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71.
Adsorption of benzene on the V2O5/-Al2O3 catalysts was studied in the temperature interval from 443 to 493 K and at partial pressures of the adsorbate ranging from 1 to 400 Pa. The adsorption isotherms were plotted. The isosteric heats and various entropy characteristics of adsorption were determined. Mobility of benzene in the adsorption layer is restricted compared to the model of ideal dimeric gas. The adsorbed amounts of benzene and chlorobenzene are compared. 相似文献
72.
N. V. Pervukhina M. N. Sokolov N. É. Fedorova V. E. Fedorov 《Journal of Structural Chemistry》2001,42(5):833-837
The crystal structures of two new dimer compounds of Re(V) containing an [OReOReO]4+ fragment have been studied. Re2O3Cl4(3,5-Me2pzH)4 (I): space group P21/n, Z = 4, a = 10.180(3), b = 18.132(3), c = 16.601(2) , = 94.60(2)°, V = 3054.4(1) 3, d
calc = 2.059 g/cm3, R
1 = 0.0513, wR2 = 0.1493 for 4701 Ihkl > 2 I of 4926 measured reflections; Re2O3Cl2(-3,5-Me2pz)2(3,5-Me2pzH)22[(3,5-Me2pzH2)Cl] (II): space group P21/n, Z = 4, a = 16.904(2), b = 14.573(1), c = 17.401(2) , = 107.23(1)°, V = 4094.2(7) 3, d
calc = 1.848 g/cm3, R
1 = 0.025, wR2 = 0.0514 for 6102 Ihkl > 2 I of 6315 measured reflections (Enraf-Nonius CAD-4 diffractometer, MoK, graphite monochromator). Compound I has a molecular structure, where molecules are dimers Re2O3Cl4(3,5-Me2pzH)4 with a bridging O atom. In II, the dominant motif is the ReOCl(3,5-Me2pzH) fragments bridged by the pyrazole molecules and the O atom. 相似文献
73.
B. S. Fedorov N. I. Golovina L. S. Barinova V. V. Arakcheeva G. V. Lagodzinskaya M. V. Loginova R. F. Trofimova V. Z. Laishev V. F. Lazarev S. P. Smirnov I. Sh. Abdrakhmanov A. I. Firkin L. O. Atovmyan 《Russian Chemical Bulletin》1992,41(12):2185-2188
1,1,4,4-Tetranitrobutane-2,3-diol reacts with formaldehyde, forming 2,2-dinitropropane-1,3-diol or a cyclic ether — 4,4-dinitro-2,3-dihydroxytetrahydrofuran — as a function of the reaction conditions.Institute of Chemical Physics, Chernogolovka, Russian Academy of Sciences, 142432 Chernogolovka. Translated fromIzvestiya Akademii Nauk, Seriya Khimicheskaya, No. 12, pp. 2755–2759, December, 1992. 相似文献
74.
Biosensors based on enzyme field-effect transistors for determination of some substrates and inhibitors 总被引:3,自引:0,他引:3
Dzyadevych SV Soldatkin AP Korpan YI Arkhypova VN El'skaya AV Chovelon JM Martelet C Jaffrezic-Renault N 《Analytical and bioanalytical chemistry》2003,377(3):496-506
This paper is a review of the authors' publications concerning the development of biosensors based on enzyme field-effect transistors (ENFETs) for direct substrates or inhibitors analysis. Such biosensors were designed by using immobilised enzymes and ion-selective field-effect transistors (ISFETs). Highly specific, sensitive, simple, fast and cheap determination of different substances renders them as promising tools in medicine, biotechnology, environmental control, agriculture and the food industry.The biosensors based on ENFETs and direct enzyme analysis for determination of concentrations of different substrates (glucose, urea, penicillin, formaldehyde, creatinine, etc.) have been developed and their laboratory prototypes were fabricated. Improvement of the analytical characteristics of such biosensors may be achieved by using a differential mode of measurement, working solutions with different buffer concentrations and specific agents, negatively or positively charged additional membranes, or genetically modified enzymes. These approaches allow one to decrease the effect of the buffer capacity influence on the sensor response in an aim to increase the sensitivity of the biosensors and to extend their dynamic ranges.Biosensors for the determination of concentrations of different toxic substances (organophosphorous pesticides, heavy metal ions, hypochlorite, glycoalkaloids, etc.) were designed on the basis of reversible and/or irreversible enzyme inhibition effect(s). The conception of an enzymatic multibiosensor for the determination of different toxic substances based on the enzyme inhibition effect is also described.We will discuss the respective advantages and disadvantages of biosensors based on the ENFETs developed and also demonstrate their practical application. 相似文献
75.
[reaction: see text] Radical/polar crossover reactions of derivatives of 1-(2-cyclobutenyl)-2-(2-iodoaryl)ethanones with acetone promoted by samarium diiodide and HMPA provide 1-(1-hydroxy-1-methylethyl)-2,2a,4,8b-tetrahydro-1H-cyclobuta[a]naphthalen-3-one derivatives in about 50% isolated yield. This reaction shows promise for construction of the BCD ring fragment of the penitrems. 相似文献
76.
Resonant interaction through the continuum between two intense electromagnetic waves of different frequencies during ionization of an atom is considered. A general solution of the problem is found by using a procedure based on the application of the Laplace transform to the equations for the time-dependent amplitudes of the probability. When one of the EM waves is considerably weaker than the other, the dynamics of the absorption of light by an atom are investigated, and a final value for the ionization probability in the illumination region is found.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 1, pp. 63–70, January, 1978. 相似文献
77.
Fluorescence of the single tryptophan of cutinase: temperature and pH effect on protein conformation and dynamics 总被引:1,自引:0,他引:1
Martinho JM Santos AM Fedorov A Baptista RP Taipa MA Cabral JM 《Photochemistry and photobiology》2003,78(1):15-22
The cutinase from Fusarium solani pisi is an enzyme with a single L-tryptophan (Trp) involved in a hydrogen bond with an alanine (Ala) residue and located close to a cystine formed by a disulfide bridge between two cysteine (Cys) residues. The Cys strongly quenches the fluorescence of Trp by both static and dynamic quenching mechanisms. The Trp fluorescence intensity increases by about fourfold on protein melting because of the disruption of the Ala-Trp hydrogen bond that releases the Trp from the vicinity of the cystine residue. The Trp forms charge-transfer complexes with the disulfide bridge, which is disrupted by UV light irradiation of the protein. This results in a 10-fold increase of the Trp fluorescence quantum yield because of the suppression of the static quenching by the cystine residue. The Trp fluorescence anisotropy decays are similar to those in other proteins and were interpreted in terms of the wobbling-in-cone model. The long relaxation time is attributed to the Brownian rotational correlation time of the protein as a whole below the protein-melting temperature and to protein-backbone dynamics above it. The short relaxation time is related to the local motion of the Trp, whose mobility increases on protein denaturation. 相似文献
78.
B. L. Korsunskii G. V. Sitonina B. S. Fedorov F. I. Dubovitskii L. T. Eremenko 《Russian Chemical Bulletin》1989,38(4):710-713
1. | The thermal decomposition of N,N-dinitroamines is homogeneous and unimolecular in the gas phase. The limiting step of the process is the rupture of the N-NO2 bond. |
2. | The activation parameters of the process imply that the dinitroamine group is more reactive than the mononitroamine group in thermal decomposition. The energy of dissociation of the N-NO2 bond in dinitroamines is 42 kJ/mole less than in mononitroamines. |
3. | Nitrogen dioxide and acetaldehyde do not influence the kinetics of thermal decomposition of dinitroamines due to their high reactivity. |
79.
D.N. Kravtsov A.S. Peregudov E.M. Rokhlina L.A. Fedorov 《Journal of organometallic chemistry》1974,77(2):199-224
Metal—proton and metal—metal exchange reactions have been studied by PMR for thiophenol, 2-methylthiophenol, 2,6-dimethylthiophenol, benzyl mercaptan and their C6H5HG, (C6H5)3Sn and (C6H5)3Pb derivatives in chlorobenzene and pyridine solutions. In chlorobenzene the metal—metal exchange has been found to proceed in many cases at a greater rate than the metal—proton type, the exchange mobility of hydrogen and organometallic groups in chlorobenzene increasing in the order (C6H5)3Sn<H<(C6H5)3Pb<C6H5Hg. In the case of the (C6H5)3Sn and (C6H5)3Pb groups, pyridine accelerates the metal—proton exchange to a greater extent than the metal—metal exchange.The influence of various factors on the exchange reactions has been studied Analysis of the experimental findings and literature data has led to the conclusion that most probably the mechanism of the exchange reactions involves an associative pathway, the ease of exchange being mainly determined by the ability of the migrating group to form a cyclic transition state with delocalized bonds. The data on the exchange equilibria of the organometallic derivatives of 2-methylthiophenol and 2,6-dimethylthiophenol with thiophenol and its derivatives demonstrate that the C6H5HgS, (C6H5)3SnS and (C6H5)3PbS groups have equal steric requirements when involved in non-bonded interactions with o-methyl substituents. 相似文献
80.
The vibrational structure of the endohedral cluster fullerene Sc(3)N@C(78) is studied by FTIR spectroscopy, Raman spectroscopy and DFT-based quantum chemical calculations. Remarkably good agreement between experimental and calculated spectra is achieved and a full assignment of the Sc(3)N-based vibrational modes is given. Significant differences in the vibrational structure of the endohedral cluster fullerene Sc(3)N@C(78) and the empty, charged C(78) (6-): 5 (D(3h)') are rationalized by the strong coupling between the Sc(3)N cluster and the fullerene cage. This coupling has its origin in a significant overlap of the Sc(3)N and C(78) molecular orbitals, and causes atomic-charge and bond-length redistributions compared to the neutral C(78) and the C(78) (6-) anion. An ionic model is not sufficient to describe the electronic, geometric and vibrational structure of the Sc(3)N@C(78) nitride cluster fullerene. 相似文献