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排序方式: 共有593条查询结果,搜索用时 15 毫秒
91.
Diev VV Stetsenko ON Tung TQ Kopf J Kostikov RR Molchanov AP 《The Journal of organic chemistry》2008,73(6):2396-2399
1,3-Dipolar cycloaddition of C-aryl,N-aryl (or N-methyl) nitrones with a number of 1,2-diphenylcyclopropenes substituted at the C(3) position occurs with the formation of expected "normal" cycloadducts (with N-methylnitrones) and products of their subsequent transformations. Among them are corresponding alpha-acetophenyl aziridines and tetra (or penta) -arylpyrroles. Aziridines and the normal cycloadducts can be also thermally converted to such arylpyrroles with moderate to good yields. Substitution at the C(3( position of cyclopropenes by an electron acceptor group decreases the reactivity of cyclopropenes. 相似文献
92.
Aydin Aytuna Vyacheslav Zakharyuta 《Proceedings of the American Mathematical Society》2008,136(5):1733-1742
The main theorem of this note is the following refinement of the well-known Lelong-Bremermann Lemma: converges to uniformly on each compact subset of .
Let be a continuous plurisubharmonic function on a Stein manifold of dimension Then there exists an integer , natural numbers , and analytic mappings such that the sequence of functions
In the case when is a domain in the complex plane, it is shown that one can take in the theorem above (Section 3); on the other hand, for -circular plurisubharmonic functions in the statement of this theorem is true with (Section 4). The last section contains some remarks and open questions.
93.
David G. Kwabi Vyacheslav S. Bryantsev Thomas P. Batcho Daniil M. Itkis Carl V. Thompson Yang Shao‐Horn 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2016,128(9):3181-3186
Understanding and controlling the kinetics of O2 reduction in the presence of Li+‐containing aprotic solvents, to either Li+‐O2− by one‐electron reduction or Li2O2 by two‐electron reduction, is instrumental to enhance the discharge voltage and capacity of aprotic Li‐O2 batteries. Standard potentials of O2/Li+‐O2− and O2/O2− were experimentally measured and computed using a mixed cluster‐continuum model of ion solvation. Increasing combined solvation of Li+ and O2− was found to lower the coupling of Li+‐O2− and the difference between O2/Li+‐O2− and O2/O2− potentials. The solvation energy of Li+ trended with donor number (DN), and varied greater than that of O2− ions, which correlated with acceptor number (AN), explaining a previously reported correlation between Li+‐O2− solubility and DN. These results highlight the importance of the interplay between ion–solvent and ion–ion interactions for manipulating the energetics of intermediate species produced in aprotic metal–oxygen batteries. 相似文献
94.
Reversed‐phase ion‐pair high‐performance liquid chromatography assay of polyprenyl diphosphate oligomer homologues
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A reversed‐phase ion‐pair high‐performance liquid chromatography procedure was developed for the separation of polyprenyl diphosphate oligomer homologues obtained chemically from plant polyprenols. Tetrabutylammonium phosphate was used as the ion‐pair reagent, and the dependence of the separation quality on pH of ion‐pair reagent was investigated for the first time. The procedure is applicable for the control of commercial available polyprenyl monophosphates (the active components of veterinary drugs Phosprenyl and Gamapren) for the possible presence of polyprenyl diphosphate byproducts. 相似文献
95.
Igor V. Ukrainets Svitlana V. Shishkina Vyacheslav N. Baumer Olga V. Gorokhova Lidiya A. Petrushova Galina Sim 《Acta Crystallographica. Section C, Structural Chemistry》2016,72(5):411-415
The fact that molecular crystals exist as different polymorphic modifications and the identification of as many polymorphs as possible are important considerations for the pharmaceutic industry. The molecule of N‐benzyl‐4‐hydroxy‐1‐methyl‐2,2‐dioxo‐1H‐2λ6,1‐benzothiazine‐3‐carboxamide, C17H16N2O4S, does not contain a stereogenic atom, but intramolecular hydrogen‐bonding interactions engender enantiomeric chiral conformations as a labile racemic mixture. The title compound crystallized in a solvent‐dependent single chiral conformation within one of two conformationally polymorphic P212121 orthorhombic chiral crystals (denoted forms A and B). Each of these pseudo‐enantiomorphic crystals contains one of two pseudo‐enantiomeric diastereomers. Form A was obtained from methylene chloride and form B can be crystallized from N,N‐dimethylformamide, ethanol, ethyl acetate or xylene. Pharmacological studies with solid–particulate suspensions have shown that crystalline form A exhibits an almost fourfold higher antinociceptive activity compared to form B. 相似文献
96.
Khozikov V Kosobokova O Citver G Tyshko G Gavrilov DN Gudkov G Gorfinkel V 《Electrophoresis》2007,28(3):317-321
A novel, nondamaging method for experimental characterization of the formation and propagation of high-resistivity zones in CE, based on the measurement of time-dependent Joule heating on the outer capillary surface is proposed. The method detects propagation of resistive regions in capillaries in real time and allows the estimation of their velocity and resistance. The presented experimental data are in agreement with the results of the computer simulation as well as with previous data on the subject. The proposed method is useful for the development of new polymers as well as for the refinement and optimization of new CE protocols. 相似文献
97.
Let V be a vector space over a field or skew field F, and let U be its subspace. We study the canonical form problem for bilinear or sesquilinear forms
98.
Vyacheslav S. Rychkov 《Mathematische Nachrichten》2001,224(1):145-180
Characterizations via convolutions with smooth compactly supported kernels and other distinguished properties of the weighted Besov–Lipschitz and Triebel–Lizorkin spaces on ℝn with weights that are locally in Ap but may grow or decrease exponentially at infinity are investigated. Square–function characterizations of the weighted Lp and Hardy spaces with the above class of weights are also obtained. A certain local variant of the Calderón reproducing formula is constructed and widely used in the proofs. 相似文献
99.
100.
Dmytro Iurashev Giovanni Campa Vyacheslav V. Anisimov Ezio Cosatto 《Combustion Theory and Modelling》2017,21(6):1148-1175
Currently, gas turbine manufacturers frequently face the problem of strong acoustic combustion driven oscillations inside combustion chambers. These combustion instabilities can cause extensive wear and sometimes even catastrophic damages to combustion hardware. This requires prevention of combustion instabilities, which, in turn, requires reliable and fast predictive tools. This work presents a three-step method to find stability margins within which gas turbines can be operated without going into self-excited pressure oscillations. As a first step, a set of unsteady Reynolds-averaged Navier–Stokes simulations with the Flame Speed Closure (FSC) model implemented in the OpenFOAM® environment are performed to obtain the flame describing function of the combustor set-up. The standard FSC model is extended in this work to take into account the combined effect of strain and heat losses on the flame. As a second step, a linear three-time-lag-distributed model for a perfectly premixed swirl-stabilized flame is extended to the nonlinear regime. The factors causing changes in the model parameters when applying high-amplitude velocity perturbations are analysed. As a third step, time-domain simulations employing a low-order network model implemented in Simulink® are performed. In this work, the proposed method is applied to a laboratory test rig. The proposed method permits not only the unsteady frequencies of acoustic oscillations to be computed, but the amplitudes of such oscillations as well. Knowing the amplitudes of unstable pressure oscillations, it is possible to determine how these oscillations are harmful to the combustor equipment. The proposed method has a low cost because it does not require any license for computational fluid dynamics software. 相似文献