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491.
We study the optimal transport problem in sub-Riemannian manifolds where the cost function is given by the square of the sub-Riemannian
distance. Under appropriate assumptions, we generalize Brenier–McCann’s theorem proving existence and uniqueness of the optimal
transport map. We show the absolute continuity property of Wassertein geodesics, and we address the regularity issue of the
optimal map. In particular, we are able to show its approximate differentiability a.e. in the Heisenberg group (and under
some weak assumptions on the measures the differentiability a.e.), which allows us to write a weak form of the Monge–Ampère
equation. 相似文献
492.
The splitting of the T2 stretching vibration into B2 and E modes on passing from Td to D2d symmetry is discussed for M2XO4 molecules (M = Li, Na, K, Cs, In and T1. X = Cr, Mo, W and S). Correlations between XO stretching force constants, OXO bond angles and cation polarizabilities are made. 相似文献
493.
R. Teghil L. DAlessio A. Santagata M. Zaccagnino D. Ferro D. J. Sordelet 《Applied Surface Science》2003,210(3-4):307-317
A Nd:glass laser with pulse duration of 250 fs and 1.3 ps has been used to evaporate a Al65Cu23Fe12 quasicrystalline target. The gaseous phase obtained from the ablation process has been characterised by several techniques such as emission spectroscopy, quadrupole mass spectrometry and ICCD imaging, used to study the plume composition, energy and morphology. The results show that the ablation processes in the short-pulse regimes are very different to the nanosecond one. In particular the plume angular distribution shows a characteristic high cosine exponent and the composition is completely stoichiometric and independent from the laser fluence. Furthermore the mass spectra indicate the presence of clusters, both neutral and ionised and the emission from the target suggest a rapid thermalisation leading to the melting of the surface. To clarify the ablation process some films have been deposited, on oriented silicon, at different experimental conditions and analysed by scanning electron microscopy, atomic force microscopy, energy dispersive X-ray analysis and X-ray diffraction. The analyses show the presence of nanostructured films retaining the target stoichiometry but consisting of different crystalline and non crystalline phases. In particular the nanostructure supports the hypothesis of the melting of the target during the ablation and a mechanism of material ejection is proposed for both picosecond and femtosecond regimes. 相似文献
494.
Summary The diffusion equations of primary cosmic-ray nuclei in the atmosphere have been solved, assuming different shapes of the
prmary energy spectra, and deriving a new simple analytical form of the solutions. Variations in the upper atmosphere of the
spectra and charge ratios of the different groups of nuclei are derived.
Riassunto Sono state risolte le equazioni di diffusione dei nuclei primari della radiazione cosmica nell'atmosfera, consderando differenti forme degli spettri di energia primari, e ottenendo una nuova e semplice forma analitica delle soluzioni. Si presentano le variazioni, nell'alta atmosfera, degli spettri e dei rapporti di carica dei diversi gruppi di nuclei.
Резюме Решаются диффузионные уравнения для распространения ядер первичного космического излучения в атмосфере, предполагая различные формы спектров первичных энергий, и получается новая простая аналитическая форма решений. Для верхних слоев атмосферы выводятся изменения спектров и зарядовых отношений для различных групп ядер.相似文献
495.
496.
M. Alessio L. Allegri D. Fargion S. Improta N. Iucci M. Parisi G. Villoresi N. L. Zangrilli 《Il Nuovo Cimento C》1991,14(1):53-60
Summary An extraordinary increase in cosmic-ray intensity has been recorded on September 29, 1989 by the Rome detectors (rigidity
threshold ∼6.2 GV). We show the time evolution of the event as recorded at Rome in the nucleonic component and in the total
ionizing and muon components; as well as at Campo Imperatore (2300 m a.s.l. near Rome) in the nucleonic component by a special
monitor designed for the detection of solar-neutron events. The one-minute time resolution of the Campo Imperatore data offers
the possibility to follow in detail the development of the event for most of the time. The possible contribution of solar
neutrons to the early phase of the Campo Imperatore event has been not clarified so far, further results may be obtained by
the analysis of the multiplicity data registered in the event. 相似文献
497.
Serli B Zangrando E Iengo E Mestroni G Yellowlees L Alessio E 《Inorganic chemistry》2002,41(15):4033-4043
The reactivity of ruthenium(II)- and ruthenium(III)-chloride-dimethyl sulfoxide precursors and of the antimetastatic drug [ImH][trans-RuCl(4)(dmso-S)(Im)] (NAMI-A, Im = imidazole, dmso = dimethyl sulfoxide) toward NO was investigated. Treatment of [(dmso)(2)H][trans-RuCl(4)(dmso-S)(2)] and mer-RuCl(3)(dmso)(3) with gaseous NO yielded [(dmso)(2)H][trans-RuCl(4)(dmso-O)(NO)] (1) and mer,cis-RuCl(3)(dmso-O)(2)(NO) (2), respectively. Thus, coordination of the strong pi-acceptor NO induces a S to O linkage isomerization of the dmso trans to it to avoid competition for pi-electrons. In light-protected nitromethane solutions, complex 2 equilibrates slowly with the two isomers mer-RuCl(3)(dmso-S)(dmso-O)(NO) (3), with NO trans to Cl, and mer-RuCl(3)(dmso-S)(dmso-O)(NO) (4), with NO trans to dmso-O; the equilibrium mixture consists of ca. 64% 2, 3% 3, and 33% 4. Treatment of the Ru(II) precursor trans-RuCl(2)(dmso-S)(4) with gaseous NO in CH(2)Cl(2) solution yielded the nitrosyl-nitro derivative trans,cis,cis-RuCl(2)(dmso-O)(2)(NO)(NO(2)) (5). Finally, [(Im)(2)H][trans-RuCl(4)(Im)(NO)] (6) was prepared by treatment of [ImH][trans-RuCl(4)(dmso-O)(NO)] (1Im) with an excess of imidazole in refluxing acetone. The spectroscopic features are consistent with the [Ru(NO)](6) formulation for all complexes, that is, a diamagnetic Ru(II) nucleus bound to NO(+). Compounds 1, 2, 5, and 6 were characterized also by X-ray crystallography; they all show a linear nitrosyl group, with short Ru-NO bond distances consistent with a strong d(pi) --> pi NO back-bonding. An unusual inertness of O-bonded dmso was observed in compound 1. Complexes 1, 2, 3, 5, and 6 are all redox active in DMF solutions showing irreversible reductions whose peak potentials depend on the other ligands attached to the Ru metal center. The site of reduction is the NO(+) moiety. The reduced complexes are not stable and release a Cl(-) or NO(2)(-) ligand followed by the NO(*) radical. The chemical reactions following electron transfer are all fast (rate constant >100 s(-1) at 293 K). The Ru product species are not redox active within the DMF window. 相似文献
498.
Zanoni G Porta A De Toma Q Castronovo F Vidari G 《The Journal of organic chemistry》2003,68(16):6437-6439
Enantioselective synthesis of natural PGJ(2) has been accomplished for the first time starting from the commercially available enantiopure aldehyde 7 in 10% overall yield. The key reaction was a novel prostaglandin class interconversion, i.e., an allylic 1,3-transposition across alcohol 9 derived from compound 14 in 73% overall yield. In principle, the unnatural enantiomer of PGJ(2) could be obtained starting from the commercially available enantiopure monobenzoate 7a following our strategy. 相似文献
499.
Kemel Arafet Natalia Serrano-Aparicio Alessio Lodola Adrian J. Mulholland Florenci V. Gonzlez Katarzyna
widerek Vicent Moliner 《Chemical science》2021,12(4):1433
The SARS-CoV-2 main protease (Mpro) is essential for replication of the virus responsible for the COVID-19 pandemic, and one of the main targets for drug design. Here, we simulate the inhibition process of SARS-CoV-2 Mpro with a known Michael acceptor (peptidyl) inhibitor, N3. The free energy landscape for the mechanism of the formation of the covalent enzyme-inhibitor product is computed with QM/MM molecular dynamics methods. The simulations show a two-step mechanism, and give structures and calculated barriers in good agreement with experiment. Using these results and information from our previous investigation on the proteolysis reaction of SARS-CoV-2 Mpro, we design two new, synthetically accessible N3-analogues as potential inhibitors, in which the recognition and warhead motifs are modified. QM/MM modelling of the mechanism of inhibition of Mpro by these novel compounds indicates that both may be promising candidates as drug leads against COVID-19, one as an irreversible inhibitor and one as a potential reversible inhibitor.QM/MM simulations identify the mechanism of reaction of N3, a covalent peptidyl inhibitor of SARS-CoV-2 main protease. Modelling of two novel proposed compounds, B1 and B2, suggests that reversibility of covalent inhibition could be tailored. 相似文献
500.
Srichandan Padhi Marco Masi Sujogya K. Panda Walter Luyten Alessio Cimmino 《Natural product research》2020,34(18):2573-2580
AbstractA new 6-benzyl-γ-pyrone (1), named aspergyllone was isolated from the culture filtrates of an endolichenic fungus Aspergillus niger Tiegh, obtained from lichen thallus Parmotrema ravum (Krog & Swinscow) Serus, collected in India. 1 was isolated for the first time from an endolichenic fungus together with six other known metabolites identified as aurasperones A (2) and D (3), asperpyrone A (4), fonsecinone A (5), carbonarone A (6) and pyrophen (7). The compounds were tested against a panel of human, plant, food borne and fish pathogens. Aspergyllone showed strong selective antifungal activity against Candida parapsilosis (Ashford) Langeron & Talice, with an IC50 of 52?µg/mL. Aurasperone A and pyrophen showed moderate to strong antimicrobial activity inhibiting seven different test pathogens, being pyrophen active with IC50 ranging from 35 to 97?µg/mL. 相似文献