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排序方式: 共有675条查询结果,搜索用时 15 毫秒
581.
Andrzej Kasperczuk Tadeusz Pisarczyk Tomasz Chodukowski Zofia Kalinowska Sergey Gus’kov Nikolai Demchenko Jiri Ullschmied Eduard Krousky Miroslav Pfeifer Jiri Skala Daniel Klir Jozef Kravarik Pavel Kubes Jakub Cikhardt Karel Rezac Pawel Pisarczyk 《Central European Journal of Physics》2013,11(5):575-579
This paper describes the investigation of the influence of target material atomic number (Z) on the laser-produced plasma pressure. For this reason, several target materials representing a wide range of atomic numbers (Z = 3.5 - 73), i.e. plastic (CH), Al, Cu, Ag, and Ta, were used. The results presented show that the plasma pressure decreases with growing atomic number but in a limited range of Z only. For higher Z, starting approximately from Z = 47 (Ag), the plasma pressure becomes constant, as confirmed by interferometric measurements and x-ray plasma imaging. 相似文献
582.
Yun-Pil Shim Anand Sharma Chang-Yu Hsieh Pawel Hawrylak 《Solid State Communications》2010,150(41-42):2065-2068
We show how nanostructuring of a metallic gate of a field-effect transistor (FET) converts the electron channel of an FET to an artificial Haldane chain with a gap in the energy spectrum. A specially designed gate structure creates a chain of triple quantum dot molecules. The electrons localized in the molecules realize a spin-half Heisenberg chain with spin–spin interactions alternating between ferromagnetic and antiferromagnetic. The quantum state of an FET is a semiconductor implementation of an integer spin-one antiferromagnetic Heisenberg chain with a unique correlated ground state and a finite energy gap, originally conjectured by Haldane. 相似文献
583.
Agata Kowalczyk Anna Maria Nowicka Rafal Jurczakowski Pawel Niedzialkowski Tadeusz Ossowski Zbigniew Stojek 《Electroanalysis》2010,22(1):49-59
Interactions of dsDNA and ssDNA, at the surface of gold and silver electrodes, with three novel anthraquinone derivatives: 3‐(9′,10′‐dioxo‐9′,10′‐dihydro‐anthracen‐1‐yl)‐7,11‐di(carboxymethyl)‐3,7,11‐triazatridecanedioic acid, (AQ‐1); 1‐(9′,10′‐dioxo‐9′,10′‐dihydro‐anthracen‐1yl)‐9‐carboxymethyl‐5‐methyl‐1,5,9‐triazaundecanoicacid, (AQ‐2); and N‐(2‐(9,10‐dioxo‐9,10‐dihydro‐anthracen‐1‐ylamino)ethyl)‐2‐(1,4,10,13‐tetraoxa‐7,16‐diazacyclooctadecan‐7‐yl)acetamide, (AQ‐3) are studied. These derivatives are well soluble in water and phosphate buffer solutions. The square wave voltammetric behavior of these redox indicators is described and the parameters of interactions with DNA are reported. It is also pointed out that these compounds can be employed as the hybridization indicators. The difference in the binding ability of the particular redox indicator to single and double stranded DNA can be used for the detection of the complementary nucleic acids. 相似文献
584.
Deidre M. Cleland Garth Irwin Dr. Pawel Wagner Dr. David L. Officer Prof. Keith C. Gordon Prof. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2009,15(15):3682-3690
Interchromophoric communication – when darkness falls : This study investigates the electronic communication between various hole‐transporting (HT) ligands and a rhenium(phenanthroline) centre to which they are coordinated. It is found that when the conjugation within the HT ligand is increased, the energy of a non‐emissive HT ligand electronic transition is sufficiently lowered so that it interacts with, and partially deactivates, emission from the rhenium(phenanthroline) moiety (see figure).
585.
If a certain optimization problem is NP-hard or even harder, one could expect that the chances of solving it optimally should rather decrease with an increase of the problem size. We reveal, however, that the opposite occurs for a strongly NP-hard problem, which requires sequencing n jobs through an m machine flow shop so as to minimize the makespan. In particular, we empirically examine optimality rates (the probability of being optimal) of the famous NEH heuristic of Nawaz et al. [Nawaz, M., Enscore, Jr., E., Ham, I., 1983. A heuristic algorithm for the m-machine, n-job flow-shop sequencing problem. Omega, The International Journal of Management Science 11, 91–95] and two improved versions of NEH. By using millions of simulation trials and a new effective lower bound on the shortest makespan, we observe relatively high optimality rates of the three heuristics for small values of m. Rather surprisingly, for larger values of n, the heuristics become more frequently optimal as n increases. Neither theoretical nor empirical studies of optimality rates of flow shop heuristics have been conducted so far, and – to the best of our knowledge – no similar studies are known in the field of operations research. 相似文献
586.
Chemical properties of epitaxially grown bimetallic layers may deviate substantially from the behavior of their constituents. Strain in conjunction with electronic effects due to the nearby interface represent the dominant contribution to this modification. One of the simplest surface processes to characterize reactivity of these substrates is the dissociative adsorption of an incoming homo-nuclear diatomic molecule. In this study, the adsorption of O(2) on various epitaxially grown Pt films on Ru(0001) has been investigated using infrared absorption spectroscopy and thermal desorption spectroscopy. Pt/Ru(0001) has been chosen as a model system to analyze the individual influences of lateral strain and of the residual substrate interaction on the energetics of a dissociative adsorption system. It is found that adsorption and dissociative sticking depends dramatically on Pt film thickness. Even though oxygen adsorption proceeds in a straightforward manner on Pt(111) and Ru(0001), molecular chemisorption of oxygen on Pt/Ru(0001) is entirely suppressed for the Pt/Ru(0001) monolayer. For two Pt layers chemisorbed molecular oxygen on Pt terraces is produced, albeit at a very slow rate; however, no (thermally induced) dissociation occurs. Only for Pt layer thicknesses N(Pt) ≥ 3 sticking gradually speeds up and annealing leads to dissociation of O(2), thereby approaching the behavior for oxygen adsorption on genuine Pt(111). For Pt monolayer films a novel state of chemisorbed O(2), most likely located at step edges of Pt monolayer islands is identified. This state is readily populated which precludes an activation barrier towards adsorption, in contrast to adsorption on terrace sites of the Pt/Ru(0001) monolayer. 相似文献
587.
588.
J Malig AW Stephenson P Wagner GG Wallace DL Officer DM Guldi 《Chemical communications (Cambridge, England)》2012,48(70):8745-8747
Exfoliation of graphite was achieved using a free-base porphyrin 1 resulting in an efficient fabrication of single-layer nanographene (NG)- hybrid platelets that can be further functionalized with other nanomaterials. The novel nanographene-porphyrin hybrids reveal efficient charge transfer in the excited state. 相似文献
589.
The density functional calculations suggest that the expansion of the corrin macrocycle's N(4) core by 0.06-0.10 ? leads to an appreciable lowering of 100-150 mV vs. saturated calomel electrode in the reduction potentials of two biologically important B(12) cofactors namely methylcobalamin and adenosylcobalamin respectively. This redox tuning of B(12) cofactors may encourage the electron transfer-based activation mechanism for B(12)-dependent enzymes. 相似文献
590.
Niko Guskos Grzegorz Zolnierkiewicz Janusz Typek Aleksander Guskos Pawel Berczynski Dimitri Petridis 《Central European Journal of Physics》2012,10(1):166-171
Solids containing an extended network of free radicals have been prepared and studied by magnetic resonance techniques in
the 4–290 K temperature range. One solid contained additionally a small amount of magnetic γ-Fe2O3 in the form of nanoparticle agglomerates. The solid without agglomerates displayed only a narrow, single resonance line centered
at g
eff
= 2.0043. The magnetic resonance measurements of the solid with γ-Fe2O3 agglomerates gave a spectrum composed of two lines attributed to two different magnetic centers: a narrow line due to free
radicals and a broad line arising from magnetic iron oxide agglomerates. In the high temperature range the integrated intensities
of both lines decreased with decreasing temperature. The resonance field of the broad line shifted to lower magnetic fields
upon lowering the temperature with the gradient ΔH
r
/ΔT = 2.3 G/K, while the narrow line shifted towards higher magnetic fields. The linewidth of the broader line increased with
decreasing temperature while for the narrow lines in both samples this change was small. The magnetic iron oxide clusters
produce a magnetic field which acts on the free radicals network and its strength depends essentially on the concentration
of clusters. The reorientation process in the free radicals network is more intense in the sample without magnetic clusters. 相似文献