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971.
D. S. Lutsik-Maksim V. I. Timokhin A. B. Zaborovskii R. E. Pristanskii A. A. Turovskii C. Chatgilialoglu 《Russian Journal of General Chemistry》2004,74(10):1508-1512
Kinetics and mechanism of liquid-phase oxidation of tert-butyldimethylsilane t-BuMe2SiH with molecular oxygen in the temperature range 297–350K were studied. Reaction orders in silane, initiator, and oxygen were evaluated. The major product of the oxidation of t-BuMe2SiH is tert-butyldimethylsilyl hydroperoxide t-BuMe2SiOOH. It was shown for the first time that the major reaction product is a silyl hydroperoxide. A kinetic scheme of the oxidation of t-BuMe2SiH is offered and discussed.Translated from Zhurnal Obshchei Khimii, Vol. 74, No. 10, 2004, pp. 1625–1630.Original Russian Text Copyright © 2004 by Lutsik-Maksim, Timokhin, Zaborovskii, Pristanskii, Turovskii, Chatgilialoglu.This revised version was published online in April 2005 with a corrected cover date. 相似文献
972.
The phenylseleno group (PhSe) has evolved in recent years as a very useful and versatile functionality. Its facile introduction into organic molecules and its subsequent oxidative or reductive removal, has allowed many important synthetic transformations.1–7 Due to the fact that, similarly to halogens, it can exist either as an electrophilic species (PhSe+) or as a nucleophilic one (PhSe-), this group can be introduced either via nucleophilic substrates (e.g. carbanions, olefins), or via electrophilic ones (e.g. epoxides, halides), as illustrated in Scheme 1. Another valuable aspect of the phenylseleno group is that it can be readily oxidized to the corresponding selenoxide(PhSe(O)—), which undergoes β-hydrogen abstraction and syn-elimination to form olefins, under relatively mild conditions (Scheme 2(a)). Furthermore, this group can be substituted with hydrogen, upon the action of an appropriate reducing agent (Scheme 2(b)).The great synthetic utility of the phenylseleno group is apparent from its extensive utilization in numerous natural products syntheses,1 as well as many other synthetic studies.2–7 相似文献
973.
C. Cerjan R. Hedges C. Holt W. P. Reinhardt K. Scheibner J. J. Wendoloski 《International journal of quantum chemistry》1978,14(4):393-418
The theories of the dilatation, r → r eiθ, and translation, x → x + iq, transformations as related to the Stark problem are reviewed, and new results obtained. Results for the hydrogen atom n = 1 and n = 2 levels and the 1P0, 2s2p H? shape resonance in dc fields are presented, and the extension to the ac Stark effect made. Spectral estimates are made using the technique of the numerical range and via discussion of several model problems, using both coordinate rotation and coordinate translation. 相似文献
974.
The reaction of 1,4,6,9-tetraoxa-5-phospha(V)spiro[4,4]nonane 1 with ethyl vinyl ether gives a spirophosphorane containing a PC bond, 5-(β-ethosyethyl)-1,4,6,9-tetra-oxa-5-phospha(V) spiro[4,4]nonane 2 (radical reaction), and a tricoordinated phosphorus compound, 2-(3,5-di-oxa-4-methylheptanoxyl)-1,3,2-dioxaphospholane 3 (ionic reaction). 2,2,3,3,7,7,9-Heptamethyl-1,4,6-trioxa-9-aza-5-phospha(V) spiro[4,4]nonane 6 gives exclusively a spirophosphorane containing a PC bond, 5(β-ethoxyethyl)-2,2,3,3,7,7,9-heptamethyl-1,4,6-trioxa-9-aza-5-phospha(V)spiro[4,4]nonane 7. The reaction of 1 with alcohol or ethyleneglycol and enamine yields a pentaoxyspirophosphorane and an amine by an oxidation-reduction condensation. Suggested mechanisms of these reactions are presented. 相似文献
975.
It is demonstrated that a previously developed topological expression for the total π-electron energy of aromatic molecules provides a good qualitative account of localization energies. The logarithm of the ratio of the algebraic structure counts for the ground state and the localized reaction intermediate is the principle energy determining factor. This expression fails for hydrocarbons with unusually small HOMO-LUMO separations. An alternative topological expression that includes a correction for this situation provides an excellent non-empirical explanation for the successful empirical use of Dewar reactivity numbers in correlating exact localization energies. The present analysis provides an explanation for the success of the traditional resonance structure counting technique in predicting relative rates of aromatic substitution. The analysis develop applied only to alternant hydrocarbons. 相似文献
976.
R. L. Laurence J. C. Slattery 《Journal of polymer science. Part A, Polymer chemistry》1967,5(6):1327-1340
A study of sorption in a copolymer of ethylene and propylene is presented. Long-time sorption and desorption measurements provided the actual diffusion coefficient in the limit of zero concentration gradient. An analysis of the diffusion–sorption data reinforced the Frisch hypothesis about diffusion in a polymer matrix. The better solvent deforms the microstructure, allowing a more marked dependence of the diffusivity upon concentration. 相似文献
977.
Experimental investigations on binary liquid mixtures near the critical mixing point are presently leading to a controversy about the anomaly in the thermal conductivity. A photopyroelectric technique is used to determine the thermal conductivity and the effusivity of the binary liquid mixture n-butoxyethanol-water at its critical concentration near the critical mixing point. It is proven that, contrary to previous reports, there is no critical enhancement in the thermal conductivity. The specific heat capacity is calculated from these results and compared with the results from measurements performed by adiabatic scanning calorimetry. 相似文献
978.
Harold C. Beachell Jean C. Peterson 《Journal of polymer science. Part A, Polymer chemistry》1969,7(8):2021-2029
A linear polyurethane of high molecular weight was prepared in solution by the polyaddition of equimolar amounts of ethylene glycol and methylene bis(4-phenyl isocyanate). The polymer was fractionated by using a direct sequential extraction procedure, with a solvent–nonsolvent system consisting of N,N′-dimethylformamide (DMF) and acetone (A). The resulting fractions were characterized by viscosity and lightscattering measurements. The relationship between the intrinsic viscosity and molecular weight was found in DMF at 25°C. to be [η] = 3.64 × 10?4M0.71. The unperturbed polymer chain dimensions were determined from intrinsic viscosity measurements carried out under experimentally determined theta conditions. 相似文献
979.
A new synthesis of 5-chloro- and 5-bromo-1,7-naphthyridine, using 8-amino-1,7-naphthyridine as starting material is described. On amination with potassium amide in liquid ammonia, the 5-bromo compound undergoes a tele-amination into 8-amino- and 2-amino-1,7-naphthyridine and a Chichibabin reaction yielding 8-amino-5-bromo-1,7-naphthyridine. The reaction with the 5-chloro compound occurs at a much lower rate than the 5-bromo compound and only gives 8-amino-5-chloro-1,7-naphthyridine in a small yield. Convincing 1H-nmr evidence is presented, showing that the 5-bromo- and 5-chloro-1,7-naphthyridine give addition of the amide ion at position 8 and that the 5-chloro compound also gives addition at position 2. 相似文献
980.
Total emission, phosphoroscopically resolved emission, excitation and mean lifetime in the excited triplet state were measured for three organic molecules of petrochemical interest in EPA rigid glass at 77° K. Fluorescence was also measured at room temperature in n-heptane. Methods for the determination of these three molecules in individual solutions are presented and compared with known methods by absorption spectroscopy. An attempt was made to quantify a blend of the three components by luminescence techniques. 相似文献