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991.
Application of chromium‐doped fullerene as a carrier for thymine and uracil nucleotides: Comprehensive density functional theory calculations 下载免费PDF全文
Ali Shokuhi Rad Sadegh Mehdi Aghaei Elaheh Aali Majid Peyravi Mohsen Jahanshahi 《应用有机金属化学》2018,32(2)
The interactions of the nucleobases thymine (C5H6N2O2) and uracil (C4H4N2O2) with Cr‐doped C20 fullerene (C19Cr) are investigated by performing density functional theory calculations. The adsorption of these nucleobases on C19Cr leads to two distinct geometries (P1 and P2) differing in the orientation of the nucleobases. The interaction of the nucleobases with the C19Cr nanocluster is highly exothermic, revealing that they are chemically adsorbed on C19Cr. The results show that the binding energy of the thymine–C19Cr complex is slightly higher than that of the uracil–C19Cr complex. In addition, the P2 geometry is more stable compared to P1 due to the higher binding energy in the former configuration. However, based on the results of natural bond orbital and frontier molecular orbitals analyses, the C19Cr nanocage has higher reactivity with the nucleobases in P1 geometry in comparison with P2 due to the larger charge transfer and orbital hybridization in the former geometry. Moreover, the band gap of the C19Cr nanocage decreases after interaction with the nucleobases, and interestingly the impact is more pronounced for P1 geometry, confirming the higher sensitivity of C19Cr to the nucleobases in P1 geometry. Our findings reveal the promising potential of C19Cr as an organometallic carrier for nucleobases thymine and uracil. 相似文献
992.
Chuanming Zong 《Expositiones Mathematicae》2014,32(4):297-364
Packing, covering and tiling is a fascinating subject in pure mathematics. It mainly deals with arrangement patterns and efficiencies of geometric objects. This subject has a long and rich history, even back to Kepler, Newton, Lagrange and Gauss. Inspired by its applications and with the help of computing methods, in recent years it has become a very active research area in mathematics once again. Most of the fundamental problems in this subject can be characterized as simple sounding but challenging. This subject has important applications in many other areas such as Number Theory, Logic, Complex Analysis, Optimization, Coding Theory, Crystallography, Material Science, Industry, and even Biology. In spite of the long history, many of its key problems are still open, even in the plane. The purpose of this paper is to present a comprehensive review for packing, covering and tiling in the two-dimensional spaces. We will focus on the key problems, the fundamental results, the creative ideas, some important applications, and some significant connections with other areas. 相似文献
993.
This presented study is to make comparison of cross sections to produce 117Sb and 90Nb via different reactions with particle incident energy up to 70 MeV as a part of systematic studies on particle-induced activations on enriched Sn, Y2O3 and ZrO2 targets, theoretical calculation of production yield, calculation of required thickness of target and suggestion of optimum reaction to produce Antimony-117 and Niobium-90. 相似文献
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Akiko Ohno Nana Kawasaki Kiyoshi Fukuhara Haruhiro Okuda Teruhide Yamaguchi 《Magnetic resonance in chemistry : MRC》2010,48(2):168-172
Complete NMR analysis of oxytocin (OXT) in phosphate buffer was elucidated by one‐dimensional (1D)‐ and two‐dimensional (2D)‐NMR techniques, which involve the assignment of peptide amide NH protons and carbamoyl NH2 protons. The 1H? 15N correlation of seven amide NH protons and three carbamoyl NH2 protons were also shown by HSQC NMR of OXT without 15N enrichment. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
997.
Mika Tiainen Hannu Maaheimo Pasi Soininen Reino Laatikainen 《Magnetic resonance in chemistry : MRC》2010,48(2):117-122
The one‐ and two‐bond 13C isotope shifts, typically ?1.5 to ?2.5 ppb and ?0.7 ppb respectively, in non‐cyclic aliphatic systems and up to ?4.4 ppb and ?1.0 ppb in glucose cause effects that need to be taken into account in the adaptive NMR spectral library‐based quantification of the isotopomer mixtures. In this work, NMR spectral analyses of some 13C‐labelled amino acids, D ‐glucose and other small compounds were performed in order to obtain rules for prediction of the 13C isotope effects on 1H chemical shifts. It is proposed that using the additivity rules, the isotope effects can be predicted with a sufficient accuracy for amino acid isotopomer applications. For glucose the effects were found strongly non‐additive. The complete spectral analysis of fully 13C‐labelled D ‐glucose made it also possible to assign the exocyclic proton signals of the glucose. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
998.
A new variant of SQ–SQ pulse sequence (SQSQh) for relative sign determination and detection of small silicon–carbon couplings over more than one bond is presented. In the SQSQh sequence, proton detection replaces carbon detection used in the original SQ–SQ pulse sequence (SQSQc). The theoretical gain in sensitivity was experimentally tested on two samples (trimethylsiloxyethane, 1, and 1,2,4‐tris(trimethylsiloxy)benzene, 2), the experimentally found gain provided by the SQSQh over the SQSQc method varied between 6 and 8. The method can be applied to linear spin systems, i.e. to systems where the silicon is coupled to the carbon in question and to any hydrogen not necessarily bonded to the carbon. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
999.
Wayne E. Steinmetz 《Magnetic resonance in chemistry : MRC》2010,48(7):565-570
Granatin B, a complex ellagitannin extracted from pomegranate fruit, has two equilibrating isomers, form a and form b. A full ensemble of proton and carbon‐13 NMR methods over a wide range of temperature enabled a complete assignment of the more abundant isomer and showed it to be form b. This result is based on the NMR data for granatin alone and agrees with the previous determinations which were based on a combination of chemical methods and a partial assignment of the NMR spectra. The new NMR spectra also yield exchange rates for the hydroxyl protons as a function of temperature. A molecular model involving hydrogen bonding provides an explanation for the exchange data. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
1000.
Gilles Casano Maxime Robin Pascale Barbier Vincent Peyrot Robert Faure 《Magnetic resonance in chemistry : MRC》2010,48(9):738-744
The complete 1H and 13C NMR assignment of 9 acetamidochalcones, 18 acetamidoflavones, 18 aminoflavones, 9 acetamidoflavonols and 9 aminoflavonols has been performed using one‐ and two‐dimensional NMR techniques including COSY, HMQC and HMBC experiments. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献