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991.
Abstract
A novel metal–organic framework based on 6-methylpyridine-2,4-dicarboxylic acid N-oxide (MPDCO) ligand, [Co(MPDCO)(bix)0.5(H2O)2] n (bix = 1,4-bis(imidazol-1-ylmethyl)-benzene), has been prepared and structurally characterized. Single crystal X-ray analysis shows that it crystallizes in the monoclinic space group of P21/n with four independent lattice parameters a = 10.269(2) ?, b = 10.462(2) ?, c = 15.875(4) ?, and β = 107.657(4)°, and it has four independent molecules in the unit cell (Z = 4). A one-dimensional (1-D) helical chain was formed through the MPDCO spacer and Co2+ centers along the a-axis. Then, these 1-D chains were further interconnected by the bidentate ligand bix to afford an infinite puckered 2-D herringbone framework with (6,3) topology. And a 3-D supramolecular network was formed through the strong intermolecular hydrogen bonds. 相似文献992.
993.
§ 1.Preliminary LetEbeareflexiveBanachspacewithanorm‖·‖ ,E′itsdualspaceand〈· ,·〉thepairbetweenE′andE .SupposethatHisaHilbertspacewiththenorm |·|andinnerproduct (· ,·)suchthatE H E′ ,( 1°)wheretheformersaredenseinthelattersandthecorrespondingidenticalmapsarecont… 相似文献
994.
995.
Pei Tang Qi-Feng Chen Ling Wang Qiao-Hong Chen Xi-Xian Jian Feng-Peng Wang 《Tetrahedron》2012,68(27-28):5668-5676
O-Demethylation at C-1 in the C19-diterpenoid alkaloids is very challenging. In this paper, it was firstly observed that 10-OH group in deltaline (1) is a determining factor for the O-demethylation reaction. After removal of this hydroxyl group, 1-O-methyl group in the corresponding deltaline analogs can be readily removed by treatment with HBr–HOAc. Meanwhile, the C-14 atom in bromides 18 or 20 can be extruded under basic condition probably via a sequence, including Grob fragmentation, aerobic oxidation, deformylation, and SN2 nucleophilic substitution, to give enone 21 (70%) and oxetane 22 (14%). The structure of compound 22 was confirmed by X-ray crystallographic analysis of its derivative 21. 相似文献
996.
997.
Xinyi Cui Xiaogang Chu Zweigenbaum Jerry A. Yanyan Fang Wei Yong Yun Ling 《Chromatographia》2010,71(1-2):139-142
This study evaluated the screening of Sudan dyes in salty egg using liquid chromatography/time-of-flight mass spectrometry (LC–TOF-MS). With this technology, accurate mass measurements were made to generate elemental compositions of ions and to provide complementary structural information. This approach is useful for the elucidation of organic pollutants at trace levels in complex food extracts and in the present study salty egg samples were analyzed for the presence of Sudan IV. TOF accurate mass elemental composition data of Sudan IV were found to be crucial for structural elucidation which was applied to the investigation of nine salty egg samples.
相似文献998.
Ling Lin Dong‐Lin Chen Xiao‐Yu Liu Qiao‐Hong Chen Feng‐Peng Wang 《Helvetica chimica acta》2010,93(1):118-122
Trichocarpinine ( 1 ), the first hetidine–hetisine type bisditerpenoid alkaloid, was isolated from the whole herbs of Aconitum tanguticum var. trichocarpum. Its structure was determined by a combination of spectroscopic techniques, including HR‐ESI‐MS and 1D‐ and 2D‐NMR experiments. Its plausible biogenetic pathway was proposed as well (Scheme). 相似文献
999.
Ling Yang Rong-Zhen Liao Wan-Jian Ding Kai Liu Jian-Guo Yu Ruo-Zhuang Liu 《Theoretical chemistry accounts》2012,131(9):1-12
Mechanisms for the formation of the Schiff base from acetaldehyde and butylamine, glycine and phosphatidylethanolamine based on Dmol3/DFT calculations were realized. For the case of phosphatidylethanolamine, calculations were done under periodic boundary conditions, in an amine-phospholipid monolayer model with two molecules of phosphatidylethanolamine by cell. All models contained explicit aqueous solvent. In the three cases, a neutral amino group is used to model the nucleophilic attack on the carbonyl group of acetaldehyde, and water molecules form hydrogen bond networks. These networks were involved in the reactions by performing as proton-transfer carriers, important in some steps of reactions, and stabilizing reaction intermediates. In all the studied reactions, they take place in two steps, namely: (1) formation of a carbinolamine and (2) its dehydration to the Schiff base, being the dehydration the rate-determining step of the process, consistent with available experimental evidence for similar reactions. The main difference between the studied reactions is found in the value for relative free energy for the intermediates and transition states in the second step; these values are lower in the cases of glycine and phosphatidylethanolamine in comparison with butylamine, due the influence of their molecular environments. Based on the results, the aminophospholipid surface environment and carboxylic group of glycine may boost Schiff base formation via a neighboring catalyst effect. 相似文献
1000.