zusammenfassung 相似文献
85.
Vanessa L. Campo 《Tetrahedron》2009,65(27):5343-7358
This work describes the synthesis in solution of a series of related diketopiperazines with potential biological activities: cyclo(l-Pro-l-Ser), cyclo(l-Phe-l-Ser), cyclo(d-Phe-l-Ser) and the corresponding glycosylated analogs of the latter, cyclo[d-Phe-l-Ser(αGlcNAc)] and cyclo[d-Phe-l-Ser(βGlcNAc)]. The synthetic approach involved coupling reactions of -OH or O-glycosylated serine benzyl esters with NFmoc-protected amino acids (Pro or Phe), followed by one-pot deprotection-cyclization reaction in the presence of 20% piperidine in DMF. 相似文献
86.
Manuel van Gemmeren Marino Börjesson Andreu Tortajada Shang-Zheng Sun Keisho Okura Prof. Ruben Martin 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2017,129(23):6658-6662
A switchable site-selective catalytic carboxylation of allylic alcohols has been developed in which CO2 is used with dual roles, both facilitating C−OH cleavage and as a C1 source. This protocol is characterized by its mild reaction conditions, absence of stoichiometric amounts of organometallic reagents, broad scope, and exquisite regiodivergency which can be modulated by the type of ligand employed. 相似文献
87.
Valeria Romanucci Armando Zarrelli Annalisa Guaragna Cinzia Di Marino Giovanni Di Fabio 《Tetrahedron letters》2017,58(12):1227-1229
New phosphorylating reagents 1 and 2 were prepared in three steps from 4-hydroxybenzaldehyde. They showed good efficiency in the solid phase synthesis of 5′-phosphate monoester nucleosides. End-phosphate DNA sequence synthesis demonstrated the efficiency of the new reagents (1 and 2) according to the general procedure of automated DNA synthesis. The oxidation of P(III) to P(V) and the removal of benzyl protecting groups were achieved in a single step by treatment with a 0.02 M I2/pyridine/H2O solution. Due to this one-pot treatment, it is possible to use the phosphorylating reagents (1 and 2) for the synthesis of base-sensitive ODNs. The reagents 1 and 2 are unique among phosphorylating reagents. 相似文献
88.
This paper presents a comparative study between a carbon molecular sieve (CMS) membrane and a commercial CMS adsorbent; these materials are suited for selective gas permeation and adsorption-based gas separations, respectively. The purpose of this analysis is to better understand the mass transport mechanism in CMS membranes and how it is related to the material's structure. The structural characterization based on the adsorption of CO2 at 0 °C revealed that the adsorbent has a greater micropore volume, a smaller mean pore width and a micropore size distribution shifted to the left, when compared to the membrane. This translates into a lower adsorption capacity of the membrane towards N2, Ar, CO2 and O2 at 29.5 °C and 0–7 bar. The adsorption kinetics were also studied and the pressure-dependence of the apparent time constants established; different models were used to predict the experimental results, emphasizing the very important role of the ultramicroporosity on the properties of the materials. The CMS membrane exhibited a pore blockage effect when permeating O2 and CO2. Further morphologic characterization was performed by SEM, X-ray diffraction and mercury porosimetry. 相似文献
89.
Päivi Mäki-Arvela Elena V. Murzina Betiana Campo Teemu Heikkilä Anne-Riikka Leino Krisztian Kordas Dorit Wolf Anton V. Tokarev Dmitry Yu. Murzin 《Research on Chemical Intermediates》2010,36(4):423-442
Lactose oxidation was investigated at 70 °C and at pH 8 using oxygen as an oxidant over a comprehensive set of commercially
available mono- and multi-metallic as well as promoted Pd catalysts with active carbon, alumina and calcium carbonate as catalyst
supports. An optimum cluster size of 6–10 nm resulted in the highest initial turnover frequencies. High conversion levels
above 90% were achieved on Pd/C catalyst, as well as over Pd/Al2O3 and (Pd–Pb)/CaCO3, whereas (Pd–V)/C catalyst gave only 30% conversion after 200 min. The latter catalyst was relatively inactive due to its
high support acidity and profound deactivation during oxidation. Besides the main oxidation product, lactobionic acid, also,
lactulose was generated as a result of lactose isomerisation under alkaline conditions. The electrochemical potentials of
the catalysts were measured during lactose oxidation. The main result of these measurements was that, when the electrochemical
potential of the catalyst increased very quickly, its oxidation activity was low due to metal over-oxidation. The selectivities
to the desired product, lactobionic acid, were relatively high, above 80% for most of the catalysts, except for (Pd–V)/C.
Furthermore, the selectivity to the lactobionic acid decreased with increasing metal dispersion, thus, indicating that the
optimum metal particle sizes for producing high amounts of lactobionic acid is above 3 nm. 相似文献
90.