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91.
Jaroslav Milbauer 《Fresenius' Journal of Analytical Chemistry》1918,57(4):161-162
Ohne Zusammenfassung 相似文献
92.
This contribution is focused on an acceleration of branch and bound algorithms for the uncapacitated facility location problem. Our approach is based on the well-known Erlenkotters’ procedures and Körkels’ multi-ascent and multi-adjustment algorithms, which have proved to be the efficient tools for solving the large-sized instances of the uncapacitated facility location problem. These two original approaches were examined and a thorough analysis of their performance revealed how each particular procedure contributes to the computational time of the whole algorithms. These analyses helped us to focus our effort on the most frequent procedures. The unique contribution of this paper is a new dual ascent procedure. This procedure leads to considerable acceleration of the lower bound computation process and reduces the resulting computational time. To demonstrate more efficient performance of amended algorithms we present the results of extensive numerical experiments. 相似文献
93.
94.
Pradeep K. Jaiswal Vashundhra Sharma Jaroslav Prikhodko Irina V. Mashevskaya Sandeep Chaudhary 《Tetrahedron letters》2017,58(22):2077-2083
For the first time, an efficient, simple, synthetic green protocol for the one-pot synthesis of functionalized 2-oxo-benzo[1,4]oxazines 24–29 in water under ultrasound irradiation is presented. As compared to conventional methods, the present protocol avoids traditional chromatography and purification steps and furnished the target molecules in excellent yields (upto 98%) with no side products. The methodology was also demonstrated on gram scale synthesis. Moreover, functionalized 2-oxo-quinoxaline analogues 31–33, another class of bio-active heterocyclic scaffolds, were also prepared using this method. For the first time, this protocol was successfully applied in the synthesis of the anticancer indole alkaloid, Cephalandole A 35. 相似文献
95.
Jaroslav Menčík 《Meccanica》2007,42(1):19-29
The paper reviews the current state of the depth-sensing indentation (sometimes called nanoindentation), where the information
on material behaviour and properties is obtained from the indenter load and depth, measured continuously during loading and
unloading. It is shown how the contact parameters and principal characteristics are determined using pointed or spherical
indenters. Indentation tests can be used for the measurement of hardness and elastic modulus, and also of the yield stress
and for the construction of stress–strain diagrams, for the determination of the work of indentation and its components. Most
devices use monotonic loading and unloading, but some also enable measurement under a small harmonic signal added to the basic
monotonously increasing load. This makes possible continuous measurement of contact stiffness and the study of dynamic properties
and the determination of properties of coatings. One section is devoted to the measurement on viscoelastic-plastic materials,
where the delayed deforming must be considered during the measurement as well as in data evaluation. Instrumented indentation
can also be used for the study of creep under high temperatures. The paper also discusses the errors arising in depth-sensing
measurements and informs briefly about some other possibilities of the method. 相似文献
96.
Marc Ostermeier Dipl.‐Chem. Marie‐Anne Berlin Dipl.‐Chem. Robert M. Meudtner Dr. Serhiy Demeshko Dr. Franc Meyer Prof. Dr. Christian Limberg Prof. Dr. Stefan Hecht Prof. Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(33):10202-10213
2,6‐Bis(1,2,3‐triazol‐4‐yl)pyridine (btp) ligands with substitution patterns ranging from strongly electron‐donating to strongly electron‐accepting groups, readily prepared by means of Cu‐catalyzed 1,3‐dipolar cycloaddition (the “click” reaction), were investigated with regard to their complexation behavior, and the properties of the resulting transition‐metal compounds were compared. Metal–btp complexes of 1:1 stoichiometry, that is, [Ru(btp)Cl2(dmso)] and [Zn(btp)Br2], could be isolated and were crystallographically characterized: they display octahedral and trigonal‐bipyramidal coordination geometries, respectively, and exhibit high aggregation tendencies due to efficient π–π stacking leading to low solubilities. Metal–btp complexes of 1:2 stoichiometry, that is, [Fe(btp)2]2+ and [Ru(btp)2]2+, could also be synthesized and their metal centers show the expected octahedral coordination spheres. The iron compounds exhibit quite a complex magnetic behavior in the solid state including spin crossover near room temperature, and hysteresis and locking into high‐spin states on tempering at 400 K, depending on the substituents on the btp ligands. Cyclic voltammetry studies of [Ru(btp)2]2+ reveal strong modulation of the oxidation potentials by more than 0.6 V and a clear linear correlation to the Hammett constant (σpara) of the substituent at the pyridine core. Isothermal titration calorimetry was used to measure the thermodynamics of the FeII–btp complexation process and enabled accurate determination of the complexation enthalpies, which display a linear relationship with the σpara values for the terminal phenyl substituents. Detailed NMR spectroscopic studies finally revealed that in the case of FeII complexation, dynamics are rapid for all investigated btp derivatives in acetonitrile, while replacing FeII by RuII or changing the solvent to dichloromethane effectively slows down ligand exchange. The results nicely demonstrate the utility of substituent parameters, originally developed for linear free‐energy relationships to explain reactivity in organic reactions, in coordination chemistry, and to illustrate the potential to custom‐design btp ligands and complexes thereof with predictable properties. The fast equilibration of the [Fe(btp)2]2+ complexes together with their tunable stability and interesting magnetic properties should enable the design of dynamic metallosupramolecular materials with advantageous properties. 相似文献
97.
98.
Amadej Juranovi?Krištof Kranjc Franc PerdihSlovenko Polanc Marijan Ko?evar 《Tetrahedron》2011,67(19):3490-3500
A comparative study of the reaction pathway of the cycloaddition of various vinyl-containing dienophiles on a set of substituted 3-acylamino-2H-pyran-2-ones under microwave-assisted and high-pressure conditions is presented. In the course of the reaction both the intermediate products, i.e., the 2-oxabicyclo[2.2.2]oct-5-ene (the exo/endo selectivity depended upon the dienophile) and the alkoxycyclohexadiene systems, were isolated and comprehensively characterized; this included X-ray diffraction analyses. The role of the base (DABCO) as an organocatalyst was further elucidated. 相似文献
99.
100.
Černý Miroslav Šandera Pavel Pokluda Jaroslav 《Czechoslovak Journal of Physics》1999,49(10):1495-1501
Ab initio calculation of ideal strength of cubic crystals under three-axial tension was performed using the LMTO-ASA method. Computed values are in a good agreement with those obtained previously by means of semi-empirical polynomial approach. The values of equilibrium lattice parameter obtained in the framework of ab initio method are well comparable with the experimental data whereas a less satisfactory agreement was achieved in the case of bulk moduli. 相似文献