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11.
Dr. Igor L. Dalinger Dr. Irina A. Vatsadze Dr. Tatyana K. Shkineva Dr. Alexandr V. Kormanov Dr. Marina I. Struchkova Dr. Kyrill Yu. Suponitsky Dr. Anatoly A. Bragin Dr. Konstantin A. Monogarov Dr. Valery P. Sinditskii Dr. Aleksei B. Sheremetev 《化学:亚洲杂志》2015,10(9):1987-1996
A new family of energetic compounds, nitropyrazoles bearing a trinitromethyl moiety at the nitrogen atom of the heterocycle, was designed. The desirable high‐energy dense oxidizers 3,4‐dinitro‐ and 3,5‐dinitro‐1‐(trinitromethyl)pyrazoles were synthesized in good yields by destructive nitration of the corresponding 1‐acetonylpyrazoles. All of the prepared compounds were fully characterized by multinuclear NMR and IR spectroscopy, as well as by elemental analysis. Single‐crystal X‐ray diffraction studies show remarkably high density. Impact sensitivity tests and thermal stability measurements were also performed. All of the pyrazoles possess positive calculated heats of formation and exhibit promising energetic performance that is the range of 1,3,5‐trinitroperhydro‐1,3,5‐triazine and pentaerythritol tetranitrate. The new pyrazoles exhibit positive oxygen balance and are promising candidates for new environmentally benign energetic materials. 相似文献
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13.
Alexandr V. Kostochka 《Combinatorica》2002,22(2):275-285
Dedicated to the memory of Paul Erdős
Let f(r,p,t) (p > t >= 1, r >= 2) be the maximum of the cardinality of a minimum transversal over all r-uniform hypergraphs possessing the property that every subhypergraph of with p edges has a transversal of size t. The values of f(r,p,2) for p = 3, 4, 5, 6 were found in [1] and bounds on f(r,7,2) are given in [3]. Here we prove that for large p and huge r.
Received September 23, 1999
RID="*"
ID="*" This work was partially supported by the grant 99-01-00581 of the Russian Foundation for Fundamental Research and the
Dutch–Russian Grant NWO-047-008-006. 相似文献
14.
15.
Igor Dubenko Tapas Samanta Arjun Kumar Pathak Alexandr Kazakov Valerii Prudnikov Shane Stadler Alexander Granovsky Arcady Zhukov Naushad Ali 《Journal of magnetism and magnetic materials》2012
The studies of magnetocaloric properties, phase transitions, and phenomena related to magnetic heterogeneity in the vicinity of the martensitic transition (MT) in Ni–Mn–In and Ni–Mn–Ga off-stoichiometric Heusler alloys are summarized. The crystal structure, magnetocaloric effect (MCE), and magnetotransport properties were studied for the following alloys: Ni50Mn50−xInx, Ni50−xCoxMn35In15, Ni50Mn35−xCoxIn15, Ni50Mn35In14Z (Z=Al, Ge), Ni50Mn35In15−xSix, Ni50−xCoxMn25+yGa25−y, and Ni50–xCoxMn32−yFeyGa18. It was found that the magnetic entropy change, ΔS, associated with the inverse MCE in the vicinity of the temperature of the magneto-structural transition, TM, persists in a range of (125-5) J/(kg K) for a magnetic field change ΔH=5 T. The corresponding temperature varies with composition from 143 to 400 K. The MT in Ni50Mn50−xInx (x=13.5) results in a transition between two paramagnetic states. Associated with the paramagnetic austenite-paramagnetic martensite transition ΔS=24 J/(kg K) was detected for ΔH=5 T at T=350 K. The variation in composition of Ni2MnGa can drastically change the magnetic state of the martensitic phase below and in the vicinity of TM. The presence of the martensitic phase with magnetic moment much smaller than that in the austenitic phase above TM leads to the large inverse MCE in the Ni42Co8Mn32−yFeyGa18 system. The adiabatic change of temperature (ΔTad) in the vicinity of TC and TM of Ni50Mn35In15 and Ni50Mn35In14Z (Z=Al, Ge) was found to be ΔTad=−2 K and 2 K for ΔH=1.8 T, respectively. It was observed that |ΔTad|≈1 K for ΔH=1 T for both types of transitions. The results on resistivity, magnetoresistance, Hall resistivity in some In-based alloys are discussed. 相似文献
16.
Fredholm boundary value problems for perturbed systems of dynamic equations on time scales 下载免费PDF全文
Ravi P. Agarwal Martin Bohner Alexandr Boı̆chuk Olexandr Strakh 《Mathematical Methods in the Applied Sciences》2015,38(17):4178-4186
This paper offers conditions ensuring the existence of solutions of linear boundary value problems for systems of dynamic equations on time scales. Utilizing a method of Moore–Penrose pseudo‐inverse matrices leads to an analytical form of a criterion for the existence of solutions in a relevant space and, moreover, to the construction of a family of linearly independent solutions of such problems in a general case with the number of boundary conditions (defined by a linear vector functional) not coinciding with the number of unknowns of a system of dynamic equations. As an example of an application of the presented results, the problem of bifurcation of solutions of boundary value problems for systems of dynamic equations on time scales with a small parameter is considered. 相似文献
17.
Nikolay L. Eremeev Alexandr V. Kukhtin Eugenia A. Belyaeva Novella F. Kazanskaya 《Applied biochemistry and biotechnology》1999,76(1):45-55
Temperature dependencies of kinetic and equilibrium parameters of urea hydrolysis catalyzed by native urease and the urease
immobilized in a thermosensitive poly-N-isopropylacrylamide gel have been studied. The swelling ratio of the collapsed urease-containing
gel is shown to increase in the presence of urea. Below a lower critical solution temperature (LCST) of the polymer, the immobilized
u reaseactually has thesame catalytic properties as the native enzyme. At temperatures above LCST, the observed catalytic
activity of the immobilized enzyme depends chiefly not only on the thermoreversible matrix state, but also on gel water content. 相似文献
18.
Alexandr V. Yatsenko Ksenia A. Paseshnichenko 《Acta Crystallographica. Section C, Structural Chemistry》2001,57(8):961-964
The crystal structures of the brown–yellow and orange polymorphs of the title compound, 4‐[(2‐nitrophenyl)diazenyl]phenol, C12H9N3O3, have been determined and their visible reflection spectra recorded. Both structures adopt a stacking arrangement with interstack hydrogen bonds. Ab initio and semi‐empirical (AM1 and INDO‐CISD) calculations were performed in order to rationalize the difference in colour. It can be attributed neither to the subtle distinctions in molecular geometry nor to the effect of intermolecular electrostatic interactions. The most probable origin of this difference is the mixing of intramolecular n π* and intermolecular charge‐transfer excitations. 相似文献
19.
Yichen Wu Sbastien Bouvet Susana Izquierdo Alexandr Shafir 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(9):2643-2647
Among halogenated aromatics, iodoarenes are unique in their ability to produce the bench‐stable halogen(III) form. Earlier, such iodine(III) centers were shown to enable C?H functionalization ortho to iodine via halogen‐centered rearrangement. The broader implications of this phenomenon are explored by testing the extent of an unusual iodane‐directed para C?H benzylation, as well as by developing an efficient C?H coupling with sulfonyl‐substituted allylic silanes. Through the combination of the one‐shot nature of the coupling event and the iodine retention, multisubstituted arenes can be prepared by sequentially engaging up to three aromatic C?H sites. This type of iodine‐based iterative synthesis will serve as a tool for the formation of value‐added aromatic cores. 相似文献
20.
Angel A. J. Torriero Stephen W. Feldberg Jie Zhang Alexandr N. Simonov Alan M. Bond 《Journal of Solid State Electrochemistry》2013,17(12):3021-3026
The potential of a quasi-reference electrode can be determined by introducing an internal reference redox system (IRRS) which comprises either the oxidizable or reducible form of a reversible (and, ideally, outer-sphere) redox couple and then observing the cyclic voltammetric responses. The objective is to choose the IRRS so that the cyclic voltammetric response for the simultaneously present electroactive analyte system (ANS) can be observed independently of the IRRS response. We identify three fundamental paradigms describing the relative positioning of the IRRS and ANS on the potential scale, the operative redox components for the IRRS and ANS, and the starting potential (E start), reversing potential (E rev), and ending potential (E end) for the cyclic voltammetric scan as follows: paradigm A, an optimal paradigm which can produce completely independent cyclic voltammetric responses for the IRRS or for ANS; paradigm B, a less-than-optimal paradigm which can produce an independent cyclic voltammetry (CV) response for the ANS or a mixed response for the IRRS with that response on top of the ANS response; paradigm C, a problematic paradigm that can produce an independent CV response for the IRRS or a mixed response for the ANS with that response on top of the IRRS response; and any mixed response produces a thermodynamically favored redox cross-reaction which couples the IRRS and ANS systems and which can complicate the analysis of the ANS and IRRS responses. The conclusion is that paradigm C is to be avoided. 相似文献