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991.
A simple, convenient, environmentally benign, and mild synthetic method has been established to afford highly decorated indenodihydropyridine and dihydropyridine derivatives employing a green solvent ethyl-l-lactate and an organo-catalyst (±)lactic acid. A wide range of functional groups were tolerated in the developed protocol. The target molecules were obtained in moderate to good yields applying the current method. 相似文献
992.
993.
Dr. Quentin Bonnin Tereza Edlová Dr. E. Daiann Sosa Carrizo Prof. Dr. Paul Fleurat-Lessard Dr. Stéphane Brandès Dr. Hélène Cattey Dr. Philippe Richard Prof. Dr. Pierre Le Gendre Dr. Adrien T. Normand 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(72):18175-18187
Cationic amidotitanocene complexes [Cp2Ti(NPhAr)][B(C6F5)4] (Cp=η5-C5H5; Ar=phenyl ( 1 a ), p-tolyl ( 1 b ), p-anisyl ( 1 c )) were isolated. The bonding situation was studied by DFT (Density Functional Theory) using EDA-NOCV (Energy Decomposition Analysis with Natural Orbitals for Chemical Valence). The polar Ti−N bond in 1 a–c features an unusual inversion of σ and π bond strengths responsible for the balance between stability and reactivity in these coordinatively unsaturated species. In solution, 1 a–c undergo photolytic Ti−N cleavage to release Ti(III) species and aminyl radicals ⋅ NPhAr. Reaction of 1 b with H3BNHMe2 results in fast homolytic Ti−N cleavage to give [Cp2Ti(H3BNHMe2)][B(C6F5)4] ( 3 ). 1 a–c are highly active precatalysts in olefin hydrogenation and silanes/amines cross-dehydrogenative coupling, whilst 3 efficiently catalyzes amine-borane dehydrogenation. The mechanism of olefin hydrogenation was studied by DFT and the cooperative H2 activation key step was disclosed using the Activation Strain Model (ASM). 相似文献
994.
This paper describes the development of a lattice Boltzmann (LB) model for a binary gas mixture, and applications to channel flow driven by a density gradient with diffusion slip occurring at the wall. LB methods for single component gases typically use a non‐physical equation of state in which the relationship between pressure and density varies according to the scaling used. This is fundamentally unsuitable for extension to multi‐component systems containing gases of differing molecular masses. Substantial variations in the species densities and pressures may exist even at low Mach numbers; hence, the usual linearized equation of state for small fluctuations is unsuitable. Also, existing methods for implementing boundary conditions do not extend easily to novel boundary conditions, such as diffusion slip. The new model developed for multi‐component gases avoids the pitfalls of some other LB models. A single computational grid is shared by all the species, and the diffusivity is independent of the viscosity. The Navier–Stokes equation for the mixture and the Stefan–Maxwell diffusion equation are both recovered by the model. Diffusion slip, the non‐zero velocity of a gas mixture at a wall parallel to a concentration gradient, is successfully modelled and validated against a simple one‐dimensional model for channel flow. To increase the accuracy of the scheme, a second‐order numerical implementation is needed. This may be achieved using a variable transformation method that does not increase the computational time. Simulations were carried out on hydrogen and water diffusion through a narrow channel for varying total pressure and concentration gradients. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
995.
996.
Ratnakar N. Asolkar Ahilya Singh Paul R. Jensen William Aalbersberg Brad K. Carté Klaus-D. Feussner Ramesh Subramani Antonio DiPasquale Arnold L. Rheingold William Fenical 《Tetrahedron》2017,73(16):2234-2241
Six cytotoxic and antimicrobial metabolites of a new bromo-phenazinone class, the marinocyanins A-F (1–6), were isolated together with the known bacterial metabolites 2-bromo-1-hydroxyphenazine (7), lavanducyanin (8, WS-9659A) and its chlorinated analog WS-9659B (9). These metabolites were purified by bioassay-guided fractionation of the extracts of our MAR4 marine actinomycete strains CNS-284 and CNY-960. The structures of the new compounds were determined by detailed spectroscopic methods and marinocyanin A (1) was confirmed by crystallographic methods. The marinocyanins represent the first bromo-phenazinones with an N-isoprenoid substituent in the skeleton. Marinocyanins A-F show strong to weak cytotoxicity against HCT-116 human colon carcinoma and possess modest antimicrobial activities against Staphylococcus aureus and amphotericin-resistant Candida albicans. 相似文献
997.
998.
Fernando Castañeda Paul Silva M. Teresa Garland Ata Shirazi Clifford A. Bunton 《Phosphorus, sulfur, and silicon and the related elements》2013,188(8):2152-2168
The phosphonium ylidic diesters, methyl and ethyl isopropyl and, methyl and ethyl t-butyl triphenylphosphoranylidene malonates, 1a,b and 2a,b , respectively, have the syn-anti conformation in solution, as in the crystal, and the bulkier alkoxy group is oriented towards phosphorus. The 1 H NMR spectra show that in 1a,b , the isopropyl group is oriented towards the face of a phenyl group, consistent with π shielding in the 1 H signals, and examination of the 1 H coupled 13 C NMR spectra allows assignment of the acyl carbon signals. Computed bond lengths and angles for isolated molecules are similar to those in the crystal, and the geometry and the NMR spectra indicate extensive ylidic resonance. Estimated partial atomic charges on the ester oxygens are more negative when they are oriented towards, rather than away from, phosphorus. 相似文献
999.
Ernst Peter Müller Paul Peringer Roland Aeschimann Thomas Maetzke Walter Petter 《Phosphorus, sulfur, and silicon and the related elements》2013,188(3-4)
Abstract Reaction of the 2-azidoalcohol 1 with 2-phenyl1-1,3,2-dioxaphospholane leads to a 4:1 mixture of the pentacoordinate phosphorane 3 and the diazadiphosphetidine 4. In solution, these compounds are in equilibrium, presumably involving the not detectable iminophosphorane 2. A single X-ray analysis carried out on 3 proves the structure of this type of compound which has been postulated earlier as intermediate in the synthesis of aziridines from azidoalcohols1,2 相似文献
1000.
Paul M. Cullis Anna Iagrossi Andrew J. Rous 《Phosphorus, sulfur, and silicon and the related elements》2013,188(3-4):559-562
Abstract The stereochemical courses of phosphoryl transfer reactions in aprotic solvents and thiophosphoryl transfer reactions in protic solvent have been determined. The extensive racemisation observed in both instances is discussed in terms of metaphosphate and thiometaphosphate intermediates of significant life-times. 相似文献