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501.
Dariusz Dereniowski 《Discrete Applied Mathematics》2006,154(8):1198-1209
In this paper we consider the edge ranking problem of weighted trees. We prove that a special instance of this problem, namely edge ranking of multitrees is NP-hard already for multitrees with diameter at most 10. Note that the same problem but for trees is linearly solvable. We give an O(logn)-approximation polynomial time algorithm for edge ranking of weighted trees. 相似文献
502.
Thierry Girasole Grard Gouesbet Grard Grhan Jean Noël Le Toulouzan Janusz Mroczka Kuan F. Ren Dariusz Wysoczanski 《Particle & Particle Systems Characterization》1997,14(5):211-218
An experimental set-up has been designed to record maps of intensity distribution for two orthogonal polarizations allowing the retrieval of average information along the optical path. A wide variety of the signatures of different samples is given to characterize the spatial orientation of a cloud of infinite cylinders by using a light scattering method. The information contained in the images is discussed and compared with numerical predictions. 相似文献
503.
Marek Milewski Justyna Baksalary Paweł Antkowiak Włodzimierz Augustyniak Michał Binkowski Jerzy Karolczak Dariusz Komar Andrzej Maciejewski Marian Szymański Wojciech Urjasz 《Journal of fluorescence》2000,10(2):89-89
Spectral and photochemical properties of three aromatic thioketones, 4H-1-benzopyran-4-thione and its two alkyl derivatives, in their second excited singlet and two lowest triplet states have been a subject of stationary and time-resolved studies. Quantum yields of emissions from the above-mentioned states as well as lifetimes of these states have been measured. The results indicate an important role of intermolecular solvent-induced processes in deactivation of the excited states of the thioketones studied. The possible mechanism of these processes involves hydrogen atom abstraction and/or formation of exciplex. For relatively high thione concentrations, the contribution of self-quenching in deactivation of the triplet states becomes significant. The effect of the alkyl chain in a thione molecule on deactivation parameters is discussed. 相似文献
504.
Miosz Frydrych Daria Pakua Bogna Sztorch Dariusz Brzkalski Robert E. Przekop Bogdan Marciniec 《Molecules (Basel, Switzerland)》2021,26(14)
The functionalization of mono- and octahydrospherosilicate with vinylboranes and allylboranes via hydrosilylation reaction in the presence of a Karstedt’s platinum (0) catalyst is presented. This is the catalytic route to obtain a new class of silsesquioxanes containing boron atoms in their structure in high yields (>90%) and with satisfactory selectivity. The obtained compounds were fully characterized by spectroscopic (1H, 13C, 29Si NMR) and spectrometric methods (MALDI-TOF-MS), as well as thermal analysis (TGA). The obtained compounds were subjected to thermal tests, characterizing the processes of melting, thermal evaporation, sublimation and thermal decomposition. 相似文献
505.
506.
Complexation of iron(III) with the heterodonor chelating agent 3,5-di-tert-butylsalicylidene benzoylhydrazine, H2(3,5-tBu2)salbh, in the absence or presence of a base affords the complex cation [Fe{H(3,5-tBu2)salbh}2]+ or the neutral compound [Fe{H(3,5-tBu2)salbh}{(3,5-tBu2)salbh}], respectively, as revealed by single-crystal X-ray analyses. Such a synthetic and crystallographic demonstration of the coordination versatility of an aroylhydrazone toward iron is uncommon. The oxidation and spin states of the iron have been verified with magnetic and spectroscopic measurements. 相似文献
507.
Photoinduced dissociation of two Mo-CN bonds in [Mo(CN)8]4- affords the octahedral complex anion [Mo(CN)6]2-. This hexacyanomolybdate(IV) ion is also obtainable from tetracyanooxomolybdate via a thermal substitutional synthetic route. The anion represents the missing link in the ligand-field photolysis of octacyanomolybdate(IV); it is characterized by means of single-crystal X-ray diffraction, thermogravimetric analysis, and magnetic susceptibility measurements as well as IR, Raman, 1H and 13C NMR, and electronic spectroscopy. 相似文献
508.
Explicitly correlated Gaussian functions have been used to perform very accurate variational calculations for the ground states of (7)Li and (7)Li(-). The nuclear motion has been explicitly included in the calculations (i.e., they have been done without assuming the Born-Oppenheimer (BO) approximation). An approach based on the analytical energy gradient calculated with respect to the Gaussian exponential parameters was employed. This led to a noticeable improvement of the previously determined variational upper bound to the nonrelativistic energy of Li(-). The Li energy obtained in the calculations matches those of the most accurate results obtained with Hylleraas functions. The finite-mass (non-BO) wave functions were used to calculate the alpha(2) relativistic corrections (alpha=1c). With those corrections and the alpha(3) and alpha(4) corrections taken from Pachucki and Komasa [J. Chem. Phys. 125, 204304 (2006)], the electron affinity (EA) of (7)Li was determined. It agrees very well with the most recent experimental EA. 相似文献
509.
Kowalczyk J Barski P Witt D Grzybowski BA 《Langmuir : the ACS journal of surfaces and colloids》2007,23(5):2318-2321
Various types of asymmetric disulfides can be synthesized under mild conditions and in excellent yields by a method involving dialkoxylthiophosphoranesulfenyl halide precursors. This straightforward, rapid procedure is used to prepare a series of disulfides bearing neutral, acidic, and basic terminal groups as well as groups commonly used in biospecific self-assembled monolayers. 相似文献
510.
Ma YC Wang XQ Hou FF Ma J Luo M Lu S Jin P Terevsky N Chen A Xu I Pate AV Gorecki D 《Natural product communications》2011,6(5):645-650
A simple, sensitive and reliable reversed phase Rapid Resolution Liquid Chromatography (RRLC) method was developed and validated for six biologically active compounds (salidroside, tyrosol, rosarin, rosavin, rosin and rosiridin) in Rhodiola rosea L. roots and powder extracts. The method uses a Phenomenex C18 (2)-HST column at 40 degrees C with a neutral gradient system mobile phase (H20 and acetonitrile), a flow rate of 1.0 mL/min, and UV detection wavelengths set at 205 and 254 nm, simultaneously. Baseline separation of the six active compounds was achieved within 8 minutes. The average percentages of rosavins (rosarin, rosavin, and rosin) in authentic R. rosea roots and root powder extracts were quantitatively determined and a characteristic R. rosea roots RRLC profile was established. The RRLC method is accurate and sensitive; in addition, it effectively increases the sample analysis throughput compared with conventional HPLC. 相似文献