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91.
Körner A Larsson A Piculell L Wittgren B 《The journal of physical chemistry. B》2005,109(23):11530-11537
A systematic study of the dissolution of dry, polydisperse poly(ethylene oxide) (PEO) samples, obtained from mixtures of low-molecular-weight and high-molecular-weight PEO, was made. During the dissolution process, the individual release of the low- and high-molecular-weight fractions was monitored. The high-molecular-weight/low-molecular-weight ratio controls the release rate, and the fraction of high-molecular-weight polymers dominates the effect on the overall release rate in mixed PEO tablets. Both fractions are released at the same rate during the main part of the dissolution process; however, during the initial dissolution period a fractionation occurs. The release rate is not a unique function of the average molecular weight of the polymer, but also depends on the polydispersity. By contrast, the average dimension of a polymer coil, as given by the intrinsic viscosity, gives a good prediction of the release rate irrespective of the polydispersity or details of the molecular weight distribution. 相似文献
92.
Suseeladevi Asha Kunduchi Periya Vijayalakshmi Benny K. George 《International journal of quantum chemistry》2019,119(17):e25972
Electrochemical stability and noncovalent interactions escorting the cyclic ammonium-based ionic liquids composed of N-alkyl-substituted N-methyl pyrrolidinium (Pyr1R) (R = methyl, ethyl, propyl, butyl, pentyl, hexyl) cations and four anions hexafluorophosphate (PF6), tetrafluoroborate (BF4), bis(trifluoromethylsulfonyl-imide (TFSI), and trifluoromethane sulfonate (TFO) have been analyzed using the density functional theory. Electronic structures, electrochemical window, frontier orbital energy difference (HOMO-LUMO gap), binding energies, vibrational spectra of these ion pairs were characterized. It has been established that ion pair formation is largely reigned by C H⋯F interactions between anionic fluorine for BF4− and PF6− anions and C H⋯O interactions between anionic oxygen for TFSI and TFO anions and pyrrolidinic proton, methyl, or alkyl group protons of the cations. The effect of alkyl chain length and pairing anions of the alkyl substituted N-methyl pyrrolidinium-based ionic liquids on the electrochemical window was investigated. The results revealed that the HOMO energy of pairing anions is the key factor to decide the electrochemical window. Further quantification of noncovalent interactions in terms of electrostatic and hydrogen bonding interactions has been brought out employing a novel method with the aid of Mulliken and Merz-Singh-Kollman charges, prevailed in pyrrolidinium-based ionic liquids. 相似文献
93.
94.
The electron transfer process in bacterial reaction centers is investigated. It is found that the side indole group Trp M252
in Rb sphaeroides (Trp M250 in Rps viridis) assists tunneling electron transfer by a distance of ∼14Å from pheophytin to quinone.
Reported at the VIIIth International Conference on Spectroscopy of Porphyrins and Their Analogs, Minsk, September 22–26, 1998.
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 66, No. 4, pp. 496–500, July–August, 1999. 相似文献
95.
Sverker Fredriksson Magnus Jändel Tomas Larsson 《Zeitschrift fur Physik C Particles and Fields》1982,14(1):35-39
The bulk of data from deep inelasticep, eD, μp, μN, νp and νN scattering is fitted with a new diquark model of nucleons. The proton is found to be mostly in au(ud) 0 state, where the (ud)0 diquark has spin and isospin zero. There is hence no trace ofSU(6) symmetry among diquarks in nucleons. 相似文献
96.
J. H. Bowie P. Y. White J. C. Wilson F. C. V. Larsson S.-O. Lawesson J.
Madsen C. Nolde G. Schroll 《Journal of mass spectrometry : JMS》1977,12(4):191-195
+E spectra derived from the non-decomposing anion of some sulphur compounds are independent of the pressure of the collision gas. The compounds chosen for study contain peaks produced from either ortho effects or skeletal rearrangement fragments in their conventional positive ion spectra. The dissociative +E spectra are either devoid of skeletal rearangement ions or alternatiely contain such peaks in small abundance. In contrast, peaks derived from ortho reactions are present in high abundance. 相似文献
97.
Börje Folkesson Ragnar Larsson 《Journal of Electron Spectroscopy and Related Phenomena》1982,26(2):157-166
A series of simple thiocyanato complex ions have been investigated as their tetraphenylphosphonium and potassium salts. The binding energies of N, C and S were determined as well as those of the metals. From the first-mentioned data effective charge-values were estimated for the atoms of the ligands. For this purpose linear relations Eb = kq + Eb0 were used that had been previously established within a scheme having C1s (phenyl) as the internal standard.From the data thus obtained the effective charge on the metal atoms was estimated. For elements where we have sufficient data the same type of linear relation seems to he followed. Tentatively valid examples are Eb(Ni) = 6.74qNi + 848.3 eV and Eb(Pd) = 4.45qPd + 333.9 eV.In this interpretation the atoms of the metals are considered to be positively charged and surrounded by the negative charge of the electrons occupying the s band.It is further suggested for complexes with pronounced π backbonding (Pt(SCN)42?, Pd(SCN)42? and Hg(SCN)42?) that the C 1s binding energy measured for the carbon atom of the SCN? ligand is composed of the ionisation energy from the 1s level and an additional term corresponding to the intraligand π → π* transition. 相似文献
98.
99.
Benny Sudakov 《Combinatorica》2005,25(4):487-498
Let 3 ≤ r < s be fixed integers and let G be a graph on n vertices not containing a complete graph on s vertices. The main aim of this paper is to provide a new lower bound on the size of the maximum subset of G without a copy of complete graph Kr. Our results substantially improve previous bounds of Krivelevich and Bollobás and Hind.
* Research supported in part by NSF grants DMS-0106589, CCR-9987845 and by the State of New Jersey. Part of this research
was done while visiting Microsoft Research. 相似文献
100.
Susanne Flygare Mats-Olle M⇘nnsson Per-Olof Larsson Klaus Mosbach 《Applied biochemistry and biotechnology》1982,7(1-2):59-61
Lactate dehydrogenase has been purified by precipitation with a bis-ligand. The precipitating agent in this case was Bis-NAD. This approach of affinity precipitation is also applicable to other enzymes. 相似文献