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991.
Jaroslav Stejskal Irina Sapurina Miroslava Trchová Ivana Šeděnková Jana Kovářová Jitka Kopecká Jan Prokeš 《Chemical Papers》2015,69(10):1341-1349
Polypyrrole nanotubes were prepared by the oxidation of pyrrole with iron(III) chloride in a reaction mixture containing methyl orange. They were subsequently coated with polyaniline or poly(p-phenylenediamine) in situ during the oxidation of respective monomers in their presence. A part of the coaxial nanotubes was deprotonated using ammonia solution. The conductivity of polypyrrole nanotubes of 60 S cm?1, was reduced after the coating, and again after the deprotonation, but maintained at a level above 10?4 S cm?1. Infrared and Raman spectra reflect the presence of the polymer overlayer deposited on the polypyrrole template. Thermogravimetric analysis was used as a tool for the analytical carbonisation of samples in an inert nitrogen atmosphere. The conversion of conducting polymers to nitrogen-containing carbon nanotubes was confirmed using Raman spectra. 相似文献
992.
José Miguel Hidalgo-Herrador Aleš Vráblík Petr Jíša Radek Černý Jana Hamerníková 《Chemical Papers》2015,69(8):1075-1083
Demand for high-value petroleum products is increasing and crude oils and their distillation products are becoming heavier. The thermal cracking of a vacuum residue (VR) from REB (Russian Export Blend) crude oil was carried out in an autoclave. LCO (light cycle oil), naphtha, and brown coal (BC) were added with the aim of studying their effect on the final products composition. The elemental analysis (%C, %N, %H, %S) was performed and dynamic viscosity, density, GC of gases (“Refinery Gas Analysis”), solubility in hexane and toluene, and simulated distillation were examined in raw materials, gaseous, and liquid products. As anticipated, due to its high aromatics content, the addition of LCO proved the best option, obtaining the highest yield of lighter liquids. The naphtha addition resulted in a slight increment of heavier products in the gaseous phase and higher yields to solids. The literature does not contain any extensive studies of the addition of BC to VR in the hydrovisbreaking process. The addition of BC resulted in an increment in the yield of the gaseous product and assumed the highest relative total consumption of hydrogen during the reaction. 相似文献
993.
Luke F. Gamon Joses G. Nathanael Bethany I. Taggert Fraser A. Henry Jana Bogena Prof. Uta Wille 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(42):14924-14930
The fragmentation–rearrangement of peptide backbones mediated by nitrogen dioxide, NO2., was explored using di‐, tri‐, and tetrapeptides 8 – 18 as model systems. The reaction, which is initiated through nonradical N‐nitrosation of the peptide bond, shortens the peptide chain by the expulsion of one amino acid moiety with simultaneous fusion of the remaining molecular termini through formation of a new peptide bond. The relative rate of the fragmentation–rearrangement depends on the nature of the amino acids and decreases with increasing steric bulk at the α carbon in the order Gly>Ala>Val. Peptides that possessed consecutive aromatic side chains only gave products that resulted from nitrosation of the sterically less congested N‐terminal amide. Such backbone fragmentation–rearrangement occurs under physiologically relevant conditions and could be an important reaction pathway for peptides, in which sections without readily oxidizable side chains are exposed to the air pollutant NO2.. In addition to NO2.‐induced radical oxidation processes, this outcome shows that ionic reaction pathways, in particular nitrosation, should be factored in when assessing NO2. reactivity in biological systems. 相似文献
994.
Microbial cell biosensors, where cells are in direct connection with a transducer enabling quantitative and qualitative detection of an analyte, are very promising analytical tools applied mainly for assays in the environmental field, food industry or biomedicine. Microbial cell biosensors are an excellent alternative to conventional analytical methods due to their specificity, rapid detection and low cost of analysis. Nowadays, nanomaterials are often used in the construction of biosensors to improve their sensitivity and stability. In this review, the combination of microbial and other individual cells with different nanomaterials (carbon nanotubes, graphene, gold nanoparticles, etc.) for the construction of biosensors is described and their applications are provided as well. 相似文献
995.
The total least squares (TLS) and truncated TLS (T-TLS) methods are widely known linear data fitting approaches, often used also in the context of very ill-conditioned, rank-deficient, or ill-posed problems. Regularization properties of T-TLS applied to linear approximation problems Ax ≈ b were analyzed by Fierro, Golub, Hansen, and O’Leary (1997) through the so-called filter factors allowing to represent the solution in terms of a filtered pseudoinverse of A applied to b. This paper focuses on the situation when multiple observations b 1,..., b d are available, i.e., the T-TLS method is applied to the problem AX ≈ B, where B = [b 1,..., b d ] is a matrix. It is proved that the filtering representation of the T-TLS solution can be generalized to this case. The corresponding filter factors are explicitly derived. 相似文献
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The formulae for the free energy, when the driving distributions in Generalized Random Energy Model (GREM) are of the form
for γ ≥ 1 are derived. The large deviation technique allows the use of different distributions at different levels of the
GREM. As an illustration we consider, in detail, a two level GREM with exponential and Gaussian distributions. This simple
case itself leads to interesting phenomena. 相似文献