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51.
Claude Balny Jennifer Canva Pierre Douzou Jean Bourdon 《Photochemistry and photobiology》1969,10(6):375-382
Abstract— Chemiluminescence and photochemiluminescence of systems generating excited (singlet) molecular oxygen has been studied at low temperature in fluid media. A possible interpretation is proposed: that dimers of singlet oxygen are directly or indirectly responsible for the observed emission, the species [1 δg +1 σg+ ] predominating. Energy transfer to a fluorescent molecule is possible only when conditions of spectral overlap, required for transfer by inductive resonance, are fulfilled. Evidence is also presented for the formation of a transient complex between oxygen and a sensitiser or acceptor molecule [S…O2 ], which is the precursor of singlet oxygen in these systems. However, other possible mechanisms cannot be excluded. 相似文献
52.
Pénicaud A Poulin P Derré A Anglaret E Petit P 《Journal of the American Chemical Society》2005,127(1):8-9
Upon reduction with alkali metals, single-wall carbon nanotubes (SWNTS) are shown to form polyelectrolyte salts that are soluble in polar organic solvents without any sonication, use of surfactants, or functionalization whatsoever, thus forming true thermodynamically stable solutions of naked SWNTs. 相似文献
53.
Stphane Chalais Andr Cornlis Andr Gerstmans Wacaw Koodziejski Pierre Laszlo Arthur Mathy Pierre Mtra 《Helvetica chimica acta》1985,68(5):1196-1203
Multiple chlorinations and arylations at the tertiary positions of adamantane are promoted by FeCl3-doped K10 montmorillonite in CCl4 or in aromatic solvents. The process, remarkably easy to implement, can be tailored to selective formation of monosubstituted 1-adamantyl derivatives or 1,3-disubstituted adamantanes. The process achieves alkylation at the meta- and para-positions of toluene leading to a purely statistical distribution and displays no substrate specificity in competition experiments between toluene and benzene. 相似文献
54.
Andrzej Małecki Jalees A.K. Tareen Jean Pierre Doumerc Louis Rabardel Jean Claude Launay 《Journal of solid state chemistry》1985,56(1):49-57
Kinetics of thermal decomposition in vacuum of Co3O4 powder as well as single crystals has been investigated. Discrepancies with the results of previous authors have been discussed. Decomposition of Co3O4 proceeds through formation of a compact layer of CoO and hence diffusion is the rate-limiting factor. The experimental curves α(t) be described for 0.05 < α < 0.85 using a modified Ginstling-Brounshtein equation: 1 ? 2α/3 ? (1 ? α)2/3 = ktn where the activation energy varies with the degree of decomposition. 相似文献
55.
Le Paih J Monnier F Dérien S Dixneuf PH Clot E Eisenstein O 《Journal of the American Chemical Society》2003,125(39):11964-11975
The reaction of a variety of alkynes RCtbd1;CH with a variety of carboxylic acids R(1)CO(2)H, in the presence of 5% of RuCl(COD)C(5)Me(5), selectively leads to the dienylesters (1E,3E)-RCH(1)=CH(2)-CH(3)=C(R)(O(2)CR(1)). The reaction also applies to amino acid and dicarboxylic acid derivatives. It is shown that the first step of the reaction consists of the head-to-head alkyne coupling and of the formation of the metallacyclic biscarbene-ruthenium complex isolated for R = Ph and catalyzing the formation of dienylester. D-labeled reactions show that the alkyne protons remain at the alkyne terminal carbon atoms and carboxylic acid protonates the C(1) carbon atom. QM/MM (ONIOM) calculations, supporting a mixed Fischer-Schrock-type biscarbene complex, show that protonation occurs preferentially at the carbene carbon C(1) adjacent to Ru, in the relative cis position with respect to the Ru-Cl bond, to give a mixed C(1)alkyl-C(4)carbene complex in which the C(4) carbene is conjugated with the noncoordinated C(2)=C(3) double bond. This 16-electron intermediate has a weak stabilizing alpha agostic C-H bond. This most stable isomer appears to have a C(4) center more accessible to the nucleophilic addition which accounts for the experimentally observed product. 相似文献
56.
A theoretical model of the evaporation of a pure liquid layer is developed. We focus on the influence of an inert gaseous component, in addition to vapor, on surface-tension-driven Bénard instabilities. It is assumed that the gas phase is perfectly mixed at some distance from the liquid-gas interface (given composition, pressure, and temperature). If this distance is not much larger than the liquid layer thickness, it is shown that a reduction of the full two-layer problem to a one-layer problem is possible, provided the evaporation rate is not too large. An analytical expression is given for the corresponding dimensionless heat transfer coefficient (a generalized, wavenumber-dependent Biot number) at the evaporating interface. The approach is validated through a comparison with a direct numerical resolution of the full two-layer problem. 相似文献
57.
Ichiya Ninomiya Toshiko Kiguchi Chiyomi Hashimoto Derek H.R. Barton Xavier Lusinchi Pierre Milliet 《Tetrahedron letters》1985,26(35):4183-4186
The addition of a sacrificial enamine (such as indole), or of a vinyl ether (like dihydropyran) to an indoline during dehydrogenation by phenylseleninic anhydride dramatically improves the yield of the corresponding indole. This is due to scavenging of Se11 phenylselenenating species. 相似文献
58.
Crystals of Li0.33 MoO3 (blue), Rb0.23MoO3 (blue) and Cs0.31MoO3 (red) were grown by electrolysis from MoO3M2MoO4 melts (M =alkali metal) with composition 70–77 mole% MoO3. Melts richer in M2MoO4 produced MoO2 only. Correlation is made between bronze formation and the coordination of Mo in the melt and in the equilibrium solid phase M2Mo4O13. Li0.33MoO3 and Cs0.31MoO3 are semiconductors with high-temperature-range activation energies 0.16 and 0.12 eV. Rb0.23MoO3 has an electrical behavior similar to that of blue KxMoO3 with a semiconductor-metal transition at (170 ± 5) K. ESR spectra observed in Li0.33MoO3 and Rb0.23MoO3 single crystals at 4.2 K show extensive delocalization of the 4d1 electron associated with Mo(V) centers. Attempts to grow molybdenum bronzes containing Ca or Y were unsuccessful. 相似文献
59.
The face selectivity (endo-face vs. exo-face attack onto the exocyclic s-cis-butadiene moiety) of the [4+2]cycloadditions of 5,6-bis((D)methylidene)-2-bicyclo-[2.2.2]octene ( 11 ) to strong dienophiles has been determined in benzene at 25°. It is ca. 95/5, 75/5, 70/30, 60/40 and 50/50 for N-phenyltriazolinedione (NPTAD), tetracyanoethylene (TCE), dimethyl acetylenedicarboxylate (DMAD), maleic anhydride (MA) and singlet oxygen (1O2), respectively. The endo-face preference is probably due to a participation of the homoconjugated double bond at C(2), C(3) which makes the etheno bridge more polarizable than the ethano bridge in 11. The absence of face selectivity with 1O2 is consistent with an entropy-controlled mechanism involving the intermediacy of an exciplex. 相似文献
60.
Annette Marchand Pierre Gerval Françoise Duboudin M.-H. Gaufryau Marguerite Joanny Pierre Mazerolles 《Journal of organometallic chemistry》1984,267(1):93-106
Intermediates with π-bonded Si or Ge are generated during gas phase pyrolysis of 1,2-disila- or 1,2-digerma-cyclohex-4-enes.Compounds such as R2MMR2 are successfully trapped by addition or [2 + 2] and [4 + 2] cycloadditions. These results were proved by mass spectrometry. 相似文献