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431.
The branching ratio of the excited-state population at the conical intersection between the S(1) and S(0) energy surfaces (Φ(CI)) of a protonated Schiff base of all-trans retinal in protic and aprotic solvents was studied by multipulse ultrafast transient absorption spectroscopy. In particular, pump-dump-probe experiments allowed to isolate the S(1) reactive state and to measure the photoisomerization time constant with unprecedented precision. Starting from these results, we demonstrate that the polarity of the solvent is the key factor influencing the Φ(CI) and the photoisomerization yield. 相似文献
432.
Niko S. Radulovi? Goran A. Bogdanovi? Polina D. Blagojevi? Vidosav S. Deki? Rastko D. Vuki?evi? 《Journal of chemical crystallography》2011,41(4):545-551
Abstract
X-Ray analyses of 4-(naphthalen-1-ylamino)-3-nitro-chromen-2-one and 3-nitro-4-phenylamino-chromen-2-one showed that the mentioned compounds crystallize in the space groups P1- (triclinic crystal system; unit cell parameters: a = 8.087(2) ?, b = 9.241(3) ?, c = 10.911(3) ?, α = 93.77(3)°, β = 102.51(3)°, γ = 106.44(2)°, V = 756.4(4) ?3 and Z = 2) and P212121 (orthorhombic crystal system; unit cell parameters: a = 4.9274(9) ?, b = 14.725(3) ?, c = 17.866(4) ?, α = β = γ = 90°, V = 1296.3(5) ?3 and Z = 4), respectively. The analyses of crystal structures and gas phase conformations, inferred from single X-ray crystallographic and molecular modeling experiments, respectively, showed that the changes in π delocalization of the farmacoactive formal 3-amino-2-nitro-acrylic acid derivatives might explain the observed significant difference of the antimicrobial and antioxidant activities and spectral properties of two 4-arylamino-3-nitro-coumarin derivatives. 相似文献433.
434.
Nicolaou KC Pihko PM Bernal F Frederick MO Qian W Uesaka N Diedrichs N Hinrichs J Koftis TV Loizidou E Petrovic G Rodriquez M Sarlah D Zou N 《Journal of the American Chemical Society》2006,128(7):2244-2257
Syntheses of the three key building blocks (65, 98, and 100) required for the total synthesis of the proposed structure of azaspiracid-1 (1a) are described. Key steps include a TMSOTf-induced ring-closing cascade to form the ABC rings of tetracycle 65, a neodymium-catalyzed internal aminal formation for the construction of intermediate 98, and a Nozaki-Hiyama-Kishi coupling to assemble the required carbon chain of fragment 100. The synthesized fragments, obtained stereoselectively in both their enantiomeric forms, were expected to allow for the construction of all four stereoisomers proposed as possible structures of azaspiracid-1 (1a-d), thus allowing the determination of both the relative and absolute stereochemistry of the natural product. 相似文献
435.
The first total synthesis of (+)-crassalactone B (2) and a new syntheses of (+)-crassalactone C (3) has been achieved starting from d-glucose. The natural products 2 and 3 can be selectively accessed by changing the conditions for TBDPS cleavage in the final intermediate 16. The synthesized natural products were evaluated for their cytotoxic activity against a panel of human tumour cell lines. 相似文献
436.
437.
Goran Djankovi? 《Central European Journal of Mathematics》2012,10(2):748-760
In this paper we study the orthogonality of Fourier coefficients of holomorphic cusp forms in the sense of large sieve inequality.
We investigate the family of GL
2 cusp forms modular with respect to the congruence subgroups Γ1(q), with additional averaging over the levels q ∼ Q. We obtain the orthogonality in the range N ≪ Q
2−δ
for any δ > 0, where N is the length of linear forms in the large sieve. 相似文献
438.
Maria Carta Leonarda Vugrin Dr. Goran Miletić Dr. Marina Juribašić Kulcsár Prof. Dr. Pier Carlo Ricci Dr. Ivan Halasz Prof. Dr. Francesco Delogu 《Angewandte Chemie (International ed. in English)》2023,62(33):e202308046
Typically induced by the mechanical processing of powders in ball mills, mechanochemical transformations are considered to result from the application of mechanical force to solid reactants. However, the undeniable deep connection between the dynamic compaction of powders during impacts and the overall transformation degree has yet to be disclosed. In the present work, we show that the square planar bis(dibenzoylmethanato)NiII coordination compound undergoes trimerization when its powder experiences even a single ball impact. Based on systematic experiments with individual ball impacts and analysis by Raman spectroscopy, we provide here quantitative mapping of the transformation in the powder compact and deduce bulk reaction kinetics from multiple individual impacts. 相似文献
439.
Sanja B. Kokanov Nenad R. Filipović Aleksandar Višnjevac Milan Nikolić Irena Novaković Goran Janjić Berta Barta Holló Sandra Ramotowska Paulina Nowicka Mariusz Makowski Özlem Uğuz Atıf Koca Tamara R. Todorović 《应用有机金属化学》2023,37(1):e6942
Interest in Cd complexes has been growing in recent years. Cd complexes are considered a potential solution in the search for novel antibiotics that can fight antimicrobial resistance. In addition, Cd complexes draw attention to material chemistry. The main objective of this work was to prepare the first Cd(II) complexes with anionic forms of pyridine-based thiazolyl hydrazone (THs) ligands HLS2 [(E)-4-(4-methoxyphenyl)-2-(2-[pyridine-2-ylmethylene]hydrazinyl)thiazole] and HLS3 [(E)-2-(2-[pyridine-2-ylmethylene]hydrazinyl)-4-(p-tolyl)thiazole] and perform their structural and spectroscopic characterization, as well as stability in solution and upon heating. Studies related to their biological activities and possible electrochromic applications are also being conducted. Complexes [Cd(HLS2)2] ( 1 ) and [Cd(HLS3)2] ( 2 ) have been characterized by a single-crystal X-ray diffraction and computational analysis of intermolecular interactions responsible for their solid-state structures was performed. Thermal stability of 1 and 2 in the solid-state was analyzed by TGA/MS, where as their solution stability was determined by the spectrophotometric titration method. Electrochemical and in situ UV–Vis spectroelectrochemical analyses of 1 and 2 were carried out to determine redox mechanisms and the influence of the substituents and electrolytes on their redox responses. The antioxidant capacity of both complexes was tested in antioxidant assays, while their antimicrobial activity was tested against five Gram-positive and four Gram-negative bacteria, as well as against three fungi. The obtained results indicate their potent antioxidant capacity. The antimicrobial activity of investigated compounds on almost all tested bacterial strains was stronger than that of the standard antibiotic erythromycin. The results of docking studies indicate that the minor groove DNA is the possible biological target of 1 and 2 . 相似文献
440.
A number of interesting thermotropic mesophases and transitions occur in main-chain polyethers and copolyethers based on aliphatic spacers and various semi-flexible mesogens of the general 1-(4'-hydroxyphenyl)-2-(2-R-4-hydroxyphenyl)ethane (RBPE) or 1-(4'-hydroxybiphenyl-4-yl)-2-(4-hydroxyphenyl)propane (TPP) type. The unusual effects described here are (i) nematic-nematic transition, (ii) smectic-B (crystal-B) phase and its shear-induced orientation, (iii) calamitic columnar phase, and (iv) nematic-columnar phase sequence. 相似文献