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121.
G. van Veen E. C. Kruissink E. B. M. Doesburg J. R. H. Ross L. L. van Reijen 《Reaction Kinetics and Catalysis Letters》1978,9(2):143-148
The activities and stabilities of coprecipitated Ni/Al2O3 methanation catalysts depend markedly on their preparation and pretreatment. The results are discussed in relation to the structure of the precipitate and to changes which occur during calcination and reduction.
Ni/Al2O3 . , .相似文献
122.
Zusammenfassung Es seiG eine endliche Untergruppe der orthogonalen Gruppe (det=±1) des
k
mitk=2 oder 3 undN eine endliche Menge von Punkten des
k
, welche unterG invariant ist. Dies gibt Anlass zu einer Permutationsdarstellung vonG im Vektorraum der komplexen Funktionen aufN.In Abschn. 3 wird für eine symmetriegerechte Basis angegeben. Dabei sind die Funktionswerte jeweils exakt tabelliert.
Im Buch [1] wurden lediglich die Diedergruppen behandelt (in Abschn. 3.1). 相似文献
Let G be a finite subgroup of the orthogonal group (det=±1) of k wherek=2 or 3 and letN be a finite set of points of k , which is invariant underG. In this way one gets a permutation representation ofG in the vector space of the complex functions onN.In Section 3, a symmetry adapted basis is given for , where the function values are tabulated exactly.
Im Buch [1] wurden lediglich die Diedergruppen behandelt (in Abschn. 3.1). 相似文献
123.
M. van den Berg 《Physica A》1981,108(1):169-179
The free energy ? per particle and the two-particle distribution function g have been expressed as functionals of the nearest-neighbour interaction Φ(x) for a variety of boundary conditions. For some boundary conditions and potentials Φ(x), ? and g behave singularly at a critical density 相似文献
124.
125.
Exact renormalization group equations are derived for a position-space renormalization of spin systems with weak long-range forces. It is shown how an apparent dependence of the critical exponents on the choice of the renormalization group can be resolved via the mechanism of dangerous irrelevant variables and that this same mechanism is responsible for the breakdown of hyperscaling. The dimensiond=4 can be seen to be a borderline dimension above which classical critical exponents are expected. 相似文献
126.
J. Hala G. F. W. Searle T. J. Schaafsma A. van Hoek P. Pancoska K. Blaha K. Vacek 《Photochemistry and photobiology》1986,44(4):527-534
Fluorescence-detected magnetic resonance of triplets in zero magnetic field (FDMR), fluorescence fading (FF) due to triplet-formation, both at 4.2 K, and prompt fluorescence decay kinetics (FDK) at room temperature have been measured for free pheophorbide- a (f-Pheo) and bound (b-Pheo) to a synthetic polypeptide (L-L ys -L-A la -L-A la )n , dissolved in dimethylformamide (DMF). Fluorescence decay kinetics measurements of f-Pheo in DMF yielded 1-5 ns lifetimes, for b-Pheo in DMF a ~ 50 ps decay-component was found emitting at 730–750 nm. Zero-field splitting parameters |D| and |E| of the lowest triplet state T1 were determined from FDMR spectra as (337 and 24) 10-4 cm-1 for f-Pheo and (359 and 25) 10-4 cm-1 for b-Pheo, both in DMF. Decay rate constants of the three spin levels of T1 of b-Pheo ( K x = 1200 50 s-1 , k y = 440 25 s-1 , k z = 80 5 s-1 ) and relative steady-state populations (Nx = 28 2%, Ny = 47 2%, Nz = 26 2%) determined from FF curves predict a fluorescence decrease at the D–E and D + E FDMR transitions, whereas experimentally a fluorescence increase is observed. The FDMR sign-inversion results from singlet-singlet energy transfer from b-Pheo monomers to their aggregates, followed by fast intersystem crossing to T1 . These results indicate that aggregates are formed by two or more b-Pheo molecules at different positions on the folded polypeptide chain. This situation resembles that in chlorophyll-proteins, containing low-lying traps, resulting from interaction of chromophores with other chromophores and with the protein environment. 相似文献
127.
Use of a hard sphere model and the concept of an effective hard sphere diameter of a colloidal particle with its associated double layer is reported. This method allows rapid determination of the order-disorder transition in colloidal dispersions and yields reasonable estimates of the osmotic pressures compared with “exact” Monte Carlo calculations. 相似文献
128.
A. Obrebski R. Hergenröder K. Niemax 《Zeitschrift für Physik D Atoms, Molecules and Clusters》1989,14(4):289-292
A remarkable narrowing of the Doppler profile of the calcium 4s 2 1 S 0–4s4p 3 P 1 line have been measured by laser enhanced ionization spectroscopy in a thermionic diode. By variation of the laser intensity and the calcium number density, and by analysis of the line profiles, there is evidence that energy pooling in higher states due to the collision of two and also three excited 4s4p 3 P 1 atoms is responsible for the effect. 相似文献
129.
The site of animation for 1-alkyl-3-carbamoylpyridinium chlorides in liquid ammonia is dependent on the identity of the 1-alkyl substituent. For the methyl, ethyl and n-propyl derivatives exclusively 6-adducts are found. Adduct formation takes place at C-6 and C-4, when the 1-substituent is an i-propyl or t-butyl group. The adduct ratio for the latter compounds is determined by the size of the substituent. 1-Aryl derivatives exhibit amination at C-2 and C-6 and the adduct ratios are dependent on the temperature. When the aryl substituent is a 2,4,6-trimethylphenyl group the 4-adduct is detected as well. A comparison is made between the sites of oxidation of these compounds by rabbit liver aldehyde oxidase and the covalent amination pattern in liquid ammonia. It is shown that covalent animation as a “model” for the enzymic activity of aldehyde oxide1 is particularly valuable in cases where the enzyme reaction is controlled by steric factors. 相似文献
130.
H J van Manen R H Fokkens N M Nibbering F C van Veggel D N Reinhoudt 《The Journal of organic chemistry》2001,66(13):4643-4650
The noncovalent synthesis of "layer-block" metallodendrimers containing hydrophobic shells of covalent dendritic wedges at the periphery is described. Starting from first- and second-generation Fréchet wedges having phosphines at their focal point, convergent dendritic growth yields third- and fourth-generation metallodendrimers in which the coordination of nitriles, pyridines, and phosphines to SCS Pd(II) pincers is used as the assembly motif. In this convergent growth, the number of terminal hydrophobic phosphine wedges increases with generation. The solubility of the dendritic structures in apolar organic solvents such as chloroform and dichloromethane increases accordingly, in contrast to previously reported metallodendrimers. All dendritic structures were characterized by (1)H and (31)P NMR spectroscopy, elemental analysis, and MALDI-TOF mass spectrometry. 相似文献