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1.
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3.
We generalize a variational principle for the mean spherical approximation for a system of charged hard spheres in 3D to arbitrary
dimensions. We first construct a free energy variational trial function from the Debye-Hückel excess charging internal energy
at a finite concentration and an entropy obtained at the zero-concentration limit by thermodynamic integration. In three dimensions
the minimization of this expression with respect to the screening parameter leads to the mean spherical approximation, usually
obtained by solution of the Ornstein-Zernike equation. This procedure, which interpolates naturally between the zero concentration/coupling
limit and the high-concentration/ coupling limit, is extended to arbitrary dimensions. We conjecture that this result is also
equivalent to the MSA as originally defined, although a technical proof of this point is left for the future. The Onsager
limitT ΔS
MSA
/ΔE
MSA
→ 0 for infinite concentration/coupling is satisfied for all d ≠ 2, while ford=2 this limit is 1.
On leave from Department of Physics, University of Puerto Rico, Mayagüez Campus, Mayagüez, Puerto Rico, 00681. 相似文献
4.
Directed Feynman paths in 1 + 1 dimensions that acquire random phases are examined numerically and analytically. This problem is relevant for the behavior of the conductance in two-dimensional amorphous insulators in the variable-range-hopping regime. Large-scale numerical simulations were performed on a model with short-range correlations. For the scaling of the transverse fluctuations ( tν), we obtain ν = 0.68 ± 0.025; and for the r.m.s free-energy fluctuations ( tω), we obtain ω = 0.335 ± 0.01. Up to 100 000 random samples were used for times as large as 2000. These results seem to exclude a recent conjecture that ν = 3/4 and ω = 1/2. Two versions of a model with long-range correlations are solved and shown to yield ν = 1/2; a physical explanation is given. 相似文献
5.
A. Weisz E. Iberkleid A. Mandelbaum W. Blum W. J. Richter 《Journal of mass spectrometry : JMS》1987,22(1):3-5
Low energy CID mass spectra of m/z 173, C8H13O4+, obtained from the diethyl ester of cis,syn,cis-l,2,3,3a,4,5,5a,6,7,8-decahydroindacene-4,5-dicarboxylic acid and cis,syn,cis-l,2,3,4,5,6,7,8,8a,9,10,10a-dodecahydrophenanthrene-9,10-dicarboxylic acid indicate they have the structure of protonated diethyl maleate. This finding together with previous deuterium labelling results suggest that the formation of this ion from both precursors takes place by migration of a hydrogen atom from an allylic δ-position followed by the concerted cleavage of two allylic C? C bonds in analogy to the ground state retro-Diels–Alder fragmentation. 相似文献
6.
A. Dellen R. -P. Nordbeck K. Blum 《Zeitschrift für Physik D Atoms, Molecules and Clusters》1994,30(2):169-172
Rotationally resolved excitation of the a1Δg and b1∑ g + states of O2 is considered. Results for the relevant state multipoles are given. The anisotropy produced by electron impact is visualised by figures of the angular distribution of the molecular axes in the excited states. 相似文献
7.
We extend our sol-gel methodology of one-pot sequences of reactions with opposing reagents to an enzyme/metal-complex pair. Sol-gel entrapped lipase and sol-gel entrapped RhCl[P(C(6)H(5))(3)](3) or Rh(2)Co(2)(CO)(12) were used for one-pot esterification and C-C double bond hydrogenation reactions, leading to saturated esters in good yields. When only the enzyme is entrapped, the homogeneous catalysts quench its activity and poison it. Thus, when 10-undecenoic acid and 1-pentanol were subjected in one pot to the entrapped lipase and to homogeneously dissolved RhCl[P(C(6)H(5))(3)](3) under hydrogen pressure, only 7% of the saturated 1-pentyl undecanoate was obtained. The yield jumped 6.5-fold when both the enzyme and the catalyst were immobilized separately in silica sol-gel matrixes. Similar one-pot esterifications and hydrogenations by sol-gel entrapped lipase and heterogenized rhodium complexes were carried out successfully with the saturated nonoic, undecanoic, and lauric acids together with several saturated and unsaturated alcohols. The use of (S)-(-)-2-methylbutanol afforded an optically pure ester. The heterogenized lipase is capable of inducing asymmetry during esterification with a prochiral alcohol. Both the entrapped lipase and the immobilized rhodium catalysts can be recovered simply by filtration and recycled in further runs without loss of catalytic activity. 相似文献
8.
Garraffo HM Spande TF Jain P Kaneko T Jones TH Blum MS Ali TM Snelling RR Isbell LA Robertson HG Daly JW 《Rapid communications in mass spectrometry : RCM》2001,15(16):1409-1415
Chemical ionization tandem mass spectrometry (CI-MS/MS) of alkaloids with ammonia reagent gas and collision-activated dissociation as well as EI-MS/MS were applied to the tetraponerine alkaloids in extracts from six pseudomyrmecine ants of the genus Tetraponera. The MS/MS techniques along with gas chromatography Fourier transform infrared (GC/FTIR) spectra allowed identification in two extracts of seven of the eight known tetraponerines. The EI-MS/MS fragmentations proved diagnostic for the ring system and the CI-MS/MS patterns for the C-8 or C-9 substitution, while the Bohlmann bands in FTIR spectra were diagnostic for the C-8 or C-9 configurations. An Indian ant (T. allaborans) had T-2, T-4 and T-8, while a Chinese ant (T. binghami) had T-5, T-6, T-7 and T-8. Four other ants, T. rufonigra (India), T. penzigi (Africa), T. clypeata (Africa) and T. sp. cf. emeryi (Africa), had no tetraponerines. 相似文献
9.
The preparation of 3b,4a,7b,8a-tetrahydro-4H,8H-pyreno[4,5-b:9,10-b']bisazirine and of 1a,6b,7a,12b-tetrahydro-1H,7H-dibenz[3,4:7,8]anthra[1,2-b:5,6-b']bisazirine is described. The corresponding diepoxides were reacted with sodium azide in aqueous acetone and the mixtures of trans-azido alcohols, so formed, were cyclized by tri-n-butylphosphine. 相似文献
10.
This review presents the recent advances in the achievement of organized proteo-lipidic nanostructures based on Langmuir-Blodgett technology and their potential applications in the nanobioscience area. By using the self-assembled properties of amphiphilic biomolecules at the air-water interface, the Langmuir-Blodgett (LB) technique offers the possibility to prepare ultrathin layers suitable for biomolecule immobilization at the molecular level. This review will provide a general overview of the enzyme association with preformed Langmuir-Blodgett films in connection with their potential applications in biosensing device developments, and then introduce the design of a new functionalised biomimetic nanostructure with oriented recognition site. The potential applications of such an organized proteo-lipidic nanostructure for biocatalysis investigations of an immobilised enzyme in a biomimetic situation and for the development of bioelectronic devices are finally discussed. 相似文献