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181.
Kozlowski PM Andruniow T Jarzecki AA Zgierski MZ Spiro TG 《Inorganic chemistry》2006,45(14):5585-5590
Density functional theory (DFT)-based normal mode calculations have been carried out on models for B12-cofactors to assign reported isotope-edited resonance Raman spectra, which isolate vibrations of the organo-Co group. Interpretation is straightforward for alkyl-Co derivatives, which display prominent Co-C stretching vibrational bands. DFT correctly reproduces Co-C distances and frequencies for the methyl and ethyl derivatives. However, spectra are complex for adenosyl derivatives, due to mixing of Co-C stretching with a ribose deformation coordinate and to activation of modes involving Co-C-C bending and Co-adenosyl torsion. Despite this complexity, the computed spectra provide a satisfactory re-assignment of the experimental data. Reported trends in adenosyl-cobalamin spectra upon binding to the methylmalonyl CoA mutase enzyme, as well as on subsequent binding of substrates and inhibitors, provide support for an activation mechanism involving substrate-induced deformation of the adenosyl ligand. 相似文献
182.
183.
Joanna Iwaniec Tadeusz Uhl Wies?aw J. Staszewski Andrzej Klepka 《Nonlinear dynamics》2012,70(1):125-140
The paper investigates changes in determinism of undamaged and cracked aluminium plates with respect to excitation frequencies. Harmonic excitation of frequencies corresponding to structural resonances has been used to vibrate the plates. Vibration responses have been analysed using recurrence plots and recurrence quantification analysis. The smallest sufficient embedding dimension has been estimated using the false nearest neighbour??s algorithm. Mutual information analysis has been applied to determine the relevant time delays. The results demonstrate that performed analysis indicates changes in dynamic behaviour of the plates with respect to various excitation frequencies and crack modes. 相似文献
184.
Alim Mohammad A. Bak Tadeusz Atanacio Armand J. Ionescu Mihail Kennedy Brendan Price William S. Du Plessis Johan Pourmahdavi Maryam Zhou Meifang Torres Allan Nowotny Janusz 《Ionics》2017,23(12):3517-3531
Ionics - This work reports the effect of tantalum (0.1–1 at.% Ta) on the photocatalytic performance of TiO2 annealed at 1373 and 1673 K in air. It was shown that addition of... 相似文献
185.
Buszewski B Ligor T Jezierski T Wenda-Piesik A Walczak M Rudnicka J 《Analytical and bioanalytical chemistry》2012,404(1):141-146
In this work, a chromatographic method for identification of volatile organic compounds was compared with canine recognition. Gas chromatography and mass spectrometry (GC-TOF MS) were used for determination of concentrations of trace gases present in human breath. The technique enables rapid determination of compounds in human breath, at the parts per billion level. Linear correlations were from 0.83-234.05 ppb, the limit of detection was the range 0.31-0.75 ppb, and precision, expressed as relative standard deviation (RSD), was less than 10.00 %. Moreover, trained dogs are able to discriminate breath samples of patients with diagnosed cancer. We found a positive correlation between dog indications and the ethyl acetate and 2-pentanone content of breath (r = 0.85 and r = 0.97, respectively). The methods presented for detection of lung cancer markers in exhaled air could be used as a potential non-invasive tool for screening. In addition, the canine method is relatively simple and inexpensive in comparison with chromatography. 相似文献
186.
Tadeusz Jankowski 《Nonlinear Analysis: Theory, Methods & Applications》2012,75(2):913-923
We use a fixed point theorem due to Avery and Peterson to establish the existence of at least three non-negative solutions of some nonlocal boundary value problems to third order differential equations with advanced arguments. An example is given to illustrate the main results. 相似文献
187.
Barbara Szafranowska Katarzyna
lepokura Tadeusz Lis 《Acta Crystallographica. Section C, Structural Chemistry》2012,68(12):i71-i82
The synthesis and crystal structures of a series of six crystalline potassium salts of hypodiphosphoric acid, H4P2O6, are reported, namely potassium hydrogen phosphonophosphonate, K+·H3P2O6−, (I), dipotassium dihydrogen hypodiphosphate monohydrate, 2K+·H2P2O62−·H2O, (II), dipotassium dihydrogen hypodiphosphate dihydrate, 2K+·H2P2O62−·2H2O, (III), pentapotassium hydrogen hypodiphosphate dihydrogen hypodiphosphate dihydrate, 5K+·HP2O63−·H2P2O62−·2H2O, (IV), tripotassium hydrogen hypodiphosphate tetrahydrate, 3K+·HP2O63−·4H2O, (V), and tetrapotassium hypodiphosphate tetrahydrate, 4K+·P2O64−·4H2O, (VI). All the hypodiphosphate anions, viz. H3P2O6−, H2P2O62−, HP2O63− and P2O64−, adopt a staggered conformation. The P—P bond lengths [2.1722 (7)–2.1892 (10) Å] do not depend on the basicity of the anion. The compounds are organized into different types of one‐, two‐ or three‐dimensional polymeric hydrogen‐bonded networks, or simply exist in the form of isolated or dimeric units. The coordination numbers of the K+ cations range from 6 to 9, and the cationic sublattices are polymeric one‐, two‐ or three‐dimensional networks, or isolated [KO6] or dimeric [K2O12] polyhedra. 相似文献
188.
Tadeusz Micha?owski Agustin G. Asuero Maja Ponikvar-Svet Marcin Toporek Andrzej Pietrzyk Maciej Rymanowski 《Journal of solution chemistry》2012,41(7):1224-1239
The paper compares two approaches to the simulated argentometric titration of cyanide with the use of the modified Liebig?CDenigès (L-D) method, carried out according to GATES and applied with (1) classical and (2) pH-static titrations. Both approaches are discussed thoroughly and the results obtained from calculations are presented graphically. The calculations are performed with the use of an iterative computer program, based on charge and concentration balances and expressions for equilibrium constants, providing all physicochemical knowledge of the dynamic system in question. This way, physicochemical knowledge on complex electrolytic systems can be gained during the analytical procedure, i.e., the physicochemical and analytical knowledge are interrelated. The simulations follow the analytical procedures applied in experimental titrations and so provide an example of searching for the best a priori conditions for the quantitative analysis of cyanide. The computer program for pH-static titrations (described in this paper) enables one to carry out the simulation procedures with different preliminary data (concentrations, volumes). 相似文献
189.
Tadeusz Kosztołowicz Katarzyna D. Lewandowska 《Central European Journal of Physics》2012,10(3):645-651
We consider here two different models describing subdiffusion. One of them is derived from Continuous Time Random Walk formalism
and utilizes a subdiffusion equation with a fractional time derivative. The second model is based on Sharma-Mittal nonadditive
entropy formalism where the subdiffusive process is described by a nonlinear equation with ordinary derivatives. Using these
two models we describe the process of a substance released from a thick membrane and we find functions which determine the
time evolution of the amount of substance remaining inside this membrane. We then find ‘the agreement conditions’ under which
these two models provide the same relation defining subdiffusion and give the same function characterizing the process of
the released substance. These agreement conditions enable us to determine the relation between the parameters occuring in
both models. 相似文献
190.