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611.
We report here a novel synthetic route for the preparation of well-defined and faceted nanocrystals of ternary rare earth oxychlorides based on the ligand exchange and condensation of rare earth halides and alkoxides in the presence of coordinating solvents. Nanocubes, faceted 2D nanosheets, and nanodisk morphologies are obtained as a result of preferential growth along specific crystallographic directions dictated by the choice of the rare earth ion and the capping ligand. The synthetic approach reported here represents a unique low-temperature route for the preparation of LnOCl in the PbFCl matlockite phase. The synthetic strategy can further be adapted to incorporate dopant ions. The potential applicability of these nanostructures as phosphors is illustrated by demonstrating the upconversion of near-infrared illumination to green and red emission by Er(3+):GdOCl nanocrystals. 相似文献
612.
In situ photoexcitation of silver-doped titania nanopowders for activity against bacteria and yeasts
Kowal K Wysocka-Król K Kopaczyńska M Dworniczek E Franiczek R Wawrzyńska M Vargová M Zahoran M Rakovský E Kuš P Plesch G Plecenik A Laffir F Tofail SA Podbielska H 《Journal of colloid and interface science》2011,362(1):50-57
Photocatalytic and in situ microbial activity of the amorphous and annealed states of Ag-doped and un-doped titania were examined. Studies on their structure, morphology, composition, and the photo-absorption characteristics of these materials were performed. These results were correlated with the photocatalytic and microbial activity against methicillin resistant Staphylococcus aureus K324 (MRSA), methicillin susceptible S. aureus ATCC 25923 (MSSA), Escherichia coli PA 170, and yeasts Candida albicans ATCC 90028. The annealed powders containing anatase form of titania exhibited relatively higher photocatalytic activity,corresponding to activity against MRSA,when exposed to UV-A radiation. In comparison, amorphous powders exhibited low photoactivity and showed poor antibacterial performance against MRSA under UV-A exposure. Doping of amorphous titania with Ag resulted in an anti-MRSA effect without exposure to UV radiation. In the Ag-doped crystalline anatase samples, the size of Ag primary nanocrystallites increased, which led to the decrease in the surface concentration of Ag and detriment anti-MRSA activity. 相似文献
613.
Sanders HM Iafisco M Pouget EM Bomans PH Nudelman F Falini G de With G Merkx M Strijkers GJ Nicolay K Sommerdijk NA 《Chemical communications (Cambridge, England)》2011,47(5):1503-1505
CryoTEM demonstrates that a CNA35-bearing liposomal MRI contrast agent selectively binds to poorly assembled collagen type I as opposed to well-assembled collagen fibrils, whereas monomeric CNA35 binds to all forms of collagen. It is shown that upon conjugation to liposomes and micelles CNA35 loses its ability to dissociate ordered collagen fibrils and thereby to create its own binding sites. 相似文献
614.
615.
Gustav Sievers Ulrich Hasse Fritz Scholz 《Journal of Solid State Electrochemistry》2012,16(4):1663-1673
The nucleation and growth of platinum on polycrystalline gold was studied by chronoamperometry, cyclic voltammetry, and atomic
force microscopy before and after treatment of the gold surface with hydroxyl (OH•) radicals. Two different procedures of mechanical polishing of the gold surface (“coarse polish” and “fine polish”) were
applied before the treatment with OH• radicals. The nucleation and growth of Pt was much better reproducible on electrodes which underwent a “coarse polish”. The
treatment of the Au surface with OH• radicals decreased the number of active sites; however, the nucleation growth mode remained the same (3-D instantaneous).
The spontaneous Pt deposition (no externally applied potential) on Au was unaffected by the treatment with OH• radicals. In situ atomic force microscopy experiments showed that the Pt starts to grow only on some of the Au grains, most
probably on those which have active sites on their surface. This leads to a roughening of the electrode surface upon Pt deposition.
Treatment with OH• radicals did only quantitatively diminish the amount of deposited Pt, but qualitatively the imaging of the Pt growth remained
the same. Obviously, the OH• radicals lead to a knockout (decreasing number) of active sites for Pt nucleation, while the nature of the remaining active
sites stays unaffected. 相似文献
616.
Nuernberger P Wolpert D Weiss H Gerber G 《Physical chemistry chemical physics : PCCP》2012,14(3):1185-1199
We report on femtosecond laser-induced catalytic reactions of carbon monoxide and hydrogen on single crystal surfaces under high vacuum conditions. Several product molecules are synthesized, among them also species for whose formation at least three reactants are required. By applying closed-loop optimal control, we manipulate these reactions and selectively optimize the ratio of different bond-forming reaction channels, in contrast to previous quantum control experiments aiming at bond-cleavage. Further experiments explore the nontrivial control mechanism and its sensitivity to the relative proportion of the two reactant gases. 相似文献
617.
Hornuss C Wiepcke D Praun S Dolch ME Apfel CC Schelling G 《Analytical and bioanalytical chemistry》2012,403(2):555-561
Propofol in exhaled breath can be detected and monitored in real time by ion molecule reaction mass spectrometry (IMR-MS).
In addition, propofol concentration in exhaled breath is tightly correlated with propofol concentration in plasma. Therefore,
real-time monitoring of expiratory propofol could be useful for titrating intravenous anesthesia, but only if concentration
changes in plasma can be determined in exhaled breath without significant delay. To evaluate the utility of IMR-MS during
non-steady-state conditions, we measured the time course of both expiratory propofol concentration and the processed electroencephalography
(EEG) as a surrogate outcome for propofol effect after an IV bolus induction of propofol. Twenty-one patients scheduled for
routine surgery were observed after a bolus of 2.5 mg kg−1 propofol for induction of anesthesia. Expiratory propofol was measured using IMR-MS and the cerebral propofol effect was
estimated using the bispectral index (BIS). Primary endpoints were time to detection of expiratory propofol and time to onset
of propofol’s effect on BIS, and the secondary endpoint was time to peak effect (highest expiratory propofol or lowest BIS).
Expiratory propofol and changes in BIS were first detected at 43 ± 21 and 49 ± 11 s after bolus injection, respectively (P = 0.29). Peak propofol concentrations (9.2 ± 2.4 parts-per-billion) and lowest BIS values (23 ± 4) were reached after 208 ± 57
and 219 ± 62 s, respectively (P = 0.57). Expiratory propofol concentrations measured by IMR-MS have similar times to detection and peak concentrations compared
with propofol effect as measured by the processed EEG (BIS). This suggests that expiratory propofol concentrations may be
useful for titrating intravenous anesthesia. 相似文献
618.
We initiate the study of the spherically symmetric Einstein–Klein–Gordon system in the presence of a negative cosmological
constant, a model appearing frequently in the context of high-energy physics. Due to the lack of global hyperbolicity of the
solutions, the natural formulation of dynamics is that of an initial boundary value problem, with boundary conditions imposed
at null infinity. We prove a local well-posedness statement for this system, with the time of existence of the solutions depending
only on an invariant H
2-type norm measuring the size of the Klein–Gordon field on the initial data. The proof requires the introduction of a renormalized
system of equations and relies crucially on r-weighted estimates for the wave equation on asymptotically AdS spacetimes. The results provide the basis for our companion
paper establishing the global asymptotic stability of Schwarzschild-Anti-de-Sitter within this system. 相似文献
619.
In certain regimes and for relative small applied fields, magnetic domain walls behave as mechanical particles in a viscous fluid. By analogy their dynamic can be described with an evolution equation of the form Mq̈ + β–1 q̇ = H (1) where M and are the effective wall mass and wall mobility, and H is an applied forcing. These effective parameters depend on the particular geometrical configuration and dynamical model considered. We present a method that can be used to systematically estimate the wall mass and wall mobility in terms of the static wall geometry and various physical constants. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
620.
Bernd A. Kniehl Gustav Kramer 《The European Physical Journal C - Particles and Fields》1999,6(3):493-501
Approximately taking into account the higher-order effects due to multiple-gluon initial-state radiation, we extract from
the latest Tevatron data of prompt hadroproduction the leading colour-octet matrix elements within the nonrelativistic-QCD (NRQCD) factorization formalism proposed
by Bodwin, Braaten, and Lepage. We find that the matrix elements which describe the formation of mesons from colour-octet pairs in the angular-momentum states and , with , which are responsible for the excess of the predicted cross section of inelastic photoproduction over the existing HERA data at high values of the inelasticity variable , are significantly reduced. We conclude that it is premature to proclaim a discrepancy between the Tevatron and HERA measurements
of inclusive production in the NRQCD framework. We also consider mesons originating from the radiative feed down of promptly produced mesons.
Received: 10 March 1998 / Revised version: 22 April 1998 / Published online: 30 July 1998 相似文献