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561.
Unravelling Secondary Structure Changes on Individual Anionic Polysaccharide Chains by Atomic Force Microscopy 下载免费PDF全文
Larissa Schefer Dr. Jozef Adamcik Prof. Dr. Raffaele Mezzenga 《Angewandte Chemie (International ed. in English)》2014,53(21):5376-5379
The structural conformations of the anionic carrageenan polysaccharides in the presence of monovalent salt close to physiological conditions are studied by atomic force microscopy. Iota‐carrageenan undergoes a coil–helix transition at high ionic strength, whereas lambda‐carrageenan remains in the coiled state. Polymer statistical analysis reveals an increase in persistence length from 22.6±0.2 nm in the random coil, to 26.4±0.2 nm in the ordered helical conformation, indicating an increased rigidity of the helical iota‐carrageenan chains. The many decades‐long debated issue on whether the ordered state can exist as single or double helix, is conclusively resolved by demonstrating the existence of a unimeric helix formed intramolecularly by a single polymer chain. 相似文献
562.
Jozef Rychlý Agnes Lattuati-DerieuxBertrand Lavédrine Lyda Matisová-RychláMarta Malíková Katarína CsomorováIvica Janigová 《Polymer Degradation and Stability》2011,96(4):462-469
The thermooxidative and thermal stability of polyether- and polyester-type polyurethane foams were investigated by non-isothermal chemiluminescence (CL), differential scanning calorimetry (DSC) and thermogravimetry (TG). In the presence of air and humidity, the effect of various routes and conditions of polyurethane ageing (induced thermally or by light) on the chemiluminescence, DSC and thermogravimetry patterns was assessed. The rate constants determined from non-isothermal thermogravimetry and chemiluminescence measurements at 250 °C and their not very pronounced dependence on the atmosphere of degradation indicated that depolymerisation of the polyurethane containing the aliphatic polyester and aromatic polyisocyanate moieties preceded or occurred in parallel with thermal oxidation. Under conditions of 50% relative humidity, samples of the polyester-type polyurethane, aged either by light or thermally, as well as specimens of the polyether-type polyurethane, aged by light, gave increased amounts of carbonaceous residue when heated in nitrogen to 550 °C. 相似文献
563.
Aleš Hrdlička Linda Zaorálková Michaela Galiová Tereza Čtvrtníčková Viktor Kanický Vítězslav Otruba Karel Novotný Pavel Krásenský Jozef Kaiser Radomír Malina Kateřina Páleníková 《Spectrochimica Acta Part B: Atomic Spectroscopy》2009
An acoustic signal was used for the internal standardization of laser-induced breakdown spectroscopy (LIBS) of a glazed wall tile. For the LIBS analyses, 1064 nm and 532 nm wavelengths of the Nd:YAG laser were utilized. The tile was depth profiled by a single-spot ablation from the glaze into the substrate. Some lines of major elements Si(I) 252.418, Si(I) 252.851, Al(I) 257.509, Cr(I) 295.368, Al(I) 309.271 nm and Ti(II) 334.904 nm were monitored. The decrease in the optical emissions during the ablation was successfully compensated for by normalization to the square power of the acoustic signal in the interval of 290–340 nm. This approach failed for the lines between 250–270 nm. The results were the same for both lasing wavelengths despite different irradiances. The acquired profiles are in good agreement with the reference X-ray fluorescence measurement. 相似文献
564.
For any d?5 and k?3 we construct a family of Cayley graphs of degree d, diameter k, and order at least k((d?3)/3)k. By comparison with other available results in this area we show that our family gives the largest currently known Cayley graphs for a wide range of sufficiently large degrees and diameters. © 2009 Wiley Periodicals, Inc. J Graph Theory 64: 87–98, 2010 相似文献
565.
The crossing function of a graphG with orientable genusn is defined as a mapping \(f:\{ \not 0,1, \ldots ,n\} \to \{ \not 0,1,2, \ldots \} \) for whichf(k)=cr k (G) the crossing number ofG on the orientable surface of genusk. It is proved that any decreasing convex function \(f:\{ \not 0,1, \ldots ,n\} \to \{ \not 0,1,2, \ldots \} \) with \(f(n) = \not 0\) is the crossing function of some connected graph. 相似文献
566.
Implementation of the diagonalization‐free algorithm in the self‐consistent field procedure within the four‐component relativistic scheme 下载免费PDF全文
Marcela Hrdá Tomáš Kulich Michal Repiský Jozef Noga Olga L. Malkina Vladimir G. Malkin 《Journal of computational chemistry》2014,35(23):1725-1737
A recently developed Thouless‐expansion‐based diagonalization‐free approach for improving the efficiency of self‐consistent field (SCF) methods (Noga and ?imunek, J. Chem. Theory Comput. 2010, 6, 2706) has been adapted to the four‐component relativistic scheme and implemented within the program package ReSpect. In addition to the implementation, the method has been thoroughly analyzed, particularly with respect to cases for which it is difficult or computationally expensive to find a good initial guess. Based on this analysis, several modifications of the original algorithm, refining its stability and efficiency, are proposed. To demonstrate the robustness and efficiency of the improved algorithm, we present the results of four‐component diagonalization‐free SCF calculations on several heavy‐metal complexes, the largest of which contains more than 80 atoms (about 6000 4‐spinor basis functions). The diagonalization‐free procedure is about twice as fast as the corresponding diagonalization. © 2014 Wiley Periodicals, Inc. 相似文献
567.
[chemical reaction: see text]. We report here the synthesis of the 5'-[benzhydryloxybis(trimethylsilyloxy)]silyl-2'-methylseleno-2'-deoxyuridine phosphoramidite and its incorporation into oligonucleotides by solid-phase synthesis. The coupling yield of this phosphoramidite into oligonucleotides is higher than 99%. We also demonstrate that this 2'-methylselenophosphoramidite is compatible with the 5'-silyl-2'-ACE chemistry, for longer Se-RNA solid-phase synthesis. Our preliminary NMR study on the synthesized 2'-Se-DNA has revealed a U(Se)-A base pair and a duplex structure formation when its complementary strand was present. 相似文献
568.
Ewa Gorecka Natasa Vaupotic Damian Pociecha Mojca Cepic Jozef Mieczkowski 《Chemphyschem》2005,6(6):1087-1093
The behaviour of polar, broken-layer-type columnar phases made of bent molecules (B(1Rev) and B(1RevTilted)) was studied under an applied electric field. There are two competing mechanisms of ferroelectric switching in the polar B(1RevTilted) columnar phase: collective rotation around the long molecular axis and collective rotation around the tilt cone. The proposed model shows that the main factor discriminating the type of switching is the width of the column cross-section. 相似文献
569.
Anna Zep Dr. Michal M. Wojcik Dr. Wiktor Lewandowski Kaja Sitkowska Aleksander Prominski Prof. Jozef Mieczkowski Dr. Damian Pociecha Prof. Ewa Gorecka 《Angewandte Chemie (International ed. in English)》2014,53(50):13725-13728
The properties of liquid‐crystalline (LC) hybrid systems made of inorganic nanoparticles grafted with photosensitive azo compounds are presented. For materials with a large density of azo ligands at the surface, the LC structure can be reversibly melted by UV light, and the return to the LC state does not require the absorption of visible light. For systems with a lower density of azo ligands, UV light causes shortening of the distance between metal sublayers in the lamellar phase. Interestingly, the azo derivatives attached to the nanoparticle surface show very different kinetics of cis/trans conformational change as compared to the free molecules. The cis form of free ligands in solution is stable for days, whereas the isomerization of molecules attached to the nanoparticle surface to the trans form takes only a few minutes. Apparently, owing to the crowded environment, azo ligands immobilized at a metal surface behave as they would in the condensed state. 相似文献
570.